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Observation of Coffee Ring Transformation Under the Influence of Nanosecond Electrical Discharges in Drying Drops
Alexander E. Dubinov, Julia P. Kozhayeva and Victoria S. Ryabukha

In this paper, the influence of pulsed-periodic sequence of nanosecond electrical discharges on drying drops of coffee was examined. In the absence of discharges the well-known “coffee ring effect” on metal foil was observed. However, after exposure to discharges, the stain of dried droplets had another look and structure. The fundamental significance of the work is to provide a new method of controlling of coffee rings by using nanosecond repetitively pulsed electric discharges affecting the top of the drying droplets. In particular, it turned out that the coffee particles were distributed more evenly over the area of the stain due to electrohydrodynamic flows that occur in the drop under the action of discharges. This effect can be used, for example, in inkjet printing.

Keywords: Drying drop, coffee ring effect, electric discharge

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