ME-FIRST: A Metasurface-Enhanced Fingerprint InfraRed Spectroscopic Tool for Fluid Analytes

TL;DR

The paper introduces ME-FIRST, a metasurface-enhanced IR spectroscopic tool that significantly improves sensitivity for analyzing complex fluid analytes, with potential applications in clinical biofluid diagnostics.

Contribution

It develops and validates a novel metasurface-based IR spectroscopy platform that enhances light-matter interaction across the fingerprint range for fluid analyte detection.

Findings

Achieved ~60-fold electric field enhancement at resonant peaks.

Demonstrated sensitive detection of L-lysine vibrational modes.

Validated device performance through numerical simulations and experiments.

Abstract

Infrared (IR) spectroscopy has emerged as a pivotal tool in biomedical diagnostics, offering label-free spectral biomarkers for the detection of numerous diseases, particularly in the fingerprint region. However, the lack of rapid and sensitive IR spectroscopic techniques for analyzing complex fluid analytes remains a critical challenge in clinical practice. To address this limitation, we present a Metasurface-Enhanced Fingerprint InfraRed Spectroscopic Tool (ME-FIRST) that enhances light-matter interactions in sub-wavelength volumes through plasmonic resonances across the entire fingerprint range from $1900 cm^{-1}$ to $1000 cm^{-1}$. Numerical simulations reveal confined and enhanced electric near-field, with an average probing depth of ~100 nm and enhancement factor $|E/E_0|$ of ~60-fold at resonant peaks. The ME-FIRST device is further experimentally fabricated and validated, and as a proof of concept, we demonstrate the sensing of molecular vibrational modes with a considerable sensitivity in L-lysine over the full fingerprint IR spectral range. The proposed ME-FIRST presents a promising platform for high-sensitivity IR spectroscopy of fluid analytes, paving the way for clinical applications of infrared spectroscopy in biofluid analysis and pathological scenarios.