title: Picoliter droplet formation on thin optical fiber tips.
abstract: In this paper, we present experimental results on how minute droplets are formed on fiber optic end faces. Results show that reproducible picoliter volumes can be generated when fibers are retracted from an aqueous phase contained under an inert fluorinated immiscible liquid, with a coefficient of variation (CV) of 0.7-2.3%. The droplet formation was analyzed as a function of the fiber diameter, retraction speed, and wettability. Experiments reveal a volume-determining critical equilibrium contact angle between 60 degrees and 75 degrees , defining the onset of fiber end-face dewetting. The dynamics of the droplet snap-off progression was characterized using high-speed imaging in order to explain the observed wettability-volume dependency.
authors.affiliation: Department of Mechanical Engineering, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
authors.forename: Suguru
authors.initials: S
authors.lastname: Uemura
authors.forename: Mårten
authors.initials: M
authors.lastname: Stjernström
authors.forename: Johan
authors.initials: J
authors.lastname: Sjödahl
authors.forename: Johan
authors.initials: J
authors.lastname: Roeraade