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Differential Diffractive Reflectance Modulation Sensing

Kumawat, Nityanand and Prashanth, Gurusiddappa R and Varma, Manoj M (2012) Differential Diffractive Reflectance Modulation Sensing. In: Conference on Frontiers in Biological Detection - From Nanosensors to Systems IV, JAN 21-22, 2012 , San Francisco, CA, USA.

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Abstract

We fabricated a reflectance based sensor which relies on the diffraction pattern generated from a bio-microarray where an underlying thin film structure enhances the diffracted intensity from molecular layers. The zero order diffraction represents the background signal and the higher orders represent the phase difference between the array elements and the background. By taking the differential ratio of the first and zero order diffraction signals we get a quantitative measure of molecular binding while simultaneously rejecting common mode fluctuations. We improved the signal-to-noise ratio by an order of magnitude with this ratiometric approach compared to conventional single channel detection. In addition, we use a lithography based approach for fabricating microarrays which results in spot sizes as small as 5 micron diameter unlike the 100 micron spots from inkjet printing and is therefore capable of a high degree of multiplexing. We will describe the real-time measurement of adsorption of charged polymers and bulk refractometry using this technique. The lack of moving parts for point scanning of the microarray and the differential ratiometric measurements using diffracted orders from the same probe beam allows us to make real-time measurements in spite of noise arising from thermal or mechanical fluctuations in the fluid sample above the sensor surface. Further, the lack of moving parts leads to considerable simplification in the readout hardware permitting the use of this technique in compact point of care sensors.

Item Type: Conference Proceedings
Additional Information: Conference on Frontiers in Biological Detection - From Nanosensors to Systems IV, San Francisco, CA, JAN 21-22, 2012
Keywords: Label-free biosensing;real-time measurement;thin film reflectance
Department/Centre: Other Centres/Units > Centre for Nano Science and Engineering
Date Deposited: 05 Jul 2012 07:55
Last Modified: 05 Jul 2012 07:55
URI: http://eprints.iisc.ernet.in/id/eprint/44777

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