Hydrogel‐Based Janus Micromotors Capped with Functional Nanoparticles for Environmental Applications

Abstract Janus nano/micromotors have been developed into various sizes, shapes, and functions for a blaze of applications especially in biomedical and environmental fields. Here, a fabrication method of Janus micromotors is reported by capping hydrogel microspheres with functional nanoparticles (NPs). Microspheres are prepared in droplet microfluidics relying on hydrogel polymerization to obtain spheres with diameters from 20 to 500 µm. By solidifying a hydrogel layer onto microspheres, functional NPs of MnO₂ (catalyst of H₂O₂), TiO₂ (photocatalyst), and Fe₃O₄ (magnetic guidance) are adhered onto microspheres resulting in Janus micromotors revealing different functionalities. Dynamics of Janus micromotors (diameter around 250 µm) are explored by analyzing their trajectories in terms of mean squared displacement when immersed in H₂O₂ solutions of different concentrations, illuminated by light and guided in an external magnetic field. TiO₂ Janus micromotors perform well for water purification tasks as is exemplarily demonstrated with a degradation of Methylene Blue dye in water. The proposed fabrication method is versatile and enables to achieve adjustable coverage of a microsphere with NPs as well as to realize multifunctional Janus micromotors by adhering different NPs (e.g., MnO₂ and Fe₃O₄) on a sphere. This method provides an attractive way to fabricate multifunctional Janus micromotors in a cost‐effective manner for environmental applications.