Dynamic mode of viscoelastic capsules in steady and oscillating shear flow.

Because capsules exhibit viscoelasticity and shear resistance, the study of their dynamic motion under external flow is vital for biomedical and industrial applications. Toward this end, the present study uses the finite-element method to delve into the motion and deformation of viscoelastic capsules under steady and oscillating shear flow. In the steady shear, the effect of membrane viscosity is not obvious enough, which only slows the phase angle of capsules, which is consistent with previous work. However, the effect of membrane viscosity is more significant in the oscillatory shear, and we find that the deformation of capsules is affected by both viscosity and elasticity and exhibits two modes: For shear amplitudes γ₀ < 0.06 or frequencies f > 0.3 Hz, the capsules essentially return to their original shape after being deformed. For amplitudes γ₀ ≥ 0.06 or frequencies f ≤ 0.3 Hz, the capsules are strongly deformed and cannot return to their original state, which easily leads to membrane wrinkles and stress concentration. The results of this study systematically illustrate the dynamic behavior of viscoelastic capsules, which is critical to expound a capsule for use in drug transport, cell screening, and physiological processes. [ABSTRACT FROM AUTHOR]