Catalytic microrotor driven by geometrical asymmetry.

An asymmetric gear with homogeneous surface properties is, here, presented as a prototype to fabricate catalytic microrotors. The driving torque arises from the diffusiophoretic effect induced by the concentration gradients generated by catalytic chemical reactions at the gear surface. This torque produces a spontaneous and unidirectional rotation of the asymmetric gear. By means of mesoscopic simulations, we prove and characterize this scenario. The gear rotational velocity is determined by the gear-solvent interactions, the gear geometry, the solvent viscosity, and the catalytic reaction ratio. Our work presents a simple way to design self-propelled microrotors, alternative to existing catalytic bi-component, or thermophoretic ones.