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Superhydrophobic sand repels water
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Williams, Hollis (2023) Superhydrophobic sand repels water. The Physics Teacher, 61 (2). pp. 138-139. doi:10.1119/5.0065235 ISSN 1943-4928.
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Official URL: https://doi.org/10.1119/5.0065235
Abstract
A key concept in current fluid dynamics and its applications to biology and technology is a phenomenon known as wetting. Wetting is familiar from everyday life and is simply the ability of a liquid to stay in contact with a solid surface. The wettability depends on the properties of the liquid and the solid and can be characterized by the static equilibrium contact angle θ (the angle at which the liquid–gas interface meets the liquid–solid interface). A contact angle below 90° indicates favorable wetting such that a drop of the liquid would spread over a large amount of the flat solid surface, whereas a high contact angle indicates that very little of the solid is wetted (this can be seen in Fig. 1, which shows various stages of surface wetting in terms of the equilibrium contact angle). Nevertheless, this theory generally sounds quite dry or difficult to visualize when explained to students for the first time. The theory of the contact angle also contains some controversies and has undergone some recent developments. We propose a simple classroom demonstration with superhydrophobic sand that gives a concrete visualization of “superhydrophobicity” and outline how the phenomenon can be explained macroscopically with wetting theory. There are several interesting physical effects that are due to superhydrophobicity: experimental studies have found, for example, that superhydrophobic spheres always splash when they impact a body of liquid. In terms of applications, there are various possibilities for water storage with superhydrophobic sand outlined in the chemistry literature.
Item Type: | Journal Article | ||||||||
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Subjects: | Q Science > QD Chemistry T Technology > TA Engineering (General). Civil engineering (General) T Technology > TP Chemical technology |
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Divisions: | Faculty of Science, Engineering and Medicine > Engineering > Engineering | ||||||||
SWORD Depositor: | Library Publications Router | ||||||||
Library of Congress Subject Headings (LCSH): | Hydrophobic surfaces, Fluid dynamics, Wetting , Wetting agents , Surface chemistry | ||||||||
Journal or Publication Title: | The Physics Teacher | ||||||||
Publisher: | American Association of Physics Teachers (AAPT) | ||||||||
ISSN: | 1943-4928 | ||||||||
Official Date: | February 2023 | ||||||||
Dates: |
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Volume: | 61 | ||||||||
Number: | 2 | ||||||||
Page Range: | pp. 138-139 | ||||||||
DOI: | 10.1119/5.0065235 | ||||||||
Status: | Peer Reviewed | ||||||||
Publication Status: | Published | ||||||||
Reuse Statement (publisher, data, author rights): | This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Hollis Williams, "Superhydrophobic Sand Repels Water", The Physics Teacher 61, 138-139 (2023) https://doi.org/10.1119/5.0065235 and may be found at https://doi.org/10.1119/5.0065235 | ||||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||||
Date of first compliant deposit: | 17 March 2023 | ||||||||
Date of first compliant Open Access: | 20 March 2023 |
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