Binary cation enhanced, high conductive hydrogels comprised of oxidized hyaluronic acid and polyethylenimine for wearable strain sensors.

Hydrogels are widely adopted in flexible electronics, yet their mechanical and electrochemical stability under harsh conditions remains challenging. In this study, we develop a novel hyaluronic acid-based double network (DN) hydrogel featuring exceptional mechanical robustness (6.29 MJ m-3), low-temperature resistance (-50 °C), and good self-healing ability (93% self-healing efficiency). The hydrogels are synthesized through the covalent bonding of oxidized hyaluronic acid (OHA) and polyethyleneimine (PEI) via Schiff-base reaction as the primary network, with polymeric acrylic acid (PAA) forming the secondary network, followed by immersion in LiCl and ZnSO4 solutions. The optimized hydrogel exhibits conductivity as high as 16.67 mS·cm-1 (-25 °C, 5.56 mS·cm-1). Furthermore, the hydrogel demonstrates excellent strain sensing sensitivity (~400%, GF = 2.73; 400-900%, GF = 6.41; 900-1400%, GF = 9.98), enabling the detection of both large and small human movements (for example, pulse). This work illustrates a reference of binary cation enhanced DN hydrogels for practical application in low-temperature environment.