Identification of the mechanical properties of microcapsules using diffuse approximation

A novel inverse analysis procedure based on diffuse approximation is presented to characterize the mechanical behavior of microcapsules. The method consists in flowing a dilute suspension of capsules through a prismatic microfluidic channel with a cross-section size comparable to the capsule diameter. For each capsule, we record its deformed profile and deduce from it a series of geometrical quantities and the capsule velocity. The unknowns are the membrane mechanical properties and the exact mean velocity of the background flow when the capsule is captured. A full mechanical model of the motion and deformation of a capsule is used to generate an exhaustive database of simulated profiles for different values of the input parameters: the capillary number and the size ratio. From the set of quantities obtained experimentally as well as the precomputed database, diffuse approximation efficiently estimates the unknown values of the input parameters of the flowing capsule. The shear modulus can then be determined with high precision provided that the capsule is sufficiently deformed to exhibit a parachute shape at the rear.