Shape Governs the Motion of Chemically Propelled Janus Swimmers

Artificial self-propelled micro- and nanoengines, or swimmers, have been increasingly attracting the interest of experimental and theoretical groups. They work at low Reynolds number, where inertia does not sustain motion once the driving force stops, and often require complicated chemistry in both structural and dynamical terms. Here we design and investigate computationally with a coarse-grained model some very simple devices, in the form of chemically propelled Janus swimmers, that is, asymmetrical colloidal particles that catalyze the formation of products characterized by poor interactions with part of the body of the particle. The results show that these simple systems display propulsive motion comparable to that of more complicated micro- and nanoscale engines. We also find that in analogy to the behavior of macroscopic motors the particle shape greatly matters and influences not only the random diffusion, as in Stokes-Einstein law, but also the efficiency of the propulsive motion.