  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.
