Measurements of deformations and electrical potentials in a charged porous medium

When a biological tissue is subjected to a mechanical load, an electrical potential gradient is generated. Such potential gradient is associated with the flow of charged particles through a matrix with fixed charges. A deformation of the matrix causes a fluid flow relatively to the solid matrix. This fluid flow tends to separate the freely moving ions in the fluid from the oppositely charged particles, that are attached to the matrix. In this way, an electrical field is created collinear to the fluid flow. This results in an electrical potential. A similar effect appears when charged particles start moving because of a chemical load. In this study, uniaxial confined swelling and compression experiments were performed on a hydrogel that mimics the behaviour of biological tissues. The deformation of the sample and the electrical potential difference over the sample, caused by varying mechanical and chemical loads, were measured successfully.