You searched for +publisher:"Georgia Tech" +contributor:("Levent Degertekin").
Showing records 1 – 26 of
26 total matches.
Georgia Tech
1.
Hochman, Michael.
Investigation of acoustic crosstalk effects in CMUT arrays.
Degree: MS, Mechanical Engineering, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/42782 
► Capacitive Micromachined Ultrasonic Transducers (CMUTs) have demonstrated significant potential to advance the state of medical ultrasound imaging beyond the capabilities of the currently employed piezoelectric…
(more)
▼ Capacitive Micromachined Ultrasonic Transducers (CMUTs) have demonstrated significant potential to advance the state of medical ultrasound imaging beyond the capabilities of the currently employed piezoelectric technology. Because they rely on well-established micro-fabrication techniques, they can achieve complex geometries, densely populated arrays, and tight integration with electronics, all of which are required for advanced intravascular ultrasound (IVUS) applications such as high-frequency or forward-looking catheters. Moreover, they also offer higher bandwidth than their piezoelectric counterparts. Before CMUTs can be effectively used, they must be fully characterized and optimized through experimentation and modeling. Unfortunately, immersed transducer arrays are inherently difficult to simulate due to a phenomenon known as acoustic crosstalk, which refers to the fact that every membrane in an array affects the dynamic behavior of every other membrane in an array as their respective pressure fields interact with one another. In essence, it implies that modeling a single CMUT membrane is not sufficient; the entire array must be modeled for complete accuracy.
Finite element models (FEMs) are the most accurate technique for simulating CMUT behavior, but they can become extremely large considering that most CMUT arrays contain hundreds of membranes. This thesis focuses on the development and application of a more efficient model for transducer arrays first introduced by Meynier et al. [1], which provides accuracy comparable to FEM, but with greatly decreased computation time. It models the stiffness of each membrane using a finite difference approximation of thin plate equations. This stiffness is incorporated into a force balance which accounts for effects from the electrostatic actuation, pressure forces from the fluid environment, mass and damping from the membrane, etc. For fluid coupling effects, a Boundary Element Matrix (BEM) is employed that is based on the Green's function for a baffled point source in a semi-infinite fluid. The BEM utilizes the nodal mesh created for the finite difference method, and relates the dynamic displacement of each node to the pressure at every node in the array. Use of the thin plate equations and the BEM implies that the entire CMUT array can be reduced to a 2D nodal mesh, allowing for a drastic improvement in computation time compared with FEM.
After the model was developed, it was then validated through comparison with FEM. From these tests, it demonstrated a capability to accurately predict collapse voltage, center frequency, bandwidth, and pressure magnitudes to within 5% difference of FEM simulations. Further validation with experimental results revealed a close correlation with predicted impedance/admittance plots, radiation patterns, frequency responses, and noise current spectrums. More specifically, it accurately predicted how acoustic crosstalk would create sharp peaks and notches in the frequency responses, and enhance side lobes and nulls in the angular…
Advisors/Committee Members: Dr. F. Levent Degertekin (Committee Chair), Dr. Karim Sabra (Committee Member), Dr. Suresh Sitaraman (Committee Member).
Subjects/Keywords: Analytical model; Acoustic crosstalk; CMUT; Ultrasonic transducers; Crosstalk; Finite element method; Computer simulation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Hochman, M. (2011). Investigation of acoustic crosstalk effects in CMUT arrays. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/42782
Chicago Manual of Style (16th Edition):
Hochman, Michael. “Investigation of acoustic crosstalk effects in CMUT arrays.” 2011. Masters Thesis, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/42782.
MLA Handbook (7th Edition):
Hochman, Michael. “Investigation of acoustic crosstalk effects in CMUT arrays.” 2011. Web. 24 Jan 2021.
Vancouver:
Hochman M. Investigation of acoustic crosstalk effects in CMUT arrays. [Internet] [Masters thesis]. Georgia Tech; 2011. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/42782.
Council of Science Editors:
Hochman M. Investigation of acoustic crosstalk effects in CMUT arrays. [Masters Thesis]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/42782
2.
Oral, Hasan Giray.
Modeling time-resolved interaction force mode AFM imaging.
Degree: MS, Mechanical Engineering, 2012, Georgia Tech
URL: http://hdl.handle.net/1853/43691
► Intermittent contact mode atomic force microscopy has been widely employed for simultaneous topography imaging and material characterization. The work in the literature includes both qualitative…
(more)
▼ Intermittent contact mode atomic force microscopy has been widely employed for simultaneous topography imaging and material characterization. The work in the literature includes both qualitative and quantitative methods. Regular AFM cantilevers are generally used in these methods, yet these cantilevers come with certain limitations. These limitations result from the very nature of cantilever probes. They are passive force sensors with insufficient damping. This prevents having active and complete control on tip-sample forces, causing sample damage and inaccurate topography measurement. Ideally, an AFM probe should offer high bandwidth to resolve interaction forces, active control capability for small interaction force and stable operation, and sufficient damping to avoid transient ringing which causes undesired forces on the sample. Force sensing integrated readout and active tip (FIRAT) probe offers these properties. A special imaging mode, time-resolved interaction force (TRIF) mode imaging can be performed using FIRAT probe for simultaneous topography and material property imaging. The accuracy of topography measurement of samples with variations in elastic and adhesive properties is investigated via numerical simulations and experiments. Results indicate that employing FIRAT probe's active tip control (ATC) capability during TRIF mode imaging provides significant level of control over the tip-sample forces. This improves the accuracy of topography measurement during simultaneous material property imaging, compared to conventional methods. Moreover, Active tip control (ATC) preserves constant contact time during force control for stable contact while preventing loss of material property information such as elasticity and adhesive forces.
Advisors/Committee Members: F. Levent Degertekin (Committee Chair), Peter J. Hesketh (Committee Member), Todd Sulchek (Committee Member).
Subjects/Keywords: FIRAT probe; Time-resolved interaction forces; AFM; Active tip control; Material property imaging; Modeling; Atomic force microscopy; Probes (Electronic instruments)
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Oral, H. G. (2012). Modeling time-resolved interaction force mode AFM imaging. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/43691
Chicago Manual of Style (16th Edition):
Oral, Hasan Giray. “Modeling time-resolved interaction force mode AFM imaging.” 2012. Masters Thesis, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/43691.
MLA Handbook (7th Edition):
Oral, Hasan Giray. “Modeling time-resolved interaction force mode AFM imaging.” 2012. Web. 24 Jan 2021.
Vancouver:
Oral HG. Modeling time-resolved interaction force mode AFM imaging. [Internet] [Masters thesis]. Georgia Tech; 2012. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/43691.
Council of Science Editors:
Oral HG. Modeling time-resolved interaction force mode AFM imaging. [Masters Thesis]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/43691
3.
Banser, Frederic Allen.
Micromachined biomimetic optical microphones with improved packaging and power consumption.
Degree: MS, Mechanical Engineering, 2012, Georgia Tech
URL: http://hdl.handle.net/1853/43696
► Low noise, directional microphones are critical for hearing aid applications. This thesis is focused on further development of a biomimetic micromachined directional microphone based on…
(more)
▼ Low noise, directional microphones are critical for hearing aid applications. This thesis is focused on further development of a biomimetic micromachined directional microphone based on the ear structure of the Ormia Ochracea, a parasitic fly able to locate sound sources in the audio frequency range with high accuracy. The development efforts have been on implementing a version of the microphone for a behind the ear (BTE) package while improving the overall optical efficiency and noise level, demonstrating pulsed laser operation for reduced power consumption, and electrostatic control of the microphone diaphragm position for stable operation over a long time.
The new packaging method for the microphone addressed the need for tighter placement tolerances along with a redesigned diaphragm and integration of a microscale optical lens array to improve the optical efficiency of the device. The completed packages were characterized for sensitivity improvement and optical efficiency. The overall optical efficiency was significantly increased from less than 1% to the photo diode array collecting 50% of the emitted optical power from the Vertical Cavity Surface Emitting Laser (VCSEL). This, coupled with the new diaphragm design, improved the acoustic performance of the microphones. Consequently, the noise levels recorded on the devices were about 31 dBA SPL, more than 15dB better than conventional directional microphones with nearly 10 times larger port spacing.
Since the application for this technology is hearing aids, the power consumed by the working device needs to be at an acceptable level. The majority of the power used by the microphone is from continuously operating the VCSEL with 2mW optical output power. To reduce this power requirement, it was suggested to pulse the VCSEL at high enough frequency with low duty cycle so that the acoustic signals can be recovered from its samples. In this study, it was found that the VCSEL can be pulsed with little to no degradation in signal to noise ratio as long as the thermal mechanical noise dominated the noise spectrum. The results also indicated that a pulse train with a duty cycle of around 20% can be used without a major loss of performance in the device, meaning the device can effectively run at 1/5 of its original power under pulsed operation mode.
Finally, a control technique to overcome some inherent problems of the microphone was demonstrated. Since the optical sensitivity of the microphone depends on the gap between the diaphragm grating and the integrated mirror, it is important to keep that bias gap constant during long term operation against environmental variations and charging effects. Using a simple electrostatic bias controller scheme, the sensitivity variation of the microphone was improved by a factor of 7.68 with bias control. Overall, this thesis has addressed several important aspects of a micromachined biomimetic microphone and further demonstrated its feasibility for hearing aid applications.
Advisors/Committee Members: Dr. F. Levent Degertekin (Committee Chair), Dr. Todd Sulchek (Committee Member), Dr. Venkatesh Sundaram (Committee Member).
Subjects/Keywords: Microphone characterization; Pulsing operation; Optical microphone; Directional microphone; Biomimetic; Packaging; Biomimetic materials; Microphone; Hearing aids; Parasitic insects
…MICROPHONES WITH IMPROVED PACKAGING AND
POWER CONSUMPTION
Approved by:
Dr. F. Levent Degertekin… …Cunefare, who allowed me to use their equipment and test facilities at Georgia
Tech.
iv
TABLE…
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Banser, F. A. (2012). Micromachined biomimetic optical microphones with improved packaging and power consumption. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/43696
Chicago Manual of Style (16th Edition):
Banser, Frederic Allen. “Micromachined biomimetic optical microphones with improved packaging and power consumption.” 2012. Masters Thesis, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/43696.
MLA Handbook (7th Edition):
Banser, Frederic Allen. “Micromachined biomimetic optical microphones with improved packaging and power consumption.” 2012. Web. 24 Jan 2021.
Vancouver:
Banser FA. Micromachined biomimetic optical microphones with improved packaging and power consumption. [Internet] [Masters thesis]. Georgia Tech; 2012. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/43696.
Council of Science Editors:
Banser FA. Micromachined biomimetic optical microphones with improved packaging and power consumption. [Masters Thesis]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/43696
4.
Anderson, Shaun David.
Space-time-frequency processing from the analysis of bistatic scattering for simple underwater targets.
Degree: PhD, Mechanical Engineering, 2012, Georgia Tech
URL: http://hdl.handle.net/1853/45771
► The development of low-frequency SONAR systems, using a network of autonomous systems in unmanned vehicles, provides a practical means for bistatic measurements (i.e. when the…
(more)
▼ The development of low-frequency SONAR systems, using a network of autonomous systems in unmanned vehicles, provides a practical means for bistatic measurements (i.e. when the source and receiver are widely separated, thus allowing multiple viewpoints of a target). Furthermore, time-frequency analysis, in particular Wigner-Ville analysis, takes advantage of the evolution of the time dependent echo spectrum to differentiate a man-made target (e.g. an elastic spherical shell, or cylinder) from a natural one of the similar shape (e.g. a rock). Indeed, key energetic features of man-made objects can aid in identification and classification in the presence of clutter and noise. For example, in a fluid-loaded thin spherical shell, an energetic feature is the mid-frequency enhancement echoes (MFE) that result from antisymmetric Lamb waves propagating around the circumference of the shell, which have been shown to be an acoustic feature useful in this pursuit. This research investigates the enhancement and benefits of bistatic measurements using the Wigner-Ville analysis along with acoustic imaging methods. Additionally, the advantage of joint space-time-frequency coherent processing is investigated for optimal array processing to enhance the detection of non-stationary signals across an array. The proposed methodology is tested using both numerical simulations and experimental data for spherical shells and solid cylinders. This research was conducted as part of the Shallow Water Autonomous Mine Sensing Initiative (SWAMSI) sponsored by ONR.
Advisors/Committee Members: Karim G. Sabra (Committee Chair), Aaron D. Lanterman (Committee Member), F. Levent Degertekin (Committee Member), Lora G. Weiss (Committee Member), Peter H. Rogers (Committee Member).
Subjects/Keywords: Wigner-Ville; Space-time-frequency; Time-frequency; Noise reduction; SAS; Imaging; Bistatic; Acoustics; Scattering; Underwater acoustics; Acoustic imaging; Ultrasonic imaging; Sonar
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Anderson, S. D. (2012). Space-time-frequency processing from the analysis of bistatic scattering for simple underwater targets. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/45771
Chicago Manual of Style (16th Edition):
Anderson, Shaun David. “Space-time-frequency processing from the analysis of bistatic scattering for simple underwater targets.” 2012. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/45771.
MLA Handbook (7th Edition):
Anderson, Shaun David. “Space-time-frequency processing from the analysis of bistatic scattering for simple underwater targets.” 2012. Web. 24 Jan 2021.
Vancouver:
Anderson SD. Space-time-frequency processing from the analysis of bistatic scattering for simple underwater targets. [Internet] [Doctoral dissertation]. Georgia Tech; 2012. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/45771.
Council of Science Editors:
Anderson SD. Space-time-frequency processing from the analysis of bistatic scattering for simple underwater targets. [Doctoral Dissertation]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/45771
5.
Pardo Gonzalez, Mauricio.
MEMS-based phase-locked-loop clock conditioner.
Degree: PhD, Electrical and Computer Engineering, 2012, Georgia Tech
URL: http://hdl.handle.net/1853/43643
► Ultra narrow-band filters and the use of two loops in a cascade configuration dominate current clock conditioners based on phase-locked-loop (PLL) schemes. Since a PLL…
(more)
▼ Ultra narrow-band filters and the use of two loops in a cascade configuration dominate current clock conditioners based on phase-locked-loop (PLL) schemes. Since a PLL exhibits a low-pass transfer function with respect to the reference clock, the noise performance at very close-to-carrier offset frequencies is still determined by the input signal. Although better cleaning can be achieved with extremely narrow loops, an ultra low cut-off frequency could not be selected since the stability of the configuration deteriorates as the filter bandwidth is reduced. This fact suggests that a full-spectrum clock conditioning is not possible using traditional PLL architectures, and an alternative scheme is necessary to attenuate the very-close-to-carrier phase noise (PN). In addition, ultra-narrow loop filters can compromise on-chip integration because of the large size capacitors needed when chosen as passive. Input signal attenuation with relaxed bandwidth requirements becomes the main aspect that a comprehensive clock cleaner must address to effectively regenerate a reference signal.
This dissertation describes the Band-Reject Nested-PLL (BRN-PLL) scheme, a modified PLL-based architecture that provides an effective signal cleaning procedure by introducing a notch in the input transfer function through inner and outer loops and a high-pass filter (HPF). This modified response attenuates the reference-signal PN and reduces the size of the loop-filter capacitors substantially. Ultra narrow loops are no longer required because the notch size is related to the system bandwidth. The associated transfer function for the constitutive blocks (phase detectors and local oscillators) show that the output close-to-carrier and far-from-carrier PN sections are mainly dominated by the noise from the inner-PLL phase detector (PD) and local oscillator (LO) located in the outer loop, respectively. The inner-PLL PD transfer function maintains a low-pass characteristic with a passband gain inversely proportional to the PD gain becoming the main contribution around the carrier signal. On the other hand, the PN around the transition frequency is determined mainly by the reference and the inner-PLL LO. Their noise contributions to the output will depend on the associated passband local maxima, which is located at the BRN-PLL transition frequency. Hence, in this region, the inner-PLL LO is selected so that its effect can be held below that of the outer-PLL PD.
The BRN-PLL can use a high-Q MEMS-based VCO to further improve the transition region of the output PN profile and an LC-VCO as outer-PLL LO to reduce the noise floor of the output signal. In particular, two tuning mechanisms are explored for the MEMS-VCO: series tuning using varactors and phase shifting of a resonator operating in nonlinear regime. Both schemes are implemented to generate a tunable oscillator with no PN-performance degradation.
Advisors/Committee Members: Farrohk Ayazi (Committee Chair), Gabriel Rincón-Mora (Committee Member), Kevin Kornegay (Committee Member), Levent Degertekin (Committee Member), Maysam Ghovanloo (Committee Member).
Subjects/Keywords: Frequency-phase transfer function; MEMS VCO; LC VCO; Switching network; Root-locus; Nyquist stability criterion; Pole-zero locations; Band rejection; BRN-PLL; MEMS nonlinearity; Detuning; Power-series-based PN model; Phase-locked loops; Phase shifters; Integrated circuits
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Pardo Gonzalez, M. (2012). MEMS-based phase-locked-loop clock conditioner. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/43643
Chicago Manual of Style (16th Edition):
Pardo Gonzalez, Mauricio. “MEMS-based phase-locked-loop clock conditioner.” 2012. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/43643.
MLA Handbook (7th Edition):
Pardo Gonzalez, Mauricio. “MEMS-based phase-locked-loop clock conditioner.” 2012. Web. 24 Jan 2021.
Vancouver:
Pardo Gonzalez M. MEMS-based phase-locked-loop clock conditioner. [Internet] [Doctoral dissertation]. Georgia Tech; 2012. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/43643.
Council of Science Editors:
Pardo Gonzalez M. MEMS-based phase-locked-loop clock conditioner. [Doctoral Dissertation]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/43643
6.
Dinc, Huseyin.
A high-speed two-step analog-to-digital converter with an open-loop residue amplifier.
Degree: PhD, Electrical and Computer Engineering, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/39572
► It is well known that feedback is a very valuable tool for analog designers to improve linearity, and desensitize various parameters affected by process, temperature…
(more)
▼ It is well known that feedback is a very valuable tool for analog designers to improve linearity, and desensitize various parameters affected by process, temperature and supply variations. However, using strong global feedback limits the operation speed of analog circuits due to stability requirements. The circuits and techniques explored in this research avoid the usage of strong-global-feedback circuits to achieve high conversion rates in a two-stage analog-to-digital converter (ADC). A two-step, 9-bit, complementary-metal-oxide-semiconductor (CMOS) ADC utilizing an open-loop residue-amplifier is demonstrated. A background-calibration technique was proposed to generate the reference voltage to be used in the second stage of the ADC. This technique alleviates the gain variation in the residue amplifier, and allows an open-loop residue amplifier topology. Even though the proposed calibration idea can be extended to multistage topologies, this design was limited to two stages. Further, the ADC exploits a high-performance double-switching frontend sample-and-hold amplifier (SHA). The proposed double-switching SHA architecture results in exceptional hold-mode isolation. Therefore, the SHA maintains the desired linearity performance over the entire Nyquist bandwidth.
Advisors/Committee Members: Phillip E. Allen (Committee Chair), Paul E. Hasler (Committee Co-Chair), David Anderson (Committee Member), Levent Degertekin (Committee Member), Maysam Ghovanloo (Committee Member), Pamela Bhatti (Committee Member).
Subjects/Keywords: PGA; Calibration; SHA; Switched-buffer; Pipelined ADC; Bipolar transistors; Analog-to-digital converters; Digital electronics; Analog-to-digital converters Calibration
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Dinc, H. (2011). A high-speed two-step analog-to-digital converter with an open-loop residue amplifier. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/39572
Chicago Manual of Style (16th Edition):
Dinc, Huseyin. “A high-speed two-step analog-to-digital converter with an open-loop residue amplifier.” 2011. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/39572.
MLA Handbook (7th Edition):
Dinc, Huseyin. “A high-speed two-step analog-to-digital converter with an open-loop residue amplifier.” 2011. Web. 24 Jan 2021.
Vancouver:
Dinc H. A high-speed two-step analog-to-digital converter with an open-loop residue amplifier. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/39572.
Council of Science Editors:
Dinc H. A high-speed two-step analog-to-digital converter with an open-loop residue amplifier. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/39572
Georgia Tech
7.
Garcia, Caesar Theodore.
Packaging and Characterization of MEMS Optical Microphones.
Degree: MS, Mechanical Engineering, 2007, Georgia Tech
URL: http://hdl.handle.net/1853/19713
► Miniature microphones have numerous applications but often exhibit poor performance which can be attributed to the challenges associated with capacitive detection at small size scales.…
(more)
▼ Miniature microphones have numerous applications but often exhibit poor performance which can be attributed to the challenges associated with capacitive detection at small size scales. Optical detection methods are able to overcome some of these challenges although miniaturized integration of these optical systems has not yet been demonstrated. An optical interferometric detection scheme is presented and is implemented using micro-scale optoelectronic devices which are used primarily in fiber optic data transmission. Using basic diffraction theory, a model is developed and used to optimize the micro-optical system within a 1mm3 volume. Both omnidirectional and directional optical microphone designs are presented and a modular packaging architecture is assembled in order to test these devices. Results from the 2mm diameter omnidirectional optical microphone structure demonstrate a 26dBA noise floor. The biomimetic directional optical microphone, which has an equivalent port spacing of 1mm, demonstrates a noise floor of 34dBA. Additionally, these results demonstrate an array of two biomimetic directional optical microphones located on the same silicon chip and separated by less than 5mm. These results confirm the micro-optical detection method as an alternative to capacitive detection especially for miniaturized microphone applications and suggest that this method in its modular packaging architecture is competitive with industry leading
measurement microphones.
Advisors/Committee Members: Levent Degertekin (Committee Chair), Kenneth Cunefare (Committee Member), Peter Hesketh (Committee Member).
Subjects/Keywords: MEMS; Interferometry; Optical; Microphone; Microphone; Microelectromechanical systems; Computer simulation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Garcia, C. T. (2007). Packaging and Characterization of MEMS Optical Microphones. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/19713
Chicago Manual of Style (16th Edition):
Garcia, Caesar Theodore. “Packaging and Characterization of MEMS Optical Microphones.” 2007. Masters Thesis, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/19713.
MLA Handbook (7th Edition):
Garcia, Caesar Theodore. “Packaging and Characterization of MEMS Optical Microphones.” 2007. Web. 24 Jan 2021.
Vancouver:
Garcia CT. Packaging and Characterization of MEMS Optical Microphones. [Internet] [Masters thesis]. Georgia Tech; 2007. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/19713.
Council of Science Editors:
Garcia CT. Packaging and Characterization of MEMS Optical Microphones. [Masters Thesis]. Georgia Tech; 2007. Available from: http://hdl.handle.net/1853/19713
Georgia Tech
8.
Johnson, Jay Tillay.
Defect and thickness inspection system for cast thin films using machine vision and full-field transmission densitometry.
Degree: MS, Mechanical Engineering, 2009, Georgia Tech
URL: http://hdl.handle.net/1853/37234
► Quick mass production of homogeneous thin film material is required in paper, plastic, fabric, and thin film industries. Due to the high feed rates and…
(more)
▼ Quick mass production of homogeneous thin film material is required in paper, plastic, fabric, and thin film industries. Due to the high feed rates and small thicknesses, machine vision and other nondestructive evaluation techniques are used to ensure consistent, defect-free material by continuously assessing post-production quality. One of the fastest growing inspection areas is for 0.5-500 micrometer thick thin films, which are used for semiconductor wafers, amorphous photovoltaics, optical films, plastics, and organic and inorganic membranes. As a demonstration application, a prototype roll-feed imaging system has been designed to inspect high-temperature polymer electrolyte membrane (PEM), used for fuel cells, after being die cast onto a moving transparent substrate. The inspection system continuously detects thin film defects and classifies them with a neural network into categories of holes, bubbles, thinning, and gels, with a 1.2% false alarm rate, 7.1% escape rate, and classification accuracy of 96.1%. In slot die casting processes, defect types are indicative of a misbalance in the mass flow rate and web speed; so, based on the classified defects, the inspection system informs the operator of corrective adjustments to these manufacturing parameters. Thickness uniformity is also critical to membrane functionality, so a real-time, full-field transmission densitometer has been created to measure the bi-directional thickness profile of the semi-transparent PEM between 25-400 micrometers. The local thickness of the 75 mm x 100 mm imaged area is determined by converting the optical density of the sample to thickness with the Beer-Lambert law. The PEM extinction coefficient is determined to be 1.4 D/mm and the average thickness error is found to be 4.7%. Finally, the defect inspection and thickness profilometry systems are compiled into a specially-designed graphical user interface for intuitive real-time operation and visualization.
Advisors/Committee Members: Tequila Harris (Committee Chair), Levent Degertekin (Committee Member), Wayne Daley (Committee Member).
Subjects/Keywords: Nondestructive evaluation; Nondestructive testing; Densitometry; Thin films Defects; Computer vision; Nondestructive testing
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Johnson, J. T. (2009). Defect and thickness inspection system for cast thin films using machine vision and full-field transmission densitometry. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/37234
Chicago Manual of Style (16th Edition):
Johnson, Jay Tillay. “Defect and thickness inspection system for cast thin films using machine vision and full-field transmission densitometry.” 2009. Masters Thesis, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/37234.
MLA Handbook (7th Edition):
Johnson, Jay Tillay. “Defect and thickness inspection system for cast thin films using machine vision and full-field transmission densitometry.” 2009. Web. 24 Jan 2021.
Vancouver:
Johnson JT. Defect and thickness inspection system for cast thin films using machine vision and full-field transmission densitometry. [Internet] [Masters thesis]. Georgia Tech; 2009. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/37234.
Council of Science Editors:
Johnson JT. Defect and thickness inspection system for cast thin films using machine vision and full-field transmission densitometry. [Masters Thesis]. Georgia Tech; 2009. Available from: http://hdl.handle.net/1853/37234
Georgia Tech
9.
Parlak, Zehra.
Quantitative imaging of subsurface structures and mechanical properties at nanoscale using atomic force microscope.
Degree: PhD, Electrical and Computer Engineering, 2010, Georgia Tech
URL: http://hdl.handle.net/1853/37181
► This dissertation focuses on quantitative subsurface and mechanical properties imaging potential of AFM probes. Extensive modeling of AFM probes are presented for thorough understanding of…
(more)
▼ This dissertation focuses on quantitative subsurface and mechanical properties imaging potential of AFM probes. Extensive modeling of AFM probes are presented for thorough understanding of capabilities and limitations of current techniques, these models are verified by various experiments, and different methods are developed by utilizing force-sensing integrated read-out active tip (FIRAT), which is an active AFM probe with broad bandwidth. For quantitative subsurface imaging, a 3-D FEA model of AFM tip-sample contact is developed and this model can simulate AFM tip scan on nanoscale-sized buried structures. FIRAT probe, which is active and broadband, is utilized for interaction forces imaging during intermittent contact mode and mechanical characterization capability of this probe is investigated. It is shown that probe dynamics, stiffness, stiffness ambiguity, assumed contact mechanics, and noise are important parameters for the accuracy of mechanical properties imaging. An active tip control mechanism is introduced to limit contact forces during intermittent contact mode. In addition to these, a combined ultrasonic AFM and interaction forces imaging method is developed and modeled to solve the reduced elasticity measurement sensitivity on composite materials. This method is capable of imaging a broader range of elasticity on combination samples such as metal nanoparticles in polymers at nanoscale.
Advisors/Committee Members: Levent Degertekin (Committee Chair), Elisa Riedo (Committee Member), Hongwei Wu (Committee Member), Jennifer Michaels (Committee Member), Oliver Brand (Committee Member).
Subjects/Keywords: Atomic force microscope; AFM; Ultrasonic AFM; Nanoscale subsurface imaging; Mechanical property imaging; Tapping mode; FIRAT; Scanning probe microscopy; Imaging systems
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Parlak, Z. (2010). Quantitative imaging of subsurface structures and mechanical properties at nanoscale using atomic force microscope. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/37181
Chicago Manual of Style (16th Edition):
Parlak, Zehra. “Quantitative imaging of subsurface structures and mechanical properties at nanoscale using atomic force microscope.” 2010. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/37181.
MLA Handbook (7th Edition):
Parlak, Zehra. “Quantitative imaging of subsurface structures and mechanical properties at nanoscale using atomic force microscope.” 2010. Web. 24 Jan 2021.
Vancouver:
Parlak Z. Quantitative imaging of subsurface structures and mechanical properties at nanoscale using atomic force microscope. [Internet] [Doctoral dissertation]. Georgia Tech; 2010. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/37181.
Council of Science Editors:
Parlak Z. Quantitative imaging of subsurface structures and mechanical properties at nanoscale using atomic force microscope. [Doctoral Dissertation]. Georgia Tech; 2010. Available from: http://hdl.handle.net/1853/37181
Georgia Tech
10.
Schmittdiel, Michael C.
Active control of a diffraction grating interferometer for microscale devices.
Degree: MS, Mechanical Engineering, 2004, Georgia Tech
URL: http://hdl.handle.net/1853/7261
► This thesis describes the creation of a metrology system based upon an actively controlled diffraction grating interferometer, which measures relative linear distances. The dynamics of…
(more)
▼ This thesis describes the creation of a metrology system based upon an actively controlled diffraction grating interferometer, which measures relative linear distances. The dynamics of this sensor are estimated based on experimental testing, and a suitable controller is designed to maintain the position of the sensor in the most sensitive operating region. This controller is implemented on a field programmable gate array (FPGA) processor, which allows for flexible programming and real-time control.
The sample under test is mounted atop a three axis linear stage system, which allows the diffraction grating interferometer to scan across the surface of the device, creating maps of the static and dynamic measurements. The controller is shown to maintain the sensitivity of the sensor during this operation. This insures all data are taken on the same scale, creating more accurate results. The controller increases the signal to noise ratio as compared to the system without the controller.
The specifications of the entire metrology system are detailed including the sensor and controller bandwidth, the vertical and horizontal resolution, and the signal to noise ratio. A case study utilizing a capacitive micromachined ultrasonic transducer (cMUT) is presented. The sensor generates static and dynamic displacement maps of the surface of this MEMS device. The controller improves these measurements by maintaining a position of high sensitivity during operation.
Finally, the preliminary results of a miniaturized version of this system are presented including the implementation of two fully independent parallel sensors. This allows for array implementation of these sensors, which is crucial for the batch fabrication photolithography techniques used to create many MEMS devices. Recommendations on the future work needed to complete the array implementation are given in conjunction with methods for increasing the resolution and robustness of the macroscale system described in this thesis.
Advisors/Committee Members: Dr. Thomas R. Kurfess (Committee Chair), Dr. F. Levent Degertekin (Committee Member), Dr. William P. King (Committee Member).
Subjects/Keywords: Metrology; MEMS; Interferometers; Microscale; Diffraction gratings; Active control; Harmonic locking; Metrology; Microstructure; Detectors; Diffraction gratings; Interferometers
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Schmittdiel, M. C. (2004). Active control of a diffraction grating interferometer for microscale devices. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/7261
Chicago Manual of Style (16th Edition):
Schmittdiel, Michael C. “Active control of a diffraction grating interferometer for microscale devices.” 2004. Masters Thesis, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/7261.
MLA Handbook (7th Edition):
Schmittdiel, Michael C. “Active control of a diffraction grating interferometer for microscale devices.” 2004. Web. 24 Jan 2021.
Vancouver:
Schmittdiel MC. Active control of a diffraction grating interferometer for microscale devices. [Internet] [Masters thesis]. Georgia Tech; 2004. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/7261.
Council of Science Editors:
Schmittdiel MC. Active control of a diffraction grating interferometer for microscale devices. [Masters Thesis]. Georgia Tech; 2004. Available from: http://hdl.handle.net/1853/7261
Georgia Tech
11.
Poggi, Mark Andrew.
Interfacial and Mechanical Properties of Carbon Nanotubes: A Force Spectroscopy Study.
Degree: PhD, Chemistry and Biochemistry, 2004, Georgia Tech
URL: http://hdl.handle.net/1853/4948
► Next generation polymer composites that utilize the high electrical conductivity and tensile strength of carbon nanotubes are of interest. To effectively disperse carbon nanotubes into…
(more)
▼ Next generation polymer composites that utilize the high electrical conductivity and tensile strength of carbon nanotubes are of interest. To effectively disperse carbon nanotubes into polymers, a more fundamental understanding of the polymer/nanotube interface is needed. This requires the development of new analytical methods and techniques for measuring the adhesion between a single molecule and the sidewalls of carbon nanotubes.
Atomic Force Microscopy is an integral tool in the characterization of materials on the nanoscale. The objectives of this research were to: 1) characterize the binding force between single molecules and the backbone of a single walled carbon nanotube (SWNT), and 2) measure and interpret the mechanical response of carbon-based nano-objects to compressive loads using an atomic force microscope.
To identify chemical moieties that bind strongly to the sidewall of the nanotubes, two experimental approaches have been explored. In the first, force volume images of SWNT paper were obtained using gold-coated AFM tips functionalized with terminally substituted alkanethiols and para-substituted arylthiols. Analysis of these images enabled quantification of the adhesive interactions between the functionalized tip and the SWNT surface. The resultant adhesive forces were shown to be dependent upon surface topography, tip shape, and the terminal group on the alkanethiol.
The mechanical response of several single- and multi-walled carbon nanotubes under compressive load was examined with an AFM. When the scanner, onto which the substrate has been mounted, was extended and retracted in a cyclic fashion, cantilever deflection, oscillation amplitude and resonant frequency were simultaneously monitored. By time-correlating cantilever resonance spectra, deflection and scanner motion, precise control over the length of nanotube in contact with the substrate, analogous to fly-fishing was achieved. This multi-parameter force spectroscopy method is applicable for testing the mechanical and interfacial properties of a wide range of nanoscale objects.
This research has led to a clearer understanding of the chemistry at the nanotube/polymer interface, as well as the mechanical response of nanoscale materials. A new force spectroscopic tool, multi-parameter force spectroscopy, should be extremely helpful in characterizing the mechanical response of a myriad of nanoscale objects and enable nanoscale devices to become a reality.
Advisors/Committee Members: Lawrence A. Bottomley (Committee Chair), Boris Mizaikoff (Committee Member), F. Levent Degertekin (Committee Member), Jiri Janata (Committee Member), Robert L. Whetten (Committee Member), Thomas M. Orlando (Committee Member).
Subjects/Keywords: Composites; Nanotube composites; Single wall carbon nanotubes; Multiwall carbon nanotubes; MPFS; Multi-parameter force spectroscopy; Force spectroscopy; Atomic force microscopy; Carbon nanotubes; Spectrum analysis; Polymeric composites; Nanotubes Mechanical properties; Carbon Mechanical properties; Atomic force microscopy
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Poggi, M. A. (2004). Interfacial and Mechanical Properties of Carbon Nanotubes: A Force Spectroscopy Study. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/4948
Chicago Manual of Style (16th Edition):
Poggi, Mark Andrew. “Interfacial and Mechanical Properties of Carbon Nanotubes: A Force Spectroscopy Study.” 2004. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/4948.
MLA Handbook (7th Edition):
Poggi, Mark Andrew. “Interfacial and Mechanical Properties of Carbon Nanotubes: A Force Spectroscopy Study.” 2004. Web. 24 Jan 2021.
Vancouver:
Poggi MA. Interfacial and Mechanical Properties of Carbon Nanotubes: A Force Spectroscopy Study. [Internet] [Doctoral dissertation]. Georgia Tech; 2004. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/4948.
Council of Science Editors:
Poggi MA. Interfacial and Mechanical Properties of Carbon Nanotubes: A Force Spectroscopy Study. [Doctoral Dissertation]. Georgia Tech; 2004. Available from: http://hdl.handle.net/1853/4948
Georgia Tech
12.
Hallow, Daniel Martin.
Measurement and Correlation of Acoustic Cavitation with Cellular and Tissue Bioeffects.
Degree: PhD, Chemical Engineering, 2006, Georgia Tech
URL: http://hdl.handle.net/1853/19741
► Targeted intracellular delivery is a goal of many novel drug delivery systems to treat site-specific diseases thereby increasing the effectiveness of drugs and reducing side…
(more)
▼ Targeted intracellular delivery is a goal of many novel drug delivery systems to treat site-specific diseases thereby increasing the effectiveness of drugs and reducing side effects associated with current drug administration. The development of ultrasound-enhanced delivery is aimed at providing a targeted means to deliver drugs and genes intracellularly by utilizing ultrasound s ability to non-invasively focus energy into the body and generate cavitation, which has been found to cause transient poration of cells. To address some of the current issues in this field, the goals of this study were (i) to develop a measurement of cavitation to correlate with cellular bioeffects and (ii) to evaluate the ability of ultrasound to target delivery into cells in viable tissue. In addition, this study sought to exploit the shear-based mechanism of cavitation by (iii) developing a simplified device to expose cells to shear stress and cause intracellular uptake of molecules. This study has shown that broadband noise levels of frequency spectra processed from cavitation sound emissions can be used to quantify the kinetic activity of cavitation and provide a unifying parameter to correlate with the cellular bioeffects. We further demonstrated that ultrasound can target delivery of molecules into endothelial and smooth muscle cells in viable arterial tissue and determined approximate acoustic energies relevant to drug delivery applications. Lastly, we developed a novel device to expose cells to high-magnitude shear stress for short durations by using microfluidics and demonstrated the ability of this method to cause delivery of small and macromolecules into cells. In conclusion, this work has advanced the field of ultrasound-enhanced delivery in two major areas: (i) developing a real-time non-invasive measurement to correlate with intracellular uptake and viability that can be used as means to predict and control bioeffects in the lab and potentially the clinic and (ii) quantitatively evaluating the intracellular uptake into viable cells in tissue due to ultrasound that suggest applications to treat cardiovascular diseases and dysfunctions. Finally, by using shear forces generated in microchannels, we have fabricated a simple and inexpensive device to cause intracellular uptake of small and large molecules, which may have applications in biotechnology.
Advisors/Committee Members: Mark Prausnitz (Committee Chair), Athanassios Sambanis (Committee Member), Carson Meredith (Committee Member), Levent Degertekin (Committee Member), W. Robert Taylor (Committee Member).
Subjects/Keywords: Ultrasound; Intracellular; Drug delivery; Cavitation; Cavitation noise; Drug delivery systems; Ultrasonics in medicine
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Hallow, D. M. (2006). Measurement and Correlation of Acoustic Cavitation with Cellular and Tissue Bioeffects. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/19741
Chicago Manual of Style (16th Edition):
Hallow, Daniel Martin. “Measurement and Correlation of Acoustic Cavitation with Cellular and Tissue Bioeffects.” 2006. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/19741.
MLA Handbook (7th Edition):
Hallow, Daniel Martin. “Measurement and Correlation of Acoustic Cavitation with Cellular and Tissue Bioeffects.” 2006. Web. 24 Jan 2021.
Vancouver:
Hallow DM. Measurement and Correlation of Acoustic Cavitation with Cellular and Tissue Bioeffects. [Internet] [Doctoral dissertation]. Georgia Tech; 2006. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/19741.
Council of Science Editors:
Hallow DM. Measurement and Correlation of Acoustic Cavitation with Cellular and Tissue Bioeffects. [Doctoral Dissertation]. Georgia Tech; 2006. Available from: http://hdl.handle.net/1853/19741
Georgia Tech
13.
Edwards, Thayne Lowell.
Microfrabricated Acoustic and Thermal Field-Flow Fractionation Systems.
Degree: PhD, Electrical and Computer Engineering, 2004, Georgia Tech
URL: http://hdl.handle.net/1853/6981
► Arguments for miniaturization of a thermal field-flow fractionation system ( and956;-ThFFF) and fabrication of a micro-scale acoustic field-flow fractionation system ( and #956;-AcFFF) using similar…
(more)
▼ Arguments for miniaturization of a thermal field-flow fractionation system ( and956;-ThFFF) and fabrication of a micro-scale acoustic field-flow fractionation system ( and #956;-AcFFF) using similar methods was presented. Motivation for miniaturization of ThFFF systems was established by examining the geometrical scaling of the fundamental ThFFF theory. Miniaturization of conventional macro-scale ThFFF systems was made possible through utilization of micromachining technologies. Fabrication of the and #956;-ThFFF system was discussed in detail. The and #956;-ThFFF system was characterized for plate height versus flow rate, single component polystyrene retention, and multi-component polystyrene separations. Retention, thermal diffusion coefficients, and maximum diameter-based selectivity values were extracted from separation data and found comparable with macro-scale ThFFF system results. Retention values ranged from 0.33 to 0.46. Thermal diffusion coefficients were between 3.0×±0-8 and 5.4×±0-8 cm2/sec?? The maximum diameter-based selectivity was 1.40.
While the concept of an acoustic FFF sub-technique has been around for decades, the fabrication methods have not been available until recently. The theory was developed in full including relating sample physical properties to retention time in the FFF system. In addition to the theory, the design and fabrication of the and #956;-AcFFF was presented. Design results from an acoustic modeling program were presented with the determination of the acoustic resonant frequency. The acoustic-based systems was designed around the model results and characterized by electrical input impedance, fluidic, plate height, polystyrene suspension retention, and polystyrene mixture separation studies.
The and #956;-AcFFF system was able to retain a series of nanometer scale polystyrene samples. However, the retention data did not follow normal mode retention but did reveal the location of the steric inversion point for the power level used, around 200 nm. The results of the multiple component separation confirmed this results as the sample, which contained 110, 210, and 300 nm diameter samples, was not resolved but only broadened.
Advisors/Committee Members: A. Bruno Frazier (Committee Chair), F. Levent Degertekin (Committee Member), Faramarz Fekri (Committee Member), John Papapolymerou (Committee Member), Mark G. Allen (Committee Member).
Subjects/Keywords: Field-flow fractionation; Acoustic; Thermal; FFF; MEMS; Microfabrication
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Edwards, T. L. (2004). Microfrabricated Acoustic and Thermal Field-Flow Fractionation Systems. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/6981
Chicago Manual of Style (16th Edition):
Edwards, Thayne Lowell. “Microfrabricated Acoustic and Thermal Field-Flow Fractionation Systems.” 2004. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/6981.
MLA Handbook (7th Edition):
Edwards, Thayne Lowell. “Microfrabricated Acoustic and Thermal Field-Flow Fractionation Systems.” 2004. Web. 24 Jan 2021.
Vancouver:
Edwards TL. Microfrabricated Acoustic and Thermal Field-Flow Fractionation Systems. [Internet] [Doctoral dissertation]. Georgia Tech; 2004. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/6981.
Council of Science Editors:
Edwards TL. Microfrabricated Acoustic and Thermal Field-Flow Fractionation Systems. [Doctoral Dissertation]. Georgia Tech; 2004. Available from: http://hdl.handle.net/1853/6981
Georgia Tech
14.
Kacker, Karan.
Design and fabrication of free-standing structures as off-chip interconnects for microsystems packaging.
Degree: PhD, Mechanical Engineering, 2008, Georgia Tech
URL: http://hdl.handle.net/1853/26464
► It is projected by the Semiconductor Industry Association in their International Technology Roadmap for Semiconductors (ITRS) that by the year 2019, with the IC feature…
(more)
▼ It is projected by the Semiconductor Industry Association in their International Technology Roadmap for Semiconductors (ITRS) that by the year 2019, with the IC feature size shrinking to about 10nm, off-chip interconnects in an area array format will require a pitch of 95 µm. Also, as the industry adopts porous low-K dielectric materials, it is important to ensure that the stresses induced by the off-chip interconnects and the package do not crack or delaminate the low-K material. Compliant free-standing structures used as off-chip interconnects are a potential solution. However, there are several design, fabrication, assembly and integration research challenges and gaps with the current suite of compliant interconnects. Accordingly, as part of this research a unique parallel-path approach has been developed which enhances the mechanical compliance of the compliant interconnect without compromising the electrical parasitics. It also provides for redundancy and thus results in more reliable interconnects. Also, to meet both electrical and mechanical performance needs, as part of this research a variable compliance approach has been developed so that interconnects near the center of the die have lower electrical parasitics while the interconnects near the corner of the die have higher mechanical compliance. Furthermore, this work has developed a fabrication process which will facilitate cost-effective fabrication of free-standing compliant interconnects and investigated key factors which impact assembly yield of free-standing compliant interconnects. Ultimately the proposed approaches are demonstrated by developing an innovative compliant interconnect called FlexConnects. Hence, through this research it is expected that the developed compliant interconnect would address the needs of first level interconnects over the next decade and eliminate a bottleneck that threatens to impede the exponential growth in microprocessor performance. Also, the concepts developed in this research are generic in nature and can be extended to other aspects of electronic packaging.
Advisors/Committee Members: Dr. Suresh K. Sitaraman (Committee Chair), Dr. F. Levent Degertekin (Committee Member), Dr. Ioannis Papapolymerou (Committee Member), Dr. Madhavan Swaminathan (Committee Member), Dr. Nazanin Bassiri-Gharb (Committee Member).
Subjects/Keywords: Flip chip assembly; Compliant interconnects; First level interconnects; Chip to substrate interconnects; Wafer level packaging; Interconnects (Integrated circuit technology); Microelectronic packaging
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Kacker, K. (2008). Design and fabrication of free-standing structures as off-chip interconnects for microsystems packaging. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/26464
Chicago Manual of Style (16th Edition):
Kacker, Karan. “Design and fabrication of free-standing structures as off-chip interconnects for microsystems packaging.” 2008. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/26464.
MLA Handbook (7th Edition):
Kacker, Karan. “Design and fabrication of free-standing structures as off-chip interconnects for microsystems packaging.” 2008. Web. 24 Jan 2021.
Vancouver:
Kacker K. Design and fabrication of free-standing structures as off-chip interconnects for microsystems packaging. [Internet] [Doctoral dissertation]. Georgia Tech; 2008. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/26464.
Council of Science Editors:
Kacker K. Design and fabrication of free-standing structures as off-chip interconnects for microsystems packaging. [Doctoral Dissertation]. Georgia Tech; 2008. Available from: http://hdl.handle.net/1853/26464
Georgia Tech
15.
Çapoğlu, İlker R.
Techniques for Handling Multilayered Media in the FDTD Method.
Degree: PhD, Electrical and Computer Engineering, 2007, Georgia Tech
URL: http://hdl.handle.net/1853/16179
► We introduce supplemental methods for the finite-difference time-domain (FDTD) analysis of planar multilayered media. The invariance is allowed to be disturbed by any imperfection, provided…
(more)
▼ We introduce supplemental methods for the finite-difference time-domain (FDTD) analysis of planar multilayered media. The invariance is allowed to be disturbed by any imperfection, provided that these imperfections are local and therefore can be contained within an FDTD simulation grid. We specifically investigate two FDTD methods that were not previously developed for general multilayered media: the near-field-to-far-field transform (NFFFT) and the total-field/scattered-field (TF/SF) boundary (or the plane-wave injector). The NFFFT uses the FDTD output on a virtual surface surrounding the local imperfections and calculates the radiated field. The plane wave injector builds an incident plane wave inside a certain boundary (TF/SF boundary) while allowing any scattered fields created by the imperfections inside the boundary to exit the boundary with complete transparency. The NFFFT is applicable for any lossless multilayered medium, while the plane-wave injector is applicable for any lossy multilayered medium. After developing the respective theories and giving simple examples, we apply the NFFFT and the plane-wave injector to a series of problems. These problems are divided into two main groups. In the first group, we consider plane-wave scattering problems involving perfectly-conducting objects buried in multilayered media. In the second group, we consider problems that involve radiating structures in multilayered media. Specifically, we investigate the reciprocity of antennas radiating in the presence of an ungrounded dielectric slab using the methods developed in this study. Finally, we present our previous work on an entirely different subject, namely, the theoretical analysis of the input admittance of a prolate-spheroidal monopole fed by a coaxial line through a ground plane.
Advisors/Committee Members: Glenn S. Smith (Committee Chair), Andrew F. Peterson (Committee Member), Gregory D. Durgin (Committee Member), Levent Degertekin (Committee Member), Waymond R. Scott, Jr. (Committee Member).
Subjects/Keywords: Spheroidal antenna; Multilayered media; Finite-difference time-domain
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
ÇapoÄŸlu, Ä. R. (2007). Techniques for Handling Multilayered Media in the FDTD Method. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/16179
Chicago Manual of Style (16th Edition):
ÇapoÄŸlu, Ä°lker R. “Techniques for Handling Multilayered Media in the FDTD Method.” 2007. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/16179.
MLA Handbook (7th Edition):
ÇapoÄŸlu, Ä°lker R. “Techniques for Handling Multilayered Media in the FDTD Method.” 2007. Web. 24 Jan 2021.
Vancouver:
ÇapoÄŸlu ÄR. Techniques for Handling Multilayered Media in the FDTD Method. [Internet] [Doctoral dissertation]. Georgia Tech; 2007. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/16179.
Council of Science Editors:
ÇapoÄŸlu ÄR. Techniques for Handling Multilayered Media in the FDTD Method. [Doctoral Dissertation]. Georgia Tech; 2007. Available from: http://hdl.handle.net/1853/16179
Georgia Tech
16.
McLean, Jeffrey John.
Interdigital Capacitive Micromachined Ultrasonic Transducers for Microfluidic Applications.
Degree: PhD, Mechanical Engineering, 2004, Georgia Tech
URL: http://hdl.handle.net/1853/7625
► The goal of this research was to develop acoustic sensors and actuators for microfluidic applications. To this end, capacitive micromachined ultrasonic transducers (cMUTs) were developed…
(more)
▼ The goal of this research was to develop acoustic sensors and actuators for microfluidic applications. To this end, capacitive micromachined ultrasonic transducers (cMUTs) were developed which generate guided acoustic waves in fluid half-spaces and microchannels. An interdigital transducer structure and a phased excitation scheme were used to selectively excite guided acoustic modes which propagate in a single lateral direction. Analytical models were developed to predict the geometric dispersion of the acoustic modes and to determine the sensitivity of the modes to changes in material and geometric parameters. Coupled field finite element models were also developed to predict the effect of membrane spacing and phasing on mode generation and directionality.
After designing the transducers, a surface micromachining process was developed which has a low processing temperature of 250C and has the potential for monolithically integrating cMUTs with CMOS electronics. The fabrication process makes extensive use of PECVD silicon nitride depositions for membrane formation and sealing. The fabricated interdigital cMUTs were placed in microfluidic channels and demonstrated to sense changes in fluid sound speed and flow rate using Scholte waves and other guided acoustic modes. The minimum detectable change in sound speed was 0.25m/s, and the minimum detectable change in flow rate was 1mL/min. The unique nature of the Scholte wave allowed for the measurement of fluid properties of a semi-infinite fluid using two transducers on a single substrate. Changes in water temperature, and thus sound speed, were measured and the minimum detectable change in temperature was found to be 0.1C. For fluid pumping, interdigital cMUTs were integrated into microchannels and excited with phase-shifted, continuous wave signals. Highly directional guided waves were generated which in turn generated acoustic streaming forces in the fluid. The acoustic streaming forces caused the fluid to be pumped in a single, electronically-controlled direction. For a power consumption of 43mW, a flow rate of 410nL/min was generated against a pressure of 3.4Pa; the thermodynamic efficiency was approximately 5x10-8%. Although the efficiency and pressure head are low, these transducers can be useful for precisely manipulating small amounts of fluid around microfluidic networks.
Advisors/Committee Members: Levent Degertekin (Committee Chair), Bruno Frazier (Committee Member), Mark Prausnitz (Committee Member), Peter Hesketh (Committee Member), Wenjing Ye (Committee Member), Yves Berthelot (Committee Member).
Subjects/Keywords: Acoustic streaming; Micropump; Scholte wave; Ultrasound; Flow sensor; Fluid sensor; Microfluidics; Guided acoustic wave; Acoustic streaming; Ultrasonic transducers Design and construction; Microfluidics; Microelectromechanical systems
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
McLean, J. J. (2004). Interdigital Capacitive Micromachined Ultrasonic Transducers for Microfluidic Applications. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/7625
Chicago Manual of Style (16th Edition):
McLean, Jeffrey John. “Interdigital Capacitive Micromachined Ultrasonic Transducers for Microfluidic Applications.” 2004. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/7625.
MLA Handbook (7th Edition):
McLean, Jeffrey John. “Interdigital Capacitive Micromachined Ultrasonic Transducers for Microfluidic Applications.” 2004. Web. 24 Jan 2021.
Vancouver:
McLean JJ. Interdigital Capacitive Micromachined Ultrasonic Transducers for Microfluidic Applications. [Internet] [Doctoral dissertation]. Georgia Tech; 2004. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/7625.
Council of Science Editors:
McLean JJ. Interdigital Capacitive Micromachined Ultrasonic Transducers for Microfluidic Applications. [Doctoral Dissertation]. Georgia Tech; 2004. Available from: http://hdl.handle.net/1853/7625
Georgia Tech
17.
Shin, Heungjoo.
Fabrication of Atomic Force Microscope Probes Integrated with Microelectrodes for Micro Four-Point Porbe and SECM-AFM.
Degree: PhD, Mechanical Engineering, 2006, Georgia Tech
URL: http://hdl.handle.net/1853/10428
► This research is dedicated to develop novel batch fabrication procedures for two distinct AFM (Atomic Force Microscope) probes integrated with electrodes enabling electrical sample characterization…
(more)
▼ This research is dedicated to develop novel batch fabrication procedures for two distinct AFM (Atomic Force Microscope) probes integrated with electrodes enabling electrical sample characterization and electrochemical sample surface profiling respectively. These AFM probes allow for highly accurate control of the probe positioning, low contact force and sample surface imaging with high lateral resolution.
As an electrical characterization tool, a nickel micro four-point probe integrated with solid nickel tips was developed. Low electrical resistance of the probe and contact resistance were achieved due to the solid nickel cantilever and tips. Low aspect ratio solid metal tips reduced contact resistance resulting in stable electrical measurement. Conductivity loss easily experienced while using metal coated AFM cantilevers was overcome by solid nickel tip integration to the electrically conductive AFM cantilevers. The fabrication method introduces selective conical nickel tip etching in silicon dioxide etching chambers.
A novel batch fabrication method for SECM-AFM (Scanning Electrochemical Microscope-Atomic Force Microscope) tip integrated with a ring electrode was developed as a tool for electrochemical imaging as well as topological imaging. The electroactive area at an exactly defined distance above the apex of the AFM tip is fabricated using an inverse silicon mold technique. The electrode at a deliberately chosen distance from the end of a scanning probe tip allowing electrochemical sample imaging separated from sample topology imaging. The ring electrode coated with polymer entrapping enzymes enabled the probe to detect ATP from living epithelial cells.
Advisors/Committee Members: Peter J. Hesketh (Committee Chair), Boris Mizaikoff (Committee Member), Levent Degertekin (Committee Member), Mark G. Allen (Committee Member), William P. King (Committee Member).
Subjects/Keywords: AFM; Microelectrodes; Scanning electrochemical microscopy; Probes (Electronic instruments) Design and construction; Atomic force microscopy
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Shin, H. (2006). Fabrication of Atomic Force Microscope Probes Integrated with Microelectrodes for Micro Four-Point Porbe and SECM-AFM. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/10428
Chicago Manual of Style (16th Edition):
Shin, Heungjoo. “Fabrication of Atomic Force Microscope Probes Integrated with Microelectrodes for Micro Four-Point Porbe and SECM-AFM.” 2006. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/10428.
MLA Handbook (7th Edition):
Shin, Heungjoo. “Fabrication of Atomic Force Microscope Probes Integrated with Microelectrodes for Micro Four-Point Porbe and SECM-AFM.” 2006. Web. 24 Jan 2021.
Vancouver:
Shin H. Fabrication of Atomic Force Microscope Probes Integrated with Microelectrodes for Micro Four-Point Porbe and SECM-AFM. [Internet] [Doctoral dissertation]. Georgia Tech; 2006. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/10428.
Council of Science Editors:
Shin H. Fabrication of Atomic Force Microscope Probes Integrated with Microelectrodes for Micro Four-Point Porbe and SECM-AFM. [Doctoral Dissertation]. Georgia Tech; 2006. Available from: http://hdl.handle.net/1853/10428
Georgia Tech
18.
Demiroglu, Cenk.
Multisensor Segmentation-based Noise Suppression for Intelligibility Improvement in MELP Coders.
Degree: PhD, Electrical and Computer Engineering, 2006, Georgia Tech
URL: http://hdl.handle.net/1853/10455
► This thesis investigates the use of an auxiliary sensor, the GEMS device, for improving the quality of noisy speech and designing noise preprocessors to MELP…
(more)
▼ This thesis investigates the use of an auxiliary sensor, the GEMS device, for improving the quality of noisy speech and designing noise preprocessors to MELP speech coders. Use of auxiliary sensors for noise-robust
ASR applications is also investigated to develop speech enhancement algorithms that use acoustic-phonetic
properties of the speech signal.
A Bayesian risk minimization framework is developed that can incorporate the acoustic-phonetic properties
of speech sounds and knowledge of human auditory perception into the speech enhancement framework. Two noise suppression
systems are presented using the ideas developed in the mathematical framework. In the first system, an aharmonic
comb filter is proposed for voiced speech where low-energy frequencies are severely suppressed while
high-energy frequencies are suppressed mildly. The proposed
system outperformed an MMSE estimator in subjective listening tests and DRT intelligibility test for MELP-coded noisy speech.
The effect of aharmonic
comb filtering on the linear predictive coding (LPC) parameters is analyzed using a missing data approach.
Suppressing the low-energy frequencies without any modification of the high-energy frequencies is shown to
improve the LPC spectrum using the Itakura-Saito distance measure.
The second system combines the aharmonic comb filter with the acoustic-phonetic properties of speech
to improve the intelligibility of the MELP-coded noisy speech.
Noisy speech signal is segmented into broad level sound classes using a multi-sensor automatic
segmentation/classification tool, and each sound class is enhanced differently based on its
acoustic-phonetic properties. The proposed system is shown to outperform both the MELPe noise preprocessor
and the aharmonic comb filter in intelligibility tests when used in concatenation with the MELP coder.
Since the second noise suppression system uses an automatic segmentation/classification algorithm, exploiting the GEMS signal in an automatic
segmentation/classification task is also addressed using an ASR
approach. Current ASR engines can segment and classify speech utterances
in a single pass; however, they are sensitive to ambient noise.
Features that are extracted from the GEMS signal can be fused with the noisy MFCC features
to improve the noise-robustness of the ASR system. In the first phase, a voicing
feature is extracted from the clean speech signal and fused with the MFCC features.
The actual GEMS signal could not be used in this phase because of insufficient sensor data to train the ASR system.
Tests are done using the Aurora2 noisy digits database. The speech-based voicing
feature is found to be effective at around 10 dB but, below 10 dB, the effectiveness rapidly drops with decreasing SNR
because of the severe distortions in the speech-based features at these SNRs. Hence, a novel system is proposed that treats the
MFCC features in a speech frame as missing data if the global SNR is below 10 dB and the speech frame is
unvoiced. If the global SNR…
Advisors/Committee Members: David V. Anderson (Committee Chair), Levent Degertekin (Committee Member), Mark A. Clements (Committee Member), Paul Hasler (Committee Member), Thomas Barnwell (Committee Member).
Subjects/Keywords: Speech intelligibility; Speech quality; GEMS; Multi-sensor; Automatic speech recognition; Speech enhancement; Segmentation-based enhancement; Noise-robust automatic segmentation; Comb filter; Data marginalization; Data fusion; Missing data
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Demiroglu, C. (2006). Multisensor Segmentation-based Noise Suppression for Intelligibility Improvement in MELP Coders. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/10455
Chicago Manual of Style (16th Edition):
Demiroglu, Cenk. “Multisensor Segmentation-based Noise Suppression for Intelligibility Improvement in MELP Coders.” 2006. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/10455.
MLA Handbook (7th Edition):
Demiroglu, Cenk. “Multisensor Segmentation-based Noise Suppression for Intelligibility Improvement in MELP Coders.” 2006. Web. 24 Jan 2021.
Vancouver:
Demiroglu C. Multisensor Segmentation-based Noise Suppression for Intelligibility Improvement in MELP Coders. [Internet] [Doctoral dissertation]. Georgia Tech; 2006. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/10455.
Council of Science Editors:
Demiroglu C. Multisensor Segmentation-based Noise Suppression for Intelligibility Improvement in MELP Coders. [Doctoral Dissertation]. Georgia Tech; 2006. Available from: http://hdl.handle.net/1853/10455
Georgia Tech
19.
Graham, David W.
A Biologically Inspired Front End for Audio Signal Processing Using Programmable Analog Circuitry.
Degree: PhD, Electrical and Computer Engineering, 2006, Georgia Tech
URL: http://hdl.handle.net/1853/11549
► This research focuses on biologically inspired audio signal processing using programmable analog circuitry. This research is inspired by the biology of the human cochlea since…
(more)
▼ This research focuses on biologically inspired audio signal processing using programmable analog circuitry. This research is inspired by the biology of the human cochlea since biology far outperforms any engineered system at converting audio signals into meaningful electrical signals. The human cochlea efficiently decomposes any sound into the respective frequency components by harnessing the resonance nature of the basilar membrane, essentially forming a bank of bandpass filters. In a similar fashion, this work revolves around developing a filter bank composed of continuous-time, low-power, analog bandpass filters that serve as the core front end to this silicon audio-processing system. Like biology, the individual bandpass filters are tuned to have narrow bandwidths, moderate amounts of resonance, and exponentially spaced center frequencies. This audio front end serves to efficiently convert incoming sounds into information useful to subsequent signal-processing elements, and it does so by performing a frequency decomposition of the waveform with extremely low-power consumption and real-time operation. To overcome mismatch and offsets inherent in CMOS processes, floating-gate transistors are used to precisely tune the time constants in the filters and to allow programmability of analog components.
Advisors/Committee Members: Aaron Lanternman (Committee Chair), Hasler, Paul (Committee Chair), W Marshall Leach Jr (Committee Member), David Anderson (Committee Member), F. Levent Degertekin (Committee Member).
Subjects/Keywords: Biological inspiration; Audio signal processing; Cochlear modeling; Continous-time analog; Bandpass filter; Programmable analog; Floating gate
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Graham, D. W. (2006). A Biologically Inspired Front End for Audio Signal Processing Using Programmable Analog Circuitry. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/11549
Chicago Manual of Style (16th Edition):
Graham, David W. “A Biologically Inspired Front End for Audio Signal Processing Using Programmable Analog Circuitry.” 2006. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/11549.
MLA Handbook (7th Edition):
Graham, David W. “A Biologically Inspired Front End for Audio Signal Processing Using Programmable Analog Circuitry.” 2006. Web. 24 Jan 2021.
Vancouver:
Graham DW. A Biologically Inspired Front End for Audio Signal Processing Using Programmable Analog Circuitry. [Internet] [Doctoral dissertation]. Georgia Tech; 2006. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/11549.
Council of Science Editors:
Graham DW. A Biologically Inspired Front End for Audio Signal Processing Using Programmable Analog Circuitry. [Doctoral Dissertation]. Georgia Tech; 2006. Available from: http://hdl.handle.net/1853/11549
Georgia Tech
20.
Meacham, John Marcus.
A Micromachined Ultrasonic Droplet Generator: Design, Fabrication, Visualization, and Modeling.
Degree: PhD, Mechanical Engineering, 2006, Georgia Tech
URL: http://hdl.handle.net/1853/11571
► The focus of this Ph.D. thesis research is a new piezoelectrically driven micromachined ultrasonic atomizer concept that utilizes fluid cavity resonances in the 15 MHz…
(more)
▼ The focus of this Ph.D. thesis research is a new piezoelectrically driven micromachined ultrasonic atomizer concept that utilizes fluid cavity resonances in the 15 MHz range along with acoustic wave focusing to generate the pressure gradient required for droplet or jet ejection. This ejection technique exhibits low-power operation while addressing the key challenges associated with other atomization technologies including production of sub-5 um diameter droplets, low-temperature operation, the capacity to scale throughput up or down, and simple, low-cost fabrication. This thesis research includes device development and fabrication as well as experimental characterization and theoretical modeling of the acoustics and fluid mechanics underlying device operation. The main goal is to gain an understanding of the fundamental physics of these processes in order to achieve optimal design and controlled operation of the atomizer.
Simulations of the acoustic response of the system for various device geometries and different ejection fluid properties predict the resonant frequencies of the device and confirm that pressure field focusing occurs. High-spatial-resolution stroboscopic visualization of fluid ejection under various operating conditions is used to investigate whether the proposed atomizer is capable of operating in either the discrete-droplet or continuous-jet mode. The results of the visualization experiments combined with a scaling analysis provide a basic understanding of the physics governing the ejection process and allow for the establishment of simple scaling laws that prescribe the mode (e.g., discrete-droplet vs. continuous-jet) of ejection. In parallel, a detailed computational fluid dynamics (CFD) analysis of the fluid interface evolution and droplet formation and transport during the ejection process provides in-depth insight into the physics of the ejection process and determines the limits of validity of the scaling laws.
These characterization efforts performed in concert with device development lead to the optimal device design. The unique advantages enabled by the developed micromachined ultrasonic atomizer are illustrated for challenging fluid atomization examples from a variety of applications ranging from fuel processing on small scales to ultra-soft electrospray ionization of biomolecules for bioanalytical mass spectrometry.
Advisors/Committee Members: Andrei G. Fedorov (Committee Chair), F. Levent Degertekin (Committee Chair), Ari Glezer (Committee Member), Mark Allen (Committee Member), Mark Papania, MD (Committee Member), Yves Berthelot (Committee Member).
Subjects/Keywords: Fluid mechanics; Ink-jet printing; Ultrasonic; Atomizer; Micromachined; Ultrasonic equipment; Jets Fluid dynamics; Fluid mechanics; Drops; Atomizers
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Meacham, J. M. (2006). A Micromachined Ultrasonic Droplet Generator: Design, Fabrication, Visualization, and Modeling. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/11571
Chicago Manual of Style (16th Edition):
Meacham, John Marcus. “A Micromachined Ultrasonic Droplet Generator: Design, Fabrication, Visualization, and Modeling.” 2006. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/11571.
MLA Handbook (7th Edition):
Meacham, John Marcus. “A Micromachined Ultrasonic Droplet Generator: Design, Fabrication, Visualization, and Modeling.” 2006. Web. 24 Jan 2021.
Vancouver:
Meacham JM. A Micromachined Ultrasonic Droplet Generator: Design, Fabrication, Visualization, and Modeling. [Internet] [Doctoral dissertation]. Georgia Tech; 2006. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/11571.
Council of Science Editors:
Meacham JM. A Micromachined Ultrasonic Droplet Generator: Design, Fabrication, Visualization, and Modeling. [Doctoral Dissertation]. Georgia Tech; 2006. Available from: http://hdl.handle.net/1853/11571
Georgia Tech
21.
Lee, Wook.
Diffraction-based integrated optical readout for micromachined optomechanical sensors.
Degree: PhD, Electrical and Computer Engineering, 2006, Georgia Tech
URL: http://hdl.handle.net/1853/14006
► Highly sensitive optical displacement detection methods implemented in a small volume and with reduced power consumption have a potential to compete with commonly used capacitance…
(more)
▼ Highly sensitive optical displacement detection methods implemented in a small volume and with reduced power consumption have a potential to compete with commonly used capacitance based methods in micromechanical sensor systems. This dissertation presents the design, implementation, and characterization of a miniaturized optomechanical displacement sensor system heterogeneously integrated with a coherent laser source and optoelectronic readout as a step in realizing this potential. The sensor uses a phase-sensitive diffraction grating built on a transparent substrate to achieve interferometric sensitivity in a small volume. The device sensitivity is actively optimized via the built-in electrostatic actuation capability, which may be utilized for self calibration and force feedback operation. Optical interconnect through the backside of the sensor enables compact integration with optoelectronic components.
For optical readout, a custom-designed silicon photodiode array has been fabricated including deep reactive ion etching of through-wafer holes. The hybrid-integrated system has been implemented and characterized in an acoustic sensor application using both continuous wave and pulsed lasers to show reduced power consumption potential. Comprehensive diffraction analysis has been carried out for optical design of the integrated sensor. Furthermore, a fully-vectorial method has been formulated for general multilayered grating structures and compared with the scalar diffraction approach to investigate the effects of polarization and grating periods.
In addition, a grating-assisted resonant-cavity-enhanced (GARCE) detection method has been proposed to improve the displacement sensitivity in optomechanical microsensors. Fabrication of the GARCE structures based on both metallic and dielectric mirrors has been successfully demonstrated, and preliminary experimental results have shown a good agreement with theoretical predictions.
The concepts developed and demonstrated in this thesis form a technology platform which already had an impact in a variety of applications including optical microphones, micromachined ultrasonic transducers and transducers arrays, micromachined inertial sensors, and scanning probe microscopy.
Advisors/Committee Members: F. Levent Degertekin (Committee Chair), David S. Citrin (Committee Member), Paul E. Hasler (Committee Member), Peter J. Hesketh (Committee Member), Zhiping Zhou (Committee Member).
Subjects/Keywords: Microelectromechanical systems (MEMS)
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Lee, W. (2006). Diffraction-based integrated optical readout for micromachined optomechanical sensors. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/14006
Chicago Manual of Style (16th Edition):
Lee, Wook. “Diffraction-based integrated optical readout for micromachined optomechanical sensors.” 2006. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/14006.
MLA Handbook (7th Edition):
Lee, Wook. “Diffraction-based integrated optical readout for micromachined optomechanical sensors.” 2006. Web. 24 Jan 2021.
Vancouver:
Lee W. Diffraction-based integrated optical readout for micromachined optomechanical sensors. [Internet] [Doctoral dissertation]. Georgia Tech; 2006. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/14006.
Council of Science Editors:
Lee W. Diffraction-based integrated optical readout for micromachined optomechanical sensors. [Doctoral Dissertation]. Georgia Tech; 2006. Available from: http://hdl.handle.net/1853/14006
Georgia Tech
22.
Sharma, Ajit.
CMOS systems and circuits for sub-degree per hour MEMS gyroscopes.
Degree: PhD, Electrical and Computer Engineering, 2007, Georgia Tech
URL: http://hdl.handle.net/1853/26636
► The objective of our research is to develop system architectures and CMOS circuits that interface with high-Q silicon microgyroscopes to implement navigation-grade angular rate sensors.…
(more)
▼ The objective of our research is to develop system architectures and CMOS circuits that interface with high-Q silicon microgyroscopes to implement navigation-grade angular rate sensors. The MEMS sensor used in this work is an in-plane bulk-micromachined mode-matched tuning fork gyroscope (M² – TFG
), fabricated on silicon-on-insulator substrate. The use of CMOS transimpedance amplifiers (TIA) as front-ends in high-Q MEMS resonant sensors is explored. A T-network TIA is proposed as the front-end for resonant capacitive detection. The T-TIA provides on-chip transimpedance gains of 25MΩ, has a measured capacitive resolution of 0.02aF /√Hz at 15kHz, a dynamic range of 104dB in a bandwidth of 10Hz and consumes 400μW of power. A second contribution is the development of an automated scheme to adaptively bias the mechanical structure, such that the sensor is operated in the mode-matched condition. Mode-matching leverages the inherently high quality factors of the microgyroscope, resulting in significant improvement in the Brownian noise floor, electronic noise, sensitivity and bias drift of the microsensor. We developed a novel architecture that utilizes the often ignored residual quadrature error in a gyroscope to achieve and maintain perfect mode-matching (i.e.0Hz split between the drive and sense mode frequencies), as well as electronically control the sensor bandwidth. A CMOS implementation is developed that allows mode-matching of the drive and sense frequencies of a gyroscope at a fraction of the time taken by current state of-the-art techniques. Further, this mode-matching technique allows for maintaining a controlled separation between the drive and sense resonant frequencies, providing a means of increasing sensor bandwidth and dynamic range. The mode-matching CMOS IC, implemented in a 0.5μm 2P3M process, and control algorithm have been interfaced with a 60μm thick M2−TFG to implement an angular rate sensor with bias drift as low as 0.1°/hr ℃ the lowest recorded to date for a silicon MEMS gyro.
Advisors/Committee Members: Farrokh Ayazi (Committee Chair), Jennifer Michaels (Committee Member), Levent Degertekin (Committee Member), Paul Hasler (Committee Member), W. Marshall Leach (Committee Member).
Subjects/Keywords: MEMS; Gyroscopes; Data converters; Transimpedance amplifiers; Low-noise; Bias drift; Mode-matching; Detectors; Noise control; Transducers – Drift; Gyroscopic instruments
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Sharma, A. (2007). CMOS systems and circuits for sub-degree per hour MEMS gyroscopes. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/26636
Chicago Manual of Style (16th Edition):
Sharma, Ajit. “CMOS systems and circuits for sub-degree per hour MEMS gyroscopes.” 2007. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/26636.
MLA Handbook (7th Edition):
Sharma, Ajit. “CMOS systems and circuits for sub-degree per hour MEMS gyroscopes.” 2007. Web. 24 Jan 2021.
Vancouver:
Sharma A. CMOS systems and circuits for sub-degree per hour MEMS gyroscopes. [Internet] [Doctoral dissertation]. Georgia Tech; 2007. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/26636.
Council of Science Editors:
Sharma A. CMOS systems and circuits for sub-degree per hour MEMS gyroscopes. [Doctoral Dissertation]. Georgia Tech; 2007. Available from: http://hdl.handle.net/1853/26636
Georgia Tech
23.
Charest, Joseph Leo.
Topographic and chemical patterning of cell-surface interfaces to influence cellular functions.
Degree: PhD, Mechanical Engineering, 2007, Georgia Tech
URL: http://hdl.handle.net/1853/24621
► This dissertation aims to further the understanding of the complex communication that occurs as cells interact with topographical and chemical patterns on a biomaterial interface.…
(more)
▼ This dissertation aims to further the understanding of the complex communication that occurs as cells interact with topographical and chemical patterns on a biomaterial interface. The research accomplishes this through two aims fabricating cell substrate surface topography and chemical patterns independently using non-cleanroom approaches, and analyzing higher order cellular response to surface features. The work will impact biomaterial surface modification and fabrication which will apply to biomedical implanted devices, tissue engineering scaffolds, and biological analysis devices. The first aim seeks to apply non-traditional topographical and chemical patterning methods in order to create independent topographical and chemical patterns on cell culture substrates. Experiments use the resulting patterned substrates to quantify cellular alignment to surface topography and compare the relative influence of topographical and chemical patterns on cellular response. The combined patterning methods of imprint lithography and micro-contact printing result in a high-throughput technique applicable to a variety of materials and a range of feature sizes from nanoscale through microscale, thereby enabling future analysis of cell response to surface features. The second aim evaluates the impact of topographical and chemical features on cellular differentiation. Experiments use patterned topography overlaid with a characterized chemical model layer to evaluate the effects of topography on myoblast differentiation and alignment. Chemical patterns that independently control available cell spreading area and modulate cell-cell contact are used to investigate the impact of cell-cell contact on differentiation.
Advisors/Committee Members: Dr. William P. King (Committee Chair), Dr. Andres J. Garcia (Committee Member), Dr. F. Levent Degertekin (Committee Member), Dr. Hang Lu (Committee Member), Dr. Todd C. McDevitt (Committee Member).
Subjects/Keywords: Biomaterial; Cell-surface interface; Chemical pattern; Micropattern; Nanopattern; Topography; Cells; Keratinocytes; Cell adhesion; Biomedical materials; Surface chemistry
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Charest, J. L. (2007). Topographic and chemical patterning of cell-surface interfaces to influence cellular functions. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/24621
Chicago Manual of Style (16th Edition):
Charest, Joseph Leo. “Topographic and chemical patterning of cell-surface interfaces to influence cellular functions.” 2007. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/24621.
MLA Handbook (7th Edition):
Charest, Joseph Leo. “Topographic and chemical patterning of cell-surface interfaces to influence cellular functions.” 2007. Web. 24 Jan 2021.
Vancouver:
Charest JL. Topographic and chemical patterning of cell-surface interfaces to influence cellular functions. [Internet] [Doctoral dissertation]. Georgia Tech; 2007. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/24621.
Council of Science Editors:
Charest JL. Topographic and chemical patterning of cell-surface interfaces to influence cellular functions. [Doctoral Dissertation]. Georgia Tech; 2007. Available from: http://hdl.handle.net/1853/24621
Georgia Tech
24.
Kumar, Surajit.
Fluidic and dielectrophoretic manipulation of tin oxide nanobelts.
Degree: PhD, Mechanical Engineering, 2008, Georgia Tech
URL: http://hdl.handle.net/1853/34851
► Nanobelts are a new class of semiconducting metal oxide nanowires with great potential for nanoscale devices. The present research focuses on the manipulation of SnOâ‚‚…
(more)
▼ Nanobelts are a new class of semiconducting metal oxide nanowires with great potential for nanoscale devices. The present research focuses on the manipulation of SnOâ‚‚ nanobelts suspended in ethanol using microfluidics and electric fields. Dielectrophoresis (DEP) was demonstrated for the first time on semiconducting metal oxide nanobelts, which also resulted in the fabrication of a multiple nanobelt device. Detailed and direct real-time observations of the wide variety of nanobelt motions induced by DEP forces were conducted using an innovative setup and an inverted optical microscope. High AC electric fields were generated on a gold microelectrode (~ 20 µm gap) array, patterned on glass substrate, and covered by a ~ 10 µm tall PDMS (polydimethylsiloxane) channel, into which the nanobelt suspension was introduced for performing the DEP experiments. Negative DEP (repulsion) of the nanobelts was observed in the low frequency range (< 100 kHz) of the applied voltage, which caused rigid body motion as well as deformation of the nanobelts. In the high frequency range (~ 1 MHz - 10 MHz), positive DEP (attraction) of the nanobelts was observed. Using a parallel plate electrode arrangement, evidence of electrophoresis was also found for DC and low frequency (Hz) voltages.
The existence of negative DEP effect is unusual considering the fact that if bulk SnOâ‚‚ conductivity and permittivity values are used in combination with ethanol properties to calculate the Clausius Mossotti factor using the simple dipole approximation theory; it predicts positive DEP for most of the frequency range experimentally studied.
A fluidic nanobelt alignment technique was studied and used in the fabrication of single nanobelt devices with small electrode gaps. These devices were primarily used for conducting impedance spectroscopy measurements to obtain an estimate of the nanobelt electrical conductivity.
Parametric numerical studies were conducted using COMSOL Multiphysics software package to understand the different aspects of the DEP phenomenon in nanobelts. The DEP induced forces and torques were computed using the Maxwell Stress Tensor (MST) approach. The DEP force on the nanobelt was calculated for a range of nanobelt conductivity values. The simulation results indicate that the experimentally observed behavior can be explained if the nanobelt is modeled as having two components: an electrically conductive interior and a nonconductive outer layer surrounding it. This forms the basis for an explanation of the negative DEP observed in SnOâ‚‚ nanobelts suspended in ethanol. It is thought that the nonconductive layer is due to depletion of the charge carriers from the nanobelt surface regions. This is consistent with the fact that surface depletion is a commonly observed phenomenon in SnOâ‚‚ and other semiconducting metal oxide materials. The major research contribution of this work is that, since nanostructures have large surface areas, surface dominant properties are important. Considering only bulk electrical properties can predict misleading…
Advisors/Committee Members: Dr. Peter J. Hesketh (Committee Chair), Dr. F. Levent Degertekin (Committee Member), Dr. Martha A. Gallivan (Committee Member), Dr. Rosario A. Gerhardt (Committee Member), Dr. Samuel Graham (Committee Member), Dr. Zhong Lin Wang (Committee Member).
Subjects/Keywords: Lab-on-a-Chip (LOC); Nanowire; Nanomanipulation; Nanobelt; Nanoassembly; Tin oxide (SnO); Dielectrophoresis (DEP); Nanomaterial; Nanotechnology; Microfluidics; Microsystems (MEMS); Nanomanufacturing; Nanowires; Microfluidics; Dielectrophoresis
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Kumar, S. (2008). Fluidic and dielectrophoretic manipulation of tin oxide nanobelts. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/34851
Chicago Manual of Style (16th Edition):
Kumar, Surajit. “Fluidic and dielectrophoretic manipulation of tin oxide nanobelts.” 2008. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/34851.
MLA Handbook (7th Edition):
Kumar, Surajit. “Fluidic and dielectrophoretic manipulation of tin oxide nanobelts.” 2008. Web. 24 Jan 2021.
Vancouver:
Kumar S. Fluidic and dielectrophoretic manipulation of tin oxide nanobelts. [Internet] [Doctoral dissertation]. Georgia Tech; 2008. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/34851.
Council of Science Editors:
Kumar S. Fluidic and dielectrophoretic manipulation of tin oxide nanobelts. [Doctoral Dissertation]. Georgia Tech; 2008. Available from: http://hdl.handle.net/1853/34851
Georgia Tech
25.
Chen, Yu-Bin.
Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays.
Degree: PhD, Mechanical Engineering, 2007, Georgia Tech
URL: http://hdl.handle.net/1853/14470
► Radiative properties of a material is the core of thermal science and optics, which play critical roles in modern technologies, including microelectronics, energy conversion, and…
(more)
▼ Radiative properties of a material is the core of thermal science and optics, which play critical roles in modern technologies, including microelectronics, energy conversion, and nanotechnology. The key to modify or enhance radiative properties is employing one-, two-, and three-dimensional (1, 2, and 3D) periodic micro/nanostructures. Since their applications are not fully uncovered and very few comprehensive studies are available, the objective of this dissertation is to explore applications of periodic micro/nanostructures with modified radiative properties in modern technologies through both numerically and experimentally investigations. Theses representative applications include the thermal control in rapid thermal processing, the design of a wavelength-selective radiator for thermophotovoltaic systems, and the nanothermal manufacturing.
The theoretical foundation of the study is built on the rigorous coupled-wave analysis (RCWA) for numerical calculation of the far-field radiative properties and the electromagnetic field distribution in the near-field regime. Measurements of diffraction efficiencies are conducted on fabricated 1D and 2D periodic silicon microstructures with a laser scatterometer/diffractometer with high angular resolution. The diffraction efficiency can be employed for non-contact surface profile inspection tool because it strongly depends on structure patterns.
For better temperature control during rapid thermal processing, the dissertation performs a parametric study on radiation absorption of a generic CMOS device together with its simplified nanoscale structures. The applicability of approximation models, which homogenize micro/nanostructures into a film, is also evaluated. Next, a new concept of complex gratings is proposed for actively tailoring the radiative properties and serving as a thermophotovoltaic (TPV) radiator. The radiator exhibits a wide-band and angle-independent high transverse magnetic wave emittance matching the bandgap of TPV cells so that the energy conversion efficiency can be improved. Furthermore, the nanoscale metallic slit arrays show polarization-dependant enhanced transmission and highly localized electromagnetic energy density, which hold promising potentials in nanothermal manufacturing. Three submicrometer metallic slit arrays are fabricated on top of a silicon substrate. Their spectral transmittance is measured with a Fourier-transform infrared spectrometer and largely agrees with RCWA modeling results. In short, the dissertation clearly demonstrates that precise control and tuning of radiative properties using micro/nanofabrication are not only feasible but also may have numerous technological impacts.
Advisors/Committee Members: Dr. Zhuomin Zhang (Committee Chair), Dr. F. Levent Degertekin (Committee Member), Dr. Gee-Kung Chang (Committee Member), Dr. Pei-feng Hsu (Committee Member), Dr. Peter J. Hesketh (Committee Member).
Subjects/Keywords: Micro/Nanostructures; Gratings
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Chen, Y. (2007). Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/14470
Chicago Manual of Style (16th Edition):
Chen, Yu-Bin. “Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays.” 2007. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/14470.
MLA Handbook (7th Edition):
Chen, Yu-Bin. “Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays.” 2007. Web. 24 Jan 2021.
Vancouver:
Chen Y. Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays. [Internet] [Doctoral dissertation]. Georgia Tech; 2007. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/14470.
Council of Science Editors:
Chen Y. Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays. [Doctoral Dissertation]. Georgia Tech; 2007. Available from: http://hdl.handle.net/1853/14470
Georgia Tech
26.
Barber, Jabulani Randall Timothy.
Mechanical compression of coiled carbon nanotubes.
Degree: PhD, Chemistry and Biochemistry, 2009, Georgia Tech
URL: http://hdl.handle.net/1853/28216
► Carbon nanotubes are molecular-scale tubes of graphitic carbon that possess many unique properties. They have high tensile strength and elastic modulus, are thermally and electrically…
(more)
▼ Carbon nanotubes are molecular-scale tubes of graphitic carbon that possess many unique properties. They have high tensile strength and elastic modulus, are thermally and electrically conductive, and can be structurally modified using well established carbon chemistries. There is global interest in taking advantage of their unique combination of properties and using these interesting materials as components in nanoscale devices and composite materials.
The goal of this research was the correlation of the mechanical properties of coiled carbon nanotubes with their chemical structure. Individual nanocoils, grown by chemical vapor deposition, were attached to scanning probe tip using the arc discharge method. Using a scanning probe microscope the nanocoils are repeatedly brought into and out of contact with a chemically-modified substrate. Precise control over the length (or area) of contact with the substrate is achievable through simultaneous monitoring the cantilever deflection resonance, and correlating these with scanner movement. The mechanical response of nanocoils depended upon the extent of their compression. Nonlinear response of the nanocoil was observed consistent with compression, buckling, and slip-stick motion of the nanocoil. The chemical structure of the nanocoil and its orientation on the tip was determined using scanning and transmission electron microscopy.
The mechanical stiffness of eighteen different nanocoils was determined in three ways. In the first, the spring constant of each nanocoil was computed from the slope of the linear response region of the force-distance curve. The assumptions upon which this calculation is based are: 1) under compression, the cantilever-nanocoil system can be modeled as two-springs in series, and 2) the nanocoil behaves as an ideal spring as the load from the cantilever is applied. Nanocoil spring constants determined in this fashion ranged from 6.5x10-3 to 5.16 TPa for the CCNTs understudy. In the second, the spring constant of the nanocoil was computed from measuring the critical force required to buckle the nanocoil. The critical force method measured the force at the point where the nanocoil-cantilever system diverges from a linear region in the force curve. Nanocoil spring constants determined in this fashion ranged from 1.3x10-5 to 10.4 TPa for the CCNTs understudy. In the third, the spring constant of each nanocoil was computed from the thermal resonance of the cantilever-nanocoil system. Prior to contact of the nanocoil with the substrate, the effective spring constant of the system is essentially that of the cantilever. At the point of contact and prior to buckling or slip-stick motion, the effective spring constant of the system is modeled as two springs in parallel. Nanocoil spring constants determined in this fashion ranged from 2.7x10-3 to 0.03 TPa for the CCNTs understudy.
Using the thermal resonance of the cantilever system a trend was observed relating nanocoil structure to the calculated modulus. Hollow, tube-like…
Advisors/Committee Members: Lawrence Bottomley (Committee Chair), Aldo Ferri (Committee Member), E. Kent Barefield (Committee Member), Levent Degertekin (Committee Member), Robert Whetten (Committee Member), Satish Kumar (Committee Member), Zhong Lin Wang (Committee Member).
Subjects/Keywords: Slip-stick; Tribology; Thermal resonance spectrum; Mechanical properties; Force spectroscopy; Atomic force microscopy; Nanocoil; Multi-walled carbon nanotube; Nanospring; Nanotube; Nanotubes Mechanical properties; Carbon; Chemical structure; Springs (Mechanism)
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Barber, J. R. T. (2009). Mechanical compression of coiled carbon nanotubes. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/28216
Chicago Manual of Style (16th Edition):
Barber, Jabulani Randall Timothy. “Mechanical compression of coiled carbon nanotubes.” 2009. Doctoral Dissertation, Georgia Tech. Accessed January 24, 2021.
http://hdl.handle.net/1853/28216.
MLA Handbook (7th Edition):
Barber, Jabulani Randall Timothy. “Mechanical compression of coiled carbon nanotubes.” 2009. Web. 24 Jan 2021.
Vancouver:
Barber JRT. Mechanical compression of coiled carbon nanotubes. [Internet] [Doctoral dissertation]. Georgia Tech; 2009. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/1853/28216.
Council of Science Editors:
Barber JRT. Mechanical compression of coiled carbon nanotubes. [Doctoral Dissertation]. Georgia Tech; 2009. Available from: http://hdl.handle.net/1853/28216
. 
Open Access Theses and Dissertations
