Publications

Shear horizontal surface acoustic wave microsensor for Class A viral and bacterial detection

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.