High-strength polyacrylamide/sodium alginate-based hydrogel with extreme environmental tolerance for low-temperature strain sensing

Conductive hydrogels are ideal materials for fabricating flexible electronic devices, but their limited mechanical strength and susceptibility to dehydration and freezing constrain their application in challenging environments. This study successfully developed an environmentally adaptive polyacrylamide/alginate/Zn²⁺/Li⁺ (PAAm/Alg/Zn²⁺/Li⁺, D -PAZL) dual-network hydrogel with high mechanical strength by combining a pre-drying densification strategy with a dual metal salt permeation strategy. The resulting hydrogel showed excellent tensile strength (1.05 MPa), electrical conductivity (5.16 S/m), long-term water retention (retaining ∼73.34 % of its initial mass after 168 h at 25°C and 50 % relative humidity), freeze resistance (<-40°C), and antibacterial activity (inhibition zone diameter: E. coli = 5.3 mm, S. aureus = 5.4 mm). Notably, the incorporation of highly hygroscopic LiBr endows the hydrogel with moisture self-regenerating capabilities, enabling dehydrated hydrogels to autonomously capture moisture from the environment and achieve sustained water retention. The strain sensor constructed from D -PAZL 30 hydrogel exhibits high sensitivity (GF=3.72), rapid response/recovery times (298 ms/303 ms), and long-term cycling stability (>120 tensile cycles after 30 days of exposure in open environments), making it suitable for monitoring human activities across various scales. More importantly, the sensor maintains excellent sensing performance at −40°C (conductivity: 4.37 S/m, GF = 1.95) and can accurately transmit rescue signals via Morse code. This work provides a novel design strategy for developing flexible electronic devices suitable for extreme environments, opening new avenues for wearable technology and communication fields.