Force-driven transport through periodic entropy barriers

We analyze the transport of a point-size Brownian particle under the influence of a constant and uniform force field through a slowly varying periodic channel whose cross-sectional area variations represent effective "entropy barriers." Using generalized Taylor-Aris dispersion (macrotransport) theory for spatially periodic media, we compute the mean velocity and effective diffusion coefficient (dispersivity) describing the long-time global transport of the particle. Systematic asymptotic perturbation analysis illuminates the transport process occurring in the strong-field limit, notably the role of the mean-squared channel roughness. The results thus obtained compare favorably with Brownian dynamics simulations over the full range of driving forces.