Drop freezing: fine detection of contaminants by measuring the tip angle
Abstract
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.
Origin | Files produced by the author(s) |
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