Light-Activated, Multi-Semiconductor Hybrid Microswimmers

Using a dynamic fabrication process, hybrid, photoactivated microswimmers made from two different semiconductors, titanium dioxide (TiO2) and cuprous oxide (Cu2O) are developed, where each material occupies a distinct portion of the multiconstituent particles. Structured light-activated microswimmers made from only TiO2 or Cu2O are observed to be driven in hydrogen peroxide and water most vigorously under UV or blue light, respectively, whereas hybrid structures made from both of these materials exhibit wavelength-dependent modes of motion due to the disparate responses of each photocatalyst. It is also found that the hybrid particles are activated in water alone, a behavior which is not observed in those made from a single semiconductor, and thus, the system may open up a new class of fuel-free photoactive colloids that take advantage of semiconductor heterojunctions. The TiO2/Cu2O hybrid microswimmer presented here is but an example of a broader method for inducing different modes of motion in a single light-activated particle, which is not limited to the specific geometries and materials presented in this study.