J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia.
Soft Matter. 2018 May 2;14(17):3415-3422. doi: 10.1039/c8sm00230d.
We present an experimental realisation of two new artificial microswimmers that swim at low Reynolds number. The swimmers are externally driven with a periodically modulated magnetic field that induces an alternating attractive/repulsive interaction between the swimmer parts. The field sequence also modulates the drag on the swimmer components, making the working cycle non-reciprocal. The resulting net translational displacement leads to velocities of up to 2 micrometers per second. The swimmers can be made omnidirectional, meaning that the same magnetic field sequence can drive swimmers in any direction in the sample plane. Although the direction of their swimming is determined by the momentary orientation of the swimmer, their motion can be guided by solid boundaries. We demonstrate their omnidirectionality by letting them travel through a circular microfluidic channel. We use simple scaling arguments as well as more detailed numerical simulations to explain the measured velocity as a function of the actuation frequency.
我们展示了两种新的人工微游泳者的实验实现，它们在低雷诺数下游泳。游泳者通过周期性调制的磁场被动驱动，该磁场在游泳者部件之间产生交替的吸引力/排斥相互作用。磁场序列还调制了游泳者组件的阻力，使工作周期非互易。由此产生的净平移位移导致速度高达每秒 2 微米。游泳者可以实现全方位，这意味着相同的磁场序列可以在样品平面中的任何方向驱动游泳者。尽管它们的游泳方向由游泳者的瞬时取向决定，但它们的运动可以通过固体边界来引导。我们通过让它们穿过圆形微流道来证明它们的全方位性。我们使用简单的比例论证以及更详细的数值模拟来解释作为驱动频率函数的测量速度。
