A harsh environmental resistant and long-term stable ionic conductive hydrogel by one-step preparation for wireless health activity and physiological state detection.

Benefiting from the good electromechanical performance, ionic conductive hydrogel can easily convert the deformation into electrical signals, showing great potential in wearable electronic devices. However, due to the high water content, icing and water evaporation problems seriously limit their development. Although additives can ease these disadvantages, the accompanying performance degradation and complex preparation processes couldn't meet application needs. In this work, a convenient method was provided to prepare ionic conductive hydrogels with sensitive electromechanical performance, harsh environmental tolerance, and long-term stability without additives. Based on the hydratability between metal ions and water molecules resulting in spatial condensation of the hydrogel framework, the hydrogel exhibits good flexibility and ionic conductivity (70.3 mS/cm). Furthermore, the metal salt can bind with water molecules to reduce the vapor pressure, thus endowing the hydrogel with good freezing resistance (-40 °C) and long-term stability over a wide temperature range (-20 °C-50 °C). Based on these unique advantages, the hydrogel shows good sensitivity. Even in a harsh environment, it still maintained excellent stability (-20 °C-50 °C, GF = 2.2, R > 0.99). Assembled with a Wi-Fi device, the hydrogel sensor demonstrates good health activity and physiological state detection performance, demonstrating great potential for wearable medical devices.