A TRIPHASIC ANALYSIS OF NEGATIVE OSMOTIC FLOWS THROUGH CHARGED HYDRATED SOFT-TISSUES

Osmotic flow and ion transport in a one-dimensional steady diffusion p rocess through charged hydrated soft tissues such as articular cartila ge were analysed using the triphasic theory (Lai et al., 1991, J. biom ech. Engng 113, 245-258). It was found that solvent would flow from th e high NaCl concentration side to the low concentration side (i.e. neg ative osmosis) when the fixed charge density within the tissue (or mem brane) separating the two electrolyte (NaCl) solutions was lower than a critical value. The condition for negative osmosis was derived based on a linear version of the triphasic theory. Distributions of ion con centration and strain held within the tissue were calculated numerical ly. Quantitative results of osmotic flow rates (ordinary and negative osmosis), ion flux and electric potential across the tissue during thi s diffusion process suggest that the negative osmosis phenomenon is du e to the friction between ions and water since they could how through the tissues at different rates and different directions. Copyright (C) 1996 Elsevier Science Ltd.