Towards Large-Scale Fabrication of Self-Healable Functional Hydrogel Coatings for Anti-Fog/Frost Surfaces and Flexible Sensors

Hydrogel coatings have drawn substantial research interest owing to their great potential in developing advanced flexible devices. However, most of them cannot meet the requirement of large-scale application on diverse substrates and would lose their functionalities under harsh conditions. In this work, a large-scale and surface-independent multifunctional hydrogel coating is developed by directly painting and ultraviolet curing hybrid hydrogel precursor containing acrylamide (AM), branched polyethylenimine (PEI), CaCl 2 , and glycerol. Such a coating shows superior anti-fog and anti-frost properties owing to the hydrophilic nature and freezing-tolerance of the hydrogel. Besides, the hydrogel coating possesses excellent self-healing performance at both macro- and micro- scales because of the dynamic hydrogen bonds prevailing between the polymer chains in a gel network. Moreover, this hydrogel coating also exhibits electric conductivity due to the mobile ions present in the gel network. By patterning the hydrogel coating onto an elastic substrate, a foldable tape sensor is fabricated which can sensitively distinguish short-time click (≈0.1–0.2 s) from long-time press (≈1–2 s) and detect electrical signals corresponding to cyclic bending deformation. This work provides practical demonstration of hydrogel coatings for engineering applications where anti-fog, anti-frosting, self-healing, and electrically conductive properties are needed.