活性浴中惰性粒子形状对有效作用力的影响  

Effect of passive particle shape on effective force in active bath

作　　者：宁鲁慧 张雪 杨明成[4,5,6] 郑宁 刘鹏 彭毅 Ning Lu-Hui;Zhang Xue;Yang Ming-Cheng;Zheng Ning;Liu Peng;Peng Yi(Beijing Key Laboratory of Optical Detection Technology for Oil and Gas,China University of Petroleum-Beijing,Beijing 102249,China;Basic Research Center for Energy Interdisciplinary,College of Science,China University of Petroleum-Beijing,Beijing 102249,China;School of Physics,Beijing Institute of Technology,Beijing 100081,China;Beijing National Laboratory for Condensed Matter Physics and Laboratory of Soft Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China;School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Songshan Lake Materials Laboratory,Dongguan 523808,China)

机构地区：[1]中国石油大学(北京),油气光学探测技术北京市重点实验室,北京102249 [2]中国石油大学(北京)理学院,能源交叉学科基础研究中心,北京102249 [3]北京理工大学物理学院,北京100081 [4]中国科学院物理研究所,北京凝聚态物理国家研究中心,软物质物理实验室,北京100190 [5]中国科学院大学物理科学学院,北京100049 [6]松山湖材料实验室,东莞523808

出　　处：《物理学报》2024年第15期235-242,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:12304245,12374205,12074406);油气资源与工程全国重点实验室定向课题(批准号:PRE/DX-2407);北京凝聚态物理国家研究中心开放课题面上基金(批准号:2023BNLCMPKF014);中国石油大学(北京)科研基金(批准号:2462023YJRC031)资助的课题

摘　　要：活性物质是典型的非平衡态系统,其组成单元能够利用自身存储的能量或者周围环境的能量实现自驱动.在活性系统中,物体间的受力情况直接影响其结构和动力学行为,因此深入了解物体间的有效作用力是理解活性物质一切复杂现象的基础.本文通过光镊显微镜实验分别研究了活性大肠杆菌溶液中惰性球形聚苯乙烯胶体粒子间和板状粒子间的有效作用力,发现球形粒子间有效作用力的性质一直是短程排斥力,而板状粒子间的有效作用力则为长程吸引力,这说明惰性粒子间的有效作用力受粒子形状的影响.惰性粒子间的有效作用力主要来源于两部分的贡献,即细菌-惰性粒子间的直接碰撞,以及细菌运动产生的流场.在实验上通过对比粒子之间、粒子外侧细菌的浓度和取向有序性发现,球形粒子间的有效排斥力主要来源于细菌-粒子的直接碰撞,而板状粒子间的长程吸引力则主要源于细菌流场的贡献.本文通过光镊显微镜实验证明了惰性粒子间的有效作用力与惰性粒子的几何构型有关,为调控活性物质中的动态自组装提供了实验支撑.In active matter,the effective force between passive objects is crucial for their structure and dynamics,which is the basis for understanding the complex behaviors within active systems.Unlike equilibrium states,the factors such as the surface configuration,size,and confinement strength significantly influence the effective forces between passive particles.Previous studies have shown that the shapes of passive particles affect the aggregation of active particles,leading to different forces experienced by passive particles with different shapes.However,recently,a long-range attractive force between passive platelike particles,caused by the bacterial flow field instead of the direct bacterium-plate collisions in active bacterial suspensions,has been found.This raises an intriguing question:how does hydrodynamics affect the forces on passive particles of different shapes in different ways?In this work,we investigate the effective forces exerted on passive spherical and plate-like particles immersed in bacterial suspensions by optical-tweezers experiments.The effective force between passive particles can be calculated from the formula,Feff = k (Δd) /2,where(Δd) represents the difference in distance between the passive particles in the bacterial bath and those in the solution without bacteria,is the effective stiffness of optical traps.The Feff > 0 indicates a repulsive force between passive particles,and the Feff < 0 represents an effective attractive force between passive particles.Our results demonstrate that the passive spherical particles experience short-range repulsion,while plate-like particles are subjected to long-range attraction.This highlights the substantial effect of particle shape on their effective forces.The forces on passive particles are mainly attributed to two factors:direct bacterium-particle collisions and the bacterial flow field.The analysis of the bacterial concentration and orientation distribution around passive particles reveals that for spherical particles,the concentration of bacteria

关 键 词：活性物质 光镊 有效作用力 粒子形状 

分 类 号：O552[理学—热学与物质分子运动论]