A rotating two-tailed soft microrobot induces a frequency dependent flow-field in low Reynolds number fluids. We use this flow-field to achieve noncontact manipulation of nonmagnetic microbeads with average diameter of 30 $\mu {\rm m}$ in 2-D space. Our noncontact manipulation strategy capitalizes on exerting a rotational magnetic torque on the magnetic dipole of the microrobot. The induced flow-field enables microbeads in the surrounding fluid to orbit the microrobot along a sprocketlike trajectory due to a periodic and asymmetric flow-field caused by the two tails. A hydrodynamic model of the two-tailed microrobot and the orbiting microbeads is developed based on the method of regularized Stokeslets for computing Stokes flows. The relations between the angular velocity of the orbiting microbeads and the rotation frequency of the microrobot, their proximity ($\mathbf {p}$), and tail length ratio of the microrobots are studied theoretically and experimentally. Our simulations and experimental results show that the angular velocity of the orbiting microbeads decreases nearly as $\mid \mathbf {p}\mid ^{-2}$ with the distance to the microrobot and its tail length ratio. We also demonstrate closed-loop control of the microbeads toward target positions along sprocketlike trajectories with an average position error of $23.1\pm 9.1$ $\mu {\rm m}$ ($n=10$), and show the ability to swim away without affecting the positioning accuracy after manipulation.

中文翻译：

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非磁性无绳微珠绕双尾软微型机器人的受控非接触操作

一个旋转的双尾软微型机器人在低雷诺数流体中诱导频率相关的流场。我们使用该流场来实现对平均直径为 30 的非磁性微珠的非接触操作 $\mu {\rm m}$在二维空间中。我们的非接触式操作策略利用在微型机器人的磁偶极子上施加旋转磁扭矩。由于由两个尾部引起的周期性和不对称流场，诱导流场使周围流体中的微珠能够沿着类似链轮的轨迹围绕微型机器人运行。基于正则化 Stokeslets 计算斯托克斯流的方法，建立了双尾微型机器人和轨道微珠的流体动力学模型。轨道微珠的角速度与微型机器人的旋转频率之间的关系，它们的接近度（$\mathbf {p}$)，并从理论上和实验上研究了微型机器人的尾长比。我们的模拟和实验结果表明，轨道微珠的角速度几乎随着$\mid \mathbf {p}\mid ^{-2}$与微型机器人的距离及其尾长比。我们还展示了微珠沿链轮状轨迹朝向目标位置的闭环控制，平均位置误差为23.1 美元\下午 9.1 美元 $\mu {\rm m}$ ($n=10$)，并表现出在不影响操纵后定位精度的情况下游走的能力。