AN INVESTIGATION OF THE STARTUP TRANSIENT ELECTROKINETIC FLOW IN RECTANGULAR CHANNELS OF ARBITRARY DIMENSIONS, ZETA POTENTIAL DISTRIBUTION, AND TIME VARYING PRESSURE GRADIENT ABSTRACT OF THE THESIS An Investigation of the Startup Transient Electrokinetic Flow in Rectangular Channels of Arbitrary Dimensions, Zeta Potential Distribution, and Time Varying Pressure Gradient

Andrew Miller, Francisco Javier Diez-Garias, Andrew Miller, Francisco Javier Diez-Garias
unpublished
The solution to the startup transient electroosmotic flow in an arbitrary rectangular micro-channel is derived analytically and validated experimentally. This full two dimensional transient solution describes the evolution of the flow through five distinct time periods until a final steady state condition is reached. The derived analytical velocity solution is validated experimentally for channels of different sizes and aspect ratios under time-varying pressure gradients. The experiments used a
more » ... experiments used a Time Resolved Micro Particle Image Velocimetry technique (TR-µPIV) to visualize and measure the startup transient velocity profiles. The results of this work captured the effects of time-varying pressure gradients across the microchannels and compared them to the results derived in the analytical solutions. This was accomplished by using small reservoirs at both ends of the channel, which allowed a time-varying pressure gradient to develop with a time scale on the order of the transient electroosmotic flow. Results showed that under these common conditions, the pressure build up between the reservoirs had a significant impact both on the transient startup of the electroosmotic flow and on the later temporal development of the velocity field in the channel. Finally, analytical solutions are provided to portray the fluid velocity development in microchannels with non-uniform zeta potentials. Experimental results validate the posed solution by visualizing the transient fluid velocity in microchannels fabricated with three PDMS and one quartz glass wall. These results show that the temporal development of the microchannel's velocity field is independent of the zeta potential distribution within the device. iii
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