Asymmetric Notched Plastic Optical Fibers for Multipoint Monitoring of Simulated Muscle Contractions

This study presents a multipoint asymmetric notched polymethyl methacrylate (PMMA) fiber-optic designed for sequential and simultaneous monitoring of force and calibrated pressure across multiple points on a single fiber. The sensor was fabricated by thermal surface modification via 3-D printing and coated with biocompatible dye-elastomer composites containing phloxine B (PhB), curcumin, and methylene blue (MB), producing unique spectral signatures for independent point discrimination. A custom 3-D-printed peristalsis simulator reproduced physiological contraction dynamics, enabling controlled evaluation of the sensor under realistic loading. A detailed intensity-force-pressure calibration framework was developed, providing a deterministic mapping between spectral intensity, applied force, and pressure under the controlled simulator geometry. Spectral interpretation combined with 2-D correlation (r ≥ 0.98) with spectral unmixing (82%-92% abundance accuracy) enables precise multipoint quantification during both linear and nonlinear deformation events, including acceleration-deceleration phases and contraction intensities. Signal stability was confirmed over 12 h with relative standard deviation (RSD) ≤ 0.52 % at 0, 1 cm/s signal-to-noise ratio (SNR = 45 dB) and 0.84% at 3 cm/s (SNR = 38 dB). Sensor durability was verified by both cyclic loading and 168 h of MES and PBS buffer exposure. The results establish the proposed structure as a low-cost and versatile sensing platform for controlled biomedical monitoring research with simulator-validated feasibility for applications involving mechanical wave propagation. In vivo and ex vivo validation would be the essential next step toward clinical deployment.