Numerical study of the coupling layer between transducer and chip in acoustofluidic devices

TL;DR

This study uses numerical simulations to analyze how different coupling layers affect acoustic resonances in ultrasound acoustofluidic devices, providing insights for optimizing device design.

Contribution

It introduces a phase-based criterion to predict resonance behavior with various coupling materials and thicknesses, aiding in device optimization.

Findings

Coupling layer thickness and material influence resonance attenuation or sustenance.

A simple phase criterion predicts resonance behavior with different coupling layers.

Design control of coupling layers can optimize acoustofluidic device performance.

Abstract

We study by numerical simulation in two and three dimensions the coupling layer between the transducer and the microfluidic chip in ultrasound acoustofluidic devices. The model includes the transducer with electrodes, the microfluidic chip with a liquid-filled microchannel, and the coupling layer between the transducer and the chip. We consider two commonly used coupling materials, solid epoxy glue and viscous glycerol, as well as two commonly used device types, glass capillary tubes and silicon-glass chips. We study how acoustic resonances in ideal devices without a coupling layer is either sustained or attenuated as a coupling layer of increasing thickness is inserted. We establish a simple criterion based on the phase of the acoustic wave for whether a given zero-layer resonance is sustained or attenuated by the addition of a coupling layer. Finally, we show that by controlling the thickness and the material, the coupling layer can be used as a design component for optimal and robust acoustofluidic resonances.