Inhomogeneous dispersion and memory effects of soft suspensions in complex media

Despite the essential role of the microvasculature in maintaining overall health and functionality of tissues, blood flow and transport mechanisms in this network remain poorly understood. This is in great part because the description of blood as a simple fluid breaks down when the size of red blood cells (RBCs) is comparable to that of smaller vessels. On that scale, cell free layers are a key feature of flows in straight conduits, but the adaptation of RBCs to the complex geometry of a network remains an open question.

To study the flow of RBCs we use a biomimetic model which consists of elastic capsules which have been shown to accurately capture the fluid mechanics of RBCs in straight confined tubes [1]. We investigate the dispersion of this soft suspension in a homogenous branched network as a function of volume fraction of capsules and of capillary number (the ratio of viscous to elastic forces). We show that branching and curvature combine to create a non-uniform distribution of particles at the outlet, an effect that depends on the number of branch generations and flow parameters. Using a branched network as an inlet produces a flow characterised by regularly spaced shear bands which is radically different to that obtained using a localised capsule source to feed the channel. Either flow persists over long distances, demonstrating the potential for memory effects in large networks like the microcirculation.

[1] Chen, Q., Singh, N., Schirrmann, K., Zhou, Q., Chernyavsky, I. and Juel, A. (2023) Soft Matter 19, p. 5249