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Lab Chip

Title:		"A microfabricated optofluidic ring resonator for sensitive, high-speed detection of volatile organic compounds"
Author(s):		Scholten K; Fan X; Zellers ET;
Address:		"Applied Physics Program, University of Michigan, Ann Arbor, MI 48109-1040, USA"
Journal Title:		Lab Chip
Year:		2014
Volume:		14
Issue:		19
Page Number:		3873 - 3880
DOI:		10.1039/c4lc00739e
ISSN/ISBN:		1473-0189 (Electronic) 1473-0189 (Linking)
Abstract:		"Advances in microanalytical systems for multi-vapor determinations to date have been impeded by limitations associated with the microsensor technologies employed. Here we introduce a microfabricated optofluidic ring resonator (muOFRR) sensor that addresses many of these limitations. The muOFRR combines vapor sensing and fluidic transport functions in a monolithic microstructure comprising a hollow, vertical SiOx cylinder (250 mum i.d., 1.2 mum wall thickness; 85 mum height) with a central quasi-toroidal mode-confinement section, grown and partially released from a Si substrate. The device also integrates on-chip fluidic-interconnection and fiber-optic probe alignment features. High-Q whispering gallery modes generated with a tunable 1550 nm laser exhibit rapid, reversible shifts in resonant wavelength arising from polymer swelling and refractive index changes as vapors partition into the ~300 nm PDMS film lining the cylinder. Steady-state sensor responses varied in proportion to concentration over a 50-fold range for the five organic vapors tested, providing calculated detection limits as low as 0.5 ppm (v/v) (for m-xylene and ethylbenzene). In dynamic exposure tests, responses to 5 muL injected m-xylene vapor pulses were 710 ms wide and were only 18% broader than those from a reference flame-ionization detector and also varied linearly with injected mass; 180 pg was measured and the calculated detection limit was 49 pg without use of preconcentration or split injection, at a flow rate compatible with efficient chromatographic separations. Coupling of this muOFRR with a micromachined gas chromatographic separation column is demonstrated"
Keywords:		Limit of Detection Linear Models Microfluidic Analytical Techniques/*instrumentation Optical Fibers Optics and Photonics/*instrumentation Reproducibility of Results Volatile Organic Compounds/*analysis/isolation & purification;
Notes:		"MedlineScholten, Kee Fan, Xudong Zellers, Edward T eng Research Support, U.S. Gov't, Non-P.H.S. England 2014/08/19 Lab Chip. 2014 Oct 7; 14(19):3873-80. doi: 10.1039/c4lc00739e"