Reconfigurable assembly, disassembly, and self-propulsion of microparticles via optoelectronic tweezers

Reconfigurability and autonomous mobility are critical for micro/nanorobot systems to perform complex tasks. Here, we propose a synergistic optoelectric control strategy based on an optoelectronic tweezers (OET) platform, which enables the controllable assembly and disassembly of heterogeneous microparticles through electric field induced dipole interactions and electrohydrodynamic (EHD) flows. We find that the assembled structures exhibit stable self-propulsion and can move directionally along the boundaries of optical patterns. This self-propulsion arises from the asymmetric shadow effect induced by top illumination, which generates a lateral dielectrophoretic (DEP) driving force. Notably, the self-propulsion velocity shows an anomalous non-monotonic dependence on the AC frequency. By incorporating DEP levitation and microlens focusing effects, we further elucidate the physical mechanism. At low frequencies, increased levitation height expands the focused light spot beneath the polystyrene (PS) microparticles, reducing the shadow asymmetry below the metal microparticles and consequently weakening the lateral DEP force. Furthermore, by combining dynamic optical patterns with electric field modulation, multilevel reconfiguration of multi-particle clusters is achieved. This strategy effectively couples reconfigurable assembly with autonomous propulsion, providing a versatile pathway for the development of intelligent and modular microrobotic systems.