Simple Recipe for Electroosmotic Mixing in Microchannels
from: Lab-on-a-Chip Technology (Vol. 1): Fabrication and Microfluidics (Edited by: Keith E. Herold and Avraham Rasooly). Caister Academic Press, U.K. (2009)
Efficient mixing is often a crucial step in Lab on a Chip (LOC) devices. Yet, it has been difficult to achieve as flows in such devices are typically laminar and thus one cannot count on turbulence as a mixing mechanism in these flows. While most solutions proposed so far require the alteration of the device geometry, or the addition of electrodes in the channel walls, in this chapter we concentrate on inducing mixing in electroosmotic flow simply by using the electrodes already in place for flow pumping, as previously proposed in earlier work. The microchannel consists of two inlets and one outlet in order to bring the two liquids together. The heart of the technique lies in the modification of the voltages applied to the inlet electrodes. We recall that good mixing is obtained when the electroosmotic flow at the two inlets is pulsed out of phase, the phase difference is 90 degrees rather than 180 degrees, and the pulse volume is comparable to the intersection volume. While the technique is not new, the goal of this chapter is to present the steps needed in the form of a ready-to-use recipe, as well as provide additional details read more ...