What's the best way to find out if an [--1--] contains a specific substance, like an environmental contaminant? You could use an expensive, bulky gas chromatograph—but Harvard researchers have developed an instrument you can carry in your pocket. They describe the device, called an inverse opal, in the Journal of the American Chemical Society.

An inverse opal is a chip of layered glass that includes [--2--]. This mini-labyrinth gets treated with chemicals to modify its inner surfaces. The resulting porous chip then sucks up only liquids that have specific surface tensions. When such a liquid enters the network, it changes the chip's color over a set area. An inverse opal designed to determine if ethanol is [--3--] methanol could thus reveal the letter M if the poison is present.

With this so-called Watermark Ink writing, the chips could also serve as secret code devices. For example, [--4--] a chip with water might make a decoy word like “hello” visible. While exposure to, say, benzene, could expose a secret message, such as “ditch your gas chromatograph.
【視聽版科學(xué)小組榮譽出品】
unknown mixture numerous tiny channels laced with swabbing
能“識物”的晶片 在一種未知混合物中找出它所包含的一個指定物質(zhì)最好的方法是什么？比如說一種空氣污染物。當(dāng)然，你可以使用昂貴又笨重的氣體色譜儀。但是，哈佛大學(xué)研究人員已經(jīng)開發(fā)了一種可以隨身裝在你的口袋中的儀器。他們所描述的這種儀器被稱之為逆蛋白石，刊登在《美國化學(xué)協(xié)會期刊》中。 逆蛋白石是夾層玻璃中的一種晶片，有著數(shù)目眾多的微小通道。這種迷你迷宮通過化學(xué)物質(zhì)的處理修改其內(nèi)表面產(chǎn)生的多孔性晶片，只吸收具有特定表面張力的液體。當(dāng)一種液體進(jìn)入其構(gòu)造后邊會在設(shè)定的區(qū)域內(nèi)改變晶片的顏色。這種逆蛋白石可以設(shè)計用該鑒別乙醇中是否摻有甲醇，有毒的話，則顯示字母M。 隨著所謂的水印墨水的應(yīng)用，這種晶片也可以用作為秘密代碼設(shè)備。例如，用清水擦拭晶片可以顯示假代碼“hello”，用苯才會顯示真正的秘密信息，比如說“把你的氣體色譜儀扔了吧！”。