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Published May 2, 2005 | public
Journal Article Open

Microfluidic detection and analysis by integration of thermocapillary actuation with a thin-film optical waveguide


We demonstrate a nonintrusive optical method for microfluidic detection and analysis based on evanescent wave sensing. The device consists of a planar thin-film waveguide integrated with a microfluidic chip for directed surface flow. Microliter droplets are electronically transported and positioned over the waveguide surface by thermocapillary actuation. The attenuated intensity of propagating modes is used to detect droplet location, to monitor dye concentration in aqueous solutions, and to measure reaction rates with increasing surface temperature for a chromogenic biochemical assay. This study illustrates a few of the capabilities possible by direct integration of optical sensing with surface-directed fluidic devices.

Additional Information

©2005 American Institute of Physics (Received 12 January 2005; accepted 28 March 2005; published online 25 April 2005) This work was funded by the NASA Microgravity Fluid Physics Program and the US Army TACOM-ARDEC. One of the authors (J.P.V.) thanks Dr. P. K. Tien of Bell Labs for helpful discussions. SMT gratefully acknowledges the hospitality and financial support of the Moore Distinguished Scholar Program at the California Institute of Technolgy.


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