title: Three-dimensional measurement and visualization of internal flow of a moving droplet using confocal micro-PIV.
abstract: This paper presents a micro-flow diagnostic technique, 'high-speed confocal micro-particle image velocimetry (PIV)', and its application to the internal flow measurement of a droplet passing through a microchannel. A confocal micro-PIV system has been successfully constructed wherein a high-speed confocal scanner is combined with the conventional micro-PIV technique. The confocal micro-PIV system enables us to obtain a sequence of sharp and high-contrast cross-sectional particle images at 2000 frames s(-1). This study investigates the confocal depth, which is a significant parameter to determine the out-of-plane measurement resolution in confocal micro-PIV. Using the present confocal micro-PIV system, we can measure velocity distributions of micro-flows in a 228 microm x 171 microm region with a confocal depth of 1.88 microm. We also propose a three-dimensional velocity measurement method based on the confocal micro-PIV and the equation of continuity. This method enables us to measure three velocity components in a three-dimensional domain of micro flows. The confocal micro-PIV system is applied to the internal flow measurement of a droplet. We have measured three-dimensional distributions of three-component velocities of a droplet traveling in a 100 microm (width) x 58 microm (depth) channel. A volumetric velocity distribution inside a droplet is obtained by the confocal micro-PIV and the three-dimensional flow structure inside the droplet is investigated. The measurement results suggest that a three-dimensional and complex circulating flow is formed inside the droplet.
authors.affiliation: Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo, Japan. hkino@iis.u-tokyo.ac.jp
authors.forename: Haruyuki
authors.initials: H
authors.lastname: Kinoshita
authors.forename: Shohei
authors.initials: S
authors.lastname: Kaneda
authors.forename: Teruo
authors.initials: T
authors.lastname: Fujii
authors.forename: Marie
authors.initials: M
authors.lastname: Oshima
mesh_terms: D044085:Microfluidics / Q000379:methods*; D018613:Microscopy, Confocal