Fabrication of\nHigh-Speed Microswimmers by Spray Drying\nTechnology for Oil Removal

Janus-microswimmers, as efficient self-propelled materials,\nhave\ngarnered considerable attention, particularly for their potential\napplications in nonagitated liquids, like natural aquatic systems.\nHowever, current microswimmers face challenges such as unconfined\ndiffusion areas and small-scale production. Herein, we propose a scalable\nspray-drying-assisted strategy for the efficient production of Janus-microswimmers.\nThe Janus structures are fabricated by the assembly of polystyrene\nmicroparticles and SiO<sub>2</sub>/polydopamine nanoparticles in the\nmicrodroplets, and the single-side propulsion microswimmers are subsequently\nobtained by loading MnO<sub>2</sub>. By catalyzing the decomposition\nof H<sub>2</sub>O<sub>2</sub> to produce oxygen, the speed of these\nmicroswimmers is much faster than those of other reported continuous-motion\nmicroswimmers. Interestingly, the microswimmers are self-propelled\nand gather in the proximity of water surface, and the extent of the\nconfined area is controllable. This range-confined motion, distinct\nfrom the traditional irregular motion, offers a novel perspective\non the behavioral patterns of Janus-microswimmers. Furthermore, by\nin situ loading of Fe<sub>3</sub>O<sub>4</sub> nanoparticles, the\nmicroswimmers can be sensitively induced and controlled in their movement\ndirection by a magnetic field. As a proof-of-concept, by harnessing\nthe hydrophobic components of the microswimmers, we successfully recover\nfloating oil films in a simulated natural water body, offering a promising\napproach for the remediation of petroleum pollution in the environment.