Modelling of a novel design of microfluidic based acoustic sensor

This paper reports the initial investigation on a novel acoustic sensor design based on micro fluidic technology. The report includes the proposed design structure and the simulation of key structure materials that affect the performance of such sensor. Simulation works included the analysis of acoustic response of the membrane and the damping effect when the cavity gap is filled with liquid or electrolyte material. For membrane analysis three different materials, silicon nitride (Si₃N₄), Teflon and Polydimethylsiloxane (PDMS) are simulated to obtain the most responsive material with respect to acoustic pressure signal. PDMS was found to be the most responsive material with the deflection sensitivity of 1.6 μm/Pa. Both Si₃N₄ and Teflon yielded a sensitivity of 0.034 μm/Pa and 0.67 μm/Pa respectively. In damping analysis, Propylene Carbonate electrolyte was used as a backing layer that filled the cavity gap. With the PDMS was selected as the membrane structure, harmonic analysis was performed to investigate the damping effect caused by electrolyte material on resonance frequency and deflection sensitivity. Result showed that with the proposed design structure and electrolyte backing layer, the harmonic frequency was shifted to a lower value with the maximum deflection was reduced by about 50%. The result also suggests the needs for selecting the right gap material for micro fluidic application that can compromise the damping and the response of the membrane.