Publications

Nordquist, Christopher N.; Olsson, Roy H.; Branch, Darren W.; Dyck, Christopher D.; Pluym, Tammy P.

Abstract not provided.

Branch, Darren W.; Clews, Peggy J.; Olsson, Roy H.

Abstract not provided.

Branch, Darren W.; Burton, Roger B.; Cular, Stefan C.

Abstract not provided.

Nordquist, Christopher N.; Olsson, Roy H.; Branch, Darren W.; Pluym, Tammy P.; Yarberry, Victor R.; Dyck, Christopher D.

Abstract not provided.

Nordquist, Christopher N.; Olsson, Roy H.; Branch, Darren W.; Pluym, Tammy P.; Yarberry, Victor R.

Abstract not provided.

IEEE MTT-S International Microwave Symposium Digest

Crespin, Emily R.; Olsson, Roy H.; Wojciechowski, Kenneth W.; Branch, Darren W.; Clews, Peggy J.; Hurley, Richard B.; Gutierrez, J.

Fully integrated switchable filter have been successfully demonstrated using a ra CMOS SOI process in conjunction with an a (AlN) microresonator process. Single pole-mul were developed in the CMOS SOI process th multi-project wafer runs while the filters were aluminum nitride based microresonators. Each concurrent design cycles and was demonstrated to integration. After design improvements to bo full monolithic integration was implem microresonator filters with the CMOS switc compatibility of the two technologies. A four ch switchable bank of 7MHz bandwidth filters demonstrated exhibiting approximately 8 dB of 60dB of stop band rejection. © 2012 IEEE.

Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)

Ziaei-Moayyed, M.; Habermehl, Scott D.; Branch, Darren W.; Clews, Peggy J.; Olsson, Roy H.

This work demonstrates a lateral overtone bulk acoustic resonator (LOBAR), which consists of an aluminum nitride (AlN) transducer coupled to a suspended thin silicon carbide (SiC) film fabricated using standard CMOS-compatible processes. The LOBAR design allows for high transduction efficiency and quality factors, by decoupling the transduction and energy storage schemes in the resonator. The frequency and bandwidth of the resonator were lithographically defined and controlled. A LOBAR operating at 2.93GHz with a Q greater than 100,000 in air was fabricated and characterized, having the highest reported f×Q product of any acoustic resonator to date.

Branch, Darren W.

Abstract not provided.

Ziaei-Moayyed, M.; Olsson, Roy H.; Habermehl, Scott D.; Branch, Darren W.; Clews, Peggy J.

Abstract not provided.

Olsson, Roy H.; Wojciechowski, Kenneth W.; Branch, Darren W.

Recently reported narrow bandwidth, <;2%, aluminum nitride microresonator filters in the 100-500 MHz range offer lower insertion loss, 100x smaller size, and elimination of large external matching networks, when compared to similar surface acoustic wave filters. While the initial results are promising, many microresonators exhibit spurious responses both close and far from the pass band which degrade the out of band rejection and prevent the synthesis of useful filters. This paper identifies the origins of several unwanted modes in overtone width extensional aluminum nitride microresonators and presents techniques for mitigating the spurious responses.

Forsythe, James C.; Branch, Darren W.; McKenzie, Amber T.

While individual neurons function at relatively low firing rates, naturally-occurring nervous systems not only surpass manmade systems in computing power, but accomplish this feat using relatively little energy. It is asserted that the next major breakthrough in computing power will be achieved through application of neuromorphic approaches that mimic the mechanisms by which neural systems integrate and store massive quantities of data for real-time decision making. The proposed LDRD provides a conceptual foundation for SNL to make unique advances toward exascale computing. First, a team consisting of experts from the HPC, MESA, cognitive and biological sciences and nanotechnology domains will be coordinated to conduct an exercise with the outcome being a concept for applying neuromorphic computing to achieve exascale computing. It is anticipated that this concept will involve innovative extension and integration of SNL capabilities in MicroFab, material sciences, high-performance computing, and modeling and simulation of neural processes/systems.

Progress in Biomedical Optics and Imaging - Proceedings of SPIE

Cooley, Erika J.; Kruizinga, Pieter; Branch, Darren W.; Emelianov, Stanislav

Elucidating the role of calcium fluctuations at the cellular level is essential to gain insight into more complex signaling and metabolic activity within tissues. Recent developments in optical monitoring of calcium transients suggest that cells integrate and transmit information through large networks. Thus, monitoring calcium transients in these populations is important for identifying normal and pathological states of a variety of systems. Though optical techniques can be used to image calcium fluxes using fluorescent probes, depth penetration limits the information that can be acquired from tissues in vivo. Alternatively, the calcium-sensitive dye arsenazo III is useful for optical techniques that rely on absorption of light rather than fluorescence for image contrast. We report on the use of arsenazo III for detection of calcium using photoacoustics, a deeply penetrating imaging technique in which an ultrasound signal is generated following localized absorption of light. The absorbance properties of the dye in the presence of calcium were measured directly using UV-Vis spectrophotometry. For photoacoustic studies, a phantom was constructed to monitor the change in absorbance of 25 μM arsenazo III at 680 nm in the presence of calcium. Subsequent results demonstrated a linear increase in photoacoustic signal as calcium in the range of 1 - 20 μM complexed with the dye, followed by saturation of the signal as increasing amounts of calcium were added. For delivery of the dye to tissue preparations, a liposomal carrier was fabricated and characterized. This work demonstrates the feasibility of using arsenazo III for photoacoustic monitoring of calcium transients in vivo. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Branch, Darren W.; Edwards, Thayne L.; Huber, Dale L.; Brozik, Susan M.; Brozik, Susan M.

The rapid autonomous detection of pathogenic microorganisms and bioagents by field deployable platforms is critical to human health and safety. To achieve a high level of sensitivity for fluidic detection applications, we have developed a 330 MHz Love wave acoustic biosensor on 36{sup o} YX Lithium Tantalate (LTO). Each die has four delay-line detection channels, permitting simultaneous measurement of multiple analytes or for parallel detection of single analyte containing samples. Crucial to our biosensor was the development of a transducer that excites the shear horizontal (SH) mode, through optimization of the transducer, minimizing propagation losses and reducing undesirable modes. Detection was achieved by comparing the reference phase of an input signal to the phase shift from the biosensor using an integrated electronic multi-readout system connected to a laptop computer or PDA. The Love wave acoustic arrays were centered at 330 MHz, shifting to 325-328 MHz after application of the silicon dioxide waveguides. The insertion loss was -6 dB with an out-of-band rejection of 35 dB. The amplitude and phase ripple were 2.5 dB p-p and 2-3{sup o} p-p, respectively. Time-domain gating confirmed propagation of the SH mode while showing suppression of the triple transit. Antigen capture and mass detection experiments demonstrate a sensitivity of 7.19 {+-} 0.74{sup o} mm{sup 2}/ng with a detection limit of 6.7 {+-} 0.40 pg/mm{sup 2} for each channel.

Ravula, Surendra K.; Branch, Darren W.; Westlake, Karl W.; Brener, Igal B.

Abstract not provided.

Branch, Darren W.

Recently, the generalized method for calculation of the 16-element Green's function for analysis of surface acoustic waves has proven crucial to develop more sophisticated transducers. The generalized Green's function provides a precise relationship between the acoustic stresses and electric displacement on the three mechanical displacements and electric potential. This generalized method is able to account for mass loading effects which is absent in the effective permittivity approach. However, the calculation is numerically intensive and may lead to numerical instabilities when solving for both the eigenvalues and eigenvectors simultaneously. In this work, the general eigenvalue problem was modified to eliminate the numerical instabilities in the solving procedure. An algorithm is also presented to select the proper eigenvalues rapidly to facilitate analysis for all types of acoustic propagation. The 4 x 4 Green's functions and effective permittivities were calculated for materials supporting Rayleigh, leaky, and leaky longitudinal waves as demonstration of the method.

Ravula, Surendra K.; Branch, Darren W.; Westlake, Karl W.; Brener, Igal B.

Abstract not provided.

2007 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2007, Technical Proceedings

Ravula, Surendra K.; Branch, Darren W.; Sigman, Jennifer; Clem, Paul G.; Kaduchak, Gregory; Brener, Igal B.

Flow cytometry is an indispensable tool in clinical diagnostics, for example in cancer, AIDS, infectious disease outbreaks, microbiology, and others. The cost and size of existing cytometers precludes their entry into field clinics, water monitoring, agriculture/veterinary diagnostics, and rapidly deployable biothreat detection. Much of the cost and footprint of conventional cytometers is dictated by the high speed achieved by cells or beads in a hydrodynamically focused stream. This constraint is removed by using ultrasonic focusing in a parallel microfluidic architecture. In this paper, we describe our progress towards a microfabricated flow cytometer that uses bulk and microfabricated planar piezoelectric transducers in glass microfluidic channels. In addition to experimental data, initial modeling data to predict the performance of our transducers are discussed.

Branch, Darren W.; Sigman, Jennifer K.; Clem, Paul G.; Brener, Igal B.

Abstract not provided.

Branch, Darren W.; Sigman, Jennifer K.; Clem, Paul G.; James, Conrad D.; Brener, Igal B.

Abstract not provided.

Proposed for publication in Journal of Microelectro Mechanical Systems.

Branch, Darren W.; Meyer, Grant D.; Bourdon, Christopher B.

Abstract not provided.

Branch, Darren W.; Brozik, Susan M.

Crucial to low-level detection of biowarfare agents in aqueous environments is the mass sensitivity optimization of Love-wave acoustic sensors. The present work is an experimental study of 36{sup o} YX cut LiTaO{sub 3} based Love-wave devices for detection of pathogenic spores in aqueous conditions. Given that the detection limit (DL) of Love-wave based sensors is a strong function of the overlying waveguide, two waveguide materials have been investigated, which are polyimide and polystyrene. To determine the mass sensitivity of Love-wave sensor, bovine serum albumin (BSA) protein was injected into the Love-wave test cell while recording magnitude and phase shift across each sensor. Polyimide had the lowest mass detection limit with an estimated value of 1-2 ng/cm{sup 2}, as compared to polystyrene where DL = 2.0 ng/cm{sup 2}. Suitable chemistries were used to orient antibodies on the Love-wave sensor using adsorbed protein G. The thickness of each biofilm was measured using ellipsometry from which the surface concentrations were calculated. The monoclonal antibody BD8 with a high degree of selectivity for anthrax spores was used to capture the non-pathogenic simulant B. thuringiensis B8 spores. Bacillus Subtilis spores were used as a negative control to determine whether significant non-specific binding would occur. Spore aliquots were prepared using an optical counting method, which permitted removal of background particles for consistent sample preparation. This work demonstrates that Love-wave devices can be used to detect B. anthracis simulant below reported infectious levels.

Branch, Darren W.; Brozik, Susan M.

Impedance based, planar chemical microsensors are the easiest sensors to integrate with electronics. The goal of this work is a several order of magnitude increase in the sensitivity of this sensor type. The basic idea is to mimic biological chemical sensors that rely on changes in ion transport across very thin organic membranes (supported Bilayer Membranes: sBLMs) for the sensing. To improve the durability of bilayers we show how they can be supported on planar metal electrodes. The large increase in sensitivity over polyelectrolytes will come from molecular recognition elements like antibodies that bind the analyte molecule. The molecular recognition sites can be tied to the lipid bilayer capacitor membrane and a number of mechanisms can be used to modulate the impedance of the lipid bilayers. These include coupled ion channels, pore modification and double layer capacitance modification by the analyte molecule. The planar geometry of our electrodes allows us to create arrays of sensors on the same chip, which we are calling the ''Lipid Chip''.