Dip-Coating Crystallization on a Superhydrophobic Surface: A Million Mounted Crystals in a 1 cm2 Array
Dip-Coating Crystallization on a Superhydrophobic Surface: A Million Mounted Crystals in a 1 cm2 Array
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DOI：
10.1021/ja2011548
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发表时间：
2011-04-20
影响因子：
15
通讯作者：
McCarthy, Thomas J.
中科院分区：
文献类型：
--
作者：
Krumpfer, Joseph W.;McCarthy, Thomas J.
通过光刻法将硅晶片（二氧化硅表面）图案化以包含3 μ m（宽）× 6 μ m（长）× 40 μ cm（高）的正方形阵列（中心到中心间距20 μ m）中的交错菱形柱。使用与十三氟辛基二甲基氯硅烷的气相反应使这些表面疏水化，并表现出“超疏水性”（水接触角θ（A）/θ（R）= 169度/156度）。当晶片的一部分浸入水中并从水中取出时，超疏水表面出现，显然完全干燥。使用氯化钠水溶液作为液浴进行相同的步骤，在每个柱的顶部可以观察到盐的单个晶体。使用4.3M氯化钠水溶液的“浸涂结晶”产生尺寸类似于1 μ m的晶体。浓度较低的溶液，1 M NaCl，使晶体具有类似于500 nm的尺寸。这些实验表明，从水中出现并且“表面上完全干燥”的超疏水表面实际上装饰有微米大小（几毫微微升）的固着水滴，这些水滴会迅速蒸发。这种简单的技术可用于制备非常小的液滴或液池（具有受控的组成）和用于制备受控尺寸的结晶物质阵列（浸涂结晶）。
Silicon wafers (silicon dioxide surfaces) were patterned by photolithograpy to contain 3 mu m (width) x 6 pm (length) x 40 mu cm (height) staggered rhombus posts in a square array (20 mu m center-to-center spacing). These surfaces were hydrophobized using a vapor phase reaction with tridecafluorooctyldimethylchlorosilane and exhibit "superhydrophobicity" (water contact angles of theta(A)/theta(R) = 169 degrees/156 degrees). When a section of a wafer is submerged in and withdrawn from water, the superhydrophobic surface emerges, apparently completely dry. lithe same procedure is performed using aqueous sodium chloride as the liquid bath, individual crystals of the salt can be observed on the top of each of the posts. "Dip-coating crystallization" using an aqueous sodium chloride solution of 4.3 M produces crystals with similar to 1 mu m dimensions. A less concentrated solution, 1 M NaCl, renders crystals with similar to 500 nm dimensions. These experiments suggest that superhydrophobic surfaces that emerge from water and are "apparently completely dry" are, in fact, decorated with micrometer-size (several femtoliters) sessile water drops that rapidly evaporate. This simple technique is useful for preparation of very small liquid drops or puddles (of controlled composition) and for preparation of arrays of controlled size, crystalline substances (dip-coating crystallization).