Centrifugation of Microparticles Inside a Sessile Droplet on a Micromachined Silicon Chip Using Acoustic Tweezers

This paper reports the first demonstration of acoustic tweezers to manipulate microparticles in a sessile droplet over a functional surface-micromachined silicon chip fabricated with polysilicon micromechanical sensing structures. The proposed plug-and-play setup comprises two interchangeable parts: a detachable silicon micromachined sensor chip (acting as a superstrate) and a surface acoustic wave (SAW) device substrate. The SAW device provides the off-chip acoustic source from which Rayleigh waves couple into the functional silicon chip. We demonstrate concentration of initially randomly dispersed microparticles in a water droplet loaded on the functional silicon chip by means of acoustic streaming forces using a drive power of 1 W.