Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA.
Institute for Molecular Engineering, University of Chicago, Chicago, IL, USA.
Soft Matter. 2021 Mar 18;17(10):2985-2993. doi: 10.1039/d0sm01873b.
Synthetic soft matter systems, when driven beyond equilibrium by active processes, offer the potential to achieve dynamical states and functions of a complexity found in living matter. Emulsions offer the basis of a simple yet versatile system for identification of the physicochemical principles underlying active soft matter, but how multiple internal phases within emulsion droplets (e.g., Janus morphologies) organize to impact emergent dynamics is not understood. Here, we create multiphase oil droplets with ultralow interfacial tensions but distinct viscosities, and drive them into motion in aqueous micellar solutions. Preferential solubilization of select components of the oil both drives the droplet motion and yields a progression of internal phase morphological states with distinct symmetries. We find the active droplets to exhibit five dynamical states during morphogenesis. By quantifying microscopic flow fields, we show that it is possible to map the diverse droplet behaviors to squirmer models of spherical microswimmers in Stokes flow, thus showing that multiphase droplets offer the basis of a versatile platform with which to study and engineer the hydrodynamics of microswimmers.
合成软物质系统在活性过程的驱动下超越平衡时，具有实现复杂动力学状态和功能的潜力，这些功能在生命物质中被发现。乳液为识别活性软物质的物理化学原理提供了一个简单而多功能的基础，但乳液液滴内的多个内相（例如，Janus 形态）如何组织以影响涌现动力学尚不清楚。在这里，我们创建了具有超低界面张力但粘度不同的多相油滴，并将它们驱动到水胶束溶液中运动。油的特定成分的优先溶解既驱动了液滴的运动，又产生了具有不同对称性的内部相形态状态的连续变化。在形态发生过程中，我们发现活性液滴表现出五种动力学状态。通过量化微观流动场，我们表明可以将不同的液滴行为映射到斯托克斯流中球形微游泳者的 squirmer 模型，从而表明多相液滴提供了一个通用平台的基础，可用于研究和设计微游泳者的流体动力学。
