Description
Red blood cells (RBCs) can display a wide range of behaviours, depending on the capillary number (Ca, ratio of viscous to surface tension forces) and confinement parameters. However, real RBCs are not easily available, biodegradable and highly variable. Since they do not contain a nucleus, we propose to model RBCs as membrane-encapsulated liquid droplets, which gives flexibility to tune their physical properties.
Our first generation of capsules relied on nested capillaries to produce a double emulsion, which forms elastic capsules by curing the middle polymer phase. The capsules are deflated by osmosis to reproduce the high physiological ratio of surface area to volume in RBCs [1]. We find that a selectively functionalized microfluidic chip constitutes a faster, more robust method to produce the double emulsion and allows for parallelization [2].
The second generation of capsules aims to better recapitulate RBC deformation in flow. For this, we make the capsules softer to extend the range of available flow conditions parametrised by Ca, we match the high viscosity ratio of the RBC core to the surrounding fluid and approximate the RBC biconcave shape. We proceed to explore the motion and deformation of this generation of capsules under shear flow, by comparison with typical RBC dynamics [3]. This allows us to benchmark single capsules for the subsequent study of suspension flows in complex media, to identify the role of mechanics in the microcirculation under healthy and diseased conditions.
References
[1] Chen, Q., Singh, N., Schirrmann, K., Zhou, Q., Chernyavsky, I. L., & Juel, A. (2023). Robust fabrication of ultra-soft tunable PDMS microcapsules as a biomimetic model for red blood cells. Soft Matter, 19(28), 5249–5261.
[2] Deshpande, S., Caspi, Y., Meijering, A. E. C., & Dekker, C. (2016). Octanol-assisted liposome assembly on chip. Nature Communications, 7.
[3] Mendez, Simon & Abkarian, Manouk. (2019). Single red blood cell dynamics in shear flow and its role in hemorheology. 10.1201/b21806-5.