Controlling droplet deposition with polymer additives
Controlling droplet deposition with polymer additives
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DOI：
10.1038/35015525
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发表时间：
2000-06-15
期刊：
影响因子：
64.8
通讯作者：
Vovelle, L
中科院分区：
文献类型：
--
作者：
Bergeron, V;Bonn, D;Vovelle, L
控制液滴对固体表面的影响对于各种涂层和沉积工艺都很重要-例如，用除草剂和杀虫剂处理植物需要精确的目标，以满足严格的毒理学法规。然而，叶片的外部蜡状层是一种非润湿基质，导致喷雾液滴反弹;通常只有不到50%的初始喷雾被植物保留（1）。虽然非润湿水滴在疏水表面上的冲击和随后的回缩已经是大量实验和理论工作的主题（2-7），但非牛顿流变效应尚未被详细考虑。在这里，我们报告说，通过添加非常少量的柔性聚合物的水相，我们可以抑制液滴反弹的疏水表面上，并显着改善沉积，而不显着改变溶液的剪切粘度。我们的结果可以理解，考虑到非牛顿拉伸粘度，它提供了一个很大的阻力下降后，冲击回缩，从而抑制液滴反弹。
Controlling the impact of drops onto solid surfaces is important for a wide variety 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(1). 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(2-7), 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.