Diffusion of self-propelled Janus tracer in polymeric environment

Janus particles (two-faced, one attractive and one repulsive) with self-propulsion model catalytic nanomotors in biological environments. Understanding their dynamics in crowded media matters for drug delivery applications.

We ran molecular dynamics simulations of a self-propelled Janus probe in a dense colloidal suspension. The finding: rotational diffusion increases with crowding, contrary to naive hydrodynamic predictions.

The mechanism is steric, not viscoelastic. Frequent collisions with neighboring particles deliver random angular kicks that speed up rotation. The effect should therefore appear in any sufficiently dense environment, not just polymer solutions, which clarifies the physical picture compared to previous explanations.

My first research project, from an undergraduate summer program in my first year. The simulations required long runs to converge rotational diffusion coefficients.