A transparent, highly conductive, and ultrastretchable co-crosslinked hydrogel for high-sensitivity and wide-range wearable strain sensors.

Hydrogels, celebrated for their biocompatibility and flexibility, hold immense potential for monitoring physiological activities. However, it remains a formidable challenge to design hydrogels that simultaneously deliver exceptional mechanical properties (e.g. ultra-high stretchability, skin-like softness, and anti-fracture toughness) with superior conductivity, transparency, and robust environmental adaptability to meet practical application requirements. Herein, we report a one-step fabrication of transparent and conductive hydrogels with superior anti-fracture and deformability through hydrophobic homogenous cross-linking of poly(acrylamide) (PAAM) with PSS-Octavinyl substituted (POSS) and divinyl benzene (DVB) co-crosslinkers, further reinforced by robust Li-mediated hydrated hydrogen bond networks. The resulting hydrogel exhibits super reversible deformation (stretchability: > 3000 %), excellent toughness (fracture stresses: > 180 kPa), and strong crack propagation resistance (fatigue threshold: > 0.89 MJ m). More importantly, it possesses superior functional properties, including superior ionic conductivity (4.34 S m), skin-like softness (Young's modulus: 5-20 kPa), and outstanding anti-freezing and moisture-retention capabilities. Leveraging these attributes, we integrated this high-performance conductive hydrogel into a wearable biosensor powered by artificial neural networks for efficient limb-signal recognition. As a result, the synthesized hydrogel and its corresponding device are anticipated to play a pivotal role in gesture-based communication scenarios, such as traffic control and interactions with individuals with linguistic impairments.