Surface-acoustic-wave-driven acoustic tweezing in a silicon microfluidic chip.

Abstract

Surface acoustic wave (SAW)-driven acoustic tweezers have been widely explored for high-resolution ultrasonic sample manipulation. Among these, hybrid acoustic tweezers comprising a reusable SAW chip and a disposable glass or silicon microfluidic chip as a superstrate offer advantages such as reduced experimental costs and minimized cross-contamination between experiments. However, maximizing the acoustic pressure within the microfluidic channel requires efficient acoustic coupling between the SAW and the microfluidic structure. In this work, we investigate the frequency-dependent characteristics of acoustophoresis of 50 MHz hybrid acoustic tweezers composed of a SAW chip and a silicon microfluidic chip. We elucidate the role of the bulk acoustic wave resonances in the silicon substrate in facilitating the formation of acoustic standing waves within the microfluidic channel. Experimental results demonstrate the generation of acoustic pressures up to 2.1 ± 0.5 MPa inside the channel. The fabricated device was successfully used to probe the transient viscoelastic deformation of HEK293T cells and to trap motile cells Tetrahymena. These findings highlight the potential of the propose hybrid acoustic tweezers as a platform for acoutsto-mechanical testing of soft matter and biological samples.