Forces at superhydrophobic and superamphiphobic surfaces
2020 (English)In: Current Opinion in Colloid & Interface Science, ISSN 1359-0294, E-ISSN 1879-0399, Vol. 47, p. 46-57Article in journal (Refereed) Published
Abstract [en]
Forces exerted at surfaces and interphases due to formation of gaseous (air or vapor) bridges describe the extreme liquid repellence in superhydrophobicity (SH) and amphiphobicity. The neighboring research areas of liquid capillary bridges and that of interactions between hydrophobic surfaces are highly valuable reference systems. We review recent findings with particular focus on the three-phase contact line and surface forces. Although macroscopic contact angles (>150°), low contact angle hysteresis (<10°, but can be high; parahydrophobic or petal type) and low roll-off angle (≤5–10°) are adequate criteria for SH and superamphiphobicity (SA) for most studies, a detailed understanding requires a view related to mechanisms. Experimental studies of liquid drop–substrate and particle–substrate adhesion in hydrophobic, SH, and SA systems are summarized by relating measured forces to the wetting tension, γcosθ. A low wetting tension value is a necessary but not sufficient criterion for SH and SA systems. The picture emerging from detailed force distance studies is that extreme liquid repellence in SH and SA systems is a progression of liquid repellence due to hydrophobicity, in which force curves can be explained by capillary forces of constant volume of the gaseous capillary. In SH and SA, neither the capillary force equation assuming constant volume nor constant pressure of the gaseous capillary explains experimental force measurements as the capillary increases in both volume and pressure. In recent experimental studies, a transition is observed into nonconstant volume and pressure which suggests an SH and SA wetting transition from constant volume or pressure to a capillary growth as driven by the γA and the PV works but also by forces at the three-phase contact SLV (solid-liquid-vapor) line, viz. pinning forces, Fpin and Fdepin, and line energy, (τL)SLV, terms. Supported by calculations of the different contributions, we suggest this transition being an appropriate definition for the onset of (appreciable) SH and SA. © 2019 The Author(s)
Place, publisher, year, edition, pages
Elsevier Ltd , 2020. Vol. 47, p. 46-57
Keywords [en]
Capillary force, Contact angle, Hydrophobicity, Laplace pressure, Line tension, Pinning, Superamphiphobicity, Superhydrophobicity, Surface force, Wetting, Liquids, Magnetic bubbles, Surface forces
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:ri:diva-43356DOI: 10.1016/j.cocis.2019.11.012Scopus ID: 2-s2.0-85077750466OAI: oai:DiVA.org:ri-43356DiVA, id: diva2:1389045
Note
Funding details: 2016–01362; Funding details: Stiftelsen för Strategisk Forskning, SSF; Funding details: Stiftelsen Nils och Dorthi Troëdssons Forskningsfond, 898/16; Funding text 1: This work is part of the project “Nanoscopic forces between liquid super repellent surfaces”, funded by SSF, the Swedish Foundation for Strategic Research (grant no. FID15-0029 ) and Omya International AG . Further support is from the Formas research council (grant no. 2016–01362 ) and from the Nils and Dorthi Troëdsson Foundation for Scientific Research (grant no. 898/16 ), which also supports AS as adjunct professor at KTH. We enjoy a fruitful collaboration with Prof. Dr. Doris Vollmer, Dr. Michael Kappl, and coworkers at the Max Planck Institute for Polymer Research.
2020-01-282020-01-282020-12-01Bibliographically approved