title: Optical non-contact localization of liquid-gas interfaces on disk during rotation for measuring flow rates and viscosities.
abstract: We present a novel technique for the spatio-temporally resolved localization of liquid-gas interfaces on centrifugal microfluidic platforms based on total internal reflection (TIR) at the channel wall. The simple setup consists of a line laser and a linear image sensor array mounted in a stationary instrument. Apart from identifying the presence of usually unwanted gas bubbles, the here described online meniscus detection allows to measure liquid volumes with a high precision of 1.9%. Additionally, flow rates and viscosities (range: 1-12 mPa s, precision of 4.3%) can be sensed even during rotation at frequencies up to 30 Hz.
authors.affiliation: Laboratory for MEMS Applications, Department of Microsystems Engineering-IMTEK, University of Freiburg, Georges-Koehler-Allee 103, Freiburg, 79110, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Hoffmann
authors.forename: Lutz
authors.initials: L
authors.lastname: Riegger
authors.forename: Frederik
authors.initials: F
authors.lastname: Bundgaard
authors.forename: Daniel
authors.initials: D
authors.lastname: Mark
authors.forename: Roland
authors.initials: R
authors.lastname: Zengerle
authors.forename: Jens
authors.initials: J
authors.lastname: Ducrée
mesh_terms: D002498:Centrifugation / Q000295:instrumentation*; D005740:Gases / Q000737:chemistry*; D005990:Glycerol / Q000737:chemistry; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D055620:Optical Phenomena; D012399:Rotation; D062211:Spatio-Temporal Analysis; D014783:Viscosity
chemical_list: D005740:Gases; D005990:Glycerol