Department of Mechanical Engineering, Clemson University, Clemson, South Carolina, USA.
Electrophoresis. 2022 Jan;43(1-2):167-189. doi: 10.1002/elps.202100090. Epub 2021 May 24.
Insulator-based dielectrophoresis (iDEP) has been increasingly used for particle manipulation in various microfluidic applications. It exploits insulating structures to constrict and/or curve electric field lines to generate field gradients for particle dielectrophoresis. However, the presence of these insulators, especially those with sharp edges, causes two nonlinear electrokinetic flows, which, if sufficiently strong, may disturb the otherwise linear electrokinetic motion of particles and affect the iDEP performance. One is induced charge electroosmotic (ICEO) flow because of the polarization of the insulators, and the other is electrothermal flow because of the amplified Joule heating in the fluid around the insulators. Both flows vary nonlinearly with the applied electric field (either DC or AC) and exhibit in the form of fluid vortices, which have been utilized to promote some applications while being suppressed in others. The effectiveness of iDEP benefits from a comprehensive understanding of the nonlinear electrokinetic flows, which is complicated by the involvement of the entire iDEP device into electric polarization and thermal diffusion. This article is aimed to review the works on both the fundamentals and applications of ICEO and electrothermal flows in iDEP microdevices. A personal perspective of some future research directions in the field is also given.
基于绝缘子的介电泳（iDEP）已越来越多地用于各种微流控应用中的粒子操纵。它利用绝缘结构来压缩和/或弯曲电场线，以产生用于粒子介电泳的场梯度。然而，这些绝缘子的存在，特别是那些具有锐利边缘的绝缘子，会引起两种非线性电动流动，如果足够强，可能会干扰粒子的线性电动运动，并影响 iDEP 的性能。一种是由于绝缘子的极化引起的感应电荷电渗流（ICEO）流动，另一种是由于绝缘子周围流体中放大的焦耳加热引起的电热流动。这两种流动都随施加的电场（直流或交流）呈非线性变化，并以流体涡旋的形式表现出来，这在促进某些应用的同时，在其他应用中也被抑制。对 iDEP 的深入了解有助于提高其效果，这涉及到整个 iDEP 设备的电极化和热扩散。本文旨在回顾 iDEP 微器件中 ICEO 和电热流动的基础和应用方面的工作。还给出了该领域中一些未来研究方向的个人观点。
