Fabrication of High-Speed Microswimmers by Spray Drying Technology for Oil Removal

Janus-microswimmers, as efficient self-propelled materials, have garnered considerable attention, particularly for their potential applications in nonagitated liquids, like natural aquatic systems. However, current microswimmers face challenges such as unconfined diffusion areas and small-scale production. Herein, we propose a scalable spray-drying-assisted strategy for the efficient production of Janus-microswimmers. The Janus structures are fabricated by the assembly of polystyrene microparticles and SiO2/polydopamine nanoparticles in the microdroplets, and the single-side propulsion microswimmers are subsequently obtained by loading MnO2. By catalyzing the decomposition of H2O2 to produce oxygen, the speed of these microswimmers is much faster than those of other reported continuous-motion microswimmers. Interestingly, the microswimmers are self-propelled and gather in the proximity of water surface, and the extent of the confined area is controllable. This range-confined motion, distinct from the traditional irregular motion, offers a novel perspective on the behavioral patterns of Janus-microswimmers. Furthermore, by in situ loading of Fe3O4 nanoparticles, the microswimmers can be sensitively induced and controlled in their movement direction by a magnetic field. As a proof-of-concept, by harnessing the hydrophobic components of the microswimmers, we successfully recover floating oil films in a simulated natural water body, offering a promising approach for the remediation of petroleum pollution in the environment.