Surface plasmon Sagnac interferometry for label-free characterization of flows in microfluidic environments

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The objective of this program is to develop a label-free, surface plasmon-based optical sensor which relies on a relativistic effect known as photon drag to characterize micron-scale fluid flows. The intellectual merit is the proposed development of a surface-plasmon Sagnac interferometer, which will enable optical mapping of low-contrast flows in nano- and microfluidic channels, using phase-sensitive detection. A fluid-circulating opto-fluidic cell will be integrated into the interferometer, and the phase shifts resulting from photon drag on counter-propagating plasmons excited in the cell will be measured. Theoretical modeling will accompany the experimental studies. Compared to existing amplitude-sensitive surface plasmon-based devices, this interferometric method allows lowering of the detection threshold by an order of magnitude. Such enhancement is crucial for on-chip gas and single molecule sensing, nano-scale flow-rate diagnostics, and micro-jet fluidic device monitoring. The transformative aspect of the proposal lies in the development of new methods for mapping micron-scale flow conditions using surface plasmon interferometry. This is potentially transformative for the development of label-free microfluidic sensors for lab-on-chip systems, enabling rapid, non-interacting and accurate diagnostics of local flow fields. The technological broader impacts are on future sensing technologies, through the development of plasmonic sensors able to diagnose microscopic fluid flows, as well as detect microturblence and electrical currents. The educational broader impacts include student training students will acquire valuable expertise in plasmonic sensing and microfluidic fabrication and operation techniques. Students professional development is also addressed through participation in outreach activities, thus facilitating the development of science literacy in the broader community.