Microfluidic Fabrication of Bubble-Propelled Micromotors for Wastewater Treatment

Abstract

Bubble-propelled micromotors with controllable shapes and sizes have been developed by a microfluidic method, which serves for effective wastewater treatment. Using the emulsion from microfluidics as the template, monodisperse micromotors can be fabricated in large quantities based on phase separation and UV-induced monomer polymerization. By adjusting the volume ratio of the two immiscible oils (ethoxylated trimethylolpropane triacrylate/paraffin oil) in the initial emulsion, the geometry of the resulting micromotor can be precisely controlled from nearly spherical, hemispherical to crescent-shaped. The size of the micromotor can be manipulated by varying the fluid flow parameters. In addition, by incorporating functional nanoparticles into the asymmetric structure, the micromotor can be functionalized flexibly for water remediation. In this research, Fe₃O₄ and MnO₂ nanoparticles were successfully loaded on Janus micromotors. Fe₃O₄ nanoparticles can act as catalysts for pollutant degradation and also control the movement direction of micromotors. MnO₂ nanoparticles on the concave of the micromotor catalyzed H₂O₂ to produce bubble propulsion motion in solution, which further enhanced the degradation of pollutants. Consequently, the obtained micromotor demonstrated effective degradation of methylene blue and can be easily recovered by magnets. Furthermore, this simple and flexible strategy offers a synthetic way for anisotropic Janus particles, which will broaden their potential application.

Keywords: bubble-propelled micromotor; controllable synthesis; microfluidic; phase separation; water treatment.