Person:
Hunt, William D.

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Music, Science, and Technology

2009-03-03 , Hunt, William D. , Valk, Henry

Music and its performance have been part of our inheritance since primitive times. But what is music? How do we produce and hear it? How are popular instruments that we use to perform it, such as the guitar and piano, evolving? These and related questions will be discussed from the standpoint of current science and technology.

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Clues from Digital Radio Regarding Biomolecular Recognition

2008-10-10 , Hunt, William D.

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Analogies Between Digital Radio and Chemical Orthogonality as a Method for Enhanced Analysis of Molecular Recognition Events

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.

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Lateral field excitation of thickness shear mode waves in a thin film ZnO solidly mounted resonator

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.

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

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.

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In Situ Acoustic Temperature Measurement During Variable-Frequency Microwave Curing

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.

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Biological warfare agents

2007-03-13 , Hunt, William D.

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Functionalization of high frequency SAW RFID devices for ozone dosimetry

2009 , Westafer, Ryan S. , Levitin, Galit , Hess, Dennis W. , Bergin, Michael H. , Edmonsonx, Peter J. , Hunt, William D.

In this paper we report new work on the gravimetric detection of ozone at EPA and OSHA relevant concentrations (approximately 100 ppb) in filtered ambient air. We have extended our proof-of-concept work which used both quartz crystal microbalance (QCM) and surface acoustic wave (SAW) resonators. We now enable detection using our high frequency SAW RFID devices. Such surface wave devices are extremely sensitive to the viscosity, thickness, and uniformity of the reactive or sorbent coating. We report laboratory characterization of our polymer-coated SAW sensors operating between 200 and 600 MHz on lithium niobate substrates. Return loss measurements confirm adequate load bearing even at 550 MHz. We compare both the temperature and ozone sensitivity of the RFID devices to conventional resonators. In conclusion, we suggest the design improvements to yield a next generation of SAW RFID ozone sensors with even greater sensitivity.

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Evidence of large high frequency complete phononic band gaps in silicon phononic crystal plates

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.

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Developing nanoacoustic biosensors for loblolly pinecell culter and mill

2007-03-13 , Hunt, William D.

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