Year: 2026
Type: preprint
Abstract: Integrated photonic sensors offer a pathway toward compact chemical analysis, but their use in unprocessed complex fluids is limited by surface fouling, chemical compatibility, and the need for stable optical coupling. Here, we develop a reusable waveguide-enhanced Raman spectroscopy (WERS) platform based on chemically resilient silicon nitride waveguides and a permanently packaged fiber-to-chip interface. The sensor incorporates a spiral sensing waveguide and a robust optical input/output architecture designed to provide reproducible coupling without active alignment. Reusability was evaluated following exposure to commercial gasoline and sequential cleaning treatments. Raman signal recovery using isopropanol as a reference analyte demonstrated improved spectral performance after solvent and oxidative cleaning. As a representative application in a chemically complex matrix, the sensor was directly immersed in commercial gasoline for quantitative ethanol determination without extraction or additional sample preparation. A ratiometric signal based on the ethanol band at 885 cm-1 and a reference band at 1000 cm-1 provided a linear calibration over 10.00–21.74% v/v ethanol (R2 = 0.9323). Independent external validation across 10.00–20.00% v/v yielded 100% prediction-interval coverage, an RMSEP of 0.46% v/v, and an MAE of 0.36% v/v. These results demonstrate that chemically robust WERS with stable packaging can support reproducible, reusable Raman sensing directly in complex fuel matrices, providing a foundation for field-deployable photonic chemical analysis.
Source: ChemRxiv
Institution: Massachusetts Institute of Technology
Language: English
Topic: Photonic and Optical Devices
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221950842