交流电热流对导电岛纳米电极介电组装的影响

Influence of AC Electrothermal Flow on Dielectro-Phoretic Assembly in a Conductive-Island Nanogap Electrode System

为了获得导电岛纳米间隙电极系统中纳米颗粒介电组装成的纳米粒子链的形貌规律,在所制备出的导电岛纳米间隙电极系统中进行了纳米颗粒介电组装实验。基于纳米颗粒介电操控理论,建立了导电岛纳米间隙电极组装体系的纳米颗粒介电组装模型,并通过数值仿真方法,对该介电组装模型中的电场分布和介电组装过程中纳米颗粒所受的介电泳力、交流电热流以及两者合作用的电动力学行为进行了分析,探究了交流电热流对导电岛纳米电极介电组装的影响。实验发现:在导电岛纳米间隙电极系统中纳米颗粒的介电泳组装具有两种模式——纳米间隙之间的体组装与电极和导电岛表面上的面组装,并且组装模式的强弱程度受频率的影响,进而造成组装形成的纳米粒子链的分布和形态的不同。仿真结果表明:当频率增大到350 kHz时,纳米缝两侧电热流向发生反向;在频率为150 kHz且缝宽为500 nm时,会在整条纳米缝任意位置(端点处外)出现电热流旋涡,并且电热流旋涡会随着驱动频率的增加而减弱;随纳米缝宽度减小,电热流对纳米粒子介电组装的影响减弱。

Dielectrophoretic assembly experiments of nanoparticles in a prepared conductive-island nanogap electrode system is carried out to obtain the morphology of nanoparticle chains formed by dielectrophoretic assembly of nanoparticles in the conductive-island nanogap electrode system.A dielectrophoretic assembly model of nanoparticles in the conductive-island nanogap electrode assembly system is established based on the dielectrophoretic manipulation theory of nanoparticles.The electric field distribution in the dielectrophoretic assembly model,as well as the electrokinetic behavior of dielectrophoresis,alternating current electrothermal flow and their interaction in the assembly process,is analyzed through numerical simulation.The effects of alternating current electrothermal flow on dielectrophoretic assembly in the conductive-island nanogap electrode system are investigated.It is found that the dielectrophoretic assembly of nanoparticles in the conductive-island nanogap electrode system has two modes:the bulk assembly between the nanogaps,and the surface assembly on the surfaces of the electrode and the conductive island.Moreover,the states of the assembly mode are affected by driving frequencies,which leads to different distribution and morphology of the assembled nanoparticle chains.Simulation results show that when the frequency increases to 350 kHz,the electrothermal flow direction reverses on both sides of the nanogap;when the frequency is 150 kHz and the width of nanogap is 500 nm,the electrothermal flow vortices appear at any position of the entire nanogap(outside the end point).The electrothermal flow vortices weakens with the increase of driving frequency,and the effect of the electrothermal flow on the dielectrophoretic assembly of nanoparticles decreases with the decrease of the width of nanogaps.