科研之友
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摘要
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 (mu OFRR) sensor that addresses many of these limitations. The mu OFRR combines vapor sensing and fluidic transport functions in a monolithic microstructure comprising a hollow, vertical SiOx cylinder (250 mu m i.d., 1.2 mu m wall thickness; 85 mu m 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 similar to 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 ethyibenzene). In dynamic exposure tests, responses to 5 mu L 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 mu OFRR with a micromachined gas chromatographic separation column is demonstrated.
- 出版日期2014-10-7
