Buoyant Droplets on Functional Fibers

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• 作者：Ri毛lle de Ruiter ; Jolet de Ruiter ; H眉seyin Burak Eral ; Ciro Semprebon ; Martin Brinkmann ; Frieder Mugele
• 刊名：Langmuir
• 出版年：2012
• 出版时间：September 18, 2012
• 年：2012
• 卷：28
• 期：37
• 页码：13300-13306
• 全文大小：331K
• 年卷期：v.28,no.37(September 18, 2012)
• ISSN：1520-5827

文摘

In the absence of gravity, the wetting of droplets on fibers is characterized by the competition between an axisymmetric barrel morphology engulfing the fiber and a symmetry-broken clamshell morphology with the droplet sitting on the side of the fiber. In the generic case of nonzero buoyancy the cylindrical symmetry of the barrel morphology is broken, yet barrels and clamshells can still be distinguished based on their different interfacial topologies being multiply and simply connected, respectively. Next to contact angle and droplet size the capillary length appears as a third parameter controlling the droplet morphology. For droplets of variable size, contact angle and buoyancy are independently varied in experiments by use of electrowetting and density mismatch. This approach鈥攖ogether with the complementary numerical calculations鈥攑rovides new insights into the gradual shifts of the stability limits in the presence of an external volume force. Overall, the parameter space for stable clamshells is found to expand with increasing gravitational forces, gradually shrinking the regimes of stable barrels and bistability. In addition, a new stability limit is introduced for the clamshell morphology related to a partial detachment of the wetting liquid from the fiber, appearing toward higher droplet volumes.