磁驱动弹性微泳器通过磁滞坍缩实现自推进与独立控制
Magnetically Driven Elastic Microswimmers: Exploiting Hysteretic Collapse for Autonomous Propulsion and Independent Control
- 利用磁滞坍缩使两段弹性连接的磁珠非对称接触分离
- 单个磁场可同步控制多个泳器，速度达0.172 mm/s
- 结构简单易实现实验验证，适合靶向药物递送
在低雷诺数环境下，惯性效应可忽略，互反运动无法产生净位移，必须打破对称性才能实现推进。本研究分析由三个磁性小球通过两个弹性连接组成的直线型微泳器，其运动机制依赖于方向性外部磁场的幅值振荡。通过诱导两个弹性段发生可逆磁滞坍缩，两对磁珠周期性地非对称接触与分离。由于高阶流体动力学相互作用，每个周期后产生净位移。不同泳器可通过调节驱动幅值与频率实现独立控制，仅需一个外部磁场即可完成多泳器协同操作。采用进化优化策略对泳器几何结构和磁场形状进行优化，以获得最大游泳速度（0.172 mm/s）。该机制原理简单，实验实现可行，有望为微创医疗如靶向药物输送提供新路径。
原文摘要 · Abstract (English)
When swimming at low Reynolds numbers, inertial effects are negligible and reciprocal movements cannot induce net motion. Instead, symmetry breaking is necessary to achieve net propulsion. Directed swimming can be supported by magnetic fields, which simultaneously provide a versatile means of remote actuation. Thus, we analyze the motion of a straight microswimmer composed of three magnetizable beads connected by two elastic links. The swimming mechanism is based on oriented external magnetic fields that oscillate in magnitude. Through induced reversible hysteretic collapse of the two segments of the swimmer, the two pairs of beads jump into contact and separate nonreciprocally. Due to higher-order hydrodynamic interactions, net displacement results after each cycle. Different microswimmers can be tuned to different driving amplitudes and frequencies, allowing for simultaneous independent control by just one external magnetic field. The swimmer geometry and magnetic field shape are optimized for maximum swimming speed using an evolutionary optimization strategy. Thanks to the simple working principle, an experimental realization of such a microrobot seems feasible and may open new approaches for microinvasive medical interventions such as targeted drug delivery.
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