Confined diffusion

Drift-diffusion kinetics of a confined colloid

The drift-diffusion equation on a finite interval with reflecting boundary conditions is solved by Laplace transformation. The Green function is obtained as a series in powers of e(-hu/D), where u is the drift velocity, D the diffusion coefficient and h the width of the interval. In the drift-dominated regime hu/D >> 1, the first terms provide an exact solution in the limit of short and long times, and a good approximation in the intermediate regime. As a possible application, we discuss confined colloidal suspensions subjected to an external field.