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"Chip-Scale Universal Detection Based on Backscatter Interferometry," American Chemical Society
Article Type: White Papers
Updated: May 23, 2000
Author(s): Kelly Swinney, Dmitry Markov, Darryl J. Bornhop
An on-chip detector based on backscatter interferometry has been developed to perform subnanoliter-volume refractive index measurements. The detection system consists of a simple, folded optical train based on the interaction of a laser beam and an etched channel, consisting of two radii joined by a flat portion, thus defining a curved surface in the shape of a hemisphere in a silica (glass) plate. The backscattered light from the channel takes on the form of a high-contrast interference pattern that contains information related to the bulk properties of the fluid contained within the probe volume. Positional changes of the interference pattern (fringes) allow for the determination of delta n at the 10^-6 level, corresponding to 743 mM or 139 x 10^-15 mol or 12.8 x 10^-12 g of sucrose, in a probe volume of only 188 x 10^-12 L. A theoretical model of the on-chip backscatter interferometric detector has also been developed, evaluated, and found to be in agreement with experimental data. It is shown that the model can be used to predict general system performance for changes in the optical train such as the chip's wall thickness and channel diameter.
Copyright 2000 American Chemical Society. This paper is made available as an electronic reprint with permission of the American Chemical Society. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.