Tri-cationic copolymer hydrogels with adjustable adhesion and antibacterial properties for flexible wearable sensors

Abstract

Conductive hydrogels are widely used in the field of wearable sensors and artificial intelligence due to their excellent properties. However, most of the reported conductive hydrogels do not exhibit adjustable adhesion and antibacterial properties simultaneously, which limits their practical applications. In this work, tri-cationic polymer hydrogels (TCPHs), novel comprehensive hydrogels of zwitterionic copolymers with adjustable adhesion and antibacterial behaviours, were synthesized by free radical copolymerization under ultraviolet light excitation and characterized by NMR, FT-IR spectroscopy, and SEM. Owing to the addition of zwitterionic units, the obtained TCPHs exhibited high elongation (>770%) and mechanical strength (>670 kPa). Their conductivity and frost resistance were also superior to that of similar products. Furthermore, embedding quaternary ammonium cations into polymer chains not only gives the hydrogel excellent antibacterial ability against E. coli and S. aureus but also realizes the adjustability of adhesion properties by changing the ion density on the surface of the hydrogel. Remarkably, the adhesion strength reached 28.1 kPa even after adhesion and peeling 9 times from glass. In addition, TCPHs could be applied to accurately monitor different amplitudes of movements in different parts of the human body as flexible wearable sensors.