(481e) Improved Love-Wave Biosensor Through Advanced Interdigitated Transducer Design

We present an experimental and theoretical study of surface acoustic wave (SAW) interdigitated transducer (IDT) designs used to generate Love-waves for biosensor applications. Three IDT designs were created on 36°YX LiTaO₃ selected for its high electro-mechanical coupling and shear horizontal (SH) wave generation. These designs were selected based on a literature review of IDT designs of improved electrical characteristics within communication applications. It was shown that the sensitivity of the SAW biosensor can be significantly increased through the addition of a waveguide to generate Love-mode waves instead of SH. For the Love-mode generation to occur: 1) the waveguide material should have a lower acoustic velocity than the substrate, and 2) the waveguide material should be of lower density than the substrate. In previous studies, many materials have been shown to be efficient waveguides. Some researchers have even developed multilayer schemes to further enhance the sensors sensitivity. The most used materials are silicon dioxide, poly(methyl methacrylate), polyimide, and polystyrene. In this study, we have utilized polystyrene as the waveguide material to allow for comparison with previous studies. Parameters studied in this work were the attenuation and velocity changes of the acoustic wave due to the addition of varying thicknesses of polystyrene. Experimental data was collected using a network analyzer with time domain measurement capabilities, and theoretical results were calculated using a 3D finite element model (FEM). Two kinds of FEM analysis are carried out along each of the three delay lines: (1) An impulse input of 100 V over 1 ns is applied to study the frequency response of the device for the various IDT designs and (2) AC analysis with a 5 V peak-peak input and approx. 100 MHz frequency to study the wave propagation characteristics. Our results indicate the significant differences between IDT designs for sensor applications.