Optical fiber-based sensing platform with integrated biodegradable agar-structured transducer

Emerging applications in biochemical and biomedical sensing demand degradable and biocompatible optical fibers to replace the widespread glass and plastic waveguides. Agar prevails amongst soft optical materials as a renewable, transparent, edible, and thermoreversible gel, supporting the manufacture of lenses and waveguides. Thus, this paper proposes an agar-glycerol-made structured optical fiber integrated into a slab substrate for mechanical and chemical sensing. A 3D-printed mold creates air holes around the solid core, leading to optical losses of 2.42 dB/cm at 633 nm. Moreover, we investigated the sensor response to transverse forces by assessing the output light through specklegram analysis, yielding a practical resolution of 0.04 N. Ultimately, exposing the transducer to surrounding fluids reveals characteristic speckle field changes due to the agar syneresis and swelling effects. The preliminary results encourage further applications of the integrated optical fiber as a biocompatible and disposable sensing platform for growth media and microfluidics setups.