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Spreading dynamics of the precursor film of nanodrops on total wetting surfaces

Abstract

The spreading dynamics of a nanodrop on a total wetting surface is explored by many-body dissipative particle dynamics. Both smooth and rough surfaces with various spreading coefficients (S) are considered. The evolution of the spreading film is mainly characterized by the radius of the wetting area (Rp) and the apparent base radius (Rb) and contact angle (θ) of the spherical cap. The difference between Rp and Rb reveals the presence of the precursor film. The dynamic behavior can be described by the power law: Rp~tm, Rb~tn, and θ~t. Regardless of the surface roughness, the exponents n = 0.1 and α= 0.3 agree with the Tanner’s law and are independent of the spreading coefficient. However, the expansion of the precursor film depends on the surface roughness and the spreading coefficient. As the cavity size corresponding to roughness decreases or S increases, the exponent m can rise approximately from 0.1 to 0.2. That is, the spontaneous expansion is driven by the spreading coefficient but impeded by the surface roughness. Forced spreading of a nanodrop on a smooth surface leads to anisotropic expansion. The length along the force direction L(t) follows the power law L∝tp and the exponent p ≈ 0.274 is insensitive to S. Nonetheless, the length along the direction perpendicular to the force direction is dominated by the spontaneous spreading. Contact line pinning of the rear end is only observed for intermediate forces.

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Publication details

The article was received on 24 Jul 2017, accepted on 15 Sep 2017 and first published on 15 Sep 2017


Article type: Paper
DOI: 10.1039/C7CP04979J
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Spreading dynamics of the precursor film of nanodrops on total wetting surfaces

    Y. Weng, C. Wu, H. Tsao and Y. Sheng, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP04979J

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