An Acoustic Vortex Particle Concentrator

Abstract

In this paper, we report on a novel 'particle capturing' MEMS device for microfluid sample collection. When the resonance modes of the center-anchored surface micromachined polysilicon disk actuator inside the fluid channel are excited, time averaged acoustic force generates pressure gradients along the disk periphery. These pressure gradients are used to obtain fluid vortices by optimum design of poly-disk substrate gap and channel height. The vortices trap particles traveling in the channel due to pressure driven flow. In many ways this vortex capture device is biomimetic -it is like the single-celled organism called Vorticella, which collects food by inducing local vortices [1]. This particle concentrator paradigm gives us the tight control of the particlc capture location so that wc can integrate optical or acoustic sensors to measure the change in captured particle density over time.