서강대학교

초록/요약

We report an active micromixer utilizing vortex generation due to non-equilibrium electrokinetics near micro/nanochannel interfaces. Its design is relatively simple, consisting of a U-shaped microchannel and a set of nanochannels. We fabricated the micromixer just using a two-step reactive ion etching process. We observed strong vortex generation in fluorescent microscopy experiments. The mixing performance was evident in a combined pressure-driven and electroosmotic flows, compared to the case with a pure pressure-driven flow. We characterized the micromixer for several conditions: different applied voltages, ion concentrations, flow rates, and nanochannel widths. The experimental results show that the mixing performance is better with a higher applied voltage, a lower ion concentration, and a wider nanochannel width. We quantified the mixing characteristics in terms of mixing time. The lowest mixing time was two milliseconds with the voltage of 230 V and potassium chloride solutions of 0.1 mM. We characterized the active microfluidic mixer with different charged marker such as Rhodamine 6G, Fluorescein and micro particle. Concentration polarization around micro/nanochannel interfaces is also visualized on various parameters. By using MATLAB, we analyse vortex generation with image processing method and fast fourier transform (FFT) is performed. We expect that this research is beneficial in several applications to microfluidics and analytical chemistry.