Manchester Centre for Nonlinear Dynamics, The University of Manchester, Manchester, M13 9PL, UK.
Department of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK.
Soft Matter. 2023 Jul 19;19(28):5249-5261. doi: 10.1039/d3sm00208j.
Microcapsules with liquid cores encapsulated by thin membranes have many applications in science, medicine and industry. In this paper, we design a suspension of microcapsules which can flow and deform like red blood cells (RBCs), as a valuable tool to investigate microhaemodynamics. A reconfigurable and easy-to-assemble 3D nested glass capillary device is used to robustly fabricate water-oil-water double emulsions which are then converted into spherical microcapsules with hyperelastic membranes by cross-linking the polydimethylsiloxane (PDMS) layer coating the droplets. The resulting capsules are monodisperse to within 1% and can be made in a wide range of size and membrane thickness. We use osmosis to deflate by 36% initially spherical capsules of diameter 350 μm and a membrane thickness of 4% of their radius. Hence, we can match the reduced volume of RBCs but not their biconcave shape, since our capsules adopt a buckled shape. We compare the propagation of initially spherical and deflated capsules under constant volumetric flow in cylindrical capillaries of different confinements. We find that only deflated capsules deform broadly like RBCs over a similar range of capillary numbers - the ratio of viscous to elastic forces. Similarly to the RBCs, the microcapsules transition from a symmetric 'parachute' to an asymmetric 'slipper'-like shape as increases within the physiological range, demonstrating intriguing confinement-dependent dynamics. In addition to biomimetic RBC properties, high-throughput fabrication of tunable ultra-soft microcapsules could be further functionalized and find applications in other areas of science and engineering.
具有薄膜包裹的液体芯的微胶囊在科学、医学和工业中有许多应用。在本文中，我们设计了一种可以像红细胞（RBC）一样流动和变形的微胶囊悬浮液，作为研究微血流动力学的有价值工具。使用可重构且易于组装的 3D 嵌套玻璃毛细管装置来稳健地制造水-油-水双乳液，然后通过交联涂覆液滴的聚二甲基硅氧烷（PDMS）层将其转化为具有超弹性膜的球形微胶囊。所得胶囊的单分散性在 1%以内，并且可以在很宽的尺寸和膜厚度范围内制造。我们使用渗透作用将直径为 350 μm 且膜厚度为其半径的 4%的初始球形胶囊初始体积缩小 36%。因此，我们可以匹配 RBC 的减小体积，但不能匹配其双凹形形状，因为我们的胶囊采用了褶皱形状。我们比较了在不同约束的圆柱毛细管中恒定体积流下初始球形和收缩胶囊的传播。我们发现，只有收缩胶囊在类似的毛细数范围内（粘性力与弹性力的比值）广泛变形，类似于 RBC，从对称的“降落伞”过渡到非对称的“拖鞋”形状。同样，微胶囊在生理范围内增加时，表现出有趣的约束依赖性动力学。除了仿生 RBC 特性外，可调谐超软微胶囊的高通量制造可以进一步功能化，并在科学和工程的其他领域找到应用。
