Equilibrium phase diagram of drop-on-fiber: Coexistent states and gravity effect

Tung He Chou, Siang Jie Hong, Yu En Liang, Heng Kwong Tsao, Yu Jane Sheng

Research output: Contribution to journalArticlepeer-review

58 Scopus citations

Abstract

Drop-on-fiber is commonly observed in daily life and is closely related to digital microfluidics. The wetting behavior of droplet-on-fiber is different from that of droplet-on-plane due to the global cylindrical shape. It is generally believed that the equilibrium geometric shape of a droplet on a fiber takes either asymmetric clam-shell or axisymmetric barrel conformation in the absence of gravity. The barrel-to-clam-shell transition is determined by the stability condition. Nonetheless, experimental observations showed that both barrel and clam-shell conformations can coexist in some situations and thus indicated the existence of the multiple stable states. In this Article, the phase diagrams of droplet-on-fiber, that is, the plots of droplet volume against contact angle, are established on the basis of the finite-element simulation (Surface Evolver). When the gravity effect is absent, there are three regimes including barrel, clam-shell, and coexistence of barrel and clam-shell. As the gravity effect is considered, there exist three regimes, including (I) downward clam-shell, (II) coexistence of barrel and clam-shell, and (III) falling-off.

Original languageEnglish
Pages (from-to)3685-3692
Number of pages8
JournalLangmuir
Volume27
Issue number7
DOIs
StatePublished - 5 Apr 2011

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