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中国物理学会期刊

“十”字形自驱单元形成寡聚体的动力学行为

Dynamic behavior of oligomers formed by “十” shaped self-propelling agents

CSTR: 32037.14.aps.71.20212385
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  • 探索自驱粒子形状对自组装结构和动力学的影响是软物质研究的前沿课题. 组装基元形成的寡聚体及其动力学是大量粒子形成组装结构的基础. 本文设计了一种“十”字形自驱粒子, 发现其可以形成数种不同构型的寡聚体, 计算了寡聚体(二、三、四聚体)的均方位移、角速度、角速度分布概率、轨迹曲率分布概率等. 寡聚体的运动行为可分为两类: 一类是合力为零但力矩不为零, 寡聚体进行小半径的偏心旋转; 另一类是合力不为零力矩也不为零, 寡聚体呈现大半径的偏心旋转. 寡聚体的平动动力学在短时间尺度(大致约为1—2 s, 与其角速度有关)都呈现超扩散现象, 但转动速度受寡聚体结构影响; 力矩越大, 转动惯量越小, 角速度越大. 对于三聚体, 轨迹曲率与角速度有关, 角速度越大, 曲率也越大.

     

    In recent years, active matter has attracted tremendous research interest. Active matter displays many phenomena, such as super-diffusion, huge fluctuation and collective motion. The shape of active agent plays a critical role in the self-assembly of active matter. Understanding the oligomers’ dynamics of active agents is the first step to study the self-assembly of massive agents. Here, we design a self-properlling particle with the “十” shape using the Hexbug robot and investigate the dynamics of oligomers composed of these particles. To track the position of particles, the top of the particles is marked by black cards with white dots in the center. We find that these particles can agglomerate together to form stable oligomers consisting of two, three, or four particles. We study the dynamics by analyzing the trajectory, mean-square displacement, angular velocity, angular velocity distribution and the curvature distribution. We find that the dynamics can be divided into two types. One is the combination of eccentric rotation with small circular radius and irregular translation, which occurs in the system with the zero resultant force and nonzero torque. The other is the eccentric rotation with a large circular radius, which appears in the system in which both the resultant force and torque are not zero. In addition, we find that the translational dynamics of oligomers displays a super diffusion on a short time scale, influenced by the confirguration of oligomers. Further, the larger torque and the smaller moment of inertia result in the bigger angle speed of oligomers. Moreover, we investigate the curvature distribution of the trimer and find that the faster the angle speed of the trimer, the bigger its curvature is.

     

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