76th Annual Meeting of the APS Division of Fluid Dynamics (November 19, 2023 — November 21, 2023)

V0043: Patterning via Solutal Instabilities in Thin Films

  • Samantha McBride, Princeton University
  • Severine Atis, CNRS
  • Amir Pahlavan, Yale University
  • Kripa Varanasi, Massachusetts Institute of Technology
DOI: https://doi.org/10.1103/APS.DFD.2023.GFM.V0043

When a drop of salt water is evaporated on a superhydrophilic surface, a ring of crystals forms at the outer edge due to evaporative flux. This process is similar to the coffee-ring effect. Because the crystalline ring is hydrophilic, it creates an even stronger force for contact line pinning, which allows for a significant amount of water to evaporate before the liquid finally depins from the outer ring. The very thin fluid film evaporates and retracts, and is subject to a number of different instabilities caused by both solutal and thermal gradients. Micron- and nano-scale crystals continuously form during contact line motion due to evaporation; and these crystals leave a record of the contact line instabilities at the moment of crystallization. Thus, the resulting crystalline patterns formed from thin film instabilities create a number of extraordinary patterns. 

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