On the impact of viscous drops onto dry smooth surfaces

Palacios, Julián; Hernández, J.; Gómez, Pablo; Zanzi, Claudio; López, J.

doi:10.1007/s00348-012-1264-x

Cited by 32 publications

(13 citation statements)

References 26 publications

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“…In their experiments, localized contacts between levitated lamella and the solid surface ahead of the advancing contact line caused air bubble entrapment when reached by the contact line. Similar entrapment was evidenced in studies by Driscoll et al 43 and Palacios et al 44 In our study, the localized contacts ahead of the moving contact line are caused by the roughness asperities contacting the top of the contracting air film, as also noted by Li et al, 22 see their Fig. 1.…”

Section: Microbubble Formationsupporting

confidence: 91%

The air entrapment under a drop impacting on a nano-rough surface

Langley

Vakarelski

et al. 2018

Soft Matter

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We study the impact of drops onto a flat surface with a nano-particle-based superhydrophobic coating, focusing on the earliest contact using 200 ns time-resolution. A central air-disc is entrapped when the drop impacts the surface, and when the roughness is appropriately accounted for, the height and radial extent of the air-disc follow the scaling laws established for impacts onto smooth surfaces. The roughness also modifies the first contact of the drop around the central air-disc, producing a thick band of micro-bubbles. The initial bubbles within this band coalesce and grow in size. We also infer the presence of an air-film residing inside the microstructure, at radial distances outside the central air-disc. This is manifest by the sudden appearance of microbubbles within a few microseconds after impact. The central air-disc remains pinned on the roughness, unless it is chemically altered to make it superhydrophilic.

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Section: Microbubble Formationsupporting

confidence: 91%

The air entrapment under a drop impacting on a nano-rough surface

Langley

Vakarelski

et al. 2018

Soft Matter

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“…When these localized contacts meet the continuous wetted section, we get the entrapment of the micro-bubbles. Similar entrapment mechanism has been observed for slightly higher viscosity cases during the lamellar spreading (28)(29)(30) , but never before during the first contact of a drop. On the other hand when using the mica surface (Fig.…”

Section: First Contact Of a Drop Impacting On A Surface With Nano-metsupporting

confidence: 80%

Probing the nanoscale with high-speed interferometry of an impacting drop

Thoroddsen

Vakarelski

et al. 2017

SPIE Proceedings

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“…5b). Such bands of bubbles have been observed for impacts of viscous drops in Thoroddsen et al (2005Thoroddsen et al ( , 2010 and Palacios et al (2012).…”

Section: Low Impact Velocity Skating and Film Rupturesmentioning

confidence: 53%

Probing the nanoscale: the first contact of an impacting drop

Vakarelski

Thoroddsen

2015

J. Fluid Mech.

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When a drop impacts a solid surface, the lubrication pressure in the air deforms its bottom into a dimple. This makes the initial contact with the substrate occur not at a point but along a ring, thereby entrapping a central disc of air. We use ultra-highspeed imaging, with 200 ns time resolution, to observe the structure of this first contact between the liquid and a smooth solid surface. For a water drop impacting onto regular glass we observe a ring of micro-bubbles, owing to multiple initial contacts just before the formation of the fully wetted outer section. These contacts are spaced by a few microns and quickly grow in size until they meet, thereby leaving behind a ring of microbubbles marking the original air-disc diameter. On the other hand, no micro-bubbles are left behind when the drop impacts onto molecularly smooth mica sheets. We thereby conclude that the localized contacts are due to nanometric roughness of the glass surface and the presence of the micro-bubbles can therefore distinguish between glass with 10 nm roughness from perfectly smooth glass. We contrast this entrapment topology with the initial contact of a drop impacting onto a film of extremely viscous immiscible liquid, where the initial contact appears continuous along the ring. Here an azimuthal instability occurs during the rapid contraction at the triple line, also leaving behind micro-bubbles. For low impact velocities the nature of the initial contact changes to one initiated by ruptures of a thin lubricating air film.

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On the impact of viscous drops onto dry smooth surfaces

Cited by 32 publications

References 26 publications

The air entrapment under a drop impacting on a nano-rough surface

The air entrapment under a drop impacting on a nano-rough surface

Probing the nanoscale with high-speed interferometry of an impacting drop

Probing the nanoscale: the first contact of an impacting drop

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