Exploiting the energy of randomly moving active agents such as bacteria is a fascinating way to power a microdevice. Here we show, by simulations, that a chain-grafted disk-like colloidal particle can rotate unidirectionally and hence output work when immersed in a thin film of active particle suspension. The collective spontaneous symmetry breaking of chain configurations is the origin of the unidirectional rotation. Long persistence time, large propelling force and/or small rotating friction are keys to sustaining the collective broken symmetry and realizing the rotation. In the rotating state, we find very simple linear relations, e.g. between the mean angular speed and the propelling force. The time-evolving asymmetry of chain configurations reveals that there are two types of non-rotating state. The basic phenomena are also observed in the macroscopic granular experiments, implying the generic nature of these phenomena. Our findings provide new insights into the collective spontaneous symmetry breaking in active systems with flexible objects and also open the way to conceive new soft/deformable microdevices.

中文翻译：

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自发对称破坏诱导链在活性浴中单链旋转的胶体粒子的单向旋转

利用随机移动的活性剂（例如细菌）的能量是为微型设备提供动力的一种有趣的方式。在这里，我们通过仿真显示，链状接枝的盘状胶体颗粒可以单向旋转，因此当浸入活性颗粒悬浮液的薄膜中时可以输出功。链构型的集体自发对称性断裂是单向旋转的起源。持续时间长，推进力大和/或旋转摩擦小是维持整体破碎对称性和实现旋转的关键。在旋转状态下，我们发现非常简单的线性关系，例如在平均角速度和推进力之间。链构型随时间变化的不对称性表明，存在两种类型的非旋转状态。在宏观颗粒实验中也观察到了基本现象，这暗示了这些现象的一般性质。我们的发现为具有柔性物体的主动系统中的集体自发对称性破裂提供了新的见解，也为构想新的软/可变形微器件开辟了道路。