School of Mathematics and Statistics, The University of Melbourne , Victoria 3010, Australia.
ACS Nano. 2016 Mar 22;10(3):3087-92. doi: 10.1021/acsnano.5b06082. Epub 2016 Feb 4.
We demonstrate templating of functional materials with unexpected and intricate micro- and nanostructures by controlling the condensation, packing, and evaporation of water droplets on a polymer solution. Spontaneous evaporation of a polymer solution induces cooling of the liquid surface and water microdroplet condensation from the ambient vapor. These droplets pack together and act as a template to imprint an entangled polymer film. This breath figure (BF) phenomenon is an example of self-organization that involves the long-range ordering of droplets. Equilibrium-based analysis provides many insights into contact angles and drop stability of individual drops, but the BF phenomenon remains poorly understood thus far, preventing translation to real applications. Here we investigate the dynamics of this phenomenon to separate out the competing influences and then introduce a modulation scheme to ultimately manipulate the water vapor-liquid equilibrium independently from the solvent evaporation. This approach to BF control provides insights into the mechanism, a rationale for microstructure design, and evidence for the benefits of dynamical control of self-organization systems. We finally present dramatically different porous architectures from this approach reminiscent of microscale Petri dishes, conical flasks, and test tubes.
我们通过控制聚合物溶液上的水滴的冷凝、堆积和蒸发，展示了具有意想不到的复杂微观和纳米结构的功能材料的模板化。聚合物溶液的自发蒸发会导致液体表面冷却，周围蒸汽中的水微滴凝结。这些液滴聚集在一起，充当模板以压印缠结的聚合物膜。这种呼吸图案（BF）现象是一种涉及液滴长程有序的自组织实例。基于平衡的分析为单个液滴的接触角和稳定性提供了许多见解，但迄今为止，BF 现象仍然理解不佳，无法转化为实际应用。在这里，我们研究了这种现象的动力学，以分离出竞争的影响，然后引入一种调制方案，最终独立于溶剂蒸发来控制水蒸汽-液体平衡。这种 BF 控制方法为机制提供了深入的了解、微观结构设计的原理，并为自组织系统的动态控制带来了好处。我们最终从这种方法中展示了截然不同的多孔结构，类似于微尺度培养皿、锥形瓶和试管。
