Lamb wave coupled resonance for SAW acoustofluidics

Abstract

A surface acoustic wave (SAW)-driven acoustofluidic chip of high energy efficiency is proposed through model analysis. The chip supports propagation of Lamb waves in the lid above a fluid-filled channel. Eigenmode resonance in the on-chip channel is then achieved by coupling both the SAWs and the Lamb waves into the fluid. Specifically, the phase velocity of the Lamb mode equals the SAW speed along the substrate, and the leaky angles of both match that required by the expected channel mode. Compared to resonant SAW acoustofluidics (RSA), Lamb wave coupled RSA can make the energy tripled or higher. Meanwhile, the obtained resonance frequency deviates very slightly from the designed value, limiting the error to 0.5, while RSA chips exhibit errors as high as 5.7. The proposed design protocol can help to promote the energy efficiencies and contain the in-channel temperature rise and resonance frequency deviations in SAW acoustofluidics.