Bioinspired bicontinuous adhesive hydrogel for wearable strain sensor with high sensitivity and a wide working range.

Conductive hydrogel strain sensors demonstrate extensive potential in artificial robotics, human-computer interaction, and health monitoring, owing to their excellent flexibility and biocompatibility. Wearable strain sensors for real-time monitoring of human activities require hydrogels with self-adhesion, desirable sensitivity, and wide working range. However, balancing the high sensitivity and a wide working range remains a challenge. Herein, a marine coral exoskeleton inspired bicontinuous hydrogel (PAD-iP) for strain sensor was synthesized by in-situ copolymerization of acrylic acid (AA) and dimethylaminpropyl methacrylamide (DMAPMA) in the presence of poly(3, 4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) skeleton, using glycerol as water-retaining agent. Benefiting from the bicontinuous structure composed of electron-transported conductive, tough PEDOT:PSS skeleton and the ion-transported, flexible poly(AA-co-DMAPMA) hydrogel matrix, the strain sensor based on PAD-iP hydrogel struck an optimal balance between ultrahigh sensitivity (gauge factor up to 1049) and a broad sensing range (strain of 0-600 %). The strain sensors could be adhered directly to skin to monitor full-range human activities, physiological activities and physical vibrational signals of the local environment. The strain sensor also exhibited robustness and stable sensing properties across a wide temperature range (-20 ∼ 40 ℃). This work offers a fresh inspiration for preparation of high-performance hydrogel strain sensors.