Janus Nanomotor: Catalytic Self-Propulsion

Two hundred Janus microswimmers drift through a simulated fuel bath, each rendered as a two-tone sphere: a gold catalytic cap and a grey inert hemisphere. Decomposing hydrogen peroxide on the Pt cap sets up a local concentration gradient that self-diffusiophoretically pushes each particle along its own axis, while thermal rotational diffusion constantly reorients that axis — the same competition that turns real catalytic Janus micromotors into enhanced random walkers rather than straight-line rockets. Tune the fuel concentration, particle radius and bath temperature to watch propulsion speed, orientation-persistence time and the resulting long-time diffusion coefficient shift in real time, or switch the catalytic cap off to see the swarm collapse back into ordinary passive Brownian motion.