Tuning Kinetics to Control Droplet Shapes on Chemically Striped Patterned Surfaces

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• 作者：H. Patrick Jansen ; Kai Sotthewes ; Christian Ganser ; Christian Teichert ; Harold J. W. Zandvliet ; E. Stefan Kooij
• 刊名：Langmuir
• 出版年：2012
• 出版时间：September 18, 2012
• 年：2012
• 卷：28
• 期：37
• 页码：13137-13142
• 全文大小：296K
• 年卷期：v.28,no.37(September 18, 2012)
• ISSN：1520-5827

文摘

The typically elongated shape of droplets on chemically microstriped surfaces has been suggested to depend strongly on the kinetics during deposition. Here, we unequivocally establish the importance of impact kinetics by comparing the geometry of pico- to microliter droplets deposited from an inkjet nozzle with those obtained by conventional deposition from a syringe. For large Weber numbers, the strongly enhanced spreading during the impact in combination with direction-dependent pinning of the contact line gives rise to more spherical droplets with a low aspect ratio. The impact energy can be minimized by the prolonged firing of small picoliter droplets to form larger droplets or, as shown in the past, by using high-viscosity liquids. In the first case, the impact energy is absorbed by the liquid already present, therewith reducing the impact diameter and consequently forming markedly more elongated droplets.