Gelation of hydrogel films and coatings induced by substrate swelling.*

Hydrogel films used as membranes or coatings are essential components of devices interfaced with biological systems. Their design is greatly challenged by the need to find mild synthesis and processing conditions that preserve their biocompatibility and the integrity of encapsulated compounds. Here, we report an approach to produce hydrogel films spontaneously in aqueous polymer solutions [1]. This method uses the solvent depletion created at the surface of swelling polymer substrates to induce the gelation of a thin layer of polymer solution. Using a biocompatible polymer that self-assembles at high concentration (poly(vinyl alcohol)), hydrogel films are produced within minutes to hours with thicknesses ranging from tens to hundreds of micrometers. A simple model predicts how the solution composition, substrate geometry and swelling properties govern film growth. We also demonstrate the potential of this technique by incorporating other solutes to fabricate ceramic-hydrogel coatings for bone anchoring of osteo-articular implants and matrices for cell-encapsulation.
[1] Moreau et al. PNAS 113(47), 13295-13300 (2016).