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Lookup NU author(s): Dr Elfego Ruiz GutierrezORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
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.
Author(s): Barrio-Zhang H, Ruiz-Gutiérrez É, Armstrong S, McHale G, Wells GG, Ledesma-Aguilar R
Publication type: Article
Publication status: Published
Journal: Langmuir
Year: 2020
Volume: 36
Issue: 49
Pages: 15094-15101
Print publication date: 15/12/2020
Online publication date: 01/12/2020
Acceptance date: 12/11/2020
Date deposited: 01/12/2021
ISSN (print): 0743-7463
ISSN (electronic): 1520-5827
Publisher: American Chemical Society
URL: https://doi.org/10.1021/acs.langmuir.0c02668
DOI: 10.1021/acs.langmuir.0c02668
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