Swell induced stress in a hydrogel coating

A hydrogel can be coated on various substrates to enable multiple functions. Potential applications include biomedical devices, anti-fouling surfaces and microfluidics. In practical use, hydrogel coatings are often submerged in fluids. The swell of hydrogel coating deteriorates the interfacial bonding with the substrate. This paper presents a stress analysis of a hydrogel coating on a cylindrical metal substrate. We adopt the thermodynamic theory coupling large deformation and water migration and formulate two boundary value problems for the coating–substrate system with and without an interfacial crack. The inhomogeneous stress fields in the hydrogel coating are obtained. The influences of modulus, thickness of the hydrogel coating on the maximum radial stress at the interface are analyzed. These results may guide the design of hydrogel coating to avoid interfacial failure. Graphic abstract: The swell of a hydrogel coating deteriorates the interfacial bonding with the substrate. This paper presents a stress analysis of a hydrogel coating on a cylindrical metal substrate. We adopt the thermodynamic theory coupling large deformation and water migration, formulate two boundary value problems for the coating–substrate system with and without an interfacial crack, and obtain the inhomogeneous stress fields. These results may guide the design of hydrogel coating in future applications. [Figure not available: see fulltext.]