Theory of electromechanical spectroscopy in poroelastic media: surface detection of bulk properties

A model of electromechanically coupled poroelastic media (J.R. Sachs and A.J. Grodzinsky, 1989) is used to study the configuration of a diagnostic probe based on surface electromechanical spectroscopy. A periodic displacement or current is imposed at the surface of a layer of finite thickness. This displacement or current produces electrical (streaming) potential, mechanical displacement and stress in the bulk and at the surface of the tissue layer with the same frequency and wavelength as the imposed field. Surface boundary conditions impermeable or infinitely permeable to fluid are considered. The results suggest how surface measurements of the stress and potential can be used to determine bulk material properties of charged poroelastic materials such as cartilage. The relation between the temporal frequency and spatial wavelength of the surface excitation and the amplitude, phase, and penetration depth of the stress and potential is investigated numerically and asymptotically