Photonic Skin Based on Microfiber Bragg Grating for Pulse Wave Detection

Flexible opto-electronics facilitate a seamless and fully connected bridge between smart devices and the human body, enabling long-term and continuous health monitoring and human-machine interaction. In this study, an intelligent photonic skin based on the microfiber Bragg grating $(\boldsymbol{\mu}\mathbf{FBG})$ was proposed for tiny pulse wave detection with high sensitivity. The photonic skin comprises an optical microfiber inscribed with a Bragg grating array using the femtosecond direct-writing technique, along with a polydimethylsiloxane (PDMS) encapsulation layer. Through finite element simulation, the structure of the $\boldsymbol{\mu}\mathbf{FBG}$ photonic skin has been optimized to enhance the response of the vertical stress. Compared to commercial FBGs, the $\boldsymbol{\mu}\mathbf{FBG}$ photonic skin successfully detects high signal-to-noise ratio pulse waves with a signal strength 12 times greater. Featuring remarkable sensitivity and flexibility, the photonic skin enriches the flexible opto-electronic technique and has the application potential on the health monitoring wearable device.