Determining biosensing modes in SH-SAW device using 3D finite element analysis

Jennifer Brookes,Rory Bufacchi,Jun Kondoh,Dorothy M Duffy,Rachel A Mckendry

doi:10.1016/j.snb.2016.03.103

Abstract

Surface acoustic wave (SAW) sensors are electromechanical devices that exploit the piezoelectric effect to induce elastic (acoustic) waves which are sensitive to small perturbations: for example specific binding and recognition of disease biomarkers. Shear horizontal surface acoustic waves (SH-SAWs) are particularly suited to biosample analysis as the wave is not completely radiated and lost into the liquid medium (e.g., blood, saliva) as is the case, for example, in a device implementing Rayleigh waves. Here, using 3D finite element analysis (FEA) the nature of waves launched on a particular quartz device is investigated with respect to the cut of the quartz, the addition of gold guiding layers, and the addition of other linear elastic materials of contrasting acoustic properties. It is demonstrated that 3D FEA analysis showing the device's frequency shift with added guiding layer height reveals a proportional relationship in agreement with the Sauerbrey equation from perturbation theory. It is directly shown, given certain device parameters and a gold guiding layer, that shear horizontally polarized waves are launched on the surface with a dominant mode frequency around 250MHz. This would be an appropriate biosensing mode in Point of Care (POC) testing for the particular properties of certain disease biomarkers delivered via a liquid medium.

Highlights

IntroductionSurface acoustic wave (SAW) sensors show significant promise for Point of Care sensors with the ability to detect ng-pg/ml biomarkers (e.g., virus, bacteria, hormone), within minutes in a handheld format [1], see Fig. 1
Surface acoustic wave (SAW) sensors show significant promise for Point of Care sensors with the ability to detect ng-pg/ml biomarkers, within minutes in a handheld format [1], see Fig. 1
When searching for a dominant Shear horizontal surface acoustic waves (SH-SAWs) mode in a particular cut we are searching for a dominant y component

Summary

Introduction

Surface acoustic wave (SAW) sensors show significant promise for Point of Care sensors with the ability to detect ng-pg/ml biomarkers (e.g., virus, bacteria, hormone), within minutes in a handheld format [1], see Fig. 1. Research conducted based on the Campbell and Jones method [2], has helped to significantly improve our understanding of the role of mass, viscosity, density, shear modulus, conductivity and permittivity changes that occur on a sensor surface and how these changes translate into the SAW response. This has been with particular onus on the lithium tantalate SAW, which is well characterized for sensor response [3,4]

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