225The influence of dual opposing electrolyte gradients on diffusiophoretic mobility of spherical colloids

This paper investigates the diffusiophoretic behavior of charged particles in dual opposing electrolyte gradients, with a particular focus on the role of ion size and its influence on mobility at high κ a (ratio of the particle size to the electric double layer thickness) conditions. A theoretical framework is developed to analyze the complex interplay of chemiphoresis and electrophoresis in systems with mixed electrolytes. Key findings reveal that the ion size significantly impacts the spatial distribution of ions, resulting in distinct mobility profiles and critical points where mobility becomes independent of bulk electrolyte ratios. In single electrolytes, mobility exhibits characteristic reversals at high zeta potentials due to dominant ion–ion steric interactions. In mixed systems, the behavior is shaped by the relative bulk concentrations and the ion-specific effects of electrolytes. These findings provide critical insights into the design of microfluidic systems and expand our understanding of particle dynamics in dual-gradient environments, offering potential applications in drug delivery, diagnostics, and particle manipulation technologies.