Photocatalytic-induced bubble-propelled isotropic g-C3N4-coated carbon microsphere micromotors for dynamic removal of organic pollutants

Light-Programmable g-C3N4 Microrobots with Negative Photogravitaxis for Photocatalytic Antibiotic Degradation

Microrobots enhance contact with pollutants through their movement and flow-induced mixing, substantially improving wastewater treatment efficiency beyond traditional diffusion-limited methods. g-C3N4 is an affordable and environmentally friendly photocatalyst that has been extensively researched in various fields such as biomedicine and environmental remediation. However, compared to other photocatalytic materials like TiO2 and ZnO, which are widely used in the fabrication of micro- and nanorobots, research on g-C3N4 for these applications is still in its early stages. This work presents microrobots entirely based on g-C3N4 microtubes, which can initiate autonomous movement when exposed to ultraviolet and visible light. We observed distinct motion behaviors of the microrobots under light irradiation of different wavelengths. Specifically, under ultraviolet light, the microrobots exhibit negative photogravitaxis, while under visible light, they demonstrate a combination of 3-dimensional motion and 2-dimensional motion. Therefore, the wavelength of the light can be used for programming the motion style of the microrobots and subsequently their application. We show that the microrobots can effectively degrade the antibiotic tetracycline, displaying their potential for antibiotic removal. This exploration of autonomous motion behaviors under different wavelength conditions helps to expand research on g-C3N4-based microrobots and their potential for environmental remediation.

Advanced materials for micro/nanorobotics

Autonomous micro/nanorobots capable of performing programmed missions are at the forefront of next-generation micromachinery. These small robotic systems are predominantly constructed using functional components sourced from micro- and nanoscale materials; therefore, combining them with various advanced materials represents a pivotal direction toward achieving a higher level of intelligence and multifunctionality. This review provides a comprehensive overview of advanced materials for innovative micro/nanorobotics, focusing on the five families of materials that have witnessed the most rapid advancements over the last decade: two-dimensional materials, metal-organic frameworks, semiconductors, polymers, and biological cells. Their unique physicochemical, mechanical, optical, and biological properties have been integrated into micro/nanorobots to achieve greater maneuverability, programmability, intelligence, and multifunctionality in collective behaviors. The design and fabrication methods for hybrid robotic systems are discussed based on the material categories. In addition, their promising potential for powering motion and/or (multi-)functionality is described and the fundamental principles underlying them are explained. Finally, their extensive use in a variety of applications, including environmental remediation, (bio)sensing, therapeutics, etc., and remaining challenges and perspectives for future research are discussed.