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Published June 9, 2020 | Supplemental Material + Published
Journal Article Open

Bioinspired Disordered Flexible Metasurfaces for Human Tear Analysis Using Broadband Surface-Enhanced Raman Scattering

Abstract

Flexible surface-enhanced Raman scattering (SERS) has received attention as a means to move SERS-based broadband biosensing from bench to bedside. However, traditional flexible periodic nano-arrangements with sharp plasmonic resonances or their random counterparts with spatially varying uncontrollable enhancements are not reliable for practical broadband biosensing. Here, we report bioinspired quasi-(dis)ordered nanostructures presenting a broadband yet tunable application-specific SERS enhancement profile. Using simple, scalable biomimetic fabrication, we create a flexible metasurface (flex-MS) of quasi-(dis)ordered metal–insulator–metal (MIM) nanostructures with spectrally variable, yet spatially controlled electromagnetic hotspots. The MIM is designed to simultaneously localize the electromagnetic signal and block background Raman signals from the underlying polymeric substrate—an inherent problem of flexible SERS. We elucidate the effect of quasi-(dis)ordering on broadband tunable SERS enhancement and employ the flex-MS in a practical broadband SERS demonstration to detect human tear uric acid within its physiological concentration range (25–150 μM). The performance of the flex-MS toward noninvasively detecting whole human tear uric acid levels ex vivo is in good agreement with a commercial enzyme-based assay.

Additional Information

© 2020 American Chemical Society. This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. Received: February 14, 2020; Accepted: May 6, 2020; Published: May 18, 2020. The authors acknowledge the financial support provided by the SAMSUNG Global Research Outreach (GRO) program. The authors are also thankful for the support and resources provided by the Kavli Nanoscience Institute at Caltech. Author Contributions: V.N., R.H.S., and H.C. conceived the study. V.N., R.H.S., and H.P. performed the necessary simulations and experiments under the supervision of H.C. The manuscript was written through contributions of all the authors. SAMSUNG Global Research Outreach (GRO) program. The authors declare no competing financial interest.

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Published - acsomega.0c00677.pdf

Supplemental Material - ao0c00677_si_001.pdf

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