High-strength, low-hysteresis PVA conductive hydrogel enabled by osmotic regulation for robotic hand sensors.

Conventional conductive hydrogels, despite their excellent electrical conductivity, generally suffer from poor mechanical strength, which significantly limits their applications in high-load dynamic environments. To address this challenge, this study innovatively proposes a bidirectional infiltration regulation mechanism, successfully developing a polyvinyl alcohol-based ionic conductive hydrogel (PVA-L) that combines high strength with low hysteresis characteristics. Using PVA as the matrix, a microcrystalline cross-linked network was constructed via DMSO-assisted freeze-thaw cycling. Short-term immersion (60 s) in 1-butylsulfonic acid-3- methylimidazolium trifluoromethanesulfonate ([BSMim][OTf]) ionic liquid solution enabled rapid conductivity enhancement from an initial 3.6 mS·m-1 to 459 mS·m-1, while maintaining excellent mechanical properties (fracture stress: 3.4 MPa) and low hysteresis (hysteresis factor: 6.6 %). During the long-term immersion equilibrium diffusion phase (24 h), reverse diffusion of water molecules induced further densification of the microcrystalline network, resulting in a significant mechanical strength improvement to 7.25 MPa. As a flexible sensor, PVA-L demonstrates multi-scale dynamic response capabilities: It exhibits piecewise linear responses within 0-400 % strain range (GF: 2.9-5.4), rapid dynamic response characteristics (120/100 ms), and exceptional rate stability. Experimental validations confirmed its precision in monitoring human joint movements, robotic hand gesture recognition, and force feedback during grasping of differently sized objects, proving its reliability and response accuracy in dynamic environments. This research provides a novel sensing material solution for flexible electronic devices that simultaneously achieves high mechanical strength and superior electrical conductivity.