title: Experimental Techniques for Bubble Dynamics Analysis in Microchannels: A Review.
abstract: Experimental studies employing advanced measurement techniques have played an important role in the advancement of two-phase microfluidic systems. In particular, flow visualization is very helpful in understanding the physics of two-phase phenomenon in microdevices. The objective of this article is to provide a brief but inclusive review of the available methods for studying bubble dynamics in microchannels and to introduce prior studies, which developed these techniques or utilized them for a particular microchannel application. The majority of experimental techniques used for characterizing two-phase flow in microchannels employs high-speed imaging and requires direct optical access to the flow. Such methods include conventional brightfield microscopy, fluorescent microscopy, confocal scanning laser microscopy, and micro particle image velocimetry (micro-PIV). The application of these methods, as well as magnetic resonance imaging (MRI) and some novel techniques employing nonintrusive sensors, to multiphase microfluidic systems is presented in this review.
authors.affiliation: e-mail:  mohammma@onid.orst.edu.
authors.forename: Mahshid
authors.initials: M
authors.lastname: Mohammadi
authors.forename: Kendra V
authors.initials: KV
authors.lastname: Sharp
keywords: backlighting; bubble dynamics; confocal microscopy; flow visualization; fluorescent microscopy; magnetic resonance imaging (MRI); micro particle image velocimetry (micro-PIV); microchannel
references.citation: J Cell Sci. 2007 May 15;120(Pt 10):1703-5
references.pmid: 17502480
references.citation: Lab Chip. 2007 Feb;7(2):273-80
references.pmid: 17268631
references.citation: Phys Rev Lett. 2008 Jan 25;100(3):034504
references.pmid: 18232987
references.citation: Lab Chip. 2006 Mar;6(3):437-46
references.pmid: 16511628
references.citation: Lab Chip. 2009 Sep 7;9(17):2551-67
references.pmid: 19680579
references.citation: Phys Rev Lett. 2001 Dec 31;87(27 Pt 1):274501
references.pmid: 11800883
references.citation: Langmuir. 2008 Dec 16;24(24):13904-11
references.pmid: 19360952
references.citation: Magn Reson Imaging. 2005 Feb;23(2):387-9
references.pmid: 15833655
references.citation: Exp Fluids. 2009 Aug 1;47(2):309-320
references.pmid: 23049158
references.citation: Langmuir. 2008 Apr 15;24(8):4388-93
references.pmid: 18331069
references.citation: Lab Chip. 2004 Aug;4(4):278-86
references.pmid: 15269792
references.citation: Angew Chem Int Ed Engl. 2005 Aug 26;44(34):5447-51
references.pmid: 15966027
references.citation: Biol Bull. 1998 Aug;195(1):1-4
references.pmid: 9739546
references.citation: J Magn Reson. 2003 Mar;161(1):15-24
references.pmid: 12660107
references.citation: Lab Chip. 2006 Dec;6(12):1487-503
references.pmid: 17203152
references.citation: Anal Chem. 2007 Jun 15;79(12):4484-92
references.pmid: 17508715