Polymerizable Hydrogels for Rapid Prototyping: Chemistry, Photolithography, and Mechanical Properties

Abstract

Hydrogels are cross-linked polymeric structures which are swollen by water [1, 2]. In a more general sense, these polymeric structures can contain solvents other than water, leading to the more general term “gel.” Besides the polymer network and solvents, hydrogels can also contain particulate filler materials, typically ceramic particles. The functional and structural properties of hydrogels can be tailored quite easily, as the network density as well as the solvent content can be varied over a large range. The mechanical properties (especially the stiffness) of hydro(gels) are comparable to many biological tissues. Furthermore, the open network in combination with the mobile solvent molecules facilitates the diffusion of nutrients and dissolved gases, which makes hydrogels a widely used material in biomedicine, e.g. for the use in contact lenses [3], wound-healing bioadhesives, scaffolds for tissue engineering [4], and pharmaceutical hydrogel systems. Hydrogels are also used in a number of sensor applications, as the swelling behavior and diffusion coefficient of hydrogels depend on the ambient conditions [5].