Emerging investigator series: Engineering membrane distillation with nanofabrication: Design, performance and mechanisms

Anti-fouling and durability are two important parameters that are closely associated with the development and deployment of membrane distillation (MD). In this study, we reported a nanoimprinted, omniphobic polytetrafluoroethylene (PTFE) membrane with a hierarchical rough structure for the MD process. A highly ordered, circular surface pattern was first imparted to a PTFE membrane substrate via a nanoimprint technique. An ultrathin TiO2 layer was deposited onto the nanoimprinted membrane to create a spherical hierarchical rough structure via atomic layer deposition as well as an initiator for chemical fluorination of the membrane. The resultant, nanofabricated membrane exhibited a water contact angle of 155° and a contact angle above 100° against a range of low surface tension liquids. In addition, the nanofabricated membrane displayed a high and stable water flux of around 34 L m-2 h-1 for more than 24 hours, and nearly complete salt rejection with the presence of surfactants. Most importantly, the water flux recovery rate of the resultant membrane was more than 91.3% after three fouling-cleaning cycles, demonstrating excellent fouling reversibility. The new strategy proposed here that combines the nanoimprint technique and superhydrophobic modification sheds light on developing MD membranes with considerable durability and anti-fouling performance.