Cai Yangjun, Zhang Newby Bi-min
Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, Ohio 44325-3906, USA.
Langmuir. 2009 Jul 7;25(13):7638-45. doi: 10.1021/la901335w.
In this article, we report the development of a novel, simple, and cost-effective method for fabricating porous polymer films with controllable interpore distances, pore sizes, and arrangements using water droplets induced by Marangoni flow as templates. First, a spread-thin ethanol film on a partially water-wettable substrate is exposed to a humid airflow, facilitating the evaporation and recession of the ethanol film. Meanwhile, water in the airflow condenses on the ethanol film and accumulates near the receding contact line, which induces the formation of water fingers at the receding contact line and, finally, ordered arrays of water droplets after detachment. The formation of the hexagonal and square arrays of water droplets is due to the pinning and sliding of the water fingers on the silicone oxide (SiOx) and silicon (Si) substrates, respectively. By varying the thickness of the ethanol film spread on the Si substrate, the sliding velocity of water fingers can be tuned, subsequently leading to the fabrication of other arrangements. The interdroplet distance and droplet size can be dependently controlled by tuning the humidity of the airflow. The ordered arrays of water droplets on the substrate are then utilized to fabricate porous polymer films by dip-coating the substrate with a polystyrene solution. Films with hexagonal and square (and other arrangements) arrays of pores are fabricated on the silicon oxide (SiOx) and silicon (Si) substrates, respectively. The pore size can also be independently tuned by further condensation or evaporation of formed water droplets, leading to porous polymer films with both close- and non-close-packed arrays of pores. The ordered porous polymer films can be further used as templates for fabricating metal post patterns.
在本文中，我们报道了一种新颖、简单且经济高效的方法，该方法利用马兰戈尼流诱导的水滴作为模板来制备具有可控孔间距、孔径和排列的多孔聚合物薄膜。首先，将部分可被水润湿的基底上的乙醇薄膜摊薄，使其暴露于潮湿气流中，这有助于乙醇薄膜的蒸发和退缩。同时，气流中的水在乙醇薄膜上凝结，并在退缩的接触线附近积聚，这会在退缩的接触线处诱导形成水指，最终在分离后形成有序排列的水滴阵列。六边形和正方形水滴阵列的形成分别是由于水指在氧化硅（SiOx）和硅（Si）基底上的钉扎和滑动。通过改变铺展在Si基底上的乙醇薄膜的厚度，可以调节水指的滑动速度，进而制备出其他排列方式。通过调节气流的湿度，可以独立控制液滴间距和液滴大小。然后，利用基底上有序排列的水滴阵列，通过用聚苯乙烯溶液浸涂基底来制备多孔聚合物薄膜。分别在氧化硅（SiOx）和硅（Si）基底上制备出具有六边形和正方形（以及其他排列方式）孔阵列的薄膜。还可以通过进一步使形成的水滴凝结或蒸发来独立调节孔径，从而得到具有密排和非密排孔阵列的多孔聚合物薄膜。这些有序的多孔聚合物薄膜可进一步用作制备金属柱图案的模板。
