Dresden 2020 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 41: Droplets and Wetting (joint session DY/CPP)

DY 41.2: Talk

Wednesday, March 18, 2020, 15:15–15:30, ZEU 147

Surface wettability-induced magnitude change and sign inversion of the apparent line tension — •Binyu Zhao^1,4, 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.