Transient sensing of liquid films in microfluidic channels with optofluidic microresonators

We demonstrate that optical ring resonators can be used as time-resolved refractive index sensors embedded in microfluidic channels. The nanophotonic structures are integrated into soft silicone microchannels interfaced with a transparent hard polymer manifold and standard microfluidic connections....

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Bibliographic Details
Published in:Measurement science & technology 2010-07, Vol.21 (7), p.075204-075204
Main Authors: Grad, M, Tsai, C C, Yu, M, Kwong, D-L, Wong, C W, Attinger, D
Format: Article
Language:English
Subjects:
Channels
Detection
Droplets
Liquid films
Microfluidics
Nanostructure
Resonators
Sensors
Wavelengths
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Summary:We demonstrate that optical ring resonators can be used as time-resolved refractive index sensors embedded in microfluidic channels. The nanophotonic structures are integrated into soft silicone microchannels interfaced with a transparent hard polymer manifold and standard microfluidic connections. The steady-state sensitivity, resolution and detection limit of the sensors are characterized using aqueous saline solutions at various concentrations. Time-resolved measurements are performed by sensing thin liquid films (0--400 nm) associated with oil/water segmented flow in microfluidic channels. The influence of the interrogation wavelength is investigated, and the optimal wavelength is determined. Millisecond resolution is demonstrated by sensing the shape of a single drop as it flows past the sensor. Finally, the film thickness between the droplet and the resonator is measured for different capillary numbers and channel diameters, and compared with existing theoretical and experimental results.
ISSN:0957-0233
1361-6501
DOI:10.1088/0957-0233/21/7/075204