Drift Versus Entropic Forces in Overdamped Diffusion Through a Widening Channel

This study examines the diffusion of spherical particles in a conical widening channel, with a focus on the effects of deterministic drift and entropic forces. Through numerical simulations, we analyze the motion of particles from a reflecting boundary to an absorbing one. Properties of diffusive motion are explored by inspection of mean squared displacement and mean first passage time. The results show that the diffusion type depends on the drift strength. Without the drift, entropic forces induce effective superdiffusion; however, the increasing drift strength can counterbalance entropic forces and shift the system to standard diffusion and then effective subdiffusion. The mean squared displacement exhibits bending points for high drift values, as predicted by one-dimensional theoretical considerations. The study underscores the importance of considering deterministic and entropic forces in confined geometries.