Modeling the mechanics and the transport phenomena in hydrogels

Hydrogels are polymeric materials widely used in pharmaceutical and biomedical applications. Their uses can be improved by modeling their behavior, in particular the mechanical phenomena and the transport phenomena. The scope of this chapter is to propose a model, simple enough and with a limited number of parameters to be determined, able to capture the full behavior of a swelling hydrogel, with the aim of describing the drug release process as well as—in principle—any other application of hydrogels. The model was derived recalling the basics of the continuum mechanics, the possible approaches to estimate the Helmholtz free energy, and then writing the transport and constitutive equations for a poroelastic material, and for a more realistic poroviscoelastic material (by adding the standard linear solid model as the rheological model). A full extension to multicomponent systems, to describe the drug release phenomenon, is proposed along with a sensitivity analysis (free-swelling simulation by changing the model parameters).