Gel-controlled droplet spreading

M. Jalaal*, C. Seyfert, B. Stoeber, N. J. Balmforth

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

12 Citations (Scopus)


Spreading and stationary droplets of a thermally responsive fluid on a heated surface are studied. The fluid undergoes a reversible gel formation at elevated temperature. The spatio-temporal pattern of gel formation within the droplet is examined using an experimental method based on spectral domain optical coherence tomography and time varying speckle patterns. Two stages of gel formation can be distinguished: first, a thin crust appears starting at the contact line. Second, a gel layer appears above the heated plate and then expands upward. We attribute the first stage of gel formation to solvent evaporation and heating through the air and the second to thermal conduction through the fluid from the base. Gel formation at the contact line is likely responsible for the arrest of spreading droplets, but was not detectable with our experimental protocol at the time of contact line arrest, suggesting that this arose over a microscopic length scale. Overall, substrate heating provides an effective way to control the final shape of droplets of thermo-responsive fluids.

Original languageEnglish
Pages (from-to)115-128
Number of pages14
JournalJournal of fluid mechanics
Publication statusPublished - 25 Feb 2018
Externally publishedYes


  • Complex fluids
  • drops
  • drops and bubbles


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