Miniaturized polymer-coated FBGs for high-sensitivity biomedical pressure sensing

Continuous and real-time physiological pressure monitoring is essential for diagnosing and managing conditions such as intracranial hypertension, cardiovascular diseases, and gastrointestinal motility disorders. While fiber Bragg gratings (FBGs) offer several advantages over conventional electrical sensors, including immunity to electromagnetic interference and multiplexing capability for simultaneous multi-point sensing, their inherent low-pressure sensitivity limits their applicability in biomedical environments. This study investigates the enhancement of FBG pressure sensitivity through a polymer coating, such as polydimethylsiloxane (PDMS), is used to improve strain transfer and amplify the Bragg wavelength shift, with coating dimensions (∼500 µm) compatible with pressure guidewires or catheters. A combined approach of finite element modeling and experimental validation demonstrated that, compared to uncoated sensors, PDMS-coated FBGs achieved up to 43-fold and 154-fold sensitivity enhancements for 500 µm and 800 µm coatings on 125 µm cladding fibers, and up to 212-fold and 339-fold improvements for corresponding coatings on 80 µm cladding FBGs. Under dynamic pressure, the sensors exhibited minimum detectable pressure amplitudes of 0.5 mmHg. These enhancements bring standard FBG sensors closer to real-time, minimally invasive continuous monitoring in pressure-guided catheters. Additionally, the mechanical robustness and multiplexing potential of coated FBGs enable non-invasive applications, such as smart walkers or wearable devices, broadening their utility across clinical and rehabilitative settings.