Linear response of the human erythrocyte to mechanical stress

The human erythrocyte readily changes its shape in response to mechanical stress. Geometrical methods are used to analyze this effect in three experiments: thermal shape fluctuation (flicker), electrodeformation, and tank treading, which is the circulation of the membrane around the interior fluid in a shear flow. Comparison with existing data indicates that both flicker and tank treading represent the motion of a fluid membrane. At the same time it is a solid membrane (i.e., possessing a shear modulus) that resists large-scale shape change. This combination of fluid and solid membrane properties is in some ways paradoxical.