Ultra-stretchable, Antifatigue, Adhesive, and Self-Healing Hydrogels Based on the Amino Acid Derivative and Ionic Liquid for Flexible Strain Sensors

Multifunctional adhesive hydrogels have great potential in flexible wearable materials, smart wearable materials, and biomedical materials. However, the preparation of such hydrogels is still challenging. Here, a P(MArg-FHVI-AA) hydrogel was prepared by copolymerization of an arginine derivative monomer, ionic liquid imidazolium salt derivative monomer, and acrylic acid (AA). Based on multiple weak hydrogen bonds and electrostatic interactions, the hydrogel had the following characteristics: high transparency (>85%), ultra-stretchability (2613%), high elasticity (1000% strain cyclic for 10 times), fatigue resistance (200 cycles under 80% compressive strain), self-healing, good adhesion in air and water (37 and 32 kPa for porcine skin in air and water), and electrical conductivity. When metal ions were added to P(MArg-FHVI-AA) hydrogels, the mechanical properties of the hydrogels were enhanced (tensile strength of 109–352 kPa, stretchability of 1707–1942%), and the hydrogels exhibited stronger adhesion strength (68 kPa for porcine skin), good biocompatibility (99%), impressive antibacterial properties (100% antibacterial effect against Escherichia coli and Staphylococcus aureus), shape memory, fluorescent writing (its fluorescence intensity was 1099% of the initial), and information transfer functions. Furthermore, the P(MArg-FHVI-AA) hydrogel showed real-time performance in monitoring various motions. This work provided an idea for the construction of multifunctional and smart adhesive conductive hydrogel materials, and this hydrogel could be a promising candidate for smart wearable materials, health monitoring, and soft body materials.