title: Equilibrium phase diagram of drop-on-fiber: coexistent states and gravity effect.
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.
authors.affiliation: Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan 106.
authors.forename: Tung-He
authors.initials: TH
authors.lastname: Chou
authors.forename: Siang-Jie
authors.initials: SJ
authors.lastname: Hong
authors.forename: Yu-En
authors.initials: YE
authors.lastname: Liang
authors.forename: Heng-Kwong
authors.initials: HK
authors.lastname: Tsao
authors.forename: Yu-Jane
authors.initials: YJ
authors.lastname: Sheng
mesh_terms: D006112:Gravitation; D044085:Microfluidics; D049329:Nanostructures / Q000737:chemistry; D036103:Nanotechnology; D013499:Surface Properties