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Title: Multiplexed Optofluidic Biosensing on Deterministic Aperiodic Nano-Structures

Participants: Boston University – Seung Lee (BME ’13) and Professor Luca Dal Negro

Tufts University – David Kaplan and Florenzo Omenetto

Funding: Air Force (via the Optical Food Sensing program)

multiplexedBackground: In current optical sensing technology, light scattering and propagation phenomena in periodic systems, such as one- and two-dimensional (1D and 2D) gratings and photonic bandgap structures, are one of the major surface detection mechanisms. Their fundamental theory based on Bragg scattering and resulted single frequency response along well-defined propagation directions intrinsically limits its sensitivity to changes in nanoscale.

Description: With our collaborators, Professors David Kaplan and Florenzo Omenetto of Tufts University, we are researching inelastic and elastic scattering properties of the two-dimensional deterministic aperiodic metal nanoparticle arrays that are exploited for multiplexed biosensing applications. These arrays can be easily fabricated by standard microfabrication processes – for instance, electron beam (e-beam) lithography and e-beam evaporation. Under white light, excitation in conventional darkfield microscopy, highly organized polychromatic patterns that we called “colorimetric fingerprints” are generated in the metallic DANS, as shown in the above figure. By combining the modalities of colorimetric detection and pattern recognition on the colorimetric fingerprints, we have demonstrated significantly enhanced sensitivity beyond the traditional Bragg scattering to the presence of protein monolayers with thickness of a few tens of Angstroms (<1ng) by experimentally using dark-field scattering spectroscopy and image correlation analysis in the visible spectral range.

Integration of reliably fabricated DANS with microfluidics technology make biological detection in liquid environments easy. Biological substances, such as bacterial cells and viruses found in food and environmental toxins and contaminants, can be sensitively detected through both sensing modalities of the colorimetric fingerprints in this integrated optofluidic microdevice. Along with the high sensitivity of the colorimetric fingerprints, DANS generated by gold nanoparticles facilitate the incorporation of Surface-Enhanced Raman Spectroscopy (SERS) that provides additionally high specificity.


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