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Bioinspired membranes offer an alternative approach to improving the fouling resistance of commercial membranes for oil separations. Here, two perfluoropolyether oils, a lower viscosity Krytox 103 (K103) and a higher viscosity Krytox 107 (K107), were infused into commercial polyvinylidene fluoride (PVDF) ultrafiltration membranes to mimic the Nepenthes pitcher plant. The transmembrane pressure required to perform long-term oil permeance tests was optimized by testing the liquid-infused membranes at different applied pressures. Crystal violet staining and variable pressure scanning electron microscopy qualitatively suggest that the oil layer remained on the membranes after the oil separation experiments were conducted. Over 5 cycles, K103- and K107- liquid-infused membranes exhibited a consistent permeance of ∼ 30000 L m-2h−1 bar−1 at 1.0 bar and ∼ 14500 L m-2h−1 bar−1 at 0.5 bar, respectively. The steady performance further supports a long-lasting oil layer persists on the membrane surface and inside membrane’s pores. Next, experiments were conducted to determine the stability of the Krytox oil post accelerated cleaning tests using bleach. No structural changes to the Krytox oils were detected by thermogravimetric analysis or nuclear magnetic resonance spectroscopy. Dynamic fouling experiments using Escherichia coli K12 revealed that the liquid-infused membranes had higher flux recovery ratios (∼95 %) than the bare PVDF control membranes (∼55 %). Our results demonstrate that liquid-infused membranes exhibit chlorine stability and superior fouling resistance, presenting a promising bioinspired membrane that can be used in pressure-driven oil separation applications. 

This contribution describes a method to reduce bacteria fouling on ultrafiltration membranes by applying nanoscale line-and-groove patterns on the surface of membranes. Nanoimprint lithography was used to pattern the polysulfone membrane surfaces with a peak height of 66.2 nm and a period of 594.0 nm. Surface characterization using scanning electron microscopy and atomic force microscopy confirmed that patterning was successful over the entire stamped area of the membrane. Water permeance tests determined that the permeance decreased by 36% upon patterning. Static batch experiments that explored the attachment of Escherichia coli K12 cells to the membranes demonstrated that the patterned membranes had a 60% lower attachment of microbes than the nonpatterned membranes. Dynamic bacteria fouling experiments using E. coli cells showed that the patterned membranes had a higher flux recovery ratio (88%) compared to the nonpatterned membranes (70%). On the basis of these studies, we suggest that patterning membranes can reduce the initial attachments of microbial cells and that different pattern sizes and shapes should be investigated to gain a fundamental understanding of their influence on bacteria fouling. 

Herein, we report a controllable pathway to accelerate the polymerization kinetics of dopamine using ultrasound as a trigger. The use of ultrasound was demonstrated to dramatically accelerate the slow liquid phase reaction kinetics and increase the deposition rate of the polydopamine coating on the surface of polymeric membranes.