Low-Energy Photoresponsive\nMagnetic-Assisted Cleaning\nMicrorobots for Removal of Microplastics in Water Environments

In the global ecosystem, microplastic pollution pervades\nextensively,\nexerting profound and detrimental effects on marine life and human\nwell-being. However, conventional removal methods are usually limited\nto chemical flocculation and physical filtration but are insufficient\nto remove extremely small microplastics. Therefore, developing a comprehensive\nstrategy to address the threat posed by microplastics is imperative.\nHere, we report a low-energy photoresponsive magnetic-assisted cleaning\nmicrorobot (LMCM) composed of photocatalytic material (Ag@Bi<sub>2</sub>WO<sub>6</sub>) and magnetic nanoparticles (Fe<sub>3</sub>O<sub>4</sub>), which can be used for the active removal of microplastics from\nwater environments. Due to the diffusion electrophoresis effect, the\nlow-energy photoresponsive cleaning microrobots (LCMs) are formed\nby spontaneous assembly of Ag@Bi<sub>2</sub>WO<sub>6</sub>, which\ncan continuously adsorb microplastics in a water environment. Particularly,\nthe effective attraction distance of LCMs on microplastics exceeds\n100 μm. After assembling the Fe<sub>3</sub>O<sub>4</sub> nanoparticles,\nLMCMs can clean microplastics in groups from water environments under\nthe control of a magnetic field. Utilizing precision manipulation\nand group control, LMCMs demonstrate a remarkable 98% cleaning efficiency\nin 93 s and can be recovered under the control of the directional\nmagnetic field. This eco-friendly and energy-efficient microrobot\nis expected to provide a viable strategy to tackle the threat of microplastics\nor promote industrial microplastic removal.