液滴冷冻：通过测量尖端角度精确检测污染物
Drop freezing: fine detection of contaminants by measuring the tip angle
摘要：
在这封信中，我们表明，冻结水滴的形状对杂质的存在很敏感。我们测量在冷板上冻结的水滴的顶角。我们的图像分析方法，这表明从纯水中的盐（NaCl），聚合物（PEG）和表面活性剂（TTAB）的浓度分别开始在$10^{-6}$，$10^{-4}$和$10^{-6}$ M的溶液中的偏差稳健地捕获的尖端角的细微变化。该方法可以适用于便携式水纯度测试仪，但这项工作也强调了水冷冻的复杂性，因为它受到痕量杂质浓度的影响。
英文摘要：
In this Letter, we show that the shape of a freezing drop of water can be sensitive to the presence of impurities. We measure the tip angle of water drops frozen on a cold plate. The fine changes in tip angle are robustly captured by our image analysis method, which shows a deviation from that of pure water in solutions with salt (NaCl), polymer (PEG) and surfactant (TTAB) starting at concentrations of $10^{-6}$, $10^{-4}$ and $10^{-6}$ M respectively. The method could be adapted into a portable water purity tester, but the work also highlights the complexity of water freezing as it is influenced by trace concentrations of impurities.
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