Swimming at low Reynolds number is typically dominated by a large viscous drag, therefore microscale swimmers require non-reciprocal body deformation to generate locomotion. Purcell described a simple mechanical swimmer at the microscale consisting of three rigid components connected together with two hinges. Here we present a simple microswimmer consisting of two rigid paramagnetic particles with different sizes. When placed in an eccentric magnetic field, this simple microswimmer exhibits non-reciprocal body motion and its swimming locomotion can be directed in a controllable manner. Additional components can be added to create a multibody microswimmer, whereby the particles act cooperatively and translate in a given direction. For some multibody swimmers, the stochastic thermal forces fragment the arm, which therefore modifies the swimming strokes and changes the locomotive speed. This work offers insight into directing the motion of active systems with novel time-varying magnetic fields. It also reveals that Brownian motion not only affects the locomotion of reciprocal swimmers that are subject to the Scallop theorem, but also affects that of non-reciprocal swimmers.

中文翻译：

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可重配置的顺磁微游泳器：布朗运动影响单向驱动†

在低雷诺数下游泳通常受大的粘性阻力支配，因此，微型游泳者要求身体的不可逆变形才能产生运动。珀塞尔（Purcell）在微观尺度上描述了一种简单的机械游泳器，它由三个刚性部件和两个铰链连接在一起。在这里，我们介绍了一个简单的微扫描器，该微扫描器由两个具有不同大小的刚性顺磁性粒子组成。当放置在偏心磁场中时，这种简单的微游泳者会表现出不可逆的身体运动，并且其游泳运动可以以可控的方式进行。可以添加其他组件以创建多体微游泳器，从而使粒子协同作用并沿给定方向平移。对于某些多体游泳者而言，随机热力会折断手臂，因此，它改变了游泳行程并改变了机车速度。这项工作提供了利用新颖的时变磁场来指导有源系统运动的见解。它也揭示了布朗运动不仅影响受扇贝定理影响的相互游泳者的运动，而且影响非相互游泳者的运动。