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

Hydrogels are extensively utilized in flexible electronic devices owing to their superior ionic conductivity and excellent flexibility. However, their performance is severely compromised at low temperatures, where both the flexibility and ionic conductivity decline markedly, leading to device failure. Herein, we introduce a straightforward hydro-locking strategy to fabricate a hydrogel (PACL₃₅) with excellent low-temperature tolerance and ionic conductivity. Specifically, we developed a synergistic hydro-locking dual-salt system based on AlCl₃-Li₃Cit. This approach leverages citrate anions (Cit^3-) to form molecular bridges that effectively anchor the Al³⁺-centered bound water regions around the polymer chains. The resulting hydrogel exhibits remarkable tolerance to extreme cryogenic conditions, remaining unfrozen spanning from -170 °C to RT. It also exhibited an ultra-high tensile strain (0-4149%), high strength (2.15 MPa) and high ionic conductivity (67 mS cm^-1), while retaining the ionic conductivity (0.6 mS cm^-1) even at -80 °C. When employed as a flexible sensor, the PACL₃₅ offers precise and stable monitoring of articular motion under low-temperature conditions. In addition, a supercapacitor constructed based on the PACL₃₅ hydrogel exhibited an energy density of 10.6 μWh cm^-2 at -80 °C, highlighting its outstanding low-temperature tolerance.