Highly stretchable, self-healing, and strain-sensitive based on double-crosslinked nanocomposite hydrogel

In recent years, flexible hydrogel strain sensors have shown potential applications in artificial intelligence, such as medical monitoring, human motion detection, and intelligent robotics. It is a challenge for flexible strain sensors with stretchable and efficient healing to ensure stable sensing under repeated deformations or damage. In this study, a highly stretchable, self-healing, and strain-sensitive hydrogel was prepared from acrylic acid (AA), graphene oxide (GO), iron ions (Fe3+), and ammonium persulfate (APS) via one-step in-situ polymerization without a chemical crosslinker. The polyacrylic acid (PAA)-GO hydrogel showed dual crosslinking effect: (i) ionic coordination bonding between Fe3+ ions and the carboxylic functional groups of PAA and GO and (ii) hydrogen bonding between the polar functional groups of PAA and the oxygen-containing functional groups of PAA and GO. Because of dynamic double-crosslinked networks, the hydrogel exhibited superior stretchability (1185.53% elongation at break) and self-healing property (88.64% healing efficiency) as well as electrical self-healing performance. Moreover, strain-sensitive conductive hydrogels can be used as flexible sensors to monitor body motions (e.g., bending of fingers, wrists, and elbows) by detecting change in electrical signal and can be used as wearable sensors and for personal health monitoring.