Simultaneous microfluidic pumping and mixing using an array of asymmetric 3D ring electrode pairs in a cylindrical microchannel by the AC electroosmosis effect

Abstract

Abstract The present studies of AC electroosmosis (ACEO) micropumps for simultaneous pumping and mixing are mainly involved in the designs of the planar electrode pairs in a rectangular microchannel, such as the diagonal/herringbone shape of electrodes on top and bottom of the substrates. The two mixing samples usually flow into the left and right half of the inlet, respectively. However, the flow rate is limited because of the less electrodes on the walls, and the mixing is only appropriate for the channel of small diameters owing to the vortices appearing near the surface of electrodes. To solve the problem, we proposed an ACEO micropump with an array of asymmetric ring electrode pairs in a cylindrical microfluidic channel, and established a three-dimensional (3D) theoretical model by the standard Poisson–Boltzmann (PB) theory and convection–diffusion equation. In this paper, the two mixing samples flow into the inner and outer circular pipe of the inlet, respectively. Thus, the samples can be exchanged from the outer pipe area to the inner pipe area, so that it can strengthen the mixing by the vortices around the ring electrode surfaces in the microchannel. The microfluidic velocity field, vorticity field and concentration field are investigated in detail to explain the mechanism of pumping and mixing. To further improve the mixing performance, we designed and researched the combination sequences PnMm of ring electrode pairs based on the pumping mode of “forward driving of electrode pair” and the mixing mode of “reversal driving of electrode pair”. The simulation results show that the ring ACEO micropump with the inner and outer pipe inlet can rapidly pump the microflows and efficiently mix the samples simultaneously compared with the planar multifunctional ACEO micropumps. The numerical simulation of the ring ACEO micropump in this paper is of significant importance for the development of multifunctional microfluidic devices in biochemical field, and feasible fabrication techniques should be experimentally investigated in future studies.