8. Micro- and Nano-patterned Hydrogels Fabricated by Taking Advantage of Surface Instabilities

In this chapter, several methodologies used to generate surface instabilities on hydrogel films are reviewed. The main advantage of surface instability usage for generating nano- and micro-patterned surfaces is their low cost, ease of fabrication, and the possibility of methodology scalement for industrial processes. Surfaces instabilities are generated by a mismatch of forces or stresses between the different strata of a film. Their inhomogeneous contraction or dilatation could eventually generate out-of-plane deformations; the shape and distribution of the patterns formed on top can be controlled according to the variation of the parameters used for their generation. Particularly, hydrogels have a remarkable importance in biomedical applications due to their high biocompatibility, low toxicity, and facile chemical or physical alteration, being able to be used as a base for shape memory devices, pH- or thermoresponsive materials, or antibacterial/antibiofouling devices. In the final section of this chapter, several applications of nano- or micro-patterned surfaces generated on hydrogels are mentioned and explained.