Experimental validation of a novel particle separation mechanism using AC electroosmosis

The goal of this paper is to validate experimentally the ability to separate or upconcentrate micro particles inside micro channels using alternating current electro osmosis (ACEO). A novel device has been made containing a microchannel with interdigitated coplanar electrodes on the bottom. These electrodes make an angle with the side walls of the micro channel. An axial flow can be prescribed by an external syringe pump. As a first step, a situation is studied without any axial flow. Upon application of an AC electric field, circular flow patterns arise above the electrodes. Suspended micro particles in the liquid get confined in these vortices, probably due to a Saffman lift force. Micro-particle image velocimetry (micro-PIV) experiments have been performed. The results show a qualitative agreement with numerical simulations. In a second step axial flow is prescribed. In this situation the particles are forced to move along the length of the electrodes towards one side of the micro channel. The effectivity of this separation/upconcentration mechanism is studied by analyzing recorded images of the micro channel for different axial flow rates. Results show that the effectivity decreases with increasing flow rate.