A mixture theory for charged-hydrated soft tissues containing ivjulti-electrolytes: Passive transport and swelling behaviors

W. Y. Gu, W. M. Lai, V. C. Mow

Research output: Contribution to journalArticlepeer-review

251 Scopus citations


A new mixture theory was developed to model the mechano-electrochemical behaviors of charged-hydrated soft tissues containing multi-electrolytes. The mixture is composed of n + 2 constituents (1 charged solid phase, 1 noncharged solvent phase, and n ion species). Results from this theory show that three types of force are involved in the transport of ions and solvent through such materials: (1) a mechanochemical force (including hydraulic and osmotic pressures); (2) an electrochemical force; and (3) an electrical force. Our results also show that three types of material coefficients are required to characterize the transport rates of these ions and solvent: (1) a hydraulic permeability; (2) mechano-electrochemical coupling coefficients; and (3) an ionic conductance matrix. Specifically, we derived the fundamental governing relationships between these forces and material coefficients to describe such mechano-electrochemical transduction effects as streaming potential, streaming current, diffusion (membrane) potential, electro- osmosis, and anomalous (negative) osmosis. As an example, we showed that the well-known formula for the resting cell membrane potential (Hodgkin and Huxley, 1952a, b) could be derived using our new n + 2 mixture model (a generalized triphasic theory). In general, the n + 2 mixture theory is consistent with and subsumes all previous theories pertaining to specific aspects of charged-hydrated tissues. In addition, our results provided the stress, strain, and fluid velocity fields within a tissue of finite thickness during a one-dimensional steady diffusion process. Numerical results were provided for the exchange of Na+ and Ca++ through the tissue. These numerical results support our hypothesis that tissue fixed charge density (c(F)) plays a significant role in modulating kinetics of ions and solvent transport through charged-hydrated soft tissues.

Original languageEnglish (US)
Pages (from-to)169-180
Number of pages12
JournalJournal of biomechanical engineering
Issue number2
StatePublished - Apr 1998
Externally publishedYes

ASJC Scopus subject areas

  • Biomedical Engineering
  • Physiology (medical)


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