微系统中转矩及电渗流作用下的微粒子电动旋转操控

微粒子的电动旋转操控是表征分散系中微粒子介电特性的有效方法.低雷诺数微系统中,以Maxwell-Wagner极化理论为基础,进行了转矩作用下的微粒子电动旋转机理研究,推导了此机理作用下微粒子电动旋转峰值速度所对应的特征频率,分析了弛豫时间对粒子旋转方向的影响,对转矩作用下的微粒子电动旋转速度进行仿真;以双电层理论为基础,对电渗流导致的微粒子电动旋转机理进行定性分析,提出具有金修饰的粒子表面更适合电渗流作用下的电动旋转研究.分别以羧基修饰的聚苯乙烯微球以及表面被金修饰的聚苯乙烯微球为操控对象,进行电动旋转实关键词：微系统电动旋转转矩电渗流

Electrorotation manipulation of microparticles induced by torque and electroosmotic slip in microsystem

Electrorotation is an effective technique to characterize the electrical properties of dispersed particles. For the low Reynolds number microsystem, the mechanism of the electrorotation of microparticles induced by torque was analyzed based on the Maxwell-Wagner polarization. Characteristic frequency corresponding to the peak value of the electrorotation speed was deduced and the effect of the relaxation time on the particles' electrorotation direction was analyzed by the simulation of the electrorotation speed induced by the torque. The mechanism of the electrorotation of the microparticles induced by electroosmotic slip was qualitative analyzed based on the double layer and the idea about the gold surface being favorable to the electrorotation was proposed. Experiments on the electrorotation of the polystyrene with the carboxy surface and gold modified surface were performed, respectively. The results show that, the direction of the electrorotation of polystyrene spheres with carboxy surface is opposite to the electric field and, the corresponding frequency is higher with the torque playing the leading role. On the other hand, direction of the rotation of polystyrene spheres with the gold surface is homodromous with the electric field and the corresponding frequency is lower with the electroosmotic slip playing the leading rose.