Authors: J-K Chen and R-J Yang
Affilation: National Cheng Kung University, Taiwan
Pages: 340 - 343
Keywords: electroosmotic flow, micromxing, nonlinear electrokinetics
Electroosmotic flow (EOF) is a fundamental electrokinetic phenomenon which finds extensive use in wide varieties of practical biochip applications and analyses. Generally, the dielectric materials (PDMS, glass, etc.) used to construct microchips have low dielectric permittivities ( ) with values between 3 and 4. When a sharp corner presents in a channel, electric field penetration occurs across the sharp edge. Under the electric field penetration, vortices are formed near the sharp corner due to an established non-uniform charge concentration distribution and an induced non-uniform zeta potential distribution around the sharp corner. Such nonlinear electrokinetic phenomena were found by Takhistov et al. and Thamida et al. In this work, we use this nonlinear electrokinetic vortex to function as a mixer. PDMS is adopted as the substrate of the microchannel (Fig. 1). Micro-particles are used as tracers to aid the flow visualization. A nozzle structure is formed in the region of symmetric corners (Fig. 2). The fluid is sped up due to the nozzle structure. The contact area between two different sample fluids is increased and the mixing efficiency is enhanced due to the nonlinear electrokinetic vortices (Fig. 3).