自扩散泳微观转动马达的介观模拟  

Mesoscale simulation of self-diffusiophoretic microrotor

作　　者：沈明仁 刘锐[1] 厚美瑛[1] 杨明成[1] 陈科[1] 

机构地区：[1]中国科学院物理研究所,软物质物理重点实验室,北京凝聚态物理国家实验室,北京100190

出　　处：《物理学报》2016年第17期233-241,共9页Acta Physica Sinica

基　　金：国家重点基础研究发展计划(批准号:2015CB856800);国家自然科学基金(批准号:11474327,11404379)资助的课题~~

摘　　要：转动的微尺度马达是一类重要的微流器件.近年来,因为其重要的应用及理论价值引起了学术界的广泛关注.本文提出了一种新型的自扩散泳驱动的微观转动马达模型.通过介观动力学模拟,验证了该模型的有效性.模拟结果表明,该自扩散泳微观转动马达可以单向地自驱动转动,并且转动速度和马达表面发生的催化化学反应速率(即自产生的浓度梯度场强弱)、以及液体分子与马达之间的相互作用有关.此外,研究了两个转动马达共存时的运动行为,重点考察了马达之间的流体力学相互作用和浓度梯度场效应对马达转动的影响.该自扩散泳微观转动马达为设计实用的微流器件提供了新的思路和参考,也为研究活性胶体系统的集体行为提供了理想模型.Artificial micro-scale or nano-scale machines that are capable of converting energy to mechanical work, have long been pursued by science and engineering communities for their potential applications in microfluidics, biology and medicine. From a physics point of view, they are also ideal models to investigate fundamental statistical phenomena in non-equilibrium active matters. Inspired by bio-machines and bio-motors like ATP synthase and flagellum motors,we propose a simple design of rotary motors based on pure self-diffusiophoresis effects. The basic design of the rotor consists of three colloidal beads with different surface properties, which leads to different interactions between the beads and solvent molecules. Chemical reactions are imposed on the surface of one of the beads, which creates a source of one of the two solvent molecules and generates a local concentration gradient. The other two beads connected to the catalytic bead have different affinities to the solvent molecules, which leads to asymmetric diffusiophoretic forces on the two non-catalytic beads. A net torque is thus obtained from difference of the diffusiophoretic forces between the two non-catalytic beads. In our simulation, we employ hybrid molecular dynamics（MD） simulations and multiparticle collision dynamics（MPC） to investigate the motion of microrotors. The binary fluid is composed with A-type and B-type solvent particle whose interactions are described by multi-particle collision dynamics while beads-particle interactions are modeled by molecular dynamics. In MPC, all fluid particles execute alternating streaming and collision steps. During streaming steps, the solvents move ballistically. During collision steps, particles are sorted into square cells and only interact with particles in the same cell under a specific stochastic rotation rule. MPC algorithm locally conserves mass, linear momentum, angular momentum and energy, and properly captures thermal fluctuation, mass diffusion, dissipation and hydrodynamic interactions. I

关 键 词：自扩散泳微观转动马达 扩散泳效应 多粒子碰撞动力学 分子动力学模拟 

分 类 号：O488[理学—固体物理]