Multi-wavelength steerable visible light-driven magnetic CoO-TiO 2 microswimmers.

While current light-driven microswimmers require high light intensities, ultraviolet (UV) light or toxic fuels to propel them, powering them with low intensity UV-free visible light without fuels is essential to enable their potential high-impact applications. Therefore, in this study, a new material for light-driven microswimmers in the form of CoO is introduced. Janus CoO-TiO microswimmers powered with low-intensity, UV-free visible light inside water without using any toxic fuels like HO is proposed. The microswimmers show propulsion under full spectrum visible light with 17 times lower intensity than the mean solar intensity. They propel by breaking down water into oxygen and oxide radicals, which enables their potential applications for photocatalysis and drug delivery. The microswimmers are multi-wavelength responsive from the ultraviolet to the infrared region. The direction of swimming changes with the change of illumination from visible to UV light. In addition to being responsive, they are wavelength steerable and exhibit inherent magnetic properties enabling magnetic steering control of the CoO-TiO microswimmers. Thus, these microswimmers, which are propelled under low-intensity visible light, have direction change capability using different light wavelengths, and have steering control capability by external magnetic fields, could be used in future potential applications, such as active and local cargo delivery and active photocatalysis and hydrogen evolution.