AC Electro-Osmotic Flow

AC Electro-Osmotic Flow, Fig. 1 Equivalent RC circuit model for double-layer charging over a pair of electrodes. The inner edges of the electrodes encounter less bulk... 

AC Electro-Osmotic Flow, Fig. 2 The basic mechanism of AC electroosmosis electrochemical relaxation top) and induced-charge electroosmotic flow bottom) in response to a suddenly applied voltage across an electrode pair, (a) At first the electric field has no tangential component on the electrodes, since they are equipotential surfaces, and thus there is no electroosmotic flow, (b) Capacitive double-layer charging begins near the gap... 

AC Electro-Osmotic Flow, Fig. 3 Sketches of local broken symmetries in a periodic electrode array which lead to global time-averaged ACEO pumping ... 

AC Electro-Osmotic Flow, Fig. 5 Experimental data for ACEO pumping of KCl around a microfluidic loop, one-fifth covered by the asymmetric planar electrode array of Fig. 4a. (a) Contour plot of mean velocity versus AC frequency and RMS voltage at a bulk salt concentration of 0.1 mM (Reproduced from [3]), where electrode... 

AC Electro-Osmotic Flow, Fig. 6 (a) Comparison of ACEO pumping of water around a microfluidic loop by planar and (non-optimal) 3D electrode arrays with similar... 

AC Electro-Osmotic Flow, Fig. 7 (a) Collection of E. coli bacteria in tap water along the stagnation lines of ACEO flow on An microelectrodes at low frequency (100 Hz) and moderate voltage (1 V). (b) Preferential... 

AC Electro-Osmotic Flow - Electrical Double Layers... 

Electroosmotic flows in microchannels subjected to an axial variation of the zeta potential (see C AC electro-osmotic flow and Zeta-Potential ). 

AC Electro-osmotic Flow Electrokinetic How and Ion Transport in Nanochannels... 

AC Electro-Osmotic Flow Bead-Based Microfluidic Platforms... 

The possibility of nonlinear electroosmotic flow, varying as m oc E, seems to have been first described by Murtsovkin [1, 2], who showed that an alternating electric field can drive steady quadrupolar flow around a polarizable particle (Fig. la). This effect has recently been unified with other nonlinear electrokinetic phenomena in microfluidics [3], such as AC electro-osmotic flow (ACEO) at microelectrodes [4, 7, 8] (Fig. lb), DC electrokinetic jets at dielectric corners [5] (Fig. Ic), and nonlinear flows around metal posts [9] (Fig. Id-e). These are all cases of induced-charge electroosmosis (ICEO) - the nonlinear electroosmotic flow resulting firom the action of an electric field on its own induced diffuse charge near a polarizable surface. 

Detailed three-dimensional measurements of ICEO flows are now possible in microfluidic devices. Using particle-image velocimetry applied to thin optical slices, the ICEO flow field around a platinum cylinder has recently been reconstructed experimentally (Fig. 5b) and found to agree well with the theory, up to a scaling factor which could perhaps be attributable to compact-layer effects [6]. There has also been extensive experimental work on AC electro-osmotic flows in microfluidic devices, as discussed in a separate article. 

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