The mechano-electrokinetic properties of charged-hydrated-soft tissues and transport of interstitial water and ions within the tissues in one-dimensional steady permeation experiments were analyzed based on the triphasic mechano-electrochemical model (Lai et al., 1991). Ion diffusivity, hydraulic permeability, electrical conductivity, streaming potential, diffusion potential, streaming current, and electro-osmosis were studied both analytically and numerically. The mechanical, electrical and physicochemical events within the tissues in the filtration, diffusion and electro-osmosis processes were investigated numerically. Analyses have shown that the fixed charge density plays a significant role in controlling interstitial water flow and ion transport in charged tissues.

A generalized triphasic theory was developed to describe the behaviors of charged-hydrated-soft tissues with multi-electrolytes. From this generalized theory the well-known Hodgkin and Huxley equivalent circuit for cell membrane potential was rigorously derived. A relationship between the membrane conductance and the ion concentrations, ion valences, as well as frictional coefficients was also derived.

The effects of sodium-calcium exchange on equilibrium swelling and osmotic pressure of articular cartilage were investigated parametrically by the generalized theory. Results indicates that the existence of calcium ion in cartilage would affect the ion concentrations and osmotic pressure within the tissue, and free-swelling strain considerably.

Experimental methods for determining important material coefficients in the triphasic model such as the fixed charge density, chemical expansion stress, interphase coupling coefficient, and frictional coefficients of articular cartilage in a saline (NaCl) solution were presented. A design of experimental apparatus for the measurement of hydraulic permeability, electrical conductivity and electro-osmosis were also described. Potential technical problems in the experiments were discussed.