Micro--PIV Measurements and Numerical Simulations of Induced Charge Electro-Osmosis Around a Conducting Metal Rod

he induced charge electro-osmotic (ICEO) flow around a conducting metal rod positioned in the center of a microchannel was analyzed through physical experimentation and numerical simulation. The experimental set up consisted of a straight microchannel connecting two fluid reservoirs with a square wave AC electric field applied across the microchannel. The electric field for the experimental tests ranged from 100 V /cm to 200 V/cm at frequencies from 500 Hz to 1.5 kHz. The numerical simulations used a similar geometric setup but were exposed to both a direct current (DC) and alternating current (AC) applied electric field. The electric field strength for the DC simulations ranged from 1 V/cm to 5 V/cm and for the AC simulations was similar to the experimental test conditions. Quadrupolar ICEO flow was observed around the conducting rod by utilizing a microparticle image velocimetry technique. This result qualitatively agreed with the theoretical prediction made by Squires and Bazant (2004) and my own numerical simulations completed with the commercially available finite element package, COMSOL Multi physics 3.Sa. The flow velocity was found to be proportional to the square of the applied electric field in both the experimental and numerical results, although the magnitudes between the experimental and numerical velocities varied by multiple orders of magnitude. In the experimental results the velocity increased with increasing distance from the rod surface, reached a maximum, and then decreased to zero. This result only qualitatively matched the numerical results at a distance greater than 0.17 mm away from the rod surface. Possible reasons for this discrepancy are also discussed.