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Directed rebounding of droplets by microscale surface roughness gradients
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10.1063/1.3442500
/content/aip/journal/apl/96/23/10.1063/1.3442500
http://aip.metastore.ingenta.com/content/aip/journal/apl/96/23/10.1063/1.3442500

Figures

Image of FIG. 1.
FIG. 1.

Differences in rebound dynamics of surfaces with various uniform textures. A water droplet of and velocity impacts surfaces of different porosities. The porosity is changed by varying the center-to-center spacing of circular micropillars on a silicon substrate, treated with a passivation layer. The inset shows the snapshot of the droplet after impacting the surface. Differences in surface texture result in behaviors ranging from complete rebounding from the surface (for small ) to sticking to the surface (for large ). For all cases with uniform textures the rebounding is seen to be symmetrical.

Image of FIG. 2.
FIG. 2.

SEM image of the surface with nonuniform texture. Silicon pillars ( in diameter) are patterned on a silicon substrate with varying center-to-center distance in order to create a gradient in wetting properties (from to in static contact angle with water) along the surface. The arrows show the direction of the contact angle gradient and the associated vectoring of the droplet. Scale bar is .

Image of FIG. 3.
FIG. 3.

Vectoring of droplet rebound via gradients in surface texture. A water droplet impacts the surface at and is seen to be directed toward the right (along texture gradient). Plot shows the speed of the water droplet along the surface texture gradient (perpendicular to impact trajectory). Solid curve is the result of a simple model relating the unbalanced Young’s force (due to the wetting gradient) to the inertia of the droplet; circles are measurements of the droplet speed. Around 6.5 ms a narrow bridge forms and thereafter the top portion retains a relatively constant velocity (open circles) and is less influenced by the effects of the Young’s force imbalance than the portion that remains attached to the surface.

Image of FIG. 4.
FIG. 4.

Vectoring of a droplet upon impact with a surface of nonuniform texture. Here the incident velocity of the droplet has been reduced to . The droplet does not detach from the surface but is still vectored to the right (due to the wetting gradient). Solid curve is again the result of a simple model relating the unbalanced Young’s force to the inertia of the droplet; circles are measurements of the droplet speed.

Tables

Generic image for table
Table I.

Wetting properties of textured surfaces with porosity, .

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/content/aip/journal/apl/96/23/10.1063/1.3442500
2010-06-09
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Directed rebounding of droplets by microscale surface roughness gradients
http://aip.metastore.ingenta.com/content/aip/journal/apl/96/23/10.1063/1.3442500
10.1063/1.3442500
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