Instant strong adhesion of ultrafast gelling tough nanocomposite hydrogels for antifogging coatings and soft electronics

Tough hydrogels capable of achieving instant and strong adhesion to diverse surfaces are highly desirable for various applications such as soft electronics and antifogging coatings. However, existing hydrogel adhesives currently suffer from several limitations including slow adhesion formation, weak bonding, and poor mechanical properties. Herein, we present that strong adhesion of tough nanocomposite hydrogels can be realized instantly by rapid copolymerization of precursor solution within seconds under ambient conditions. Such tough hydrogels possessing ultrashort gelation time were prepared based on self-catalytic Fe³⁺/tannic acid redox pairs, which could activate ammonium persulfate initiator to generate abundant sulfate radicals to trigger ultrafast copolymerization of N, N-dimethylacrylamide (DMAA) and acrylic acid (AA) in the presence of Al(OH)₃ nanoparticles. The resultant hydrogels exhibit excellent mechanical properties including tensile strength of ∼1.0 MPa and compressive strength of ∼15.0 MPa, high adhesion energy of ∼1200 J m^{− 2}, and good conductivity of 0.72 S/m. Benefiting from these features, the sustainable antifogging hydrogel coatings on diverse transparent substrates can be fabricated easily based on the combined advantages of ultrafast polymerization and instant strong adhesion. Furthermore, the conductive hydrogels can be assembled into flexible strain sensors to monitor various human motions and handwriting recognition. This work provides a promising strategy to design high-performance hydrogels with instant strong adhesion, antifogging properties, and strain sensing.