Rapid Spreading of a Droplet on a Thin Soap Film

M. Motaghian, R. Shirsavar, M. Erfanifam, M. Sabouhi, E. Van Der Linden, H.A. Stone, D. Bonn, Mehdi Habibi*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


We study the spreading of a droplet of surfactant solution on a thin suspended soap film as a function of dynamic surface tension and volume of the droplet. Radial growth of the leading edge (R) shows power-law dependence on time with exponents ranging roughly from 0.1 to 1 for different surface tension differences (Δσ) between the film and the droplet. When the surface tension of the droplet is lower than the surface tension of the film (Δσ > 0), we observe rapid spreading of the droplet with R ≈ tα, where α (0.4 < α < 1) is highly dependent on Δσ. Balance arguments assuming the spreading process is driven by Marangoni stresses versus inertial stresses yield α = 2/3. When the surface tension difference does not favor spreading (Δσ < 0), spreading still occurs but is slow with 0.1 < α < 0.2. This phenomenon could be used for stretching droplets in 2D and modifying thin suspended films.

Original languageEnglish
Pages (from-to)14855-14860
Issue number46
Publication statusPublished - 23 Oct 2019

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