We demonstrate photochemically induced actuation of liquid metal marbles, which are liquid metal droplets encased in micro/nanoparticles. The WO 3 nanoparticles coated marbles are placed in H2O 2 solution, and their surfaces are illuminated with UV light. The semiconducting WO3 coating behaves as a photocatalyst to trigger a photochemical reaction, generating oxygen bubbles that propel the marble. The actuation of the marbles is investigated under different H2O 2 concentrations, light intensities, and marble dimensions. Equations describing the fundamentals of such actuations are presented. �� 2013 AIP Publishing LLC.