Polymer Science and Engineering Department, University of Massachusetts, 120 Governors Drive, Amherst, Massachusetts 01003, United States.
J Am Chem Soc. 2011 Apr 20;133(15):5764-6. doi: 10.1021/ja2011548. Epub 2011 Mar 29.
Silicon wafers (silicon dioxide surfaces) were patterned by photolithograpy to contain 3 μm (width) × 6 μm (length) × 40 μm (height) staggered rhombus posts in a square array (20 μm center-to-center spacing). These surfaces were hydrophobized using a vapor phase reaction with tridecafluorooctyldimethylchlorosilane and exhibit "superhydrophobicity" (water contact angles of θ(A)/θ(R) = 169°/156°). When a section of a wafer is submerged in and withdrawn from water, the superhydrophobic surface emerges, apparently completely dry. If the 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 ∼1 μm dimensions. A less concentrated solution, 1 M NaCl, renders crystals with ∼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).
硅片（二氧化硅表面）经过光刻形成了交错的菱形柱，其宽度为 3μm，长度为 6μm，高度为 40μm，呈正方形阵列排列（中心到中心的间距为 20μm）。这些表面通过与十三氟辛基二甲基氯硅烷的气相反应进行疏水化处理，表现出“超疏水性”（水接触角θ(A)/θ(R) = 169°/156°）。当硅片的一部分浸入和退出水时，超疏水表面会出现，表面显然完全干燥。如果使用水合氯化钠作为液体浴进行相同的处理，在每个柱子的顶部可以观察到盐的单个晶体。使用 4.3 M 的氯化钠水溶液进行“浸涂结晶”，可以得到尺寸约为 1μm 的晶体。浓度较低的溶液（1 M NaCl）会产生尺寸约为 500nm 的晶体。这些实验表明，从水中出现并“显然完全干燥”的超疏水表面实际上是由微米级（数飞升）的静止水滴装饰而成的，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（具有受控组成），以及制备具有受控尺寸的结晶物质阵列（浸涂结晶）。
