Skin-Inspired Design of Self-Healing Coatings Integrating Interface-Liquid Repellency and Corrosion Resistance.

Designing coatings with a wide spectrum of functions such as self-healing, liquid repellency, anticorrosion, and a high level of mechanical robustness is crucial in engineering applications. However, simultaneously meeting two or more conflicting requirements remains a challenge. In this work, a holistic, skin-inspired tri-layer coating is proposed to resolve the conflicting requirements of self-healing, liquid repellency, and corrosion resistance in hydrophilic polymer materials. The rational design of multiple gradients in self-healing, wetting, and strength endows a sustained liquid repellency, corrosion resistance, and self-healing even under harsh environments, as well as strong adhesion with metal substrate. The skin-inspired tri-layer coating exhibits complete self-healing even in harsh aqueous environments, owing to the synergistic interaction between layers. The tri-layer structure consists of a hydrophobic epidermis-like barrier layer, a hydrophilic self-healing polymer middle layer, and a micro-arc oxidation porous base layer that provide strong interfacial adhesion and mechanical support. The hydrophilic polymer layer, composed of polyvinyl alcohol and tannic acid, rapidly repairs damaged coating regions through hydrogen bonding and diffusion, triggered by water molecules. Meanwhile, the hydrophobic outer layer acts as a sealing barrier, limiting excessive diffusion of the hydrophilic polymer. Such an integrated skin-inspired coating strategy provides new insights into design and manufacturing multifunctional polymeric coatings to tackle the critical challenges in a variety of engineering services.