Authors: K.S. Kim, M.-S. Chun, Y.T. Byun, D.H. Woo
Affilation: Korea Institute of Science and Technology (KIST), Korea
Pages: 281 - 284
Keywords: microfluidic chip, secondary flow, electrokinetics, hydrodynamic slip, particle streak velocimetry
The curved microchannel is frequently encountered in the lab-on-chips because it provides a convenient way for increasing channel length per unit area. The behavior of electrokinetic flow with curvature-induced secondary motion was explored based on the numerical framework with full Poisson-Boltzmann/Navier-Stokes and the micro-particle streak velocimetry. Two kinds of channels are explored with the glass channel and the glass and hydrophobic polydimethylsiloxane (PDMS) channel, covering thin to thick electric double layer problem. The micro-particle streak velocimetry is performed by using an inverted epi-fluorescence microscope with tracer particle, which provides experimental verifications. We first estimate the hydrodynamic slip length on flat PDMS channel, and then validate the simulation results with curved PDMS microchannel. A collection of streak images is processed by the MatLab algorithm that determines the local velocity in terms of a ratio of the real distance to the number of pixels. The hydrodynamic slip length at PDMS surfaces estimated as about 100 nm is employed in our simulations. The streamwise velocities are obtained from both simulations and experiments, showing a fair agreement. Therefore, our simulations exactly represent the curvature induced secondary flow and provide optimum selection in applications such as stronger secondary motion for mixing.