自驱动颗粒体系中的熵力  

Entropy forces of nanoparticles in self-propelled systems

作　　者：华昀峰 章林溪[1] 

机构地区：[1]浙江大学物理系,杭州310027

出　　处：《物理学报》2017年第19期12-17,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:21374102;21674096)资助的课题~~

摘　　要：在许多纳米复合材料体系中熵力(entropy force)是普遍存在的,但由于熵力的存在会导致纳米颗粒的凝聚从而降低其许多性能,因此在大多数情况下熵力的存在对体系并无益处,所以研究如何减小熵力对体系的影响是非常重要的.不带角速度的自驱动粒子在熵力作用下会集聚在纳米颗粒(或者纳米棒)周围,这会对纳米颗粒(或者纳米棒)产生很大的相互作用力.对于纳米颗粒,在不带角速度的自驱动粒子体系中存在着非常大的排斥力.而对于纳米棒,由于纳米棒内外的不对称性,使得两个纳米棒之间会产生吸引-排斥转变,同时这个吸引-排斥转变与纳米棒之间的距离有关.当自驱动粒子加上一个自转角速度ω之后,熵力的作用就大大减弱,纳米颗粒不再集聚.研究结果有助于对非平衡态下纳米颗粒(或纳米棒)之间熵相互作用力的认识.Entropy force is fairly ubiquitous in nature, but it is not practically beneficial for most cases, thus how to reduce the entropic force of the system is very important. In this paper, by employing the overdamped Langevin dynamics simulations, we explore the entropy force between two large nanoparticles（or two nanorods） immersed in a self-propelled system. Self-propelled particles can be regarded as active matter, and the active matter is an interesting subject which has been studied theoretically and experimentally over the past few years. A great many biological and physical systems can be referred to as active matter systems, including molecular motors, swimming bacteria, self-propelled colloids, motile cells, and macroscopic animals. Active matter obtains energy from an external system under non-equilibrium conditions,and active particles with suitably designed constructions are able to convert energy input into the desired control of function, which has wide potential applications in a diversity of fields, such as drug delivery in medicine. Self-propelled particles without angular velocity would gather around the nanoparticles（or nanorods） under the effect of entropy force,which can induce large entropy force between nanoparticles. The interaction force between two nanoparticles is large enough, owing to the asymmetry of the system, and entropy force also depends on the distance between two nanoparticles（or two nanorods）. For the case of self-propelled particles with an angular velocity, the entropic effect is weak, and the larger the angular velocity, the weaker the entropic force is. Moreover, nanoparticles will no longer assemble together because of their weak entropic forces. Meanwhile, the entropy force between two nanorods can be tuned from a long repulsion into a long range attraction by changing the distance between two nanorods. The present investigation can help us understand the entropy forces in non-equilibrium systems.

关 键 词：熵力 自驱动颗粒体系 非平衡态 过阻尼郎之万方程 

分 类 号：O347.7[理学—固体力学] TB383.1[理学—力学]