Liquid-core polymer optical fibers for luminescent waveguide applications. (November 2020)

• Record Type: Journal Article
• Authors: Jakubowski, Konrad; Kerkemeyer, Wiebke; Perret, Edith; Heuberger, Manfred; Hufenus, Rudolf
• Is Part Of: Materials & design. Volume 196(2020)
• Publication Date: 2020-11
• Subjects: Optical fibers -- Molecular orientation -- Light conversion -- Strain sensor -- Semi-crystalline polymer; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2020.109131
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: Luminescent polymer optical fibers provide a flexible platform for sensor applications. Photoluminescent liquid-core polymer optical fibers (LiCo-POFs), produced by a co-extrusion of a low refractive index semi-crystalline fluoropolymer sheath with a glycerol core, are presented. Substituting a POF's solid polymer core with a transparent liquid yields luminescent waveguides with extra mechanical flexibility, enabling unique applications like strain sensing. Light conversion and guidance in LiCo-POFs were both achieved simultaneously by doping of the glycerol core with a fluorescent dye. X-ray analysis showed a strong impact of drawing on fiber sheath morphology, and in consequence on both mechanical and optical properties: as the molecular orientation of the sheath increases, tensile strength improves and light attenuation decreases. Excessive drawing leads to micro-voids in the sheath material, causing light scattering, which negatively affects both attenuation and light-conversion. It has been found that both the sheath structure and the sheath and core cross-sectional areas are important design parameters regarding the mechanical and optical performance of LiCo-POFs. A novel principle of an optical strain sensor based on self-absorption peak-shifts is demonstrated; it allows detection of sub-millimeter displacements, both in a reversible elastic as well as in an irreversible inelastic sensor range. Graphical abstract: Unlabelled Image Highlights: A method to produce flexible liquid-core polymer optical fibers (LiCo-POFs) in a continuous way is presented. Draw ratio and dye concentration are important design parameters, defining mechanical and optical properties of LiCo-POFs. Non-luminescent LiCo-POFs can be stretched up to 550%, while still guiding light. Luminescent LiCo-POFs can detect strain as fail-safe (up to 350% elongation) and reversible (up to 10% elongation) sensors.