Controlling droplet deposition with polymer additives

Controlling the impact of drops onto solid surfaces is important for a wide variey of coating and deposition processes-for example, the treatment of plants with herbicides and pesticides requires precise targeting in order to meet stringent toxicological regulations. However, the outer wax-like laye...

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Bibliographic Details
Published in:Nature (London) 2000-06, Vol.405 (6788), p.772-775
Main Authors: Bergeron, Vance, Bonn, Daniel, Martin, Jean Yves, Vovelle, Louis
Format: Article
Language:English
Subjects:
Additives
Applied sciences
Exact sciences and technology
Fluid dynamics
Herbicides
Humanities and Social Sciences
Leaves
letter
multidisciplinary
Organic polymers
Pesticides
Physicochemistry of polymers
Polymers
Properties and characterization
Science
Science (multidisciplinary)
Solution and gel properties
Viscosity
Water
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Summary:Controlling the impact of drops onto solid surfaces is important for a wide variey of coating and deposition processes-for example, the treatment of plants with herbicides and pesticides requires precise targeting in order to meet stringent toxicological regulations. However, the outer wax-like layer of the leaves is a non-wetting substrate that causes sprayed droplets to rebound; often less than 50% of the initial spray is retained by the plant. Although the impact and subsequent retraction of non-wetting aqueous drops on a hydrophobic surface have been the subjects of extensive experimental and theoretical work, non-newtonian rheological effects have not been considered in any detail. Here we report that, by adding very small amounts of a flexible polymer to the aqueous phase, we can inhibit droplet rebound on a hydrophobic surface and markedly improve deposition without significantly altering the shear viscosity of the solutions. Our results can be understood by taking into account the non-newtonian elongational viscosity, which provides a large resistance to drop retraction after impact, thereby suppressing droplet rebound.
ISSN:0028-0836
1476-4687
DOI:10.1038/35015525