Line-Charge-Mediated Concentration Enrichment in Continuous Shear Flow toward Portable Membrane-Free Water Purification

The purification and treatment of water have assumed greater significance in the context of sustainable development. Nevertheless, the conventional theory of concentration polarization inherently imposes constraints on the effective regulation and precise manipulation of ionic transport for electrochemical-based technology. In this work, we propose an extraordinary concentration enrichment mediated by a line charge down to tens of micrometers, allowing continuous extraction in shear flow. The spatiotemporal evolution of the solute concentration is experimentally observed under various applied voltages and flow rates in a microfluidic-based electrochemical device. Through numerical simulations and scaling analysis, we elucidate the trade-offs between key physical parameters to optimize enrichment performance. Furthermore, we demonstrate the cation separation in multicomponent electrolytes and the effective removal of plastic particles and cells in solutions. This portable water purification concept may extend options for drinking water access in disaster response or infrastructure-constrained environments.