Micro-patterned membranes prepared via modified phase inversion: Effect of modified interface on water fluxes and...

The introduction of patterns on a membrane-solute interface has been suggested as an effective method to tackle the reduced flux and fouling issues. Herein, the effectiveness of using spray-modified non-solvent induced phase separation (s-NIPS) to create a variety of micrometer-level structured interfaces is now studied. Circular, triangular and rectangular patterns with different dimensions were successfully created on polyacrylonitrile membranes. The rectangular pattern height was varied from 500 to 1500 µm, which resulted in a proportional increase in clean water permeance from 590 ± 47 L m^-2 h^-1 bar^-1 to 1345 ± 108 L m^-2 h^-1 bar^-1 respectively. This coincided with some BSA rejection loss for the highest patterns, indicating the fragile nature of these tall features. No significant rejection losses were found for the smaller pattern heights (145-250 µm) as compared to flat membranes, while fluxes more than doubled still. The critical pressure was also increased substantially for patterned membranes and showed a proportionality with the pattern height. These experimental findings were correlated with the reduced foulant adhesion due to a shear-induced slip boundary layer at the membrane-solution interface. Computational fluid dynamics simulations further showed higher shear stress values due to flow constriction within the membrane's valley regions. These findings indicate the high potential of s-NIPS patterned membranes in long-term industrial applications by requiring less membrane area for a given application and reducing cleaning interventions.