An anti-freezing, mechanically tough hydrogel via hydro-locking for mechanical sensors and flexible supercapacitors at low temperatures

Hydrogels are extensively utilized in flexible electronic devices due to their high electrical conductivity and excellent flexibility. However, their performance is severely compromised at low temperatures, where both flexibility and conductivity decline markedly, leading to device failure. Herein, we introduce a straightforward hydro-locking strategy fabricate hydrogel (PACL35) with excellent low-temperature tolerance and electrical conductivity. Specifically, we developed a synergistic hydro-locking dual-salt system based on AlCl₃-Li₃Cit. This approach leverages citrate anions (Cit³⁻) to form molecular bridges that effectively anchoring the Al³⁺-centered bound water regions around the polymer chains. The resulting hydrogel exhibits remarkable tolerance to extreme cryogenic conditions, remaining unfrozen over a wide temperature range from -170°C to room temperature (RT). It also exhibited ultra-high tensile strain (0–4146%), high strength (2.15 MPa) and high electrical conductivity (67 mS cm-1), while retaining conductivity (0.6 mS cm-1) even at -80℃. When employed as a flexible sensor, the hydrogel enables precise and stable monitoring of joint movements under low-temperatures conditions. In addition, a supercapacitor constructed based on PACL35 hydrogel, achieved an energy density of 10.6 μWh cm-² at -80°C, highlighting outstanding low-temperature tolerance.