Multiple Physical Bonds Cross-Linked Strong and Tough Hydrogel with Antibacterial Ability for Wearable Strain Sensor

Strong, tough, and antibacterial hydrogels are promising in the fields of human motion detection and wearable electronics. However, it remains challenging to reach the antibacterial ability without losing the mechanical properties. In this work, strong and tough Fe3+-sodium alginate/poly(acrylamide-co-acrylic acid)/Ag nanowire (Fe3+-SA/P(Am-co-Ac)/AgNWs) hydrogel with antibacterial ability was facially prepared using multiple physical bonds. The superior mechanical properties are ensured by the double network matrix and well-designed interface between the matrix and AgNWs. The antibacterial ability was realized by the introduction of AgNWs. The matrix contains the Fe3+-SA network and the Fe3+-P(Am-co-Ac) network, which are further united together via the shared Fe3+ based ionic interaction. The interfacial defects between AgNWs and the organic matrix were efficiently eliminated by the incorporation of bis (acryloyl)cystamine (BACA) as “bridge” molecules: the C═C bond on BACA was grafted onto the main chain of P(Am-co-Ac) by free radical polymerization, and the S–S bond on BACA was anchored onto the surface of AgNWs through the Ag–S metal ligand effect. Benefiting from the multiple physical bonds and well-designed interface, the as-prepared hydrogel exhibited a stretching strength of 3.87 MPa, an elongation at break of 3127%, and a fracture energy of 112.32 MJ m–3. The bacteriostatic ratio of the as-prepared hydrogel against E. coli and S. aureus bacteria was as high as 99.98% and 99.95%. Moreover, the hydrogel displayed a conductivity and strain sensitivity (GF) of 0.01 and 0.59, a broad working range of 0–500%, and 500 cycles of loading–unloading under a strain of 40%, enabling the hydrogel to be sensitive on a large scale and with subtle body movements and making hydrogel the perfect strain sensor to monitor various human motions.