- Markle, D.R. and Evans, E.A. and Hochmuth, R.M., Force relaxation and permanent deformation of erythrocyte membrane,
Biophys. J. (USA), vol. 42 no. 1
pp. 91 - 8 .
(last updated on 2007/04/10)
Force relaxation and permanent deformation processes in erythrocyte membrane were investigated with two techniques: micropipette aspiration of a portion of a flaccid cell, and extension of a whole cell between two micropipettes. In both experiments, at surface extension ratios <3:1, the extent of residual membrane deformation is negligible when the time of extension is less than several minutes. However, extensions maintained longer result in significant force relaxation and permanent deformation. The magnitude of the permanent deformation is proportional to the total time period of extension and the level of the applied force. Based on these observations, a nonlinear constitutive relation for surface deformation is postulated that serially couples a hyperelastic membrane component to a linear viscous process. In contrast with the viscous dissipation of energy as heat that occurs in rapid extension of a viscoelastic solid, or in plastic flow of a material above yield, the viscous process in this case represents dissipation produced by permanent molecular reorganization through relaxation of structural membrane components. Data from these experiments determine a characteristic time constant for force relaxation, τ, which is the ratio of a surface viscosity, η to the elastic shear modulus, μ
biomembranes;biorheology;blood;cellular biophysics;plastic deformation;