Concerning a Percolation Concept of Zeta Potential and Electrokinetic Phenomena in Bio-Systems

Abstract

The electrokinetic or zeta potential is the basic notion in theory of electrokinetic phenomena. It is defined as electric potential in the interfacial electrical double layer (EDL) at the location of the “slipping plane” versus a point in the bulk fluid away from the interface. Many interfacial/electrokinetic phenomena in biological systems can be interpreted in terms of the membrane electrical properties of the cells involved. However, the conventional definition of the zeta potential and a “slipping plane” are based on two unrealistic assumptions: (1) that one can realize a procedure of the “infinitesimal” change of the continuous layer thickness without changing its topology, during both thinning and growth, and (2) that the interface is ideally homogeneous. These assumptions are already denied with many experimental facts in modern interface science. Instead of the infinitesimal variations of the continuous layer thickness, one has to account topologic transitions from continuous to discrete EDL structures at the interface [1]. During EDL thinning, the hydrodynamic flow stops at a percolation level (effective thickness), corresponding to a discrete film. It brings us to a real and exact meaning of a mythic “slipping plane”. The zeta potential is the potential corresponding to beginning of percolation of the EDL, or shortly, the “zeta potential is the percolation potential”. This new paradigm gives effective heuristic keys for quantitative analyzing electrokinetic processes in real disperse systems with heterogeneous interfaces, in part, biointerfaces, such as transport processes in cellular ion channels, cell electrophoresis, electroosmosis, adhesion and fusion [2-3]. Refs.:1.Smorodin, V.Y. Surface (Russian), 1991, 12, 85-91.2.Smorodin, V.Y. Physical Chemistry of the USSR, 1990, 312 (6), 537-540.3. Smorodin, V.Y. Physical Chemistry of the USSR, 1991, 318 (6), 379-384.