Zhang Sheng-Jie, Yang Zong-Rui, Kuo Ju-Nan
Department of Automation Engineering, National Formosa University, No. 64, Wenhua Rd., Huwei, Yunlin 632, Taiwan.
Micromachines (Basel). 2022 Dec 17;13(12):2245. doi: 10.3390/mi13122245.
The rapid electrokinetic patterning (REP) technique has been demonstrated to enable dynamic particle manipulation in biomedical applications. Previous studies on REP have generally considered particles with a size less than 5 μm. In this study, a REP platform was used to manipulate polystyrene particles with a size of 3~11 μm in a microfluidic channel sandwiched between two ITO conductive glass plates. The effects of the synergy force produced by the REP electrothermal vortex on the particle motion were investigated numerically for fixed values of the laser power, AC driving voltage, and AC driving frequency, respectively. The simulation results showed that the particles were subject to a competition effect between the drag force produced by the toroidal vortex, which prompted the particles to recirculate in the bulk flow adjacent to the laser illumination spot on the lower electrode, and the trapping force produced by the particle and electrode interactions, which prompted the particles to aggregate in clusters on the surface of the illuminated spot. The experimental results showed that as the laser power increased, the toroidal flow range over which the particles circulated in the bulk flow increased, while the cluster range over which the particles were trapped on the electrode surface reduced. The results additionally showed that the particle velocity increased with an increasing laser power, particularly for particles with a smaller size. The excitation frequency at which the particles were trapped on the illuminated hot-spot reduced as the particle size increased. The force and velocity of polystyrene particles by the REP toroidal vortex has implications for further investigating the motion behavior at the biological cell level.
快速电动图案化（REP）技术已被证明能够在生物医学应用中实现动态粒子操纵。先前关于REP的研究通常考虑尺寸小于5μm的粒子。在本研究中，一个REP平台被用于在夹在两块ITO导电玻璃板之间的微流体通道中操纵尺寸为3至11μm的聚苯乙烯粒子。分别针对固定的激光功率、交流驱动电压和交流驱动频率，对REP电热涡旋产生的协同力对粒子运动的影响进行了数值研究。模拟结果表明，粒子受到环形涡旋产生的曳力与粒子和电极相互作用产生的捕获力之间的竞争效应，前者促使粒子在靠近下电极上激光照射点的主流体中再循环，后者促使粒子在照射点表面聚集形成团簇。实验结果表明，随着激光功率的增加，粒子在主流体中循环的环形流范围增大，而粒子在电极表面被捕获的团簇范围减小。结果还表明，粒子速度随激光功率的增加而增加，特别是对于尺寸较小的粒子。粒子被捕获在照射热点上的激发频率随着粒子尺寸的增加而降低。REP环形涡旋对聚苯乙烯粒子的作用力和速度对于进一步研究生物细胞水平的运动行为具有重要意义。
