Microrotors with Tunable Trajectory Curvatures Driven by Chemical and Photochemical Dual Engines

A major challenge in developing smart micromachines that can mimic natural microorganisms is their ability to adapt to changing environments. This study presents a matchstick-shaped microrotor consisting of a TiO2 head and a SiO2 tail, with one side coated by PtO. The TiO2 head provides photochemical propulsion under UV light, while the PtO coating provides chemical propulsion in H2O2. The microrotor rotates because of its asymmetric structure and uneven propulsion forces. Notably, under stronger UV light, the rotor orbits in tighter circles as the photochemical engine counteracts the chemical engine, with the two engines located on opposite sides of the center of mass. Additionally, microrotors with shorter SiO2 tails moved in smaller circles and were more sensitive to changes in light intensity.