Elastohydrodynamic Lubrication in Biological Systems

Abstract

Elastohydrodynamic lubrication (EHL) appears to be an important mechanism in various biological systems. In this paper, a few examples will be selected to illustrate the biological applications of EHL: microcirculation of red blood cells in capillaries, blinking of eye and contact lens, and respiratory motion between pleural surfaces and articulation in synovial joints. It is shown that the relatively large elastic deformation of the bearing surfaces associated with relatively compliant biological tissues is responsible for the major contribution of fluid film action to the lubrication at both tissue and cellular levels. Under unfavourable lubrication conditions, the articulating surfaces can be protected by the powerful effect of micro-EHL in smoothing out surface asperities and further by the glycocalyx present on the biological surfaces.