The ability to move and self-organize in response to external stimuli is a fascinating feature of living active matter. Here, the metallo-dielectric rod-shaped microswimmers are shown to have a similar behavior in the presence of an AC electric field. The silica-copper Janus microrods were fabricated using the physical vapor deposition-based glancing angle deposition technique (GLAD). When the aqueous solution of the microrods was under the influence of an external AC electric field, they were found to exhibit different phases such as clustering, swimming, and vertical standing in response to variation of the applied frequency. The swimming behavior (5–90 kHz) of the rods is attributed to the induced-charge electrophoresis (ICEP) phenomenon, whereas the dynamic clustering (<5 kHz) could be explained in terms of the electrohydrodynamic (EHD) interaction. Interestingly, the rods flip to attain the vertically standing position when responding to the applied electric field above 90 kHz. The reorientation and switching of the major axis of the rod along the field direction is attributed to the electro-orientation phenomenon. This is basically due to the dominance of the electric torque above the upper limit of the characteristic frequency, where the strength of slip flows around the microrods is predicted to be poor. The present study not only offers insight into the fundamental aspects of the dynamics and the phase behavior of rod-shaped microswimmers, but also opens an avenue to design reconfigurable active matter systems with features inspired by biological systems.

中文翻译：

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交流电场驱动金属介电棒状微型游泳器的动力学和相行为

响应外部刺激而移动和自组织的能力是活性物质的一个迷人特征。在这里，金属电介质棒状微型游泳器在交流电场存在下具有类似的行为。硅铜 Janus 微棒是使用基于物理气相沉积的掠射角沉积技术 (GLAD) 制造的。当微棒的水溶液受到外部交流电场的影响时，我们发现它们会随着施加频率的变化而表现出不同的状态，例如聚集、游动和垂直站立。视杆的游动行为（5-90 kHz）归因于感应电荷电泳（ICEP）现象，而动态聚类（<5 kHz）可以用电流体动力学（EHD）相互作用来解释。有趣的是，当响应高于 90 kHz 的外加电场时，杆会翻转以达到垂直站立位置。棒的主轴沿场方向的重新定向和切换归因于电定向现象。这基本上是由于高于特征频率上限的电扭矩占主导地位，预计微杆周围滑流的强度较差。本研究不仅深入了解了杆状微型游泳器的动力学和相行为的基本方面，而且还为设计具有受生物系统启发的特征的可重构活性物质系统开辟了一条途径。