Anisotropic biofouling behavior of sharkskin-patterned desalination membranes

Biofouling is a crucial issue in operating water treatment and desalination membranes because it deteriorates membrane performance. Topological tailoring of the membrane surface by implanting a biomimetic sharkskin (Sharklet) pattern has proven effective at mitigating biofouling. However, the anisotropic antibiofouling effect of the uniaxially aligned Sharklet-patterned membrane and its underlying mechanism remain unknown. Herein, the biofouling tendency of the Sharklet-patterned membrane was examined by gradually varying the angle between the pattern orientation and the bulk flow direction from 0° to 90°. The antibiofouling effect of the membrane was gradually enhanced as the pattern orientation angle increased. Computational simulation revealed that increasing the pattern orientation angle intensifies vortex flows and diverts local flows to a large extent while reducing the local flow parallel to the bulk flow; this flow change is hypothesized to effectively prevent foulant accumulation, consequently enhancing biofouling resistance. Furthermore, the observed anisotropic biofouling behavior was quantitatively interpreted using a microbial growth model. A larger pattern orientation angle attenuates the bulk flow component parallel to the pattern alignment, which critically suppresses the rate and extent of microbial growth, thereby mitigating biofouling. Our findings offer fundamental insights into the anisotropic antibiofouling mechanisms of uniaxially and/or biomimetically patterned membranes.