(411h) Flexible Wearable Sensor for Human-Machine Interaction in Polar Expedition at -78°C - Highly Stretchable, Sensitive, and Anti-Freezing Conductive Organic Hydrogel

Exploration of the polar regions is significant to mankind's understanding of the Earth's climate change, geological structure and biological adaptations. In addition, with the depletion of global resources, exploration of the polar regions can help to assess resource reserves, development potential and sustainable utilization methods, providing new resources to support human development. However, extreme climatic conditions increase safety risks for explorers. Flexible wearable sensors can monitor the movement and physiological health status of explorers and can improve human-machine interaction. However, the development of flexible wearables that can withstand ultra-low temperatures remains challenging. Here, we report a conductive organic hydrogel for motion monitoring over a wide temperature range from room temperature to -78°C. We chose acrylamide-carboxymethylcellulose as the matrix, introduced the biomineral calcium ions, and added hydrophobic microspheres as the cross-linking points. In addition, inspired by freeze-tolerant organisms and mussels, glycerol and the biomimetic binder branched polyethyleneimine-tannic acid were integrated into the gel network.

The prepared organic hydrogel has high conductivity (1.57 S/m), high elongation (1700%), high tensile sensitivity (GF=6.47) and pressure sensitivity (0.32 kPa^-1), and shows stable signal response in 500 cycles of loading-unloading under 400% large tensile strain, which can be used for real-time monitoring of human daily exercise and physiological health status. In addition, thanks to the synergistic effect of glycerol and calcium ions, which inhibit the hydrogen bonding between water molecules and lead to a decrease in the saturated vapor pressure of water, the organic hydrogel has excellent freeze resistance (-103.6 ℃), and flexible sensors based on this organic hydrogel can perform intelligent gesture recognition at low temperatures, and can monitor body movements and recognize various pressures even at -78 ℃. Finally, we encoded English letters through Morse code and realized wireless encrypted transmission of distress signals at -78 ℃ through a human-machine interaction mechanism, which provides security for explorers in polar environments.