Center for Life Nano Science@La Sapienza, Istituto Italiano di Tecnologia, Roma, 00161, Italy.
Istituto per le Applicazioni del Calcolo CNR, via dei Taurini 19, Rome, 00185, Italy.
Nat Commun. 2021 Jan 4;12(1):82. doi: 10.1038/s41467-020-20364-0.
Understanding the fluid-structure interaction is crucial for an optimal design and manufacturing of soft mesoscale materials. Multi-core emulsions are a class of soft fluids assembled from cluster configurations of deformable oil-water double droplets (cores), often employed as building-blocks for the realisation of devices of interest in bio-technology, such as drug-delivery, tissue engineering and regenerative medicine. Here, we study the physics of multi-core emulsions flowing in microfluidic channels and report numerical evidence of a surprisingly rich variety of driven non-equilibrium states (NES), whose formation is caused by a dipolar fluid vortex triggered by the sheared structure of the flow carrier within the microchannel. The observed dynamic regimes range from long-lived NES at low core-area fraction, characterised by a planetary-like motion of the internal drops, to short-lived ones at high core-area fraction, in which a pre-chaotic motion results from multi-body collisions of inner drops, as combined with self-consistent hydrodynamic interactions. The onset of pre-chaotic behavior is marked by transitions of the cores from one vortex to another, a process that we interpret as manifestations of the system to maximize its entropy by filling voids, as they arise dynamically within the capsule.
理解流固相互作用对于软介观材料的优化设计和制造至关重要。多核乳液是由可变形油水双液滴（核）的簇状结构组装而成的一类软流体，通常用作生物技术中实现感兴趣设备的构建块，如药物输送、组织工程和再生医学。在这里，我们研究了在微流道中流动的多核乳液的物理性质，并报告了数值证据，证明了存在丰富多样的驱动非平衡状态（NES），其形成是由流动载体在微通道内的剪切结构引发的偶极流体涡旋引起的。观察到的动态状态范围从低核面积分数下的长寿命 NES 到高核面积分数下的短寿命 NES，在高核面积分数下，由于内滴的多体碰撞以及与自洽的流体动力相互作用相结合，会产生预混沌运动。内滴从一个涡旋到另一个涡旋的转变标志着预混沌行为的开始，我们将这一过程解释为系统通过填充空隙来最大化其熵的表现，因为这些空隙是在胶囊内动态产生的。
