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Jump-to-contact instability: The nanoscale mechanism of droplet coalescence in air

Incerti, Véronique and Protat, Matthieu and Risso, Frédéric and Ondarçuhu, Thierry and Tordjeman, Philippe Jump-to-contact instability: The nanoscale mechanism of droplet coalescence in air. (2018) Physical Review Fluids, 3 (10). 102001. ISSN 2469-990X

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Official URL: https://doi.org/10.1103/PhysRevFluids.3.102001


We study experimentally by means of atomic force microscopy (AFM) the jump-to-contact instability between two droplets in air, with radii ranging between 0.7 and 74 μm. This instability which occurs at the nanoscale is responsible for droplet coalescence. The AFM experiments were conducted in contact and frequency-modulation modes where the interaction force and the frequency shift are monitored while the two droplet interfaces approach each other. The critical distance d_min at which the jump to contact takes place is determined by fitting the experimental curves by the theoretical expressions for theforce and the frequency shift. The results point out the existence of two regimes. For submicrometer droplets, d_min scales as (HReq/γ)^1/3 where Req is the equivalent droplet radius,H the Hamaker constant, and γ the surface tension of the liquid. For larger droplets,d_min no longer depends on the droplet size and scales as (H/γ)^1/2. This second scaling is the one that controls droplet coalescence in most situations.

Item Type:Article
HAL Id:hal-02047629
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Laboratory name:
Fédération de recherche FERMAT - Fluides, Energie, Réacteurs, Matériaux et Transferts (FRANCE)
Deposited On:25 Feb 2019 09:14

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