Hybrid nano-microstructured and bioinspired conductive hydrogels with tunable multifunctionality

Abstract

Conductive hydrogels with tunable multifunctionality show great potential in wearable smart devices. In this work, inspired by the nano-structured architecture strategy and natural mussel adhesive mechanism, a conductive hydrogel (AgPMP hydrogel) was fabricated through facile direct in situ polymerization. Silver nanowires (Ag NWs) and polydopamine (PDA) chains were integrated into the poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAM-co-AM)) gel matrix, with activated PNIPAM microgels (MGs) serving as nano-crosslinkers. The overall internal structure of the hydrogel presented a heterogeneous cross-linked mesh-like structure with numerous irregular wrinkles. The AgPMP hydrogel demonstrated significantly enhanced mechanical strength, achieving a remarkable stretchability of 1140% attributed to the nano-microstructured architecture built using AM-based networks, nano-crosslinkers and Ag NWs. Moreover, due to the synergistic effect of PDA and Ag NWs, the hydrogel exhibited impressive photothermal antibacterial activity. Meanwhile, in the presence of abundant active catechol groups, this hydrogel possessed adequate tissue-adhesive and self-healing abilities as well as good antioxidant properties. Notably, the AgPMP hydrogel exhibited outstanding strain-sensitive conductivity. The resultant strain sensor showed high sensitivity with a gauge factor (GF) of up to 8.35 at a strain of 250%. The stable response signals during continuous and gradual cycling proved its electrical durability and stability. Combined with the great merits of the above performance, this sensor holds great promise for detecting human movements. The relative resistance change ranged from 16% to 64% as the finger bending angle changed from 30° to 90°. Thanks to its simple fabrication process, this multifunctional conductive hydrogel is expected to have widespread potential applications in tissue engineering, soft electronic skin and human-health monitoring.