Surface micro-patterning as a promising platform towards novel polyamide thin-film composite membranes of superior performance

Novel and efficient micro-patterned polyafnide (PA) thin-film composite (TFC) membranes are successfully fabricated. Polyethersulfone support membranes are micro-patterned using two microfabrication methods, combined processes of vapor- and non-solvent-induced phase separation micro-molding, as well as micro imprinting lithography. PA layer is successfully adapted on the developed micro-patterned supports and the impact on the membrane performance as a result of the difference in micro-patterning resolution is explored. The patterned PA TFC membranes exhibit superior water permeability, similar to 2-2.4 times compared to the flat PA TFC membranes, without sacrificing the membrane selectivity. This is mainly due to the distinguishable enhancement in membrane active surface area (similar to 40-70%) and the increasing of the surface roughness upon micro-patterning. Furthermore, the concentration polarization analysis using different membrane orientations, with patterned grooves "parallel" and "perpendicular" to the direction of feed flow, and various feed concentrations is carried out. The results explicit the merits of implementing the micro-patterned TFC membranes in producing specific surface-induced mixing effects, which are found to reduce the concentration polarization, even at a high feed concentration. Moreover, the fidelity of the micro-patterning methods used in this work is comprehensively studied and different mechanisms for membrane surface patterning are proposed.