Polysaccharide-based wrinkled surfaces induced by polyion complex skin layers upon drying

We introduce a novel surface wrinkling system based on the fabrication of a polyion complex (PIC) skin layer. PIC skin layers are fabricated on the surface of chitosan (CS) films via immersion in sodium alginate (AG) solutions. After removal of excess adsorbed AG, microscopic wrinkles appear upon drying. The wrinkle size can be controlled by the immersion temperature during the formation of the skin layer because of the differences in skin layer thicknesses. In addition, we demonstrate that there is only a two-fold difference in the elastic moduli between the PIC skin layer and the CS film. Furthermore, wrinkled films can be made water resistant by thermal crosslinking of the PIC skin layer. The thermally crosslinked wrinkled surfaces composed of covalently crosslinked CS and AG demonstrate the low cell adhesiveness that is required for implantable materials. Thus, this method that combines surface wrinkling induced by a PIC skin layer and subsequent thermal crosslinking can provide a variety of wrinkled biomaterials.