Abstract
In this paper we introduce Nanoscale Optofluidic Sensor Arrays (NOSAs), which are an optofluidic architecture for performing highly parallel, label free detection of biomolecular interactions in aqueous environments. The architecture is based on the use of arrays of 1D photonic crystal resonators which are evanescently coupled to a single bus waveguide. Each resonator has a slightly different cavity spacing and is shown to independently shift its resonant peak in response to changes in refractive index in the region surrounding its cavity. We demonstrate through numerical simulation that by confining biomolecular binding to this region, limits of detection on the order of tens of attograms (ag) are possible. Experimental results demonstrate a refractive index (RI) detection limit of 7 x 10(-5) for this device. While other techniques such as SPR possess a equivalent RI detection limit, the advantage of this architecture lies in its potential for low mass limit of detection which is enabled by confining the size of the probed surface area.
Highlights
Optical techniques represent one of the most popular methods for performing sensitive and label free biomolecular detection
Though numerous different architectures have been developed (including interferometric sensors [2,3], resonant cavity sensors [4,5], whispering gallery mode sensors [6,7], surface plasma resonance (SPR) sensors [8] and photonic crystal based sensors [9,10]) in most cases detection is based on measuring the change in refractive index that results when solution phase targets bind with complimentary probes that have been predeposited on the surface
High quality factor 1D and 2D photonic-bandgap microcavity [12] sensors amplify this effect by shrinking the probed volume to the size of the optical cavity, which can be on the order of λ3
Summary
Optical techniques represent one of the most popular methods for performing sensitive and label free biomolecular detection. While the bulk refractive index sensitivity of this device is lower than that of techniques such as SPR, its chief advantage lies in the ability to confine the size of the probed volume allowing for a low mass limit of detection. As such our device should be able to detect rarer targets in a given sample size since a smaller number of them are required to impart a measurable change. We determine the sensitivity of our devices by observing the shift in the resonant wavelength of the resonators as a function of the change in refractive index of the fluid
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