Direct numerical simulation of ionic transport of non-Newtonian electrolytes through patterned surface

The transport of electrolytes and ions across ion-selective interfaces form the basis of modern electrochemical and separation technologies, including energy storage, desalination, electrochemical sensing, and microfluidic separation. While ion migration and flow dynamics in Newtonian electrolytes have been widely explored, the role of non-Newtonian rheology, particularly shear-thinning behavior, on electrokinetic transport and instabilities remains not fully understood. In this study, ion transport across patterned ion-selective membranes is investigated using numerical simulations. The coupled Poisson–Nernst–Planck and Navier–Stokes equations are solved to capture electrostatic potential, ionic migration, and fluid flow under shear-dependent viscosity. Results reveal that shear-thinning electrolytes destabilize otherwise uniform electroosmotic convection producing chaotic flow structures and variable current responses through the membrane. This destabilization lowers the threshold for the onset of convective instabilities, thereby enhancing chaotic convective mixing and promoting spatially uniform ion distributions, which elevate overlimiting currents. Moreover, shear-thinning behavior sharpens velocity and concentration gradients near the membrane surface, leading to improved ionic flux. Patterned membrane geometries further regulate ion transport by modifying electroosmotic fields and reducing permeable surface areas, thereby amplifying overall transport efficiency. Collectively, the coupling between electrolyte rheology and patterned membrane distributions enable enhanced and controllable ionic transport dynamics. These insights address critical challenges such as mitigating dendrite formation in electrochemical systems, improving operational lifetimes, and guiding the development of advanced membrane architectures. Flow and concentration fields are interpreted through ionic concentration, velocity distributions, integrated mixing efficiency, and spatial–temporal variations of ionic current densities.