Inducing AC-electroosmotic flow using electric field manipulation with insulators

Abstract

We demonstrate a new method to induce vortices with AC-EOF by shaping insulator materials near parallel electrodes, giving control of vortex organization. Interestingly, non-orthogonality of insulator walls is a requirement to induce AC-EOF.

C-Term Reduction in 3 μm Open-Tubular High-Aspect-Ratio Channels in AC-EOF Vortex Chromatography Operation

“…When the silicon above the 1 μm thick insulating oxide layer (Figure ) becomes negatively charged during the first part of the cycle, positive counterions are capacitively attracted in the solution adjacent to the 13 nm thick thermal oxide and will move upward (see Figure c for the resulting flow profile) due to the surface-parallel component of the electrical field. Simultaneously, the negative counterions at the bottom portion will be dragged downward. ,, As this occurs both at the left and at the right channel wall, it results in 4 vortices (Figure c). When the applied voltage is increased from 0 to 6 V, a gradual decrease in (C-term contribution of) the HETP value can be noticed in Figure d, visible from the slope of the linear part of the curve at high velocities.…”

“…In this simulation, the electrical model and fluid flow model are decoupled. The parameters used in this simulation are described elsewhere …”

“…Figure C displays a typical flow organization of the simulated flow inside the channel for a 2 V pp (peak-to-peak) applied voltage at 10 kHz. The simulation procedure and corresponding experimentally observed flow profiles in these types of devices are described elsewhere …”

“…The parameters used in this simulation are described elsewhere. 15 Chemicals. As a fluorescent dye, FITC−dextran (20 kDa, Sigma-Aldrich) was dissolved in H 2 O in a concentration of 50 μM.…”

50-Fold Reduction of Separation Time in Open-Channel Hydrodynamic Chromatography via Lateral Vortices

“…The idea that the fundamental mechanism reducing axial dispersion in packed columns is the enhancement of radial mixing raises the question as to whether other approaches, alternative to using solid obstacles, can be pursued to obtain the same effect. As a matter of fact, there is a consistent body of works in the literature (see, e.g., refs − and references cited therein) investigating the potential of electroosmotically induced transverse flow in enhancing transversal mixing of adsorbing and nonadsorbing solutes, which can be regarded as point tracers. However, to the best of our knowledge, no previous study focused on the impact of transversal flow on axial dispersion of finite-sized particles.…”