| Autor: |
Akerboom S; Physical Chemistry and Soft Matter, Wageningen University, Stippeneng 4, 6708 WE Wageningen, Netherlands., Kamperman M; Physical Chemistry and Soft Matter, Wageningen University, Stippeneng 4, 6708 WE Wageningen, Netherlands., Leermakers FA; Physical Chemistry and Soft Matter, Wageningen University, Stippeneng 4, 6708 WE Wageningen, Netherlands. |
| Jazyk: |
angličtina |
| Zdroj: |
Beilstein journal of nanotechnology [Beilstein J Nanotechnol] 2016 Oct 04; Vol. 7, pp. 1377-1396. Date of Electronic Publication: 2016 Oct 04 (Print Publication: 2016). |
| DOI: |
10.3762/bjnano.7.129 |
| Abstrakt: |
We use regular solution theory and implement a three-gradient model for a liquid/vapour system in contact with a complex surface topology to study the shape of a liquid drop in advancing and receding wetting scenarios. More specifically, we study droplets on an inverse opal: spherical cavities in a hexagonal pattern. In line with experimental data, we find that the surface may switch from hydrophilic (contact angle on a smooth surface θ Y < 90°) to hydrophobic (effective advancing contact angle θ > 90°). Both the Wenzel wetting state, that is cavities under the liquid are filled, as well as the Cassie-Baxter wetting state, that is air entrapment in the cavities under the liquid, were observed using our approach, without a discontinuity in the water front shape or in the water advancing contact angle θ . Therefore, air entrapment cannot be the main reason why the contact angle θ for an advancing water front varies. Rather, the contact line is pinned and curved due to the surface structures, inducing curvature perpendicular to the plane in which the contact angle θ is observed, and the contact line does not move in a continuous way, but via depinning transitions. The pinning is not limited to kinks in the surface with angles θ kink smaller than the angle θ Y . Even for θ kink > θ Y , contact line pinning is found. Therefore, the full 3D-structure of the inverse opal, rather than a simple parameter such as the wetting state or θ kink , determines the final observed contact angle. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
|
