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1.
Shieh, Bernard D.
Quantitative simulation of backscatter from tissue and blood flow for ultrasonic transducers.
Degree: MS, Mechanical Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/53843 
► Ultrasound imaging is a ubiquitous part of the modern medical diagnostics toolbox. It has widespread applications to many areas of medicine, including angiology, cardiology, nephrology,…
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▼ Ultrasound imaging is a ubiquitous part of the modern medical diagnostics toolbox. It has widespread applications to many areas of medicine, including angiology, cardiology, nephrology, urology, and obstetrics. It is often preferred over other imaging modalities, such as x-ray computed tomography (CAT) and magnetic resonance imaging (MRI) because it is non-invasive, non-ionizing, inexpensive, and has excellent penetration depth in the body.
The design, optimization, and manufacturing of ultrasound transducers used in ultrasound imaging is a challenging engineering problem. Faced with a variety of different imaging environments, ultrasound transducers must often be optimized for performance in very specific applications. This is especially true for catheter-based solutions, such as intracardiac and intravascular ultrasound, where imaging performance is strongly dependent on the strength of backscatter from tissue due to significant limitations in device size, electronics, and signal-to-noise ratio. Currently, there is a need for the accurate and fast simulation of the imaging process used in ultrasound imaging, including the ability to capture the effects of backscatter from a variety of different tissues.
This thesis discusses the development of simulation tools for the quantitative simulation of tissue backscatter and blood motion from acoustic fields coupled to spatial array transducers, based on an application of the Rayleigh speckle model to the linear systems model for acoustic diffraction from spatial array transducers. These simulation tools have potential applications in the field of medical ultrasonics, with particular attention to the areas of transducer design and optimization, beamforming and array processing, and image reconstruction. We demonstrate how the simulation tools developed here can be used to characterize array imaging performance and to investigate reconstruction performance of common flow algorithms for Doppler ultrasound imaging.
Advisors/Committee Members: Sabra, Karim (advisor), Degertekin, F. Levent (committee member), Meaud, Julien (committee member).
Subjects/Keywords: Medical ultrasound; Doppler ultrasound; Tissue backscatter; Ultrasound transducers
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APA (6th Edition):
Shieh, B. D. (2015). Quantitative simulation of backscatter from tissue and blood flow for ultrasonic transducers. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53843
Chicago Manual of Style (16th Edition):
Shieh, Bernard D. “Quantitative simulation of backscatter from tissue and blood flow for ultrasonic transducers.” 2015. Masters Thesis, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/53843.
MLA Handbook (7th Edition):
Shieh, Bernard D. “Quantitative simulation of backscatter from tissue and blood flow for ultrasonic transducers.” 2015. Web. 18 Apr 2021.
Vancouver:
Shieh BD. Quantitative simulation of backscatter from tissue and blood flow for ultrasonic transducers. [Internet] [Masters thesis]. Georgia Tech; 2015. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/53843.
Council of Science Editors:
Shieh BD. Quantitative simulation of backscatter from tissue and blood flow for ultrasonic transducers. [Masters Thesis]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/53843
2.
Lani, Shane W.
Passive acoustic imaging and monitoring using ambient noise.
Degree: MS, Mechanical Engineering, 2012, Georgia Tech
URL: http://hdl.handle.net/1853/50136
► An approximate of the Green's function can be obtained by taking the cross-correlation of ambient noise that has been simultaneously recorded on separate sensors. This…
(more)
▼ An approximate of the Green's function can be obtained by taking the cross-correlation of ambient noise that has been simultaneously recorded on separate sensors. This method is applied for two experiments, which illustrate the advantages and challenges of this technique. The first experiment is in the ultrasonic regime [5-30] MHz and uses capacitive micromachined ultrasonic transducer arrays to image the near field and compares the passive imaging to the conventional pulse-echo imaging. Both the array and target are immersed in a fluid with the sensors recording the fluid's random thermal-mechanical motion as the ambient noise. The second experiment is a passive ocean monitoring experiment, which uses spatiotemporal filtering to rapidly extract coherent arrivals between two vertical line arrays. In this case the ambient noise in the frequency band [250 1500] Hz is dominated by non-stationary shipping noise. For imaging purposes, the cross-correlation needs to extract the Green's function so that the imaging can be done correctly. While for monitoring purposes, the important feature is the change in arrivals, which corresponds to the environment changing. Results of both experiments are presented along with the advantages of this passive method over the more accepted active methods.
Advisors/Committee Members: Sabra, Karim (advisor), Degertekin, F. Levent (committee member), Romberg, Justin (committee member).
Subjects/Keywords: Ultrasound imaging; Noise imaging; Ocean monitoring; Noise; Cross-correlation; Noise monitoring; Ambient sounds; Green's functions
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APA (6th Edition):
Lani, S. W. (2012). Passive acoustic imaging and monitoring using ambient noise. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/50136
Chicago Manual of Style (16th Edition):
Lani, Shane W. “Passive acoustic imaging and monitoring using ambient noise.” 2012. Masters Thesis, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/50136.
MLA Handbook (7th Edition):
Lani, Shane W. “Passive acoustic imaging and monitoring using ambient noise.” 2012. Web. 18 Apr 2021.
Vancouver:
Lani SW. Passive acoustic imaging and monitoring using ambient noise. [Internet] [Masters thesis]. Georgia Tech; 2012. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/50136.
Council of Science Editors:
Lani SW. Passive acoustic imaging and monitoring using ambient noise. [Masters Thesis]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/50136
Georgia Tech
3.
Jung, Gwangrok.
SINGLE-CHIP REDUCED-WIRE ACTIVE CATHETER SYSTEM WITH PROGRAMMABLE TRANSMIT BEAMFORMING AND RECEIVE TIME-DIVISION MULTIPLEXING FOR INTRACARDIAC ECHOCARDIOGRAPHY.
Degree: PhD, Electrical and Computer Engineering, 2019, Georgia Tech
URL: http://hdl.handle.net/1853/64013
► A single chip reduced-wire active catheter system, which adopts programmable transmit beamforming and receive time-division multiplexing (TDM) was proposed. The front-end application-specific integrated circuit (ASIC)…
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▼ A single chip reduced-wire active catheter system, which adopts programmable transmit beamforming and receive time-division multiplexing (TDM) was proposed. The front-end application-specific integrated circuit (ASIC) is designed for driving a 64-channel 1-D piezo-transducer array or capacitive micromachined ultrasound transducer (CMUT) array in intracardiac echocardiography (ICE) catheters. ICE has become more important clinical modality in interventional ultrasound imaging. It provides real-time ultrasound imaging, guiding interventions like valve repair, placement of stents, closure of atrial septal defects (ASD) and catheter-based ablation to treat atrial fibrillation. Current ICE catheters offer a limited 2-D or 3-D field of view in spite of large number electrical interconnections to the main imaging system, which are mainly determined by the number of array elements and ground connections. In order to use ICE catheters under MRI instead of the ionizing X-ray radiation-based angiography, the number of interconnect wires in the catheter should be minimized to reduce RF-induced heating from metal connection. Furthermore, reducing the number of wires would improve the flexibility, reach, and even lower the cost of the single-use ICE catheters. Therefore, an interconnection reduction method which integrates electronics in the catheter tip would have a significant impact in the catheter-based ultrasound imaging applications.
Advisors/Committee Members: Degertekin, F. Levent (advisor), Tekes, Coskun (committee member), Ayazi, Farrokh (committee member), Inan, Omer T (committee member), Emelianov, Stanislav (committee member), Degertekin, F. Levent (committee member).
Subjects/Keywords: Analog; Intracardiac Echocardiography; Circuit; beamformer; pulser
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APA (6th Edition):
Jung, G. (2019). SINGLE-CHIP REDUCED-WIRE ACTIVE CATHETER SYSTEM WITH PROGRAMMABLE TRANSMIT BEAMFORMING AND RECEIVE TIME-DIVISION MULTIPLEXING FOR INTRACARDIAC ECHOCARDIOGRAPHY. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/64013
Chicago Manual of Style (16th Edition):
Jung, Gwangrok. “SINGLE-CHIP REDUCED-WIRE ACTIVE CATHETER SYSTEM WITH PROGRAMMABLE TRANSMIT BEAMFORMING AND RECEIVE TIME-DIVISION MULTIPLEXING FOR INTRACARDIAC ECHOCARDIOGRAPHY.” 2019. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/64013.
MLA Handbook (7th Edition):
Jung, Gwangrok. “SINGLE-CHIP REDUCED-WIRE ACTIVE CATHETER SYSTEM WITH PROGRAMMABLE TRANSMIT BEAMFORMING AND RECEIVE TIME-DIVISION MULTIPLEXING FOR INTRACARDIAC ECHOCARDIOGRAPHY.” 2019. Web. 18 Apr 2021.
Vancouver:
Jung G. SINGLE-CHIP REDUCED-WIRE ACTIVE CATHETER SYSTEM WITH PROGRAMMABLE TRANSMIT BEAMFORMING AND RECEIVE TIME-DIVISION MULTIPLEXING FOR INTRACARDIAC ECHOCARDIOGRAPHY. [Internet] [Doctoral dissertation]. Georgia Tech; 2019. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/64013.
Council of Science Editors:
Jung G. SINGLE-CHIP REDUCED-WIRE ACTIVE CATHETER SYSTEM WITH PROGRAMMABLE TRANSMIT BEAMFORMING AND RECEIVE TIME-DIVISION MULTIPLEXING FOR INTRACARDIAC ECHOCARDIOGRAPHY. [Doctoral Dissertation]. Georgia Tech; 2019. Available from: http://hdl.handle.net/1853/64013
4.
Tol, Serife.
Structure-borne elastic wave energy harvesting enhanced by metamaterial concepts.
Degree: PhD, Mechanical Engineering, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/58645
► Existing research on vibration-based energy harvesting has been mainly focused on the harvesting of vibrational energy available at a fixed position in space. Such an…
(more)
▼ Existing research on vibration-based energy harvesting has been mainly focused on the harvesting of vibrational energy available at a fixed position in space. Such an approach is convenient for designing and employing linear and nonlinear vibration-based energy harvesters, such as base-excited cantilevers with piezoelectric laminates undergoing persistent excitation that yield modal vibrations. This theoretical and experimental research is centered on the harvesting of structure-borne propagating elastic waves in one-dimensional and two-dimensional settings. Specifically, it is aimed to enhance the harvested elastic wave energy by exploiting concepts from metamaterials and phononic crystals. First, the focus is placed on a one-dimensional beam configuration for piezoelectric energy harvesting from bending waves through optimal resistive-reactive electrical loading, spatially localized obstacle for harvesting local reflections, and a multifunctional energy-harvesting electromechanical non-reflective boundary condition in a semi-infinite setting. Next, two-dimensional efficient wave energy harvesting concepts are explored by means of novel wave mirror and lens concepts in elastic plates. Mirror concepts are studied thoroughly with a focus on their scattering characteristics. In this context, structurally embedded mirrors and bandgap-based mirrors are presented. As an alternative approach for plane wave focusing, elastic lenses are designed by creating a gradient distribution of the refractive index of the phononic crystals (PC) and locally resonant (LR) unit cells. To this end, a Gradient-Index Phononic Crystal Lens (GRIN-PCL), a 3D printed GRIN-PCL, and an omnidirectional Luneburg lens are fabricated and experimentally validated. In addition, wave focusing is explored with GRIN lenses composed of LR subwavelength unit cells towards enabling enhanced low frequency energy harvesting. Overall, this work provides electroelastic models and metamaterial-based approaches to efficient elastic wave energy harvesting. Beyond enhanced energy harvesting, ramifications of this work range from MEMS implementation to 3D printed platforms for structural integration in sensing applications and nondestructive testing.
Advisors/Committee Members: Erturk, Alper (advisor), Degertekin, F. Levent (advisor), Sabra, Karim (committee member), Ruzzene, Massimo (committee member), Yu, Min-Feng (committee member).
Subjects/Keywords: Piezoelectric energy harvesting; Wave focusing; Gradient index lens; Elastic mirror; Phononic crystals; Locally resonant metamaterials
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APA (6th Edition):
Tol, S. (2017). Structure-borne elastic wave energy harvesting enhanced by metamaterial concepts. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/58645
Chicago Manual of Style (16th Edition):
Tol, Serife. “Structure-borne elastic wave energy harvesting enhanced by metamaterial concepts.” 2017. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/58645.
MLA Handbook (7th Edition):
Tol, Serife. “Structure-borne elastic wave energy harvesting enhanced by metamaterial concepts.” 2017. Web. 18 Apr 2021.
Vancouver:
Tol S. Structure-borne elastic wave energy harvesting enhanced by metamaterial concepts. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/58645.
Council of Science Editors:
Tol S. Structure-borne elastic wave energy harvesting enhanced by metamaterial concepts. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/58645
Georgia Tech
5.
Yoon, Heechul.
Combined laser, ultrasound, and elasticity imaging for comprehensive diagnosis of cancer.
Degree: PhD, Electrical and Computer Engineering, 2018, Georgia Tech
URL: http://hdl.handle.net/1853/62211
► As cancer is pathologically and biologically complex, identifying a variety of information on its morphology, functionality, molecular composition, and biomechanics is desired for precise and…
(more)
▼ As cancer is pathologically and biologically complex, identifying a variety of information on its morphology, functionality, molecular composition, and biomechanics is desired for precise and personalized diagnosis and treatment. Medical ultrasound imaging is a relatively safe, cost-effective modality that provides a cross-sectional image of anatomy in real-time, but it suffers from low contrast and does not provide quantitative functional information on tissue for better detection and assessment of a suspicious lesion. To circumvent this limitation, researchers have introduced shear-wave elasticity imaging, which noninvasively measures Young’s modulus of tissue, spectroscopic photoacoustic imaging, which quantifies chromophores distribution in tissue, phase-change contrast agents, which are useful in imaging extravascular targets, and super-resolution imaging, which provides unprecedented spatial resolution beyond the diffraction limit for molecular imaging. This research engineers these methods to further improve their respective imaging capabilities. In addition, based on the improvements in each imaging method, this research introduces combined laser, ultrasound, and elasticity (CLUE) imaging that is uniquely capable of simultaneous and synergistic probing of acoustic, optical, and mechanical imaging contrast of tissue to provide comprehensive soft tissue assessment.
Advisors/Committee Members: Emelianov, Stanislav (advisor), Degertekin, F. Levent (committee member), Lindsey, Brooks (committee member), Inan, Omer (committee member), Arvanitis, Costas (committee member).
Subjects/Keywords: Ultrasound imaging; Shear-wave elasticity imaging; Photoacoustic imaging; Perfluorohexane nanodroplets; Contrast-enhanced ultrasound imaging; Comprehensive cancer diagnosis; Multi-modal imaging
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APA (6th Edition):
Yoon, H. (2018). Combined laser, ultrasound, and elasticity imaging for comprehensive diagnosis of cancer. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/62211
Chicago Manual of Style (16th Edition):
Yoon, Heechul. “Combined laser, ultrasound, and elasticity imaging for comprehensive diagnosis of cancer.” 2018. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/62211.
MLA Handbook (7th Edition):
Yoon, Heechul. “Combined laser, ultrasound, and elasticity imaging for comprehensive diagnosis of cancer.” 2018. Web. 18 Apr 2021.
Vancouver:
Yoon H. Combined laser, ultrasound, and elasticity imaging for comprehensive diagnosis of cancer. [Internet] [Doctoral dissertation]. Georgia Tech; 2018. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/62211.
Council of Science Editors:
Yoon H. Combined laser, ultrasound, and elasticity imaging for comprehensive diagnosis of cancer. [Doctoral Dissertation]. Georgia Tech; 2018. Available from: http://hdl.handle.net/1853/62211
Georgia Tech
6.
Pourabolghasem, Reza.
Pillar-based phononic crystal structures for high-frequency applications.
Degree: PhD, Electrical and Computer Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/58148
► The physical mechanisms of phononic bandgap (PnBG) formation in the pillar-based phononic crystals (PnCs) are theoretically studied. The comparison of PnBGs in three different lattice…
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▼ The physical mechanisms of phononic bandgap (PnBG) formation in the pillar-based phononic crystals (PnCs) are theoretically studied. The comparison of PnBGs in three different lattice types (i.e., square, triangular, and honeycomb) with different pillar geometries shows that different PnBGs have varying degrees of dependency on the lattice symmetry based on the interplay of the local resonances and the Bragg effect. The details of this interplay are discussed. The significance of locally resonating pillars on PnBGs is discussed and verified by examining the PnBG position and width in perturbed lattices. It is shown that the PnBGs caused by the local resonance of the pillars are more resilient to the lattice perturbations than those caused by Bragg scattering. Furthermore, strong experimental evidence is presented for the existence of a complete phononic bandgap, for Lamb waves, in the high frequency regime (i.e., 800 MHz) for a pillar-based PnC membrane with a triangular lattice of gold pillars on top. The results of experiments are analyzed, and the physics behind the attenuation in different spectral windows is explained methodically by assessing the type of Bloch modes and the in-plane symmetry of the displacement profile. In addition, a theoretical design for a waveguide/resonator device operating at the GHz frequency range based on the pillar-based PnC membranes is presented and experimental evidence is provided for the waveguiding property of the proposed structure. Additionally, several designs for surface acoustic wave (SAW) PnCs and PnC-based waveguides are introduced and theoretically studied. These designs are optimized to provide low radiation loss and high design flexibility in terms of engineering the frequency and the number of guided modes.
Advisors/Committee Members: Adibi, Ali (advisor), Brand, Oliver (committee member), Degertekin, F. Levent (committee member), Naeemi, Azad (committee member), Jacobs, Laurence J. (committee member).
Subjects/Keywords: Acoustics; Phononics; Phononic crystal; Bandgap; Surface acoustic wave; Lamb wave; High frequency
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APA (6th Edition):
Pourabolghasem, R. (2016). Pillar-based phononic crystal structures for high-frequency applications. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/58148
Chicago Manual of Style (16th Edition):
Pourabolghasem, Reza. “Pillar-based phononic crystal structures for high-frequency applications.” 2016. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/58148.
MLA Handbook (7th Edition):
Pourabolghasem, Reza. “Pillar-based phononic crystal structures for high-frequency applications.” 2016. Web. 18 Apr 2021.
Vancouver:
Pourabolghasem R. Pillar-based phononic crystal structures for high-frequency applications. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/58148.
Council of Science Editors:
Pourabolghasem R. Pillar-based phononic crystal structures for high-frequency applications. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/58148
Georgia Tech
7.
Zahorian, Jaime S.
Fabrication technology and design for CMUTS on CMOS for IVUS catheters.
Degree: PhD, Electrical and Computer Engineering, 2013, Georgia Tech
URL: http://hdl.handle.net/1853/51730
► The objective of this research is to develop novel capacitive micromachined ultrasonic transducer (CMUT) arrays for intravascular ultrasonic (IVUS) imaging along with the fabrication processes…
(more)
▼ The objective of this research is to develop novel capacitive micromachined ultrasonic transducer (CMUT) arrays for intravascular ultrasonic (IVUS) imaging along with the fabrication processes to allow for monolithic integration of CMUTs with custom CMOS electronics for improved performance. The IVUS imaging arrays include dual-ring arrays for forward-looking volumetric imaging in coronary arteries and annular-ring arrays with dynamic focusing capabilities for side-looking cross sectional imaging applications. Both are capable of integration into an IVUS catheter 1-2 mm in diameter. The research aim of monolithic integration of CMUTs with custom CMOS electronics has been realized mainly through the use of sloped sidewall vias less than 5 µm in diameter, with only one additional masking layer as compared to regular CMUT fabrication. Fabrication of CMUTs has been accomplished with a copper sacrificial layer reducing isolation layers by 50%. Modeling techniques for computational efficient analysis of CMUT arrays were developed for arbitrary geometries and further expanded for use with larger signal analysis. Dual-ring CMUT arrays for forward-looking volumetric imaging have been fabricated with diameters of less than 2 mm with center frequencies at 10 MHz and 20 MHz, respectively, for an imaging range from 1 mm to 1 cm. These arrays, successfully integrated with custom CMOS electronics, have generated 3D volumetric images with only 13 cables necessary. Performance from optimized fabrication has reduced the bias required for a dual-ring array element from 80 V to 42 V and in conjunction with a full electrode transmit array, it was shown that the SNR can be improved by 14 dB. Simulations were shown to be in agreement with experimental characterization indicated transmit surface pressure in excess of 8 MPa. For side-looking IVUS, three versions of annular CMUT arrays with dynamic focusing capabilities have been fabricated for imaging 1 mm to 6 mm in tissue. These arrays are 840 µm in diameter membranes linked to form 8 ring elements with areas that deviate by less than 25 %. Through modeling and simulation undesirable acoustic cross between ring elements was reduced from -13 dB to -22 dB.
Advisors/Committee Members: Degertekin, F. Levent (advisor), Frazier, Bruno (committee member), Brand, Oliver (committee member), Hesketh, Peter (committee member), Michaels, Thomas (committee member).
Subjects/Keywords: Intravascular ultrasonic (IVUS); Capacitive micromachined ultrasonic transducer (CMUT); Complementary metal oxide semiconductor (CMOS); Metal oxide semiconductors, Complementary; Ultrasonic transducer; Diagnostic ultrasonic imaging; Intravascular ultrasonography
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APA (6th Edition):
Zahorian, J. S. (2013). Fabrication technology and design for CMUTS on CMOS for IVUS catheters. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/51730
Chicago Manual of Style (16th Edition):
Zahorian, Jaime S. “Fabrication technology and design for CMUTS on CMOS for IVUS catheters.” 2013. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/51730.
MLA Handbook (7th Edition):
Zahorian, Jaime S. “Fabrication technology and design for CMUTS on CMOS for IVUS catheters.” 2013. Web. 18 Apr 2021.
Vancouver:
Zahorian JS. Fabrication technology and design for CMUTS on CMOS for IVUS catheters. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/51730.
Council of Science Editors:
Zahorian JS. Fabrication technology and design for CMUTS on CMOS for IVUS catheters. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/51730
Georgia Tech
8.
Lim, Jaemyung.
Reduced-wire readout systems-on-chip for high-frequency intravascular ultrasound imaging.
Degree: PhD, Electrical and Computer Engineering, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/59800
► The objective of the proposed research is to minimize and integrate intravascular ultrasound imaging (IVUS) system on a guidewire and to develop wireless data communication…
(more)
▼ The objective of the proposed research is to minimize and integrate intravascular ultrasound imaging (IVUS) system on a guidewire and to develop wireless data communication for general capacitive micromachined ultrasonic transducer (CMUT) based ultrasound imaging system. Several innovative system- and circuit-level techniques are proposed towards the development of CMUT modeling, optimizing front-end circuits, wireless data communication, and inductive power transmission to reduce the system size and the required number of interconnections. Since it provides real-time and high-resolution images of the arteries with negligible side effects, intravascular ultra- sound (IVUS) has been a common imaging modality for cardio-vascular interventions. Current solid-state IVUS catheters (3F-8.2F in diameter) are bulky, cannot reach to lesions in narrow arteries, and require an additional catheter exchange, prolonging the critical cardio-vascular procedures. To address this issue, the way to integrate ASIC and CMUT array on a guidewire by reducing the number of connections is proposed in this research. The proposed research presents three approaches to design and implement the reduced-wire IVUS system: 1) optimized the front-end circuit with properly modeled CMUT equivalent circuits, 2) on-chip quadrature sampler with time-division multiplexing (TDM) based on the synthetic aperture imaging algorithm, and 3) impulse-radio pulse width modulation (IR-PWM) for a wireless data acquisition.
Advisors/Committee Members: Ghovanloo, Maysam (advisor), Degertekin, F. Levent (committee member), Ayazi, Farrokh (committee member), Rincón-Mora, Gabriel A. (committee member), Freear, Steven (committee member).
Subjects/Keywords: IVUS; Ultrasound imaging; Intravascular; Capacitive micromachined ultrasonic transducer; CMUT
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APA (6th Edition):
Lim, J. (2017). Reduced-wire readout systems-on-chip for high-frequency intravascular ultrasound imaging. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/59800
Chicago Manual of Style (16th Edition):
Lim, Jaemyung. “Reduced-wire readout systems-on-chip for high-frequency intravascular ultrasound imaging.” 2017. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/59800.
MLA Handbook (7th Edition):
Lim, Jaemyung. “Reduced-wire readout systems-on-chip for high-frequency intravascular ultrasound imaging.” 2017. Web. 18 Apr 2021.
Vancouver:
Lim J. Reduced-wire readout systems-on-chip for high-frequency intravascular ultrasound imaging. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/59800.
Council of Science Editors:
Lim J. Reduced-wire readout systems-on-chip for high-frequency intravascular ultrasound imaging. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/59800
Georgia Tech
9.
Woolfe, Katherine F.
Passive acoustic monitoring of the deep ocean using ambient noise.
Degree: PhD, Mechanical Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/53910
► In the ocean, changes in the speed of sound can be related to changes in water temperature. By leveraging this relationship, acoustic methods – namely…
(more)
▼ In the ocean, changes in the speed of sound can be related to changes in water temperature. By leveraging this relationship, acoustic methods – namely acoustic tomography- have been used to monitor temperature changes in the deep ocean for the purposes of providing inputs to climate change models. Traditionally, these acoustic methods involve loud, active sound sources which can be logistically challenging to operate and have been criticized for potentially disturbing marine animals. Therefore, this work demonstrates a passive acoustic method - previously only used in shallow water for short monitoring durations- that uses only recordings of low-frequency (1-40 Hz) ambient noise to continuously monitor variations in deep ocean temperature with an unprecedented degree of precision and temporal resolution. Numerical simulations were conducted to show the portions of the ocean that are monitored with this passive method. This work also provides recommendations (regarding sensor placement around the world) for future development of a global passive acoustic sensor network that makes use of distant noise sources (sea-ice or seismic sources) to extract meaningful information (whether temperature, currents, etc.) about the ocean. Finally, an optimization method is proposed to overcome one of the fundamental limitations of previous applications of this passive monitoring method: tracking oceanic fluctuations that occur over short time scales. Hence, the results of this study may assist in the development of more reliable climate models that include an enhanced understanding of the ocean’s role as a global heat sink. Finally, an optimization method was proposed to enhance the emergence rate of coherent arrivals from ambient noise correlations, thus allowing this passive monitoring method to track acoustic medium fluctuations on a shorter time scale. This optimization could also be used in other applications of noise-based passive monitoring in a rapidly fluctuating medium (seismic, structural health monitoring, biomedical, etc.).
Advisors/Committee Members: Sabra, Karim (advisor), Degertekin, F. Levent (committee member), Di Lorenzo, Emanuele (committee member), Meaud, Julien (committee member), Kuperman, William (committee member).
Subjects/Keywords: Acoustic; Oceanography
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APA (6th Edition):
Woolfe, K. F. (2015). Passive acoustic monitoring of the deep ocean using ambient noise. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53910
Chicago Manual of Style (16th Edition):
Woolfe, Katherine F. “Passive acoustic monitoring of the deep ocean using ambient noise.” 2015. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/53910.
MLA Handbook (7th Edition):
Woolfe, Katherine F. “Passive acoustic monitoring of the deep ocean using ambient noise.” 2015. Web. 18 Apr 2021.
Vancouver:
Woolfe KF. Passive acoustic monitoring of the deep ocean using ambient noise. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/53910.
Council of Science Editors:
Woolfe KF. Passive acoustic monitoring of the deep ocean using ambient noise. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/53910
Georgia Tech
10.
Loney, Drew Allan.
Coupled electrical and acoustic modeling of viscous fluid ejectors.
Degree: PhD, Mechanical Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/54247
► The focus of this dissertation is the development of a fundamental understanding of the acoustics and piezoelectric transducer governing the operation of piezoelectric inkjets and…
(more)
▼ The focus of this dissertation is the development of a fundamental understanding of the acoustics and piezoelectric transducer governing the operation of piezoelectric inkjets and horn-based ultrasonic atomizers when utilizing high viscosity working fluids. This work creates coupled, electro-mechanical analytical models of the acoustic behavior of these devices by extending models from the literature which make minimal simplifications in the handling terms that account for viscous losses. Models are created for each component of the considered fluid ejectors: piezoelectric transducers, acoustic pipes, and acoustic horns. The acoustic pipe models consider the two limited cases when either the acoustic boundary layer or attenuation losses dominate the acoustic field and are adapted to account for changes in cross-sectional area present in acoustic horns. A full electro-mechanical analytical model of the fluid ejectors is formed by coupling the component models using appropriate boundary conditions.
The developed electro-mechanical model is applied to understand the acoustic response of the fluid cavity alone and when combined with the transducer in horn-based ultrasonic atomizers. An understanding of the individual and combined acoustic response of the fluid cavity and piezoelectric transducer allow for an optimal geometry to be selected for the ejection of high viscosity working fluids. The maximum pressure gradient magnitude produced by the atomizer is compared to the pressure gradient threshold required for fluid ejection predicted by a hydrodynamic scaling analysis. The maximum working fluid viscosity of the standard horn-based ultrasonic atomizer and those with dual working fluid combinations, a low viscosity and a high viscosity working fluid to minimize viscous dissipation, is established to be on the order of 100mPas.
The developed electro-mechanical model is also applied to understand the acoustic response of the fluid cavity and annular piezoelectric transducer in squeeze type ejectors with high viscosity working fluids. The maximum pressure gradient generated by the ejector is examined as a function of the principle geometric properties. The maximum pressure gradient magnitude produced by the ejector is again compared to the pressure gradient threshold derived from hydrodynamic scaling. The upper limit on working fluid viscosity is established as 100 mPas.
Advisors/Committee Members: Fedorov, Andrei G. (advisor), Degertekin, F. Levent (advisor), Rosen, David (committee member), Ruzzene, Massimo (committee member), Hunt, William (committee member).
Subjects/Keywords: Inkjet; Viscosity; Horn-based ultrasonic atomizer; Droplet; Ultrasonic; Jetting; Acoustic
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APA (6th Edition):
Loney, D. A. (2014). Coupled electrical and acoustic modeling of viscous fluid ejectors. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54247
Chicago Manual of Style (16th Edition):
Loney, Drew Allan. “Coupled electrical and acoustic modeling of viscous fluid ejectors.” 2014. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/54247.
MLA Handbook (7th Edition):
Loney, Drew Allan. “Coupled electrical and acoustic modeling of viscous fluid ejectors.” 2014. Web. 18 Apr 2021.
Vancouver:
Loney DA. Coupled electrical and acoustic modeling of viscous fluid ejectors. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/54247.
Council of Science Editors:
Loney DA. Coupled electrical and acoustic modeling of viscous fluid ejectors. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/54247
Georgia Tech
11.
Shao, Peng.
Microscale hemispherical shell resonating gyroscopes.
Degree: PhD, Mechanical Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/54266
► MEMS gyroscopes are electromechanical devices that measure rate or angle of rotation. They are one of the fastest growing segments of the microsensor market. Advances…
(more)
▼ MEMS gyroscopes are electromechanical devices that measure rate or angle of rotation. They are one of the fastest growing segments of the microsensor market. Advances in microfabrication technologies have enabled the implementation of chip scale monolithic gyroscopes (MEMS gyroscopes) with very small form factor that are lightweight and consume little power. Over the past decade, significant amount of research have been directed towards the development of high performance and very small size MEMS gyroscopes for applications in consumer electronics such as smart phones. In this dissertation, high aspect-ratio hemispherical shell structure with continuously curved surface is utilized as the high Q resonator. Being an axial symmetric structure, the 3D hemispherical shell is able to achieve low frequency (3 ~ 5 kHz) within 2 mm X 2mm die area. Detailed analysis on energy dissipation also shows its potential to achieve ultra-high quality factor with the selection of high Q material and proper design of support structure. This dissertation presents, for the first time, the analysis, design, fabrication and characterization of a micro-hemispherical resonating gyroscope (μHRG) that has the potential to be used as a whole angle micro-gyroscope. A three-dimensional high aspect-ratio poly- and single crystalline silicon (3D HARPSS) process is developed to fabricate free-standing, stem-supported hemispherical shell with self-aligned deep electrodes for driving, sensing and quadrature control of the gyroscope. This monolithic process consists of seven lithography steps and combines 3D micro-structure with curved surfaces with the HARPSS process to create capacitive electrodes with arbitrary gaps around the micro-hemispherical shell resonator (μHSR). Polysilicon is utilized as the structural material due to its isotropic mechanical properties and the potential of achieving high quality factor. The fabrication is demonstrated successfully by prototypes of polysilicon μHRG with diameter of 1.2 mm and thickness of 700 nm. Frequency response and gyro operation are electronically measured using the integrated electrodes. Quality factor of 8,500 is measured with frequency mismatch of 105 Hz. Electronic mode matching and alignment are successfully performed by applying tuning voltages and quadrature nulling voltages. An open loop rate sensitivity scale factor of 4.42 mV/°/s was measured. Design and process optimization of the support structure improved the quality factor to 40,000. Further improvement of quality factor will enable the demonstration of high performance RIG using polysilicon μHRG.
Advisors/Committee Members: Ayazi, Farrokh (advisor), Pierron, Olivier (advisor), Brand, Oliver (committee member), Hesketh, Peter J. (committee member), Degertekin, F. Levent (committee member).
Subjects/Keywords: Gyroscopes; Quality factor; Inertial navigation
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APA (6th Edition):
Shao, P. (2014). Microscale hemispherical shell resonating gyroscopes. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54266
Chicago Manual of Style (16th Edition):
Shao, Peng. “Microscale hemispherical shell resonating gyroscopes.” 2014. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/54266.
MLA Handbook (7th Edition):
Shao, Peng. “Microscale hemispherical shell resonating gyroscopes.” 2014. Web. 18 Apr 2021.
Vancouver:
Shao P. Microscale hemispherical shell resonating gyroscopes. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/54266.
Council of Science Editors:
Shao P. Microscale hemispherical shell resonating gyroscopes. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/54266
Georgia Tech
12.
Satir, Sarp.
Modeling and optimization of capacitive micromachined ultrasonic transducers.
Degree: PhD, Electrical and Computer Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/54303
► The objective of this research is to develop large signal modeling and optimization methods for Capacitive Micromachined Ultrasonic Transducers (CMUTs), especially when they are used…
(more)
▼ The objective of this research is to develop large signal modeling and optimization methods for Capacitive Micromachined Ultrasonic Transducers (CMUTs), especially when they are used in an array configuration. General modeling and optimization methods that cover a large domain of CMUT designs are crucial, as many membrane and array geometry combinations are possible using existing microfabrication technologies. Currently, large signal modeling methods for CMUTs are not well established and nonlinear imaging techniques utilizing linear piezoelectric transducers are not applicable to CMUTs because of their strong nonlinearity. In this work, the nonlinear CMUT behavior is studied, and a feedback linearization method is proposed to reduce the CMUT nonlinearity. This method is shown to improve the CMUT performance for continuous wave applications, such as high-intensity focused ultrasound or harmonic imaging, where transducer linearity is crucial. In the second part of this dissertation, a large signal model is developed that is capable of transient modeling of CMUT arrays with arbitrary electrical terminations. The developed model is suitable for iterative design optimization of CMUTs and CMUT based imaging systems with arbitrary membrane and array geometries for a variety of applications. Finally, a novel multi-pulse method for nonlinear tissue and contrast agent imaging with CMUTs is presented. It is shown that the nonlinear content can be successfully extracted from echo signals in a CMUT based imaging system using a multiple pulse scheme. The proposed method is independent of the CMUT geometry and valid for large signal operation. Experimental results verifying the developed large signal CMUT array model, proposed gap feedback and multi-pulse techniques are also presented.
Advisors/Committee Members: Degertekin, F. Levent (advisor), Brand, Oliver (committee member), Sabra, Karim (committee member), Ghovanloo, Maysam (committee member), Bhatti, Pamela (committee member).
Subjects/Keywords: CMUTs; Ultrasound imaging; Nonlinear modeling
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APA (6th Edition):
Satir, S. (2014). Modeling and optimization of capacitive micromachined ultrasonic transducers. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54303
Chicago Manual of Style (16th Edition):
Satir, Sarp. “Modeling and optimization of capacitive micromachined ultrasonic transducers.” 2014. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/54303.
MLA Handbook (7th Edition):
Satir, Sarp. “Modeling and optimization of capacitive micromachined ultrasonic transducers.” 2014. Web. 18 Apr 2021.
Vancouver:
Satir S. Modeling and optimization of capacitive micromachined ultrasonic transducers. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/54303.
Council of Science Editors:
Satir S. Modeling and optimization of capacitive micromachined ultrasonic transducers. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/54303
13.
Zhou, Wenchao.
Interface dynamics in inkjet deposition.
Degree: PhD, Mechanical Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/51817
► Ink-jet deposition is an emerging technology that provides a more efficient, economic, scalable method of manufacturing than other traditional additive techniques by laying down droplets…
(more)
▼ Ink-jet deposition is an emerging technology that provides a more efficient, economic, scalable method of manufacturing than other traditional additive techniques by laying down droplets layer by layer to build up 3-D objects. The focus of this thesis is to investigate the material interface evolution during the droplet deposition process, which holds the key to understanding the material joining process. Droplet deposition is a complicated process and can be broken down into droplet impingement dynamics and droplet hardening. This research focuses on the study of the interface dynamics of droplet impingement. In order to study the interface dynamics, a novel metric is developed to quantify the evolving geometry of the droplet interface in both 2-D and 3-D for single and multiple droplets respectively, by measuring the similarity between the evolving droplet geometry and a desired shape. With the developed shape metric, the underlying physics of the interface evolution for single droplet impingement are examined with simulations using an experimentally validated numerical model. Results show that the Weber number determines the best achievable shape and its timing during the droplet impingement when Ohnesorge number is smaller than 1, while the Reynolds number is the determining factor when Ohnesorge number is larger than 1. A regime map is constructed with the results and an empirical splash criterion to guide the choice of process parameters for given fluid properties in order to achieve the best shape without splash for single droplet impingement. In order to study the interface dynamics for multiple droplet interaction, which is computationally prohibitive for commercial software packages, an efficient numerical model is developed based on the Lattice Boltzmann (LB) method. A new LB formulation equivalent to the phase-field model is developed with consistent boundary conditions through a multiscale analysis. The numerical model is validated by comparing its simulation results with that of commercial software COMSOL and experimental data. Results show our LB model not only has significant improvement of computational speed over COMSOL but is also more accurate. Finally, the developed numerical solver is used to study the interface evolution of multiple droplet interaction with the aid of the 3-D shape metric proposed before. Simulations are performed on a wide range of impingement conditions for two-droplet, a-line-of-droplet, and an-array-of-droplet interactions. The underlying physics of the interface coalescence and breakup coupling with the impingement dynamics are examined. For line-droplet interaction, the strategy for achieving the equilibrium shape in the shortest time is studied. An important issue is discovered for array-droplet interaction, which is the air bubble formation during the droplet interaction. The mechanism for the air bubble formation is investigated and the strategy to avoid this undesirable effect is also suggested. This thesis has largely reduced the gap between basic science of…
Advisors/Committee Members: Rosen, David W. (advisor), Fedorov, Andrei G. (committee member), Degertekin, F. Levent (committee member), Grover, Martha A. (committee member), Carr, Wallace W. (committee member).
Subjects/Keywords: Interface dynamics; Inkjet deposition; Additive manufacturing; Ink-jet printing; Three-dimensional printing; Drops; Fluid dynamics; Microstructure
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APA ·
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APA (6th Edition):
Zhou, W. (2014). Interface dynamics in inkjet deposition. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/51817
Chicago Manual of Style (16th Edition):
Zhou, Wenchao. “Interface dynamics in inkjet deposition.” 2014. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/51817.
MLA Handbook (7th Edition):
Zhou, Wenchao. “Interface dynamics in inkjet deposition.” 2014. Web. 18 Apr 2021.
Vancouver:
Zhou W. Interface dynamics in inkjet deposition. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/51817.
Council of Science Editors:
Zhou W. Interface dynamics in inkjet deposition. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/51817
14.
Varady, Mark Jordan.
Fuel reformation and hydrogen generation in direct droplet impingement reactors.
Degree: PhD, Mechanical Engineering, 2010, Georgia Tech
URL: http://hdl.handle.net/1853/42826
► Distributed hydrogen generation from liquid hydrocarbon fuels to supply portable fuel cells presents an attractive, high energy density alternative to current battery technology. Traditional unit…
(more)
▼ Distributed hydrogen generation from liquid hydrocarbon fuels to supply portable fuel cells presents an attractive, high energy density alternative to current battery technology. Traditional unit operation reactor design for hydrogen generation becomes inadequate with decrease in scale because of the unique challenges of size and weight minimization. To address the challenge of reactor scale-down, the concept of multifunctional reactors has emerged, in which synergistic combination of different unit operations is explored to achieve improved performance. The direct droplet impingement reactor (DDIR) studied here is based on this approach in which the liquid feed is atomized using a regularly spaced array of droplet generators with unparalleled control over droplet characteristics, followed by vaporization and reaction directly on the catalyst surface. Considering each droplet generator in the array as a unit cell, a comprehensive, first-principles model of the DDIR has been developed by considering the intimately coupled processes of 1) droplet transport, heating, evaporation, and impingement on the catalyst surface, 2) liquid reagent film formation, capillary penetration, and vaporization within the catalyst layer, and 3) gas phase heat and mass transfer and catalytic reactions. Simulations are performed to investigate the effect of reactor operating parameters on performance. Experimental validation of the model is carried out by visualizing droplet impingement and liquid film accumulation while simultaneously monitoring reaction product composition over a range of operating conditions. Results suggest an optimal unit cell shape for reaction selectivity based on a balance between reagent back diffusion and catalyst bed thermal resistance. Further, achieving a target throughput is best accomplished by adding together a larger number unit cells with optimized geometry and lower throughput (per unit cell) to more effectively spread heat and avoid hotspots at the catalyst interface. At the same time, conditions must be satisfied for ensuring droplet impingement on the catalyst surface, which become more stringent as unit cell throughput is decreased.
Advisors/Committee Members: Fedorov, Andrei (Committee Chair), Degertekin, F. Levent (Committee Co-Chair), Alexeev, Alexander (Committee Member), Fuller, Tom (Committee Member), Jones, Christopher (Committee Member).
Subjects/Keywords: Fuel reforming; Portable power; Fuel cell; Droplet transport; Capillary penetration; Catalytic reaction; Hydrogen; Hydrogen as fuel; Fuel cells; Microreactors; Drops
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APA (6th Edition):
Varady, M. J. (2010). Fuel reformation and hydrogen generation in direct droplet impingement reactors. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/42826
Chicago Manual of Style (16th Edition):
Varady, Mark Jordan. “Fuel reformation and hydrogen generation in direct droplet impingement reactors.” 2010. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/42826.
MLA Handbook (7th Edition):
Varady, Mark Jordan. “Fuel reformation and hydrogen generation in direct droplet impingement reactors.” 2010. Web. 18 Apr 2021.
Vancouver:
Varady MJ. Fuel reformation and hydrogen generation in direct droplet impingement reactors. [Internet] [Doctoral dissertation]. Georgia Tech; 2010. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/42826.
Council of Science Editors:
Varady MJ. Fuel reformation and hydrogen generation in direct droplet impingement reactors. [Doctoral Dissertation]. Georgia Tech; 2010. Available from: http://hdl.handle.net/1853/42826
15.
Zhou, Yusheng.
Scanning probe microscopic study of piezotronics and triboelectrification for their applications in mechanical sensing.
Degree: PhD, Materials Science and Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/53512
► Scanning probe microscopy was employed to characterize the piezotronic effect in both longitudinal and transverse force sensing modes in CdSe, and GaN nanowires, respectively. Both…
(more)
▼ Scanning probe microscopy was employed to characterize the piezotronic effect in both longitudinal and transverse force sensing modes in CdSe, and GaN nanowires, respectively. Both experimental results show exponential response of their conductivity change to applied forces. Theoretical models are also presented to explain this mechanism and quantify the relationship, where strain induced piezoelectric polarization changes the metal-semiconductor Schottky barrier height.
An in-situ method based on SPM is developed to characterize the triboelectric process, including tribo-charge intensity, multi-cycle friction effect, as well as its surface diffusion. Beyond that, effect of external electric field was investigated as an approach to manipulate the polarization and intensity. Finally, a concept of self-powered motion sensing technology is developed and demonstrated experimentally with nanometer resolution, long working distance as well as high robustness. It provides a promising solution for application areas that need ultra-low power consumption devices.
Advisors/Committee Members: Wang, Zhong Lin (advisor), Liu, Meilin (committee member), Lin, Zhiqun (committee member), Brand, Oliver (committee member), Degertekin, F. Levent (committee member).
Subjects/Keywords: Piezotronic; SPM; AFM; Triboelectrification; Mechanical sensors; Nanowires
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APA ·
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APA (6th Edition):
Zhou, Y. (2015). Scanning probe microscopic study of piezotronics and triboelectrification for their applications in mechanical sensing. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53512
Chicago Manual of Style (16th Edition):
Zhou, Yusheng. “Scanning probe microscopic study of piezotronics and triboelectrification for their applications in mechanical sensing.” 2015. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/53512.
MLA Handbook (7th Edition):
Zhou, Yusheng. “Scanning probe microscopic study of piezotronics and triboelectrification for their applications in mechanical sensing.” 2015. Web. 18 Apr 2021.
Vancouver:
Zhou Y. Scanning probe microscopic study of piezotronics and triboelectrification for their applications in mechanical sensing. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/53512.
Council of Science Editors:
Zhou Y. Scanning probe microscopic study of piezotronics and triboelectrification for their applications in mechanical sensing. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/53512
16.
Lani, Shane W.
Ultrasonic subwavelength acoustic focusing and imaging using a 2D membrane metamaterial.
Degree: PhD, Mechanical Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/54867
► A metasurface or 2D metamaterial composed of a membrane array can support an interesting acoustic wave field. These waves are evanescent in the direction normal…
(more)
▼ A metasurface or 2D metamaterial composed of a membrane array can support an interesting acoustic wave field. These waves are evanescent in the direction normal to the array and can propagate in the immersion fluid immediately above the metasurface. These waves are a result of the resonant membranes coupling to the fluid medium and propagate with a group and phase speed lower than that of the bulk waves in the surrounding fluid. This work examines and utilizes these evanescent surface waves using Capacitively Micromachined Ultrasonic Transducers (CMUT) as a specific example. CMUT arrays can generate and detect membrane displacement capacitively, and are shown to support the surface waves capable of subwavelength focusing and imaging. A model is developed that can solve for the modes of the membrane array in addition to transiently modeling the behavior of the array. It is found that the dispersive nature of the waves is dependent on the behavior of the modes of the membrane array. Two-dimensional dispersion analysis of the metasurface shows evidence of four distinct frequency bands of surface wave propagation: isotropic, anisotropic, directional band gap, and complete band gap around the first resonant frequency of the membrane. Some of the frequencies in the partial band gap show concave equifrequency contours capable of negative refraction. The dispersion and modal properties are also examined as to how they are affected by basic array parameters. Potential applications of this wave field are examined in the context of subwavelength focusing and imaging. Several methods of acoustic focusing are used on an array consisting of dense grid of membranes and several membranes spatially removed from the structure. Subwavelength acoustic focusing to a resolution of λ/5 is shown in simulations and verified with experiments. An imaging test is also performed in which a subwavelength defect is localized. This fundamental work in characterizing the waves above the membrane metasurfaces is expected to have impact and implications for transducer design, resonant sensors, 2D acoustic lenses, and subwavelength focusing and imaging.
Advisors/Committee Members: Sabra, Karim G. (advisor), Degertekin, F. Levent (advisor), Leamy, Michael (committee member), Ruzzene, Massimo (committee member), Hunt, William D. (committee member).
Subjects/Keywords: Metamaterial; Acoustic focusing; CMUT; Membrane metasurface
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APA (6th Edition):
Lani, S. W. (2015). Ultrasonic subwavelength acoustic focusing and imaging using a 2D membrane metamaterial. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54867
Chicago Manual of Style (16th Edition):
Lani, Shane W. “Ultrasonic subwavelength acoustic focusing and imaging using a 2D membrane metamaterial.” 2015. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/54867.
MLA Handbook (7th Edition):
Lani, Shane W. “Ultrasonic subwavelength acoustic focusing and imaging using a 2D membrane metamaterial.” 2015. Web. 18 Apr 2021.
Vancouver:
Lani SW. Ultrasonic subwavelength acoustic focusing and imaging using a 2D membrane metamaterial. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/54867.
Council of Science Editors:
Lani SW. Ultrasonic subwavelength acoustic focusing and imaging using a 2D membrane metamaterial. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/54867
17.
Zhang, Chaoqi.
Mechanically flexible interconnects (MFIs) for large scale heterogeneous system integration.
Degree: PhD, Electrical and Computer Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/53637
► In this research, wafer-level flexible input/output interconnection technologies, Mechanically Flexible Interconnects (MFIs), have been developed. First, Au-NiW MFIs with 65 µm vertical elastic range of…
(more)
▼ In this research, wafer-level flexible input/output interconnection technologies,
Mechanically Flexible Interconnects (MFIs), have been developed. First, Au-NiW MFIs
with 65 µm vertical elastic range of motion are designed and fabricated. The gold
passivation layer is experimentally verified to not only lower the electrical resistance
but also significantly extend the life-time of the MFIs. In addition, a photoresist
spray-coating based fabrication process is developed to scale the in-line pitch of MFIs
from 150 µm to 50 µm. By adding a contact-tip, Au-NiW MFI could realize a rematable assembly on a substrate with uniform pads and a robust assembly on a
substrate with 45 µm surface variation. Last but not least, multi-pitch multi-height
MFIs (MPMH MFIs) are formed using double-lithography and double-reflow processes,
which can realize an MFI array containing MFIs with various heights and various
pitches. Using these advanced MFIs, large scale heterogeneous systems which can provide
high performance system-level interconnections are demonstrated. For example,
the demonstrated 3D interposer stacking enabled by MPMH MFIs is promising to
realize a low profile and cavity-free robust stacking system. Moreover, bridged multiinterposer
system is developed to address the reticle and yield limitations of realizing
a large scale system using current 2.5D integration technologies. The high-bandwidth
interconnection available within interposer can be extended by using a silicon chip
to bridge adjacent interposers. MFIs assisted thermal isolation is also developed to
alleviate thermal coupling in a high-performance 3D stacking system.
Advisors/Committee Members: Bakir, Muhannad S. (advisor), Wang, Hua (committee member), Degertekin, F. Levent (committee member), Brand, Oliver (committee member), Joshi, Yogendra (committee member).
Subjects/Keywords: Advanced packaging; Heterogeneous system; Flexible interconnects; Rematable assembly; CMOS/MEMS integration; Spray-coating; Interposer
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APA (6th Edition):
Zhang, C. (2015). Mechanically flexible interconnects (MFIs) for large scale heterogeneous system integration. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53637
Chicago Manual of Style (16th Edition):
Zhang, Chaoqi. “Mechanically flexible interconnects (MFIs) for large scale heterogeneous system integration.” 2015. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/53637.
MLA Handbook (7th Edition):
Zhang, Chaoqi. “Mechanically flexible interconnects (MFIs) for large scale heterogeneous system integration.” 2015. Web. 18 Apr 2021.
Vancouver:
Zhang C. Mechanically flexible interconnects (MFIs) for large scale heterogeneous system integration. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/53637.
Council of Science Editors:
Zhang C. Mechanically flexible interconnects (MFIs) for large scale heterogeneous system integration. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/53637
18.
Gray, Jordan D.
Large scale reconfigurable analog system design enabled through floating-gate transistors.
Degree: PhD, Electrical and Computer Engineering, 2009, Georgia Tech
URL: http://hdl.handle.net/1853/34660
► This work is concerned with the implementation and implication of non-volatile charge storage on VLSI system design. To that end, the floating-gate pFET (fg-pFET) is…
(more)
▼ This work is concerned with the implementation and implication of non-volatile charge storage on VLSI system design. To that end, the floating-gate pFET (fg-pFET) is considered in the context of large-scale arrays. The programming of the element in an efficient and predictable way is essential to the implementation of these systems, and is thus explored. The overhead of the control circuitry for the fg-pFET, a key scalability issue, is examined. A light-weight, trend-accurate model is absolutely necessary for VLSI system design and simulation, and is also provided. Finally, several reconfigurable and reprogrammable systems that were built are discussed.
Advisors/Committee Members: Hasler, Paul E. (Committee Chair), Anderson, David V. (Committee Member), Ayazi, Farrokh (Committee Member), Degertekin, F. Levent (Committee Member), Hunt, William D. (Committee Member).
Subjects/Keywords: Analog computation; Floating-gate transistor; Floating-gate programming; Reprogrammable analog; Reconfigurable analog; Linear integrated circuits; Digital-to-analog converters
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APA (6th Edition):
Gray, J. D. (2009). Large scale reconfigurable analog system design enabled through floating-gate transistors. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/34660
Chicago Manual of Style (16th Edition):
Gray, Jordan D. “Large scale reconfigurable analog system design enabled through floating-gate transistors.” 2009. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/34660.
MLA Handbook (7th Edition):
Gray, Jordan D. “Large scale reconfigurable analog system design enabled through floating-gate transistors.” 2009. Web. 18 Apr 2021.
Vancouver:
Gray JD. Large scale reconfigurable analog system design enabled through floating-gate transistors. [Internet] [Doctoral dissertation]. Georgia Tech; 2009. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/34660.
Council of Science Editors:
Gray JD. Large scale reconfigurable analog system design enabled through floating-gate transistors. [Doctoral Dissertation]. Georgia Tech; 2009. Available from: http://hdl.handle.net/1853/34660
19.
Guldiken, Rasim Oytun.
Dual-electrode capacitive micromachined ultrasonic transducers for medical ultrasound applications.
Degree: PhD, Mechanical Engineering, 2008, Georgia Tech
URL: http://hdl.handle.net/1853/31806
► Capacitive Micromachined Ultrasonic Transducers (CMUTs) have been introduced as a viable alternative to piezoelectric transducers in medical ultrasound imaging in the last decade. CMUTs are…
(more)
▼ Capacitive Micromachined Ultrasonic Transducers (CMUTs) have been introduced as a viable alternative to piezoelectric transducers in medical ultrasound imaging in the last decade. CMUTs are especially suitable for applications requiring small size such as catheter based cardiovascular applications. Despite these advantages and their broad bandwidth, earlier studies indicated that the overall sensitivity of CMUTs need to be improved to match piezoelectric transducers. This dissertation addresses this issue by introducing the dual-electrode CMUT concept. Dual electrode configuration takes advantage of leveraged bending in electrostatic actuators to increase both the pressure output and receive sensitivity of the CMUTs.
Static and dynamic finite element based models are developed to model the behavior of dual-electrode CMUTs. The devices are then successfully fabricated and characterized. Experiments illustrate that the pulse echo performance is increased by more than 15dB with dual-electrode CMUTs as compared to single electrode conventional CMUT. Further device optimization is explored via membrane shape adjustment by adding a center mass to the design. Electromechanical coupling coefficient (kc2) is investigated as a figure of merit to evaluate performance improvement with non-uniform/uniform membrane dual-electrode CMUTs. When the center mass is added to the design, the optimized non-uniform membrane increases the electromechanical coupling coefficient from 0.24 to 0.85 while increasing one-way 3dB fractional bandwidth from 80% to 140% and reducing the DC bias requirement from 160V to 132V. The results of this modeling study are successfully verified by experiments. With this membrane shape adjustment, significant performance improvement (nearly 20dB) is achieved with the dual-electrode CMUT structure that enables the CMUT performance to exceed that of piezoelectric transducers for many applications.
Advisors/Committee Members: Degertekin, F. Levent (Committee Chair), Benkeser, Paul (Committee Member), Berhelot, Yves (Committee Member), Brand, Oliver (Committee Member), Hesketh, Peter (Committee Member).
Subjects/Keywords: CMUT; High bandwidth transducers; High efficieny transducers; Ultrasonics in medicine; Ultrasonic transducers; Finite element method
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APA (6th Edition):
Guldiken, R. O. (2008). Dual-electrode capacitive micromachined ultrasonic transducers for medical ultrasound applications. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/31806
Chicago Manual of Style (16th Edition):
Guldiken, Rasim Oytun. “Dual-electrode capacitive micromachined ultrasonic transducers for medical ultrasound applications.” 2008. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/31806.
MLA Handbook (7th Edition):
Guldiken, Rasim Oytun. “Dual-electrode capacitive micromachined ultrasonic transducers for medical ultrasound applications.” 2008. Web. 18 Apr 2021.
Vancouver:
Guldiken RO. Dual-electrode capacitive micromachined ultrasonic transducers for medical ultrasound applications. [Internet] [Doctoral dissertation]. Georgia Tech; 2008. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/31806.
Council of Science Editors:
Guldiken RO. Dual-electrode capacitive micromachined ultrasonic transducers for medical ultrasound applications. [Doctoral Dissertation]. Georgia Tech; 2008. Available from: http://hdl.handle.net/1853/31806
20.
Forbes, Thomas Patrick.
Electrohydrodynamics and ionization in the Array of Micromachined UltraSonic Electrospray (AMUSE) ion source.
Degree: PhD, Mechanical Engineering, 2010, Georgia Tech
URL: http://hdl.handle.net/1853/33852
► The focus of this Ph.D. thesis is the theoretical, computational, and experimental analysis of electrohydrodynamics and ionization in the Array of Micromachined UltraSonic Electrospray (AMUSE)…
(more)
▼ The focus of this Ph.D. thesis is the theoretical, computational, and experimental analysis of electrohydrodynamics and ionization in the Array of Micromachined UltraSonic Electrospray (AMUSE) ion source. The AMUSE ion source, for mass spectrometry (MS), is a mechanically-driven, droplet-based ion source that can independently control charge separation and droplet formation, thereby conceptually differing from electrospray ionization (ESI). This aspect allows for low voltage soft ionization of a variety of analytes and flexibility in the choice of solvents, providing a multifunctional interface between liquid chromatography and mass spectrometry for bioanalysis. AMUSE is a versatile device that operates in an array format, enabling a wide range of configurations, including high-throughput and multiplexed modes of operation. This thesis establishes an in-depth understanding of the fundamental physics of analyte charging and electrokinetic charge separation in order to enhance droplet charging and ionization efficiency. A detailed electrohydrodynamic (EHD) computational model of charge transport during the droplet formation cycle in the AMUSE ion source is developed, coupling fluid dynamics, pressure and electric fields, and charge transport in multiphase flow. The developed EHD model presents a powerful tool for optimal design and operation of the AMUSE ion source, providing insight into the microscopic details of physicochemical phenomena, on the microsecond time scale. Analyte charging and electrohydrodynamics in AMUSE are characterized using dynamic charge generation measurements and high-spatial-resolution stroboscopic visualization of ejection phenomena. Specific regimes of charge transport, which control the final droplet charging, have been identified through experimental characterization and simulations. A scale analysis of the ejection phenomena provides a parametric regime map for AMUSE ejection modes in the presence of an external electric field. This analysis identifies the transition between inertia-dominated (mechanical) and electrically-dominated (electrospraying) ejection, where inertial and electric forces are comparable, producing coupled electromechanical atomization. The understanding of analyte charging and charge separation developed through complimentary theoretical and experimental investigations is utilized to improve signal abundance, sensitivity, and stability of the AMUSE-MS response. Finally, these tools and fundamental understanding provide a sound groundwork for the optimization of the AMUSE ion source and future MS investigations.
Advisors/Committee Members: Degertekin, F. Levent (Committee Co-Chair), Fedorov, Andrei G. (Committee Co-Chair), Muddiman, David C. (Committee Member), Orlando, Thomas M. (Committee Member), Smith, Marc K. (Committee Member).
Subjects/Keywords: Charge transport; Ion source; Droplet ejection; Mass spectrometry; Electrohydrodynamics; Electrohydrodynamics; Electrospray ionization mass spectrometry
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APA (6th Edition):
Forbes, T. P. (2010). Electrohydrodynamics and ionization in the Array of Micromachined UltraSonic Electrospray (AMUSE) ion source. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/33852
Chicago Manual of Style (16th Edition):
Forbes, Thomas Patrick. “Electrohydrodynamics and ionization in the Array of Micromachined UltraSonic Electrospray (AMUSE) ion source.” 2010. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/33852.
MLA Handbook (7th Edition):
Forbes, Thomas Patrick. “Electrohydrodynamics and ionization in the Array of Micromachined UltraSonic Electrospray (AMUSE) ion source.” 2010. Web. 18 Apr 2021.
Vancouver:
Forbes TP. Electrohydrodynamics and ionization in the Array of Micromachined UltraSonic Electrospray (AMUSE) ion source. [Internet] [Doctoral dissertation]. Georgia Tech; 2010. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/33852.
Council of Science Editors:
Forbes TP. Electrohydrodynamics and ionization in the Array of Micromachined UltraSonic Electrospray (AMUSE) ion source. [Doctoral Dissertation]. Georgia Tech; 2010. Available from: http://hdl.handle.net/1853/33852
21.
Skow, Ellen A.
Harvesting energy from acoustic pressure fluctuations within hydraulic systems via excitation of piezoelectric stacks.
Degree: PhD, Mechanical Engineering, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/58652
► Hydraulic systems provide a unique opportunity to convert acoustic energy into electric energy due to the high intensity pressure ripple in the system. Hydraulic pressure…
(more)
▼ Hydraulic systems provide a unique opportunity to convert acoustic energy into electric energy due to the high intensity pressure ripple in the system. Hydraulic pressure energy harvesters (HPEHs) aim to provide a power source for powering or recharging wireless sensor networks on hydraulic systems through using an inherent byproduct of the pumps and actuators - the pressure ripple. HPEHs are able to connect to hydraulic systems via ports typically used for other sensors, such as for static pressure or temperature monitoring. HPEHs convert the pressure ripple into electricity by coupling the fluid fluctuations to a piezoelectric element, such as a stack or single crystal. The pressure ripple dominant frequencies are typically contained within the first or second harmonic of the pump operating frequency, which is usually in the 100s of Hz range, meaning the piezoelectric element is excited well below its resonance frequency. The combination of low-frequency excitation and high piezoelectric stack capacitance allow implementing an inductive load and resistive load in parallel with the piezoelectric stack to provide a passive resonant circuit. Using a soft PZT stack within a HPEH device and a parallel resistive load, a HPEH is able to provide 12.8 mW of AC power for a 202 kPa dynamic pressure amplitude, which corresponded to 0.31 µW/(kPa)
2 of power per squared dynamic pressure amplitude, which is sufficient to power sensors. Power needed for a wireless sensor transmitting data once every second is estimated to be 3.7 mW. This work introduces the HPEH devices, provides an electromechanical model, and investigates multiple methods to increase the power conversion efficiency and regulate the power output. There are three main parts of HPEH devices: (1) the mechanical coupling between the hydraulic fluid & piezoelectric element; (2) the piezoelectric material; and (3) an electrical circuit connected to the piezoelectric element. In regards to the mechanical coupling element, a Helmholtz resonator design is introduced and modeled for the coupling between a HPEH and the hydraulic system to provide pressure - and thus force - amplification to the piezoelectric element, resulting in a doubling of the normalized power response. For the piezoelectric material selection, a [011] cut lead indium niobate - lead magnesium niobate - lead titanate (PIN-PMN-PT) single crystal that goes through a phase transformation between ferroelectric rhombohedral and ferroelectric orthorhombic is presented as a higher power efficiency per cycle solution for HPEH devices, resulting in power output levels 100 times greater than soft PZT stacks tested. And finally for the electrical circuitry, this work provides a solution and model for power conditioning of low-voltage, low-frequency piezoelectric stack energy harvesting through the use of an inductive load in parallel with a voltage multiplier (VM), or cascade circuit. The inductive-VM circuit raised the AC voltage level from 0.59 Vrms to 2.4 VDC. A harmonic balance method model of the inductive-VM…
Advisors/Committee Members: Cunefare, Kenneth A. (advisor), Erturk, Alper (committee member), Degertekin, F. Levent (committee member), Ferri, Aldo A. (committee member), Lynch, Christopher S. (committee member).
Subjects/Keywords: Energy harvesting; Piezoelectrics; Acoustics; Hydraulics; Pressure ripple; Helmholtz resonator; Piezoelectric stacks; Ferroelectrics; Voltage multiplier; Power conditioning
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APA (6th Edition):
Skow, E. A. (2017). Harvesting energy from acoustic pressure fluctuations within hydraulic systems via excitation of piezoelectric stacks. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/58652
Chicago Manual of Style (16th Edition):
Skow, Ellen A. “Harvesting energy from acoustic pressure fluctuations within hydraulic systems via excitation of piezoelectric stacks.” 2017. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/58652.
MLA Handbook (7th Edition):
Skow, Ellen A. “Harvesting energy from acoustic pressure fluctuations within hydraulic systems via excitation of piezoelectric stacks.” 2017. Web. 18 Apr 2021.
Vancouver:
Skow EA. Harvesting energy from acoustic pressure fluctuations within hydraulic systems via excitation of piezoelectric stacks. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/58652.
Council of Science Editors:
Skow EA. Harvesting energy from acoustic pressure fluctuations within hydraulic systems via excitation of piezoelectric stacks. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/58652
22.
Torun, Hamdi.
Micromachined membrane-based active probes for biomolecular force spectroscopy.
Degree: PhD, Electrical and Computer Engineering, 2010, Georgia Tech
URL: http://hdl.handle.net/1853/39638
► Atomic force microscope (AFM) is an invaluable tool for measurement of pico-Newton to nano-Newton levels of interaction forces in liquid. As such, it is widely…
(more)
▼ Atomic force microscope (AFM) is an invaluable tool for measurement of pico-Newton to nano-Newton levels of interaction forces in liquid. As such, it is widely used to measure single-molecular interaction forces through dynamic force spectroscopy. In this technique, the interaction force spectra between a specimen on the sharp tip of the cantilever and another specimen on the substrate is measured by repeatedly moving the cantilever in and out of contact with the substrate. By varying the loading rate and measuring the bond rupture force or bond lifetime give researchers information about the strength and dissociation rates of non-covalent bonds, which in turn determines the energy barriers to overcome. Commercially available cantilevers can resolve interaction forces as low as 5 pN with 1 kHz bandwidth in fluid. This resolution can be improved to 1 pN by using smaller cantilevers at the expense of microfabrication constraints and sophisticated detection systems. The pulling speed of the cantilever, which determines the loading rate of the bonds, is limited to the point where the hydrodynamic drag force becomes comparable to the level of the molecular interaction force. This level is around 10 um/s for most cantilevers while higher pulling speeds are required for complete understanding of force spectra. Thus, novel actuators that allow higher loading rates with minimal hydrodynamic drag forces on the cantilevers, and fast, sensitive force sensors with simple detection systems are highly desirable.
This dissertation presents the research efforts for the development of membrane-based active probe structures with electrostatic actuation and integrated diffraction-based optical interferometric force detection for single-molecular force measurements. Design, microfabrication and characterization of the probes are explained in detail. A setup including optics and electronics for experimental characterization and biological experiments with the probes membranes is also presented. Finally, biological experiments are included in this dissertation.
The "active" nature of the probe is because of the integrated, parallel-plate type electrostatic actuator. The actuation range of the membrane is controlled with the gap height between the membrane and the substrate. Within this range it is possible to actuate the membrane fast, with a speed limited by the membrane dynamics with negligible hydrodynamic drag. Actuating these membrane probes and using a cantilever coupled to the membrane, fast pulling experiments with an order of magnitude faster than achieved by regular AFM systems are demonstrated.
The displacement noise spectral density for the probe was measured to be below 10 fm/rtHz for frequencies as low as 3 Hz with differential readout scheme. This noise floor provides a force sensitivity of 0.3 - 3 pN with 1 kHz bandwidth using membranes with spring constants of 1 - 10 N/m. This low inherent noise has a potential to probe wide range of biomolecules. The probes have been demonstrated for fast-pulling and…
Advisors/Committee Members: Degertekin, F Levent (Committee Chair), Bhatti, Pamela T (Committee Member), Brand, Oliver (Committee Member), Habetler, Thomas G (Committee Member), Zhu, Cheng (Committee Member).
Subjects/Keywords: Viscous drag; MEMS; Athermalization; Microelectromechanical systems; Microtechnology; Molecular recognition
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APA (6th Edition):
Torun, H. (2010). Micromachined membrane-based active probes for biomolecular force spectroscopy. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/39638
Chicago Manual of Style (16th Edition):
Torun, Hamdi. “Micromachined membrane-based active probes for biomolecular force spectroscopy.” 2010. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/39638.
MLA Handbook (7th Edition):
Torun, Hamdi. “Micromachined membrane-based active probes for biomolecular force spectroscopy.” 2010. Web. 18 Apr 2021.
Vancouver:
Torun H. Micromachined membrane-based active probes for biomolecular force spectroscopy. [Internet] [Doctoral dissertation]. Georgia Tech; 2010. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/39638.
Council of Science Editors:
Torun H. Micromachined membrane-based active probes for biomolecular force spectroscopy. [Doctoral Dissertation]. Georgia Tech; 2010. Available from: http://hdl.handle.net/1853/39638
Georgia Tech
23.
Yeon, Pyungwoo.
Distributed free-floating wireless implantable neural recording system.
Degree: PhD, Electrical and Computer Engineering, 2019, Georgia Tech
URL: http://hdl.handle.net/1853/63564
► The objective of the research is to design, implement, test, and characterize a new wireless neural interfacing tool that can simultaneously record large scale neuronal…
(more)
▼ The objective of the research is to design, implement, test, and characterize a new wireless neural interfacing tool that can simultaneously record large scale neuronal ensembles over the entire brain area for a long term (>1 yr). This thesis work includes a novel design concept for a standalone free-floating wireless implantable neural recording (FF-WINeR) system with a total volume of less than 1 mm3 as well as the development of each fundamental system component. For system operation and control, two FF-WINeR application specific integrated circuits (ASIC) with constrained silicon area and power budget were designed and tested. The specifications and features of the ASIC have been determined based on comprehensive studies on wireless power and data delivery utilizing 3-/4-coil inductive links for distributed millimeter-sized implantable medical devices (IMDs) with less than 1 mm3 volume. Moreover, approaches for an optimal geometrical design of the inductive link have been studies. To develop a user-friendly “push-pin” shaped neural probe applicable in a clinical environment, two novel process flows for micromachining the neural probes and microassembly of the FF-WINeR will be discussed. To estimate the life-span of the hermetically sealed FF-WINeR probes, an automated high-throughput hermetic failure monitoring system has been developed. Furthermore, a possible surgical procedure and a future in-vivo experimental setup for the FF-WINeR probes are proposed based on histology results from a short-term animal surgery.
Advisors/Committee Members: Ghovanloo, Maysam (advisor), Brand, Oliver (advisor), Bakir, Muhannad S. (committee member), Degertekin, F. Levent (committee member), Wang, Hua (committee member), Inan, Omer T. (committee member), Mirbozorgi, Abdollah (committee member).
Subjects/Keywords: FF-WINeR; Free-floating neural probe; MM-sized neural probe; Neural interface; Distributed neural recording; Wireless power transmission; Wireless data transmission; Hermetic failure monitoring; Microfabrication; Wireless LC sensor
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APA (6th Edition):
Yeon, P. (2019). Distributed free-floating wireless implantable neural recording system. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/63564
Chicago Manual of Style (16th Edition):
Yeon, Pyungwoo. “Distributed free-floating wireless implantable neural recording system.” 2019. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/63564.
MLA Handbook (7th Edition):
Yeon, Pyungwoo. “Distributed free-floating wireless implantable neural recording system.” 2019. Web. 18 Apr 2021.
Vancouver:
Yeon P. Distributed free-floating wireless implantable neural recording system. [Internet] [Doctoral dissertation]. Georgia Tech; 2019. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/63564.
Council of Science Editors:
Yeon P. Distributed free-floating wireless implantable neural recording system. [Doctoral Dissertation]. Georgia Tech; 2019. Available from: http://hdl.handle.net/1853/63564
Georgia Tech
24.
Bastani, Yaser.
Ferroelectric thin and ultrathin films for MEMS applications.
Degree: PhD, Mechanical Engineering, 2013, Georgia Tech
URL: http://hdl.handle.net/1853/52946
► The advent of ferroelectric thin films with strong piezoelectric response has enabled the development of new nano- and micro-electromechanical systems (NEMS/MEMS) capable of large displacements…
(more)
▼ The advent of ferroelectric thin films with strong piezoelectric response has enabled the development of new nano- and micro-electromechanical systems (NEMS/MEMS) capable of large displacements at low voltage levels, aiming to be compatible with complementary metal oxide semiconductor industry. Key to all of these applications is the ability to process ferroelectric materials with maximized electromechanical coupling and to integrate them into the devices. With the continuous drive towards miniaturization of devices for piezoelectric and electronic applications, processing of ultrathin ferroelectric films with maintained large electromechanical coupling is essential to the development of high performance NEMS and MEMS.
The piezoelectric response of ferroelectric thin films is profoundly affected by the texture and microstructural characteristics of the material and is severely reduced at sub-micron thickness ranges. For the first time, reproducible synthesis of dense, highly textured and phase-pure PZT thin films was achieved via chemical solution deposition. The consistent processing of ferroelectric thin films resulted in the elimination of the coupling effects of crystallographic anisotropy, porosity and in general microstructural characteristics on the functional properties of the films. This enabled effective study of the key parameters influencing the electromechanical response of the ferroelectric thin films, such as crystallite size (thickness dependence), chemical heterogeneities and substrate clamping.
Reproducible synthesis of highly (100)-textured PZT ultrathin films enabled the study of the size effects on the dielectric and piezoelectric response of these films in the thicknesses ranging from 20 up to 260nm. Dielectric and piezoelectric responses of the films monotonically decreased in thinner films. For PZT films at MPB, a critical thickness, ~50nm was observed below which the extrinsic contributions to the dielectric responses of the films are heavily suppressed.
After the study and acknowledgment of the severe reduction of the piezoelectric response in ferroelectric ultrathin film, several factors affecting piezoelectric response of ferroelectric films were studied in order to maximize the response especially at low film thickness ranges: chemical homogeneity, residual stresses and substrate clamping as well as using alternative material systems; relaxor ferroelectrics. In particular, a major part of the piezoelectric (and dielectric) response of the PZT has extrinsic sources such as domain or phase boundary motion and vibrations. Special attention was paid throughout this investigation into understanding extrinsic origins in PZT thin films and different approaches was utilized to further activate and enhance their contributions.
Focusing on the chemical homogeneity of the ferroelectric films, Different routes were used to process ultrathin films (<200nm) with maintained functional properties. Superior piezoelectric properties - 40% higher piezoelectric response than in conventionally processed…
Advisors/Committee Members: Bassiri-Gharb, Nazanin (advisor), Degertekin, F. Levent (committee member), Hesketh, Peter (committee member), Sandhage, Kenneth (committee member), Garmestani, Hamid (committee member), Sulchek, Todd (committee member).
Subjects/Keywords: Ferroelectric; MEMS; Thin films
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APA (6th Edition):
Bastani, Y. (2013). Ferroelectric thin and ultrathin films for MEMS applications. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/52946
Chicago Manual of Style (16th Edition):
Bastani, Yaser. “Ferroelectric thin and ultrathin films for MEMS applications.” 2013. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/52946.
MLA Handbook (7th Edition):
Bastani, Yaser. “Ferroelectric thin and ultrathin films for MEMS applications.” 2013. Web. 18 Apr 2021.
Vancouver:
Bastani Y. Ferroelectric thin and ultrathin films for MEMS applications. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/52946.
Council of Science Editors:
Bastani Y. Ferroelectric thin and ultrathin films for MEMS applications. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/52946
Georgia Tech
25.
Tasadduq, Bushra.
High throughput multi-modal microfluidic system for isolation of blood cells.
Degree: PhD, Electrical and Computer Engineering, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/60166
► In this study, we have developed a novel, multimodal microfluidic platform for cell sorting which utilizes size and adhesion as label-free biomarkers. The size biomarker…
(more)
▼ In this study, we have developed a novel, multimodal microfluidic platform for cell sorting which utilizes size and adhesion as label-free biomarkers. The size biomarker is chosen as it is a distinguishing characteristic of subpopulation of blood cells and is easily tied to hydrodynamic and inertial separation forces and fractionation methods. The adhesion biomarker is chosen to be a more specific sorting parameter since cell molecular interactions govern important physiological processes such as stem cell homing, inflammation, immune modulation, and cancer metastasis. The separation device consists of a microchannel with periodically arranged diagonal ridges. In the first part of the study, we have studied the impact of hydrodynamics caused by the diagonal ridges on microparticle flow and how it can be optimized for size based sorting. We find that the diagonal ridges create helical flow fields that impact similar particles of different z-positions differently. We have successfully demonstrated that by incorporating z-axis focusing of the sample inlet so as to position all particles to a uniform z-position, we can make consistent the particle exposure to transverse flow fields resulting in more accurate size-dependent sorting. With this key insight we have substantially improved the efficiency and accuracy of size based sorting. In the second part of this work, we have studied the impact of specific molecular attachment to the diagonal ridges on cell trajectories for use in adhesion based sorting. The unique aspect of this sorting design is the impact of the gap size on cell trajectories and cell kinetics, in which a sufficiently small gap size can lightly squeeze the cells while flowing under the ridged part of the channel to increase the surface area for interaction between the ligand on cell surface and coated receptor molecule but large enough so that biomechanical markers, stiffness and viscoelasticity, do not dominate the cell separation mechanism. This way we can flow the cells at high flow rate to achieve high throughput, while maintaining sensitivity to adhesiveness. We are able to successfully sort HL60 and Jurkat cells based on their PSGL-1 expression. We believe this simple and cost effective multimodal blood cell sorting device can be used to fulfill the unmet requirements of a point of care diagnostic tool with high throughput and purity.
Advisors/Committee Members: Sulchek, Todd (advisor), Sarioglu, Ali Fatih (committee member), Alexeev, Alexander (committee member), Brand, Oliver (committee member), Lam, Wilbur A. (committee member), Degertekin, F. Levent (committee member).
Subjects/Keywords: Cell sorting; Microfluidics
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APA (6th Edition):
Tasadduq, B. (2017). High throughput multi-modal microfluidic system for isolation of blood cells. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60166
Chicago Manual of Style (16th Edition):
Tasadduq, Bushra. “High throughput multi-modal microfluidic system for isolation of blood cells.” 2017. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/60166.
MLA Handbook (7th Edition):
Tasadduq, Bushra. “High throughput multi-modal microfluidic system for isolation of blood cells.” 2017. Web. 18 Apr 2021.
Vancouver:
Tasadduq B. High throughput multi-modal microfluidic system for isolation of blood cells. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/60166.
Council of Science Editors:
Tasadduq B. High throughput multi-modal microfluidic system for isolation of blood cells. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/60166
Georgia Tech
26.
Chen, Wei.
Design, fabrication, and reliability study of second-level compliant microelectronic interconnects.
Degree: PhD, Mechanical Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/55550
► Free-standing off-chip interconnects have high in-plane and out-of-plane compliance and are being pursued in academia and industry to reduce die stresses and to enhance interconnect…
(more)
▼ Free-standing off-chip interconnects have high in-plane and out-of-plane compliance and are being pursued in academia and industry to reduce die stresses and to enhance interconnect reliability. The geometry of the compliant interconnect, its dimensions, and the material and processes used for fabricating the interconnect influence its mechanical and electrical characteristics, fabrication and assembly yield, thermo-mechanical and drop-impact reliability, and cost of fabrication. Although studies have examined various compliant interconnect designs, a multi-objective and multi-physics design optimization of the compliant interconnect has not been adequately pursued and implemented in prototypes. The first objective of this thesis is to develop a second-level multi-path compliant interconnect for microelectronic systems by performing compliance analysis and multi-physics design optimization using analytical and numerical models; The second objective of this thesis is to develop dry-film based sequential processes to fabricate such compliant interconnects on a silicon wafer, and to assemble singulated silicon substrates on organic printed circuit boards. In particular, in this work, the fabricated interconnects form a 45 × 45 array on the 18 mm × 18 mm silicon substrate. Several variations of the interconnects have been fabricated with the arcuate beam having a width of 10, 15, and 20µm on a footprint of 280µm, and with a pitch of 400µm. The third objective of this work is to experimentally demonstrate the thermal cycling reliability of the assemblies, and to validate the results from numerical models. The fourth objective is to experimentally demonstrate that compliant interconnects can effectively isolate the silicon substrate from the board under drop impact conditions, and to determine the reliability of the interconnects under drop impact conditions. It is seen that the compliant interconnects are able to isolate the silicon substrate from the board, and the board-to-substrate strain ratios are 21.55, 9.53 and 7.01 for compliant interconnects with arcuate beam width equal to 10μm, 15μm and 20μm, respectively, compared to 2.46 for solder ball interconnects. The experimental drop impact results are used for validating the drop-impact simulation predictions. Overall, by combining cleanroom fabrication, assembly, thermal cycling and drop-impact testing with analytical and numerical models as well as design optimization, this work provides a comprehensive insight into the development of multi-path copper structures as second-level microsystem interconnects.
Advisors/Committee Members: Sitaraman, Suresh K. (advisor), Degertekin, F. Levent (committee member), Ferri, Aldo A. (committee member), Naeemi, Azad J. (committee member), Tummala, Rao R. (committee member).
Subjects/Keywords: Compliant interconnect; Microelectronic packaging; Packaging reliability
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APA (6th Edition):
Chen, W. (2015). Design, fabrication, and reliability study of second-level compliant microelectronic interconnects. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/55550
Chicago Manual of Style (16th Edition):
Chen, Wei. “Design, fabrication, and reliability study of second-level compliant microelectronic interconnects.” 2015. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/55550.
MLA Handbook (7th Edition):
Chen, Wei. “Design, fabrication, and reliability study of second-level compliant microelectronic interconnects.” 2015. Web. 18 Apr 2021.
Vancouver:
Chen W. Design, fabrication, and reliability study of second-level compliant microelectronic interconnects. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/55550.
Council of Science Editors:
Chen W. Design, fabrication, and reliability study of second-level compliant microelectronic interconnects. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/55550
Georgia Tech
27.
Schoen, Scott J.
Trans-skull Ultrasound for Imaging and Therapy.
Degree: PhD, Mechanical Engineering, 2020, Georgia Tech
URL: http://hdl.handle.net/1853/64174
► Ultrasound has emerged as a novel modality for the treatment and imaging of brain diseases. When enhanced by circulating microbubble agents, which scatter sound and…
(more)
▼ Ultrasound has emerged as a novel modality for the treatment and imaging of brain diseases. When enhanced by circulating microbubble agents, which scatter sound and vibrate in response to the incident ultrasound, it can enable a range of new therapeutic interventions and open new possibilities for imaging. Despite these advancements, the skull remains a major challenge both for therapy and imaging. This work proposes methods for fast, frequency-selective passive reconstruction of the acoustic field through human skull with applications including improved targeting for exploitation of nonlinear acoustic effects in the brain, controlling the microbubble dynamics, and super-resolution imaging.
Advisors/Committee Members: Arvanitis, Costas (advisor), Cunefare, Kenneth (committee member), Degertekin, F. Levent (committee member), Emelianov, Stanislav (committee member), Sabra, Karim (committee member), Schoen Jr, Scott J. (committee member).
Subjects/Keywords: Ultrasound; Focused Ultrasound; Angular Spectrum; Brain; Skull; Microbubbles; Imaging; Super-resolution; Nonlinear Acoustics
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APA (6th Edition):
Schoen, S. J. (2020). Trans-skull Ultrasound for Imaging and Therapy. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/64174
Chicago Manual of Style (16th Edition):
Schoen, Scott J. “Trans-skull Ultrasound for Imaging and Therapy.” 2020. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/64174.
MLA Handbook (7th Edition):
Schoen, Scott J. “Trans-skull Ultrasound for Imaging and Therapy.” 2020. Web. 18 Apr 2021.
Vancouver:
Schoen SJ. Trans-skull Ultrasound for Imaging and Therapy. [Internet] [Doctoral dissertation]. Georgia Tech; 2020. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/64174.
Council of Science Editors:
Schoen SJ. Trans-skull Ultrasound for Imaging and Therapy. [Doctoral Dissertation]. Georgia Tech; 2020. Available from: http://hdl.handle.net/1853/64174
28.
Gurun, Gokce.
Integrated electronics design for high-frequency intravascular ultrasound imaging.
Degree: PhD, Electrical and Computer Engineering, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/45860
► Close integration of front-end electronics and the transducer array within the catheter is critical for successful implementation of CMUT-based intravascular ultrasound (IVUS) imaging catheters to…
(more)
▼ Close integration of front-end electronics and the transducer array within the catheter is critical for successful implementation of CMUT-based intravascular ultrasound (IVUS) imaging catheters to enable next generation imaging tools. Therefore, this research developed and implemented custom-designed electronic circuits and systems integrated with an IC compatible transducer technology for realization of miniature IVUS imaging catheters operating at 10-50 MHz frequency range.
In one path of this research, an IC is custom designed in a 0.35-um CMOS process to monolithically integrate with a CMUT array (CMUT-on-CMOS) to realize a single-chip, highly-flexible, forward-looking (FL) IVUS imaging system. The amplifiers that are custom-designed achieved transducer thermal-mechanical noise dominated receive performance in a CMUT-on-CMOS implementation. In parallel to the FL-IVUS effort, for realization of a side-looking IVUS catheter based on an annular phased array, a dynamic receive beamformer IC is custom designed also in a 0.35-um CMOS process.
Overall, the circuits and systems developed as part of this dissertation form a critical step in the translation of the research on CMUT-based IVUS catheters into real clinical applications for better management of coronary arterial diseases.
Advisors/Committee Members: Degertekin, F. Levent (Committee Co-Chair), Hasler, Paul (Committee Co-Chair), Bhatti, Pamela T (Committee Member), Ghovanloo, Maysam (Committee Member), Michaels, Thomas E. (Committee Member), Yoganathan, Ajit (Committee Member).
Subjects/Keywords: TIA; CMUT; IVUS; CMUT electronics; CMUT-on-CMOS; Intravascular ultrasonography; Endoscopic ultrasonography; Diagnostic ultrasonic imaging; Transducers
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APA (6th Edition):
Gurun, G. (2011). Integrated electronics design for high-frequency intravascular ultrasound imaging. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/45860
Chicago Manual of Style (16th Edition):
Gurun, Gokce. “Integrated electronics design for high-frequency intravascular ultrasound imaging.” 2011. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/45860.
MLA Handbook (7th Edition):
Gurun, Gokce. “Integrated electronics design for high-frequency intravascular ultrasound imaging.” 2011. Web. 18 Apr 2021.
Vancouver:
Gurun G. Integrated electronics design for high-frequency intravascular ultrasound imaging. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/45860.
Council of Science Editors:
Gurun G. Integrated electronics design for high-frequency intravascular ultrasound imaging. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/45860
Georgia Tech
29.
Jeelani, Mohammad Kamran.
Integration and characterization of micromachined optical microphones.
Degree: MS, Mechanical Engineering, 2009, Georgia Tech
URL: http://hdl.handle.net/1853/31759
► The focus of this study is the optoelectronic integration of a micro-optical displacement detection architecture with a biomimetic MEMS microphone membrane based on the directional…
(more)
▼ The focus of this study is the optoelectronic integration of a micro-optical displacement detection architecture with a biomimetic MEMS microphone membrane based on the directional hearing mechanism of the parasitic fly Ormia Ochracea. The micromachined microphones feature optical interferometric displacement detection achieved using a commercially available Vertical Cavity Surface Emitting Laser (VCSEL) coupled with a custom designed silicon photodiode array. This design is shown to have significant advantages over conventional hearing aid microphones, which employ capacitive detection.
A Multi-Chip Module (MCM) optoelectronic package is designed to integrate the biomimetic membrane with the optical displacement detection electronics in order to produce a fully integrated acoustic sensor. The modular package components, which are fabricated using high resolution stereolithography apparatus (SLA) equipment, provide accurate optical alignment of the optoelectronic components and allow complete device integration in a package with a total volume under 0.5cc.
Characterization of the integrated microphones is described in detail, including measurements of sensitivity, noise floor and directivity. A displacement resolution of 3.5x10⁻¹³ m/√Hz was measured between 4kHz and 16kHz in an anechoic test chamber, corresponding to a dynamic range of 115dB for the optical detection architecture. The total noise SPL of the device is 35.9dBA. Unlike capacitive microphones with similar noise levels, the device developed in this work exhibits first order dipole directivity patterns between 250Hz-1kHz, with an ideal Directivity Index of 4.8dB @ 1kHz and directional attenuation exceeding 25dB. With these results the optoelectronic package presented in this work demonstrates the viability of the integrated optical biomimetic microphones in compact, low power applications, specifically directional hearing aids.
Advisors/Committee Members: Degertekin, F. Levent (Committee Chair), Baldwin, Daniel (Committee Member), Hesketh, Peter (Committee Member).
Subjects/Keywords: Optical microphones; MEMS; Microphone; Optoelectronic devices; Biomimetics; Semiconductor lasers; Hearing aids
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APA (6th Edition):
Jeelani, M. K. (2009). Integration and characterization of micromachined optical microphones. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/31759
Chicago Manual of Style (16th Edition):
Jeelani, Mohammad Kamran. “Integration and characterization of micromachined optical microphones.” 2009. Masters Thesis, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/31759.
MLA Handbook (7th Edition):
Jeelani, Mohammad Kamran. “Integration and characterization of micromachined optical microphones.” 2009. Web. 18 Apr 2021.
Vancouver:
Jeelani MK. Integration and characterization of micromachined optical microphones. [Internet] [Masters thesis]. Georgia Tech; 2009. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/31759.
Council of Science Editors:
Jeelani MK. Integration and characterization of micromachined optical microphones. [Masters Thesis]. Georgia Tech; 2009. Available from: http://hdl.handle.net/1853/31759
Georgia Tech
30.
McFarland, Andrew W.
Production and Analysis of Polymeric Microcantilever Parts.
Degree: PhD, Mechanical Engineering, 2004, Georgia Tech
URL: http://hdl.handle.net/1853/4895
► This dissertation presents work involving the manufacture and analytic modeling of microcantilever parts (length-width-thickness of roughly 500-100-10 microns). The manufacturing goals were to devise a…
(more)
▼ This dissertation presents work involving the manufacture and analytic modeling of microcantilever parts (length-width-thickness of roughly 500-100-10 microns). The manufacturing goals were to devise a means for and demonstrate repeatable production of microcantilevers from techniques not used in the integrated-circuit field, which are the exclusive means of current microcantilever production. The production of microcantilevers was achieved via a solvent casting approach and with injection molding, which produced parts from various thermoplastic polymeric materials (amorphous, semi-crystalline, fiber- and nanoclay-filled) in a repeatable fashion. Limits of the injection molding process in terms of the thinnest cantilevers possible were examined with 2 microns being the lower bound.
Subsets of the injection-molded parts were used in a variety of sensing applications, some results were successful (e.g., vapor-phase, resonance- and deflection-based sensing), while others showed poor results, likely due to experimental shortcomings (e.g., fluid-phase, deflection-based sensing). Additionally, microcantilever parts with integrated tips were injection-molded and showed to function at the same level as commercial, tipped, silicon-nitride parts when imaging an optical grating; this experimental work was the first demonstration of injection-molded parts for chemical sensing and force spectroscopy.
The scientific results were (i) the derivation of a length scale dependent bending stiffness and experimental evidence showing that such an effect was observed, (ii) the development of a new microcantilever experimental mode (surface stress monitoring via microcantilever bending resonant frequencies) and experimental validation of the technique, and (iii) a new method for determining microcantilever geometry based upon measurement of a bending, lateral, and torsional mode and experimental validation of the procedure.
Advisors/Committee Members: Colton, Jonathan (Committee Chair), Bottomley, Lawrence (Committee Member), Degertekin, F Levent (Committee Member), McDowell, David (Committee Member), Muzzy, John (Committee Member), Smith, Marc (Committee Member).
Subjects/Keywords: MEMS; Microcantilever; Micromolding; Plastics Molding; Microelectromechanical systems Materials; Injection molding of plastics
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Export
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APA (6th Edition):
McFarland, A. W. (2004). Production and Analysis of Polymeric Microcantilever Parts. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/4895
Chicago Manual of Style (16th Edition):
McFarland, Andrew W. “Production and Analysis of Polymeric Microcantilever Parts.” 2004. Doctoral Dissertation, Georgia Tech. Accessed April 18, 2021.
http://hdl.handle.net/1853/4895.
MLA Handbook (7th Edition):
McFarland, Andrew W. “Production and Analysis of Polymeric Microcantilever Parts.” 2004. Web. 18 Apr 2021.
Vancouver:
McFarland AW. Production and Analysis of Polymeric Microcantilever Parts. [Internet] [Doctoral dissertation]. Georgia Tech; 2004. [cited 2021 Apr 18].
Available from: http://hdl.handle.net/1853/4895.
Council of Science Editors:
McFarland AW. Production and Analysis of Polymeric Microcantilever Parts. [Doctoral Dissertation]. Georgia Tech; 2004. Available from: http://hdl.handle.net/1853/4895
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