Super water-repellent surfaces resulting from fractal structure
Super water-repellent surfaces resulting from fractal structure
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DOI：
10.1021/jp9616728
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发表时间：
1996-12-12
影响因子：
--
通讯作者：
Tsujii, K
中科院分区：
文献类型：
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作者：
Shibuichi, S;Onda, T;Tsujii, K
由烷基酮二聚体(AKD)制成的水滴接触角为174度的超级憎水表面。当水滴轻微倾斜时，水滴在超级防水表面上滚动而不附着。AKD是一种蜡，通过熔体凝固，在其表面自发形成一种分形结构。AKD的分形表面完全排斥水滴，在没有任何氟化处理的情况下，接触角大于170度。(3)平面接触角与分形面接触角(F)之间的关系可用方程cos theta(F)=(L/L)(D-2)cos theta表示，其中(L/L)(D-2)是表面积放大因子。固体AKD表面的分维D约为2.3。用计盒法对AKD截面的扫描电子显微镜图像进行了计算，并用计盒法估算了表征固体AKD表面分维行为的最大和最小尺寸极限L和L。测定了几种水/1，4-二氧六环混合物在AKD表面的接触角，并绘制了cos theta(I)与cos theta的关系图。Cos theta(I)与cos theta的关系图与理论预测符合得很好。这项工作表明，分形概念是开发某些新型功能材料的有力工具。
Super water-repellent surfaces showing a contact angle of 174 degrees for water droplets have been made of alkylketene dimer (AKD). Water droplets roll around without attachment on the super water-repellent surfaces when tilted slightly. The AKD is a kind of wax and forms spontaneously a fractal structure in its surfaces by solidification from the melt. The fractal surfaces of AKD repel a water droplet completely and show a contact angle larger than 170 degrees without any fluorination treatments. Theoretical prediction of the wettability of the fractal surfaces has been given in the previous paper.(3) The relationship between the contact angle of the flat surface theta and that of the fractal surface theta(f) is expressed by the equation cos theta(f) = (L/l)(D-2) cos theta where (L/l)(D-2) is the surface area magnification factor. The fractal dimension of the solid AKD surface was determined to be D approximate to 2.3 applying the box-counting method to the SEM images of the AKD cross section, L and l, which are the largest and the smallest size limits of the fractal behavior of the surface, are also estimated from the box-counting method. The contact angles of some water/1,4-dioxane mixtures on the fractal and the flat AKD surfaces were determined, and the values of cos theta(i) were plotted against cos theta. The plot of cos theta(i) against cos theta agrees well with the theoretical prediction. It has been demonstrated by this work that the fractal concept is a powerful tool to develop some novel functional materials.