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

Yu Hsuan Weng, Cyuan Jhang Wu, Heng Kwong Tsao, Yu Jane Sheng

研究成果: 雜誌貢獻期刊論文同行評審

22 引文 斯高帕斯(Scopus)

摘要

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 the 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 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 the 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.

原文???core.languages.en_GB???
頁(從 - 到)27786-27794
頁數9
期刊Physical Chemistry Chemical Physics
19
發行號40
DOIs
出版狀態已出版 - 2017

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