Congelation- and dehydration-tolerant, mechanically robust hydrogel electrolyte for durable iontronic sensors operating in open air and freezing temperatures over wide strain and pressure ranges

Conventional hydrogels have limitations in mechanical properties and are susceptible to loss of elasticity and conductivity caused by congelation and dehydration, limiting their practical uses for application in high-stress environments, open air, and freezing temperatures. This study introduces a mechanically robust, dehydration- and congelation-tolerant, and ionically conductive hydrogel electrolyte, practical for iontronic sensors working in wide pressure and strain ranges under open-air and freezing temperatures. This hydrogel electrolyte is fabricated through a reconstruction process comprising a drying-induced densification of double-network hydrogel of alginate and polyacrylamide, a structure fixation by Fe³⁺ crosslinking, and a Li⁺ infiltration. The resultant hydrogel electrolyte is tolerant to dehydration and congelation and mechanically robust, with strength and elastic modulus of a few mega-pascals comparable to those of non-conductive elastomers/rubbers used as dielectric materials. Therefore, the hydrogel electrolyte-based iontronic sensors demonstrate exceptional sensitivity and stability under compression and tension and across a wide temperature range. Further, the sensor demonstrates their practical applicability in high-stress environments from kg-range human weight to ton-range car weight. These achievements evince that iontronic sensors, based on mechanically robust and ionically conductive hydrogel electrolytes tolerant to congelation and dehydration, can be employed for practical applications.