Compressive deformation of a single microcapsule

This paper reports an experimental and theoretical study of the compressive behavior of single microcapsules; that is, liquid-filled cellular entities (approximately 65 mu m in diameter) with a thin polymeric membrane wall. An experimental technique which allows the simultaneous measurement of both the compressive displacement and the reaction forces of individual microcapsules deformed between two parallel plates up to a dimensionless approach [(compressive displacement)/(initial particle diameter)] of 60% is described. The corresponding major geometric parameters of the deformed microcapsule, such as central lateral extension as well as the failure phenomena, are reported and recorded through a microscopic visualization system. The elastic modulus, the bursting strength of the membrane, and the pressure difference across the membrane are computed by using a theoretical analysis which is also presented in this paper. This theoretical model, which was developed by Feng and Yang [J. Appl. Mech. 40, 209 (1973)] and then modified by Lardner and Pujara [in Mechanics Today, edited by S. Nemat-Nasser (Pergamon, New York, 1980), Vol. 5], considers the deformation of a nonlinear elastic spherical membrane which is filled with an incompressible fluid. The predictions of the theory are consistent with the experimental observations.