Patel Mehzabin, Radhakrishnan Anand N P, Bescher Ludovic, Hunter-Sellars Elwin, Schmidt-Hansberg Benjamin, Amstad Esther, Ibsen Stuart, Guldin Stefan
Department of Chemical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK.
Soft Matter. 2021 Jan 28;17(4):947-954. doi: 10.1039/d0sm01742f. Epub 2020 Dec 7.
Liquid-in-liquid droplets are typically generated by the partitioning of immiscible fluids, e.g. by mechanical shearing with macroscopic homogenisers or microfluidic flow focussing. In contrast, partially miscible liquids with a critical solution temperature display a temperature-dependent mixing behaviour. In this work, we demonstrate how, for a blend of methanol (MeOH) and the thermotropic liquid crystal (LC) 4-Cyano-4'-pentylbiphenyl (5CB), cooling from a miscible to an immiscible state allows the controlled formation of microdroplets. A near-room-temperature-induced phase separation leads to nucleation, growth and coalescence of mesogen-rich droplets. The size and number of the droplets is tunable on the microscopic scale by variation of temperature quench depth and cooling rate. Further cooling induces a phase transition to nematic droplets with radial configuration, well-defined sizes and stability over the course of an hour. This temperature-induced approach offers a scalable and reversible alternative to droplet formation with relevance in diagnostics, optoelectronics, materials templating and extraction processes.
液滴通常是由不混溶流体的分配产生的，例如通过宏观均质器的机械剪切或微流体流动聚焦。相比之下，具有临界溶解温度的部分互溶液体表现出温度依赖性的混合行为。在这项工作中，我们展示了对于甲醇（MeOH）和热致液晶（LC）4-氰基-4'-戊基联苯（5CB）的混合物，从互溶状态冷却到不互溶状态如何实现微滴的可控形成。接近室温引起的相分离导致富介晶微滴的成核、生长和聚结。通过改变温度猝灭深度和冷却速率，可以在微观尺度上调节微滴的大小和数量。进一步冷却会诱导向具有径向构型、尺寸明确且在一小时内稳定的向列相微滴的相变。这种温度诱导方法为液滴形成提供了一种可扩展且可逆的替代方案，在诊断、光电子学、材料模板和萃取过程中具有相关性。
