表面镀金SU-8微柱的低频电动旋转特征

依据传统Maxwell-Wagner界面极化理论, 金属微纳米粒子由于具有极高电导率, 在旋转电场作用下无明显电旋转运动. 然而, 本文针对镀金SU-8微柱开展实验研究, 发现镀金微柱在低频条件下的快速旋转运动现象. 据此, 通过考虑镀金微柱表面双电层效应, 理论分析并实验验证镀金微柱的低频电旋转特征. 首先, 建立电场中微柱的近似椭球模型, 分析固-液接触面双电层作用下的金属粒子极化机理, 推导旋转电场作用下镀金微柱的转矩公式及电旋转角速度公式. 其次, 搭建实验平台, 分别对镀金微柱在三种不同电导率溶液、100 Hz–30 MHz频率范围内的电旋转特征进行对比实验研究. 最后, 对实验结果进行分析和讨论, 并通过考虑镀金微柱与基底之间摩擦作用等因素, 验证实验研究与理论研究的一致性.关键词：表面镀金微柱电旋转双电层微流控

Electrorotation characteristics of gold-coated SU-8 microrods at low frequency

According to the theory of traditional Maxwell-Wagner interface polarization, the metal micro/nano particles have no obvious electrorotation behavior under the alternating current electric field. However, we find the opposite experimental results. In this paper, electrorotation experiments are carried out, and the basic mechanism of gold-coated SU-8 microrods is presented. Therefore the electrorotation characteristics of gold-coated microrod at low frequency are analysed by considering the surface electric double layer at the microrod-electrolyte interface. Specifically, first we establish an approximate ellipsoid model in the electric field, analyze the polarization mechanism of metal particles under the action of solid-liquid interface electric double layer, and then calculate the electrorotation torque and present an electrorotation angular speed formula of the gold-coated microrod. Secondly, electrorotation experiments of gold-coated SU-8 microrods suspended in electrolytes with different conductivities are presented in a frequency range of 100 Hz to 30 MHz. Finally, the experimental results are discussed, and compared with the theoretical analysis, showing the experimental results are in good agreement with theoretical analyses by considering the friction between the microrods and substrate.
Keywords：gold-coated microrodelectrorotationelectrical double layermicrofluidics