Light-responsive zwitterionic membrane surface modification for antifouling and antibacterial application

• Synthesized light-responsive zwitterionic azobenzene coating for UF membrane. • Coated membrane shows excellent antifouling with BSA protein during filtration. • UV–vis photoirradiation of azobenzene units cleaned foulants, restoring permeability. • Modified membrane resisted bacterial adhesion and efficiently removed bacteria under photoirradiation. • Such light-responsive self-cleaning materials can mitigate concerns about resistant bacteria. Light-responsive surface modifications offer a promising solution for reducing membrane fouling by enabling remote, contactless cleaning without altering the chemical environment. While traditional methods make membranes hydrophilic to resist fouling, biofouling remains difficult to remove and often requires harsh bactericidal treatments. With the rise of antimicrobial resistance (AMR), there is a pressing need for alternative, non-bactericidal strategies to control biofilm growth. In this study, we developed an efficient approach by coating commercial ultrafiltration polyethersulfone (PES) membranes with a copolymer of light-responsive azobenzene (AZO) and zwitterionic sulphobetaine methacrylate (SBMA). The photochemical conversion efficiency and photokinetic parameters of the copolymer, due to light-induced trans – cis-trans conversion, were systematically determined. During filtration, the modified membranes showed excellent resistance to reversible fouling with bovine serum albumin (BSA). The fouled membrane became reusable after near-complete removal of irreversible fouling, including bacteria ( Pseudomonas aeruginosa ), by activating the AZO units with UV–vis light, providing an effective strategy for fouling control.