Anti‐Fouling Water Purification Membranes with Tunable Nanopores and Designable Surface Patterns by Ice‐Confined Phase Separation

ABSTRACT Creating specific surface patterns on water purification membranes can effectively mitigate the prevalent fouling problem during water treatment. However, current patterning methods face practical challenges in achieving both tunable nanopores and designable surface patterns at the selective layer of the membrane. Here we report an ice‐confined phase separation (IC‐PS) strategy, in which the patterned ice melts and rapidly initiates the phase separation of the polymer solution, to form a patterned nanoporous selective layer. The pore size of the patterned IC‐PS membranes can be facilely tuned from 92 to 36 nm. The patterns on the IC‐PS membrane significantly improve the pure water permeance by 79% while keeping almost the same solute rejection as the flat IC‐PS membrane. In cyclic fouling evaluations for 90 h, the patterned IC‐PS membrane exhibits a lower flux decline ratio and a higher flux recovery ratio than its flat analogue. Computational fluid dynamics simulations confirm that the surface pattern‐enhanced vortices and shear stress effectively reduce foulant deposition and mitigate membrane fouling. Moreover, the IC‐PS method can be applied for multiple membrane materials, and various microstructures, such as fingerprint, lotus leaf, and fish scale, can be easily replicated to the membrane surface at high fidelity.