ABSTRACT
The swelling and shrinking behaviour of soft biological tissues is described by a four components mixture theory. In this theory four components are distinguished: a charged solid, a fluid, cations and anions. By using balance equations, constitutive equations and equations of state, a set of coupled differential equations is derived. Because of the distinction between cations and anions, we are able to describe electrical phenomena like streaming potentials. A one-dimensional finite element implementation of this model is made by using a Galerkin method, an implicit time discretization and the Newton-Raphson iteration procedure. This implementation is used to simulate confined swelling and compression experiments. It appears that physically realistic values for the stiffness, permeability and diffusion coefficients are adequate to fit the experiments. We do not need a chemical expansion stress.
