Because of the small size of the human red blood cell, it is difficult to measure the elasticity of the cell membrane. Previous techniques of measuring membrane elasticity involve high stress and strain and therefore do not adequately characterize the membrane’s elasticity near its equilibrium (biconcave) shape. In order to determine elasticity at low stress and strain, an experiment was designed to involve minimal membrane stress. In the experiment, the red cells are expelled from glass micropipettes on the order of 3 microns in internal diameter. The cell is in a folded deformed shape within the confines of the tip but once it leaves the pipette the cell returns to its biconcave shape. With the use of dimensional analysis, the characteristic relaxation times of the red cells and of geometrically similar, fluid-filled model cells are compared and a modulus of elasticity of approximately 106 dynes/cm2 is calculated.

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