Drop freezing: fine detection of contaminants by measuring the tip angle

François Boulogne (1) , Anniina Salonen (1)

1 LPS - Laboratoire de Physique des Solides

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.

Domaines: Dynamique des Fluides [physics.flu-dyn]; Matière Molle [cond-mat.soft]

François Boulogne, Anniina Salonen. Drop freezing: fine detection of contaminants by measuring the tip angle. Applied Physics Letters, 2020, 116 (10), pp.103701. ⟨10.1063/1.5144071⟩. ⟨hal-02489383⟩