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  Coffee Ring Effect

byRobert D. Deegan*, Olgica Bakajin*, Todd F. Dupont†,

Greb Huber*, Sidney R. Nagel* & Thomas A. Witten*

 Journal Name - Letters to natureVolume 389 & Year 1997

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Background Information When a spilled drop of coffee dries on a

solid surface, usually results in a ring ofparticles accumulated at the periphery of the

initial drop.

Intense research has been devoted tounderstanding, suppressing and ultimately

controlling this

so-called coffee-ring effect

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Formation of Coffee Rings However general phenomenon, driving

mechanism responsible and practicaltechnological implications of ring deposition

has to be studied.

The coffee ring pattern is due to thedifferential evaporation rates across the

drop .

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The result show that pattern is due to

capillary flow induced by the differential

evaporation rates across the drop, liquidevaporating from the edge is replenished by

liquid from the interior.

The ring formation is a ubiquitous and

robust phenomenon and it doesn't dependon the solute, the solvent, or the substrate

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Significance & Application

Ring deposition is a potentially usefultechnology impacting printing, washing and

coating processes.

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