Eco-Friendly, Self-Healing Hydrogels for Adhesiveand Elastic Strain Sensors, Circuit Repairing, and Flexible ElectronicDevices

Intelligent skinlike materials have recently attracted tremendous research interests for employing in electronic skin, soft robotics, and wearable devices. Because the traditional soft matters are restricted in unsatisfactory mechanical performances or short-term usage, these materials are adverse to practical applications. Here, intriguing conductive hydrogel materials with multifunctionality (MFHs) are fabricated by using poly(acrylic acid) (PAA), dopamine-functionalized hyaluronic acid (DHA), and Fe3+ as ionic cross-linker. The mussel-inspired networks with delicate combination of physical and chemical cross-linking possess synergistic features of inherent viscoelasticity, high stretchability (800%), and durable self-adhesiveness to various substrates. Owing to the abundant hydrogen bonds and multiple metal coordination interactions between Fe3+, catechol, and carboxylic groups, the matrix reveals repeatable thermoplasticity and autonomous self-healing property both mechanically and electrically (98% recovery in 2 s). When served as strain sensors, the MFHs can distinctly perceive complex body motions from tiny physiological signal (breathing) to large movements (knee bending) as human motion detecting devices. Moreover, the MFHs were explored as ideal material for circuit repairing, programming, and switches constructing because of their excellent properties. Consequently, these eco-friendly hydrogel ionotronic devices can be promising candidates for next-generation intelligent wearable devices and human-machine interfaces.