Cellulose nanocrystal/phytic acid reinforced conductive hydrogels for antifreezing and antibacterial wearable sensors

Abstract

Common hydrogels containing abundant water are insulating materials and lose stretchability easily below the freezing point of water, holding limited potential in emerging applications such as wearable soft devices. The introduction of compatible biomass-derived materials into hydrogel systems could be a potential solution that simultaneously enables anti-freezing ability, mechanical enhancement, and antibacterial properties. Based on such a hypothesis, here we report the facile development of biocompatible hydrogels that are capable of maintaining satisfying mechanical properties and electrical conductivity well below zero degrees centigrade. The strategy is to reinforce neat polyacrylamide (PAAm) hydrogels with biomass-derived cellulose nanocrystal (CNC) and phytic acid (PA), transforming the originally weak, insulating hydrogels into tough, highly conductive ones. Anti-freezing and antibacterial properties also emerge in the reinforced hydrogels, enabling them to work as efficient wearable sensors below zero degrees centigrade. Considering that numerous polymer hydrogel systems are compatible with CNC and PA, we believe that this simple biomass-based strategy can work universally to enhance and functionalize various weak and insulating hydrogels that are traditionally susceptible to frost and bacteria.

Keywords: Anti-freezing property; Cellulose nanocrystal; Hydrogel; Phytic acid; Strain sensor.