Experimental Demonstration of Localized Flow Control in a Microchannel Using Induced-Charge Electroosmosis

In this paper we investigate the use of induced charged electroosmosis (ICEO) as a means of providing localized flow control within bulk pressure-driven flow. Conductive posts are positioned in a microchannel in such a way that an AC electric field can be applied across them. This AC field induces an electric double layer (EDL), leading to ICEO flow around the conductive object. A pressure gradient is applied across the length of the channel to drive a background flow past the ICEO region. The combination of AC and pressure-driven flow fields is expected to create recirculation regions around the posts which could be useful for trapping particles or focusing the flow, e.g. for lab-on-a-chip applications. Numerical models of ICEO flow were developed and used to provide guidance for the design of microfluidic devices. These numerical models were also used to explore the number, position and shape of the conducting posts to create useful flow patterns. However, this paper focuses on the fabrication of and experiments within a prototypical microdevice. The device was fabricated from silicon dioxide and conducting gold pillars positioned in the glass channel. Experimental results obtained from this device have demonstrated localized ICEO-based flow control. Specifically, wake regions devoid of particles are created behind the posts.