Advanced novel asymmetric notched plastic optic fibers for sensing applications

The study introduces high-sensitivity asymmetric notched polymethyl methacrylate fiber optic sensors (AN-PMMA-FOS), which significantly outperform symmetric notched sensors, particularly in robotics and wearable healthcare, excelling in sensitivity, linearity, resolution, signal-to-noise ratio, and tunable optical specificity. These sensors provide reliable anisotropic sensing of forces and geometric changes, such as muscle contractions, outperforming traditional polymer optical fiber (POF) sensors. A novel fabrication technique using 3D printing and thermal modification of the PMMA fiber surface was developed. The sensors were produced with unmodified surfaces, surfaces functionalized with fluorescent dyes Phloxine B (PhB) or Methylene Blue or coated with UV-curable resin (ELA) composites containing PhB or Curcumin. These modifications improved the sensors’ mechanical and optical properties, enabling predefined anisotropic optical behavior. Fluorescent dye functionalization improved hydrophilicity, while ELA-dye coatings enhanced mechanical stability and optical sensitivity. Using of different dyes enhanced spectral specificity, allowing for spectral differentiation between sensors. Thermogravimetric analysis showed that pure PMMA fibers degrade at 123 °C, while functionalized and coated fibers degrade at 100 °C and 110 °C, respectively. Mechanical testing revealed reduced tensile strength in notched fibers, but functionalized and coated fibers demonstrated greater force endurance. These AN-PMMA-FOS sensors are highly suitable for advanced robotics, environmental monitoring, biomedical diagnostics, wearable healthcare, muscle strength measurement, and structural health monitoring, offering high specificity and sensitivity (>3.3 × 10-7N/div).