Contact-Angle Hysteresis and Contact-Line Friction on Slippery Liquid-like Surfaces

Barrio-Zhang, Hernán, Ruiz Gutiérrez, Élfego, Armstrong, Steven, McHale, Glen, Wells, Gary and Ledesma Aguilar, Rodrigo (2020) Contact-Angle Hysteresis and Contact-Line Friction on Slippery Liquid-like Surfaces. Langmuir, 36 (49). pp. 15094-15101. ISSN 0743-7463

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Official URL: https://doi.org/10.1021/acs.langmuir.0c02668

Abstract

Contact-line pinning and dynamic friction are fundamental forces that oppose the motion of droplets on solid surfaces. Everyday experience suggests that if a solid surface offers low contact-line pinning, it will also impart a relatively low dynamic friction to a moving droplet. Examples of such surfaces are superhydrophobic, slippery porous liquid-infused, and lubricant-impregnated surfaces. Here, however, we show that slippery omniphobic covalently attached liquid-like (SOCAL) surfaces have a remarkable combination of contact-angle hysteresis and contact-line friction properties, which lead to very low droplet pinning but high dynamic friction against the motion of droplets. We present experiments of the response of water droplets to changes in volume at controlled temperature and humidity conditions, which we separately compare to the predictions of a hydrodynamic model and a contact-line model based on molecular kinetic theory. Our results show that SOCAL surfaces offer very low contact-angle hysteresis, between 1 and 3°, but an unexpectedly high dynamic friction controlled by the contact line, where the typical relaxation time scale is on the order of seconds, 4 orders of magnitude larger than the prediction of the classical hydrodynamic model. Our results highlight the remarkable wettability of SOCAL surfaces and their potential application as low-pinning, slow droplet shedding surfaces.

Item Type: Article
Additional Information: Funding information: H.B.-Z. acknowledges financial support from Northumbria University and The University of Edinburgh via a Ph.D. Studentship. H.B.-Z. would like to thank P. Agrawal and B.V. Orme for their advice and valuable discussions. R.L.-A. acknowledges support from EPSRC (grant no. EP/P024408/1).
Subjects: F300 Physics
H800 Chemical, Process and Energy Engineering
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Elena Carlaw
Date Deposited: 23 Mar 2021 13:07
Last Modified: 31 May 2021 14:40
URI: http://nrl.northumbria.ac.uk/id/eprint/45767

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