Cartier Charles A, Drews Aaron M, Bishop Kyle J M
Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
Lab Chip. 2014 Nov 7;14(21):4230-6. doi: 10.1039/c4lc00811a.
We present a simple and effective ratcheted microfluidic mixer that uses contact charge electrophoresis (CCEP) of a micron-scale particle to rapidly mix nonpolar liquids. CCEP combines contact charging and electrostatic actuation to drive the continuous oscillatory motion of a conductive particle between two electrodes subject to a constant (DC) voltage. We show how this oscillatory motion can be harnessed to mix laminar flows by using dielectric "ramps" to direct the particle along non-reciprocal, orbital trajectories, which repeatedly stretch and fold the flowing streams. Complete mixing requires that the speed of the particle is much larger than the fluid velocity such that the particle completes many orbits as the fluid flows through the mixing region. The extent of mixing also depends strongly on the size of the particle and the shape of its trajectory; effective mixers relied on larger particles (comparable to the size of the channel) moving along non-reciprocal orbits. While the present study uses mineral oil as a convenient nonpolar liquid, we also screened fifteen common solvents to determine the applicability of CCEP for mixing other organic liquids. Owing to its simple design and low power requirements (~100 nW), the orbital mixer presented here demonstrates the utility and versatility of ratcheted electrostatic actuation in powering active microfluidic operations.
我们展示了一种简单有效的棘轮式微流体混合器，它利用微米级粒子的接触电荷电泳（CCEP）来快速混合非极性液体。CCEP结合了接触充电和静电驱动，以驱动导电粒子在施加恒定（直流）电压的两个电极之间持续振荡运动。我们展示了如何通过使用介电“斜坡”引导粒子沿着非往复的轨道轨迹运动，从而利用这种振荡运动来混合层流，该轨迹会反复拉伸和折叠流动的液流。完全混合要求粒子的速度远大于流体速度，以便在流体流过混合区域时粒子能完成许多轨道运动。混合程度还强烈依赖于粒子的大小及其轨迹的形状；有效的混合器依赖于较大的粒子（与通道尺寸相当）沿着非往复轨道运动。虽然本研究使用矿物油作为方便的非极性液体，但我们还筛选了15种常见溶剂，以确定CCEP用于混合其他有机液体的适用性。由于其设计简单且功率要求低（约100 nW），这里展示的轨道混合器证明了棘轮式静电驱动在为有源微流体操作提供动力方面的实用性和多功能性。
