Crowding competes with trapping to enhance interfacial diffusion

TL;DR

This paper investigates how crowding and trapping influence diffusion on surfaces, revealing that increased particle density can unexpectedly enhance diffusion, contrary to typical expectations.

Contribution

It introduces the concept of crowding-enhanced diffusion through simulations and theoretical analysis of a 2D lattice gas with traps.

Findings

Diffusion coefficient increases with particle density.

Crowding can counteract trapping effects to enhance diffusion.

Scaling and master equation approaches explain the phenomenon.

Abstract

Diffusion in the crowded environments of the biological membranes or materials interfaces often involves intermittent binding to surface proteins or defects. To account for this situation we study a 2-dimensional lattice gas in a field of immobilized traps. Using kinetic Monte Carlo simulations, we calculate the effective diffusion coefficient in the long-time limit as a function of the traps and particle densities. We find a remarkable result - an increase of the diffusion coefficient with particle density, an effect that we coin as crowding-enhanced diffusion. We rationalize this result using scaling arguments and the master equation approach.