Diffusioosmotic dispersion of solute in a long, narrow channel

Solute-surface interactions have garnered considerable interest in recent years as a novel control mechanism for driving unique fluid dynamics and particle transport with potential applications in fields such as biomedicine, the development of microfluidic devices, and enhanced oil recovery. In this study, we will discuss dispersion induced by the diffusioosmotic motion near a charged wall in the presence of a solute concentration gradient. Here, we introduce a plug of salt with a Gaussian distribution at the center of a channel with no background flow. As the solute diffuses, the concentration gradient drives a diffusioosmotic slip flow at the walls, which results in a circulating flow in the channel; this, in turn, drives an advective flux of the solute concentration and alters the effective diffusivity of the solute as it diffuses along the channel. We will present theoretical predictions for the solute dynamics using a multiple-timescale analysis. Furthermore, we will show a cross-sectionally averaged concentration equation with an effective diffusivity and comment on its application in diffusioosmotic transport.