-A Flexible FBG Micro-Pressure Sensor Based on a Double-Opening Slatted Arch Structure

Fiber Bragg Gratings (FBG) possess advantages such as distributed sensing capability, compact size, lightweight structure, good flexibility, high sensitivity and immunity to electromagnetic interference, making them well-suited for wearable physiological monitoring systems. However, due to the weak surface pressure caused by physiological signals like the pulse, bare FBG typically exhibits low sensitivity and is prone to spectral chirp issues resulting from uneven force distribution. To address these challenges, this study proposes a symmetric arched FBG sensing structure based on a double-opening slatted design, which amplifies micro-pressure signals on the skin surface. Additionally, the arch base and FBG are encapsulated using Polydimethylsiloxane (PDMS) hydrogel to enhance sensitivity in heart rate detection and mitigate spectral chirp effects caused by uneven stress on the grating region. Experimental results demonstrate a high-pressure sensitivity of up to 5.86 pm/kPa, with a linear correlation coefficient <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i><sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>=0.999 between wavelength and displacement within the 0–2N range. The sensor exhibits a hysteresis error of 1.6% and a repeatability error of 1.0%, enabling real-time monitoring of pulse waveform characteristic points.