Diffusiophoresis in confined geometries*

Flows containing dissolved solutes and suspended particles are found in porous media systems including aquifers, hydraulic fractures, filtration systems, and others. Solute concentration gradients can induce surprising dynamics to charged suspended particles through the action of diffusiophoresis. Through this effect, particle motions can be directed towards hard-to-reach geometries, and particles can achieve high concentrations and even clog systems. We present a diffusiophoretic approach to dramatically enhance the penetration of charged particles into confined geometries. Furthermore, we demonstrate a low-cost zeta potentiometry technique that allows the simultaneous measurement of particle and wall zeta potentials. We develop solutions for the particle dynamics in pores, and use the method of characteristics to predict particle trajectories. Results confirm the build up of maxima and minima in the propagating particle dynamics. We demonstrate systems that can rapidly concentrate particles. Results inform the design of applications to enhance particle motions in pores, and the techniques presented can be used to preconcentrate biomolecules for rapid bioassays.