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     

非对称电极表面微观形貌对交流电渗流速的影响

经典交流电渗理论是利用电场进行非机械式微流体驱动的基础.传统理论交流电渗理论以双电层理论为基础,通过耦合电场方程以及流场方程得到微电极表面交流电渗流速表达式,通常与实验流速相差较大. 以电极表面微观形貌对交流电渗流速的影响为研究目标,定义微电极表面粗糙度为微观形貌特征参数,建立了等效双电层模型,并对传统交流电渗流速公式进行了修正.理论并仿真分析了表面粗糙度对于交流电渗流速的影响,利用非对称电极对交流电渗微流体驱动进行了实验研究,并进行对比分析.结果表明,理论分析与实验结果具有较好的一致性. 关键词： 交流电渗 电极表面粗糙度 等效双电层     

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     

Microwire formation based on dielectrophoresis of electroless gold plated polystyrene microspheres

Microspheres coated with a perfectly conductive surface have many advantages in the applications of biosensors and micro-electromechanical systems.Polystyrene microspheres with the diameter of 10 μm were coated with a 50 nmthick gold layer using an electroless gold plating approach.Dielectrophoresis(DEP) for bare microspheres and shelled microspheres was theoretically analysed and the real part of the Clausius-Mossotti factor was calculated for the two kinds of microspheres.The experiments on the dielectrophoretic characterisation of the uncoated polystyrene microspheres and gold coated polystyrene microspheres(GCPMs) were carried out.Experimental results showed that the gold coated polystyrene microspheres were only acted by a positive dielectrophoretic force when the frequency was below 40M Hz,while the uncoated polystyrene microspheres were governed by a negative dielectrophoretic force in this frequency range.The gold coated polystyrene microspheres were exploited to form the microwire automatically according to their stable dielectrophoretic and electric characterisations.     

Electrohydromechanical analysis based on conductivity gradient in microchannel

Fluid manipulation is very important in any lab-on-a-chip system. This paper analyses phenomena which use the alternating current （AC） electric field to deflect and manipulate coflowing streams of two different electrolytes （with conductivity gradient） within a microfluidic channel. The basic theory of the electrohydrodynamics and simulation of the analytical model are used to explain the phenomena. The velocity induced for different voltages and conductivity gradient are computed. The results show that when the AC electrical signal is applied on the electrodes, the fluid with higher conductivity occupies a larger region of the channel and the interface of the two fluids is deflected. It will provide some basic reference for people who want to do more study in the control of different fluids with conductivity gradient in a microfluidic channel.     

Automatic microcircuit formation based on gold-coated SU-8 microrods via dielectrophoresis

To explore the application of the characteristics of metallic microparticles, alternating current electric trapping of the SU-8 microrods coated with a thin gold layer by the chemical approach is investigated. Positive dielectrophoresis is used to absorb the gold-coated SU-8 microrods at the edge of the parallel electrodes, thereby forming chains to connect the electrodes. This is a fast automatic microcircuit formation process. Moreover, a non-charged molecule is modified on the surface of the gold-coated SU-8 microrod, and the modified microrods are controlled by the alternating electric field to form a number of chains. The different chains between the parallel electrodes consist of various parallel circuits. In order to compare these chains with different electric surfaces, the impedances of the metallic and modified microrods are measured and compared, and the results show that the gold-coated microrods act as pure resistors, while the microrods functionalized by a non-charged molecule behave as good capacitors.     

面向微系统的介电泳力微纳粒子操控研究

微系统中低浓度微纳粒子的操控技术亟需改进和完善,介电泳（dielectrophoresis） 在这一领域具有很大的潜力. 以介电泳基本原理分析为基础,推导了介电泳力的复数表达式. 综合分析了影响传统介电泳力和行波介电泳力的主要因素,并建立星型电极和平行电极阵列的二维理论模型,分别作为传统介电泳力和行波介电泳力的微纳粒子操控结构. 设置相应的边界条件,利用实部、虚部耦合求解的方法,仿真计算两种电极上的介电泳力分布规律,为实验提供参数依据. 以传统介电泳力为基础,利用星型电极进行微纳粒子收集实验;以行波介电泳 关键词： 微系统 介电泳 粒子收集 定向驱动     

Entanglement and non-Markovianity of a multi-level atom decaying in a cavity

We present a paradigmatic method for exactly studying non-Markovian dynamics of a multi-level V-type atom interacting with a zero-temperature bosonic bath. Special attention is paid to the entanglement evolution and the dynamical nonMarkovianity of a three-level V-type atom. We find that the entanglement negativity decays faster and non-Markovianity is smaller in the resonance regions than those in the non-resonance regions. More importantly, the quantum interference between the dynamical non-Markovianities induced by different transition channels is manifested, and the frequency domains for constructive and destructive interferences are found.     

Force criterion of different electrolytes in microchannel

The control and handling of fluids is central to many applications of the lab-on-chip. This paper analyzes the basic theory of manipulating different electrolytes and finds the two-dimensional model. Coulomb force and dielectric force belonging to the body force of different electrolytes in the microchannel were analyzed. The force criterion at the interface was concluded, and testified by the specific example. Three basic equations were analyzed and applied to simulate the phenomenon. The force criterion was proved to be correct based on the simulation results.