Microrheometric study of damage and rupture of capsules in simple shear flow.

Capsules, which are potentially-active fluid droplets enclosed in a thin elastic membrane, experience large deformations when placed in suspension. The induced fluid-structure interaction stresses can potentially lead to rupture of the capsule membrane. While numerous experimental studies have focused on the rheological behavior of capsules until rupture, there remains a gap in understanding the evolution of their mechanical properties and the underlying mechanisms of damage and breakup under flow. We here investigate the damage and rupture of bioartificial microcapsules made of ovalbumin reticulated with terephthaloyl chloride and placed in simple shear flow. We characterize damage by identifying how the surface shear modulus of the capsule membrane changes over time. Rupture is then characterized by comparing the number and size distribution of capsules before and after exposure to shear, while varying the shear rates and time during which capsules are sheared. Our findings reveal how the percentage of ruptured capsules increases with their size, exposure time to shear, and the ratio of viscous to elastic forces at rupture.