Adhesion of Hydrogels to Fluoropolymers by Electrophoretic Fluoropolymer Coating

Although hydrogels are widely used in bio-integrated devices and soft systems, their robust adhesion to polymers with low surface energies remains a fundamental challenge. Fluoropolymers such as polytetrafluoroethylene (PTFE) are notoriously difficult to adhere to because of their chemical inertness and non-wetting surfaces. In this study, we demonstrate that water-stable adhesion between hydrogels and fluoropolymers can be achieved by engineering interfacial dipole-dipole interactions. In particular, a fluoropolymer coating was deposited on hydrogel surfaces via the electrophoretic deposition of an anionic fluoro-copolymer, resulting in a polyion-complexed interfacial layer. The coated hydrogels exhibited stable adhesion to PTFE, even in water. Notably, adhesion to PTFE displayed an on/off transition with slight changes in copolymer composition, while adhesion to other substrates remained unaffected. This unique composition sensitivity revealed that adhesion to PTFE required exceeding the critical surface density of fluorinated dipoles, which distinguishes it from conventional wetting-driven adhesion mechanisms. Consequently, this study highlights dipole-dipole interactions as a decisive design principle for bonding hydrogels to chemically inert fluoropolymers.