High tensile and antifreeze polyacrylamide hydrogel strain sensor suitable for human motion monitoring under low-temperature conditions

Abstract

Hydrogels have attracted attention for flexible sensor due to their good mechanical properties and electrical conductivity. However, hydrogels are prone to loss in flexibility and may even distort and lose their sensing ability under low-temperature conditions due to freezing, limiting their wide applications. To overcome these problems, a series of antifreeze PAM/PVA/TA/(Gly/NaCl) hydrogels were prepared through the pre-polymerization process of acrylamide (PAM), polyvinyl alcohol (PVA), and tannic acid (TA) followed by immersion in glycerol (Gly) and NaCl for different times. Among the prepared hydrogels, PAM₅/PVA₃/TA_0.4/(Gly/NaCl)₈ hydrogel exhibited remarkable flexibility, excellent antifreeze properties and excellent stimulus responsiveness. The strong hydrogen bonding interaction endowed the as-prepared hydrogel with an ultra-high tensile strength (761.1 kPa) at a maximum strain of 3360 %. The hydrogel also depicted a lower freezing point below −80 ℃ coupled with good fatigue resistance at low temperatures (-50℃). Furthermore, the hydrogel presented a GF value of 0.84 at a wide strain response range (3–500 %), indicating the ability to monitor human movement and recognize voice and handwriting signals. Overall, the proposed PAM₅/PVA₃/TA_0.4/(Gly/NaCl)₈ hydrogel with advanced sensing characteristics have tremendous potential in the field of flexible and antifreeze strain sensors, such as winter sports competitions.