A review of self-healing composite films and its development in membrane for water filtration

Membrane filtration has been widely utilized in water and wastewater treatment to cater for the globally increasing demand for clean water. However, physical damages either at a macroscopic or microscopic level that occur during membrane installation and maintenance, entering of debris into the filtration system, and pinholes formed in the fabrication process often affect membrane performance. As the detection of the microscopic damage is challenging, self-healable membrane has emerged as one of the solutions and it has been investigated in recent years. This review provides a comprehensive overview of the self-healing mechanism in polymeric composite films, focusing on both extrinsic and intrinsic mechanisms, followed by the recent breakthroughs in the development of self-healing membranes. Extrinsic self-healing incorporates microcapsules and microvascular into the membrane polymeric network, while intrinsic self-healing is based on either physical non-covalent interaction or dynamic covalent interaction of the healing agents. The detailed explanation of the self-healing mechanisms, the materials explored, and strategies employed in the design of the self-healing membrane, as well as the resulting impact on the physiochemical properties and the performance of the membrane are discussed. This review aims to provide readers with an insight into the recent advances made and the stimulus innovative techniques to enhance the self-healing ability of membranes.