Person:

Hunt, William D.

Permanent Link

https://hdl.handle.net/1853/71352

Associated Organization(s)

Organizational Unit

School of Electrical and Computer Engineering

Full item page

Publication Search Results

Now showing 1 - 10 of 11

High-Q micromechanical resonators in a two-dimensional phononic crystal slab

(Georgia Institute of Technology, 2009-02) Mohammadi, Saeed ; Eftekhar, Ali Asghar ; Hunt, William D. ; Adibi, Ali

By creating line defects in the structure of a phononic crystal (PC) made by etching a hexagonal array of holes in a 15 μm thick slab of silicon, high-Q PC resonators are fabricated using a complimentary-metal-oxide-semiconductor-compatible process. The complete phononic band gap of the PC structure supports resonant modes with quality factors of more than 6000 at frequencies as high as 126 MHz. The confinement of acoustic energy is achieved by using only a few PC layers confining the cavity region. The calculated frequencies of resonance of the structure using finite element method are in a very good agreement with the experimental data. The performance of these PC resonator structures makes them excellent candidates for wireless communication and sensing applications.
In Situ Acoustic Temperature Measurement During Variable-Frequency Microwave Curing

(Georgia Institute of Technology, 2008-10) Davis, Cleon E. ; Dickherber, Anthony ; Hunt, William D. ; May, Gary S.

Variable-frequency microwave (VFM) curing can perform the same processing steps as conventional thermal processing in minutes, without compromising intrinsic material properties. With increasing demand for novel dielectrics, there is a corresponding demand for new processing techniques that lead to comparable or better properties than conventional methods. VFM processing can be a viable alternative to conventional thermal techniques. However, current limitations include a lack of reliable temperature measuring techniques. This research focuses on developing a reliable temperature measuring system using acoustic techniques to monitor low-k polymer dielectrics cured on silicon wafers in a VFM furnace. The acoustic sensor exhibits the capability to measure temperatures from 20 degrees C to 300 degrees C with an attainable accuracy of ± 2 degrees.
Evidence of large high frequency complete phononic band gaps in silicon phononic crystal plates

(Georgia Institute of Technology, 2008-06-02) Mohammadi, Saeed ; Eftekhar, Ali Asghar ; Khelif, Abdelkrim ; Hunt, William D. ; Adibi, Ali

We show the evidence of the existence of large complete phononic band gaps (CPBGs) in two-dimensional phononic crystals (PCs) formed by embedding cylindrical air holes in a solid plate (slab). The PC structure is made by etching a hexagonal array of air holes through a freestanding plate of silicon. A fabrication process compatible with metal-oxide-semiconductor technology is used on silicon-on-insulator substrate to realize the PC devices. Measuring the transmission of elastic waves through eight layers of the hexagonal lattice PC in the ΓK direction, more than 30 dB attenuation is observed at a high frequency; i.e., 134 MHz, with a band gap to midgap ratio of 23%. We show that this frequency region matches very well with the expected CPBG found through theoretical calculations.
Analogies Between Digital Radio and Chemical Orthogonality as a Method for Enhanced Analysis of Molecular Recognition Events

(Georgia Institute of Technology, 2008-02) Edmonson, Peter J. ; Hunt, William D. ; Stubbs, Desmond D. ; Lee, Sang-Hun

Acoustic wave biosensors are a real-time, label-free biosensor technology, which have been exploited for the detection of proteins and cells. One of the conventional biosensor approaches involves the immobilization of a monolayer of antibodies onto the surface of the acoustic wave device for the detection of a specific analyte. The method described within includes at least two immobilizations of two different antibodies onto the surfaces of two separate acoustic wave devices for the detection of several analogous analytes. The chemical specificity of the molecular recognition event is achieved by virtue of the extremely high (nM to pM) binding affinity between the antibody and its antigen. In a standard ELISA (Enzyme-Linked ImmunoSorbent Assay) test, there are multiple steps and the end result is a measure of what is bound so tightly that it does not wash away easily. The fact that this "gold standard" is very much not real time, masks the dance that is the molecular recognition event. X-Ray Crystallographer, Ian Wilson, demonstrated more than a decade ago that antibodies undergo conformational change during a binding event[1, 2]. Further, it is known in the arena of immunochemistry that some antibodies exhibit significant cross-reactivity and this is widely termed antibody promiscuity. A third piece of the puzzle that we will exploit in our system of acoustic wave biosensors is the notion of chemical orthogonality. These three biochemical constructs, the dance, antibody promiscuity and chemical orthogonality will be combined in this paper with the notions of in-phase (I) and quadrature (Q) signals from digital radio to manifest an approach to molecular recognition that allows a level of discrimination and analysis unobtainable without the aggregate. As an example we present experimental data on the detection of TNT, RDX, C4, ammonium nitrate and musk oil from a system of antibody-coated acoustic wave sensors.
Lateral field excitation of thickness shear mode waves in a thin film ZnO solidly mounted resonator

(Georgia Institute of Technology, 2007-03-01) Corso, Christopher D. ; Dickherber, Anthony ; Hunt, William D.

In recent years, interest in the development of highly sensitive acoustic wave devices as biosensor platforms has grown. A considerable amount of research has been conducted on AT-cut quartz resonators both in thickness excitation and in lateral excitation configurations. In this report, we demonstrate the fabrication of a ZnO solidly mounted resonator operated in thickness shear mode (TSM) using lateral field excitation of the piezoelectric film. Theoretical Christoffel equation calculations are provided to explore the conditions for excitation of a TSM wave in c-axis-oriented ZnO through lateral excitation. The existence of a TSM wave is verified through the comparison of theoretical and experimentally obtained acoustic velocity values from frequency versus thickness measurements and water loading of the resonators. A major strength of this design is that it incorporates a simple eight-layer, single-mask fabrication process compatible with existing integrated circuit fabrication processes and can be easily incorporated into multidevice arrays. With minimal electrode optimization, we have been able to fabricate resonators with nearly 100% yield that demonstrate Q values of up to 550 and K² values of 0.88% from testing of more than 30 devices.
Rapid detection of bacterial spores using a quartz crystal microbalance (QCM) immunoassay

(Georgia Institute of Technology, 2005-08) Lee, Sang-Hun ; Stubbs, Desmond D. ; Cairney, John ; Hunt, William D.

Weaponized spores of a pathogenic bacterium such as Bacillus anthracis are a new critical threat to mankind. The occurrences in New York and south Florida in 2001 showed the potential capability of the spores to be used for mass destruction. Due to their stealthiness during the infection and resistance to harsh environment, an early and prompt detection of the spores before they endanger the population is a significant issue. In this paper, we present a method of instant identification of Bacillus subtilis (nonpathogenic simulant for Bacillus anthracis) spores by constructing a dual quartz crystal microbalance (QCM) immunosensing system. A set of 10-MHz AT-cut QCMs operating in thickness shear mode are employed in an enclosed flowcell. Specificity is maintained through the use of an immuno-sensing layer consisting of monoclonal antibodies raised against spores of a single Bacillus species. The fidelity of sensing parameters is ensured by the presence of a reference device coated with an antibody that is not specific for the target antigen. Associating the QCM response signature with the specific binding of a particular species of Bacillus spore to an antibody has implications for future identification of pathogenic substances.
Vapor phase detection of a narcotic using surface acoustic wave immunoassay sensors

(Georgia Institute of Technology, 2005-06) Stubbs, Desmond D. ; Lee, Sang-Hun ; Hunt, William D.

Currently, the narcotic sniffing dog remains the most accurate, reliable, and widely used sensing technology in the war on drugs. However, recent studies done at the Institute for Biological Detection Systems at Auburn University, Auburn, AL, have shown that in the presence of extraneous odors (nontarget odors), these animals show a higher propensity for so-called false alarms. For this reason, there have been an increasing demand for a portable, highly specific vapor-sensing device capable of distinguishing a target vapor signature in a complex odor. In this paper, we present the results of a series of experiments demonstrating real-time vapor phase detection of cocaine molecules. A distinctive response or signature was observed under laboratory conditions, where the cocaine vapors were presented using an INEL vapor generator and under “field” conditions facilitated by the Georgia Bureau of Investigation Crime Lab. For these experiments, the sensor component was an ST-X quartz resonator with a center frequency of approximately 250-MHz. anti-benzoylecgonine (anti-BZE) antibodies are attached to the electrodes on the device surface via a protein-A cross linker. We observed a large transient frequency shift accompanied by baseline shift with the anti-BZE coated sensor. After repeated experiments and the use of numerous controls, we believe that we have achieved real-time molecular recognition of cocaine molecules.
Leaky surface acoustic waves in Z-LiNbO ₃ substrates with epitaxial AlN overlays

(Georgia Institute of Technology, 2004-10) Bu, G. ; Ciplys, D. ; Shur, M. S. ; Namkoong, G. ; Doolittle, William Alan ; Hunt, William D.

The properties of leaky surface acoustic waves (LSAW) in MBE grown AIN layer on Z-cut LiNbO₃ structures have been studied by numerical simulation and experimental measurements and compared with those of Rayleigh waves in the same structure. In the range of AIN layer thicknesses studied (0
A PDA-based wireless biosensor using industry standard components

(Georgia Institute of Technology, 2004-10) Sommers, Daniel R. ; Stubbs, Desmond D. ; Hunt, William D.

This paper presents the conception, design, implementation, and validation of an original, fully functional biosensor based on surface plasmon tesonance (SPR) technology.We present the motivation for building this sensor followed by the system specification, a brief overview of the theory of operation for SPR physics, and then give a detailed description of the hardware design, software design, and immunoassay design. We present a novel, graphical approach for tracking shifts in SPR center frequency with an autocorrelation feature that minimizes component variation. Additionally, we present the wireless communications aspects of our design, which adds to its appeal for remote system deployment and autonomous operation. Our success demonstrates the immediate availability of all the hardware, software, and biological components required to construct a fully functional biosensor with industrial application.
Time-dependent signatures of acoustic wave biosensors

(Georgia Institute of Technology, 2003-06) Hunt, William D. ; Stubbs, Desmond D. ; Lee, Sang-Hun

Acoustic wave devices coated with a biolayer represent one biosensor approach for the detection of medically relevant biomolecules. In a typical application, the acoustic wave device is connected in an oscillator circuit, and the frequency shift ∆ f resulting from a biomolecular event is recorded. In this paper, we discuss our recent work in this field, which has included the use of Rayleigh wave surface acoustic wave devices for vapor phase detection as well as quartz crystal microbalance devices for liquid phase measurements. For all of the results reported herein the biofilm on the surface of the acoustic wave device consists of a layer of antibodies raised against a specific target molecule or antigen. We present our results for the vapor phase detection of small molecules such as uranine and cocaine as well as liquid phase detection of small and large molecules. The data we present from these various experiments is the signature associated with the biomolecular recognition events; that is, we record and present ∆ f(t). Finally, we present the recent results of our time-dependent perturbation theory work, which gives a potential method for resolving the acoustic wave biosensor signature into information relating to molecular structure changes during a molecular recognition event.