Emulsion patterns in the wake of a liquid-liquid phase separation front
Emulsion patterns in the wake of a liquid-liquid phase separation front
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DOI：
10.1073/pnas.1716330115
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发表时间：
2018-04-03
影响因子：
11.1
通讯作者：
Brujic, Jasna
中科院分区：
文献类型：
--
作者：
Moerman, Pepijn G.;Hohenberg, Pierre C.;Brujic, Jasna
可混溶的液体可因成分变化而相分离。在大块流体中，分离在分子长度的尺度上开始，然后粗化成宏观相。相比之下，将混合物限制在微流控液滴中会导致连续的相分离爆发，这些相分离会自组织成油环和水环，形成多层乳状液。这些非平衡图案中的间距是自相似的，在一系列液滴大小上是无标度的。我们发展了一个修正的Cahn-Hilliard模型，在该模型中，一个具有拉伸指数动力学的不混溶前沿定量地预测了层间距。此外，比例定律预测了每一层的寿命，导致内部液滴的逐步释放。类似地，在长长的矩形毛细管中，扩散锋在数小时的时间尺度上产生大规模的油条和水条。同样的理论将它们的特征长度范围与锋面的速度和质量传输率联系在一起。液-液相分离成大规模模式的控制在活细胞、封装、颗粒设计和表面图案方面具有潜在的材料应用。
Miscible liquids can phase separate in response to a composition change. In bulk fluids, the demixing begins on molecular-length scales, which coarsen into macroscopic phases. By contrast, confining a mixture in microfluidic droplets causes sequential phase separation bursts, which self-organize into rings of oil and water to make multilayered emulsions. The spacing in these nonequilibrium patterns is self-similar and scale-free over a range of droplet sizes. We develop a modified Cahn-Hilliard model, in which an immiscibility front with stretched exponential dynamics quantitatively predicts the spacing of the layers. In addition, a scaling law predicts the lifetime of each layer, giving rise to a stepwise release of inner droplets. Analogously, in long rectangular capillaries, a diffusive front yields large-scale oil and water stripes on the time scale of hours. The same theory relates their characteristic length scale to the speed of the front and the rate of mass transport. Control over liquid-liquid phase separation into large-scale patterns finds potential material applications in living cells, encapsulation, particulate design, and surface patterning.