Tuning diffusioosmosis of electrolyte solutions by hydrostatic pressure
Year: 2026
Type: article
Abstract: When two reservoirs of a distinct salinity are connected by channels or pores, a fluid flow termed diffusio-osmotic is generated. This article investigates the flow emerging in a uniformly charged long slit whose thickness exceeds the local Debye screening length. Attention is focused on the role of hydrostatic pressure drop Δp in establishing diffusioosmosis at a finite concentration difference. For a thick slit, we recover the known formula for a local diffusio-osmotic slip over a single wall, which is determined by the surface potential, salt concentration, and its gradient. An equation for the global fluid flow rate Q is presented as a sum of the diffusio-osmotic and pressure-driven contributions. Although the diffusio-osmotic term itself remains unaffected by Δp, the nonlinear concentration and surface potential profiles along the slit, and consequently, the local slip velocity are dramatically modified. We present an equation relating the local concentration to Q and employ it to derive an expression describing the surface potential variation in the slit. Since Q can easily be tuned by Δp, the variety of possible concentration and surface potential profiles becomes very rich. Our theory provides a simple explanation of recent flow rate measurements and shows that experimental data provide rather direct information about concentration and surface potential profiles in the uniformly charged slit. The relevance of our results for sensing the salt dependence of surface potentials is discussed briefly.
Source: Physics of Fluids
DOI: 10.1063/5.0344519
Language: English
Subfield: Biomedical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7202209254