An anti-freezing, mechanically tough hydrogel via Hydro-Locking for mechanical sensors and flexible supercapacitor at low temperatures

Abstract

Hydrogels are extensively utilized in flexible electronic devices owing to superior ionic conductivity and excellent flexibility. However, their performance is severely compromised at low temperatures, where both flexibility and ionic Conductivity decline markedly, leading to device failure. Herein, we introduce a straightforward hydro-locking strategy fabricate 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 anchoring 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 ultra-high tensile strain (0-4149%), high strength (2.15 MPa) and high ionic conductivity (67 mS cm -1 ), while retaining ionic Conductivity (0.6 mS cm -1 ) even at -80℃. When employed as a flexible sensor, the PACL35 offers precise and stable monitoring of articular motion under low-temperatures conditions. In addition, a supercapacitor constructed based on PACL35 hydrogel, exhibited an energy density of 10.6 μWh cm -2 at -80°C, highlighting outstanding low-temperature tolerance.