Modification of 3D-printed PLA structures using Photo-iniferter RAFT Polymerization: Toward on-demand antimicrobial water filters

Water filtration is an important application field to ensure the accessibility of clean drinking water. As requirements and contaminants vary on a local level, adjustable filter devices and their evaluation with contaminants are required. Within this work we design modular filter devices featuring an adjustable surface functionalization. For this purpose, we create 3D-printed structures fabricated of bio-based poly(lactic acid) (PLA) that are manufactured by extrusion printing. The surface of PLA is activated with amino groups that are used to install xanthates as chain transfer agents (CTA)s. Subsequently, photo-iniferter (PI)-RAFT polymerization is used to create cationic polymer brushes on the surface of PLA substrates. The polymerization is first optimized in solution and then transferred to the interface of 3D-printed devices. Multiple surface characterization techniques are employed to prove successful growth of polymer brushes on PLA. The degree of polymerization of cationic polymers is varied and found to influence the interaction of the interface with planktonic bacteria. After initial optimization studies on flat surfaces, filter devices are printed, functionalized, and used to remove bacteria from contaminated water. Significant reduction of microorganisms is detected after filtration (single filtration or cycling) and contaminating organism could also be removed from freshwater samples by simple incubation with a 3D-printed filter. The herein developed setup for producing functional filter devices and probing their performance in affinity filtration is a useful platform technology, enabling the implementation of polymer brushes for such applications. The combination of additive manufacturing and the modularity of the surface functionalization reaction enables rapid adjustability of the system.