Injectable, Tough, and Thermoplastic Supramolecular Hydrogel Coatings with Controllable Adhesion for Touch Sensing

Soft tissues in nature are anchored on the load-bearing structures of creatures, such as tendons, ligaments, and cartilages. However, mimetic hydrogel coatings that combine the unique properties of hydrogels (e.g., in situ formability, stimulus-responsiveness, strength controllability, environmental friendliness, and small molecular encapsulation) with the superior properties of substrates such as high elastic modulus and high tensile strength still require further exploration to achieve an adequately comprehensive performance. Herein, we report an approach for fabricating hydrogel coatings using an injectable, tough, and thermoplastic κ-carrageenan (κ-car)/poly(N-acryloyl glycinamide (NAGA)-co-vinyl imidazole (VI)) supramolecular hydrogel (κ-car/PNV hydrogel) with temperature-controlled adhesion by adjusting the contact at the hydrogel-substrate interface. The κ-car/PNV hydrogel with a mass ratio of NAGA to VI of 9:1 shows a sol-gel transition temperature of 85 °C, a compressive strain of 99%, a tensile strain of 1045%, fast self-recovery, durability, and the adhesive ability to handle irregular substrates. Furthermore, this supramolecular hydrogel coating forms strips and panels with slide rheostat-based touch sensing, which is minimally affected by water evaporation. This work facilitates the fabrication and application of hydrogel coatings as touch sensing devices to combine functional supramolecular hydrogels, surface coatings, and ionotronics.