IEEE Trans Biomed Eng. 2019 Feb;66(2):453-463. doi: 10.1109/TBME.2018.2849004. Epub 2018 Jun 19.
A particle-fluid flow under alternating current (ac) electrokinetics was numerically simulated to investigate the three-dimensional (3-D) particle motion in a complex electric field of a high conductivity medium generated by an electrode-multilayered microfluidic device. The simulation model coupling thermal-fluid-electrical and dispersed particle problems incorporates three ac electrokinetics (ACEK) phenomena, namely, the ac electrothermal effect (ACET), thermal buoyancy (TB), and dielectrophoresis (DEP). The electrode-multilayered microfluidic device was fabricated with 40 electrodes exposed at the flow channel sidewalls in five cross sections. The governing equations of the simulation model are solved by the Eulerian-Lagrangian method with finite volume discretization. Fluid flow simulations in three cases with or without consideration of ACET and TB are performed to clarify the contributions of these phenomena. The fluid flow is found to be composed of short-range vortices due to ACET and long-range circulation due to TB based on the features of the electrode-multilayered microfluidic device. The 3-D particle trajectory influenced by the fluid flow is compared with four values of the real part of the Clausius-Mossotti (CM) factor to evaluate the DEP phenomenon. The simulation model is validated by experiments using a cell suspension. The pattern of cell trajectories in the upper part of the flow channel measured by particle tracking velocimetry agrees with the simulated pattern. By comparison of the simulation and experiment, it is found that the cells moving straight away from the electrode on the focal plane are decelerated within the region of 60 μm from the electrode by positive-DEP with [Formula: see text]. Furthermore, the 3-D DEP-effective region and the ACET and TB dominant regions for the cells are predicted by evaluating the particle-fluid relative velocity due to DEP force with [Formula: see text]. Consequently, the flow mechanism and dominant region of each ACEK phenomenon in the device are clarified from the 3-D simulation validated by the experiments.
交流电（ac）电动动力学下的颗粒流进行数值模拟，以研究在高电导率介质中由多层微流控装置电极产生的复杂电场中的三维（3-D）颗粒运动。模拟模型耦合热-流-电和分散颗粒问题，包含三种交流电电动动力学（ACEK）现象，即交流电电热效应（ACET）、热浮力（TB）和介电泳（DEP）。多层微流控装置由 40 个电极组成，在五个横截面上暴露在流道侧壁上。模拟模型的控制方程通过有限体积离散化的欧拉-拉格朗日方法求解。在不考虑 ACET 和 TB 的情况下进行了三种情况下的流体流动模拟，以澄清这些现象的贡献。基于多层微流控装置的特点，发现流体流动由 ACET 产生的短程涡流和 TB 产生的长程循环组成。受流体流动影响的 3-D 颗粒轨迹与 Clausius-Mossotti（CM）因子实部的四个值进行比较，以评估 DEP 现象。通过使用细胞悬浮液的实验对模拟模型进行验证。使用粒子跟踪测速法测量的通道上部细胞轨迹模式与模拟模式一致。通过模拟与实验的比较，发现位于焦平面上远离电极的细胞在正 DEP 作用下，在距离电极 60μm 的区域内速度降低[Formula: see text]。此外，通过评估由于 DEP 力而产生的颗粒-流体相对速度，预测了细胞的 3-D DEP 有效区域和 ACET 和 TB 主导区域[Formula: see text]。因此，从实验验证的 3-D 模拟中阐明了装置中每个 ACEK 现象的流动机制和主导区域。
