Wearable Optical Fiber SERS Sensor Based on a Flexible "Hydrogel Tentacle" for Sweat Remote and In Situ Detection

Area of Science:

• Analytical Chemistry
• Materials Science
• Biomedical Engineering

Background:

• Wearable surface-enhanced Raman spectroscopy (SERS) sensors offer potential for sweat analysis but struggle with integrated sampling, sensing, and remote detection.
• Existing systems often lack the flexibility and robustness required for continuous, in situ monitoring in wearable applications.

Purpose of the Study:

• To develop a flexible "hydrogel tentacle" optical fiber (HTOF) SERS sensor for remote, in situ analysis of analytes in sweat.
• To create an integrated system combining sampling, sensing, and detection for wearable health monitoring.

Main Methods:

• Fabrication of a flexible hydrogel tentacle (HT) SERS substrate by in situ crosslinking a water-absorbent hydrogel with Ca2+ at an optical fiber tip.
• Utilizing the optical fiber to transmit light coupled into the HT for direct analyte sampling and SERS detection.
• Performance evaluation using 4-mercaptopyridine (4-Mpy) and application in semiquantitative recognition of sweat biomarkers with a 1D-CNN model.

Main Results:

• Achieved a high enhancement factor (EF) of 9.44 × 10^10 and a low limit of detection (LOD) of 8.69 × 10^-11 M for 4-Mpy.
• Demonstrated excellent sensor stability with 95.24% SERS activity retention after 40 days and low batch-to-batch variability (RSD of 2.64%).
• Achieved up to 91.05% accuracy in semiquantitative recognition of uric acid, creatinine, and urea using a 1D-CNN model.

Conclusions:

• The flexible HTOF SERS sensor offers a promising platform for wearable, remote, and in situ sweat analysis.
• The sensor exhibits high sensitivity, stability, and flexibility, suitable for integration into wearable devices.
• The developed system shows significant potential for non-invasive kidney disease assessment and continuous health monitoring.