Structural transitions in a ring stain created at the contact line of evaporating nanosuspension sessile drops

Askounis, Alexandros, Sefiane, Khellil, Koutsos, Vasileios and Shanahan, Martin E.R. (2013) Structural transitions in a ring stain created at the contact line of evaporating nanosuspension sessile drops. Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 87. ISSN 1539-3755

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Abstract

Monodisperse nanosuspension droplets, placed on a flat surface, evaporated following the stick-slip motion of the three-phase contact line. Unexpectedly, a disordered region formed at the exterior edge of a closely packed nanocolloidal crystalline structure during the "stick" period. In order to assess the role of particle velocity on particle structuring, we did experiments in a reduced pressure environment which allowed the enhancement of particle velocity. These experiments revealed the promotion of hexagonal packing at the very edge of the crystallite with increasing velocity. Quantification of particle velocity and comparison with measured deposit shape for each case allowed us to provide a tentative description of the underlying mechanisms that govern particle deposition of nanoparticles at the triple line of an evaporating droplet. Behavior is governed by an interplay between the fluid, and hence particle, flow velocity (main ordering parameter) and wedge constraints, and consequently disjoining pressure (main disordering parameter). Furthermore, the formation of a second disordered particle region at the interior edge of the deposit (towards bulk fluid) was found and attributed to the rapid motion of the triple line during the "slip" regime. Additionally, the magnitude of the pinning forces acting on the triple line of the same drops was calculated. These findings provide further insight into the mechanisms of the phenomenon and could facilitate its exploitation in various nanotechnological applications.

Item Type: Article
Additional Information: Erratum available at dx.doi.org/10.1103/PhysRevE.88.049903
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Depositing User: LivePure Connector
Date Deposited: 12 Sep 2018 09:30
Last Modified: 12 Sep 2018 09:30
URI: https://ueaeprints.uea.ac.uk/id/eprint/68231
DOI: 10.1103/PhysRevE.87.012301

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