Dresden 2020 – wissenschaftliches Programm
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DY 41.2: Vortrag
Mittwoch, 18. März 2020, 15:15–15:30, ZEU 147
Surface wettability-induced magnitude change and sign inversion of the apparent line tension — •Binyu Zhao1,4, Shuang Luo2, Elmar Bonaccurso3, Günter Auernhammer4, Zhigang Li2, and Longquan Chen1 — 1University of Electronic Science and Technology of China, Chengdu 610054, China — 2The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong — 3Airbus Central R & T, Materials X, Munich 81663, Germany — 4Leibniz Institute of Polymer Research Dresden, Dresden 01069, Germany
Line tension is defined, thermodynamically, as the excess free energy per unit length of the contact line as postulated by Gibbs in 1878. Despite strenuous research efforts thence, the magnitude and sign of line tension remain in a hot debate. In this study, we determined the apparent line tension from the size-dependent contact angle of sessile nanodroplets on surfaces with different wettabilities via atomic force microscopy measurements. We showed that the apparent line tension changed its magnitude with the surface wettability and its sign changed from positive to negative for droplets on surfaces with an apparent contact angle higher than a critical value. Furthermore, using molecular dynamics simulations, we analysed the potential energy of liquid molecules within the nanodroplet and in the vicinity of the three-phase contact line. This allowed us to explain the surface wettability-induced magnitude change and sign inversion of the apparent line tension form the perspective of surface thermodynamics.