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.

References in corpus (6)

• scikit-image: Image processing in Python
• Freezing as a path to build complex composites
• Universality of Tip Singularity Formation in Freezing Water Drops
• Solidification dynamic of an impacted drop
• Five-dimensional imaging of freezing emulsions with solute effects
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Cited by in corpus (4)

• Effects of Asymmetric Cooling and Surface Wettability on the Orientation of the Freezing Tip
• Solidification of a rivulet: shape and temperature fields
• Surfactant-driven instability of a divergent flow
• Marangoni-driven freezing dynamics of supercooled binary droplets