Research progress on the preparation of elastic polymer optical fibers and their applications in sensing

The rapid advancement of medical photonics has significantly increased the demand for fiber-optic devices across sensing, diagnostic, and therapeutic applications. This growing demand imposes increasingly stringent requirements on the constituent materials, necessitating exceptional mechanical flexibility, stretchability, biocompatibility, and, in many cases, biodegradability. Traditional silica-based or rigid polymer optical fibers, characterized by their high elastic modulus and inherent inflexibility, face substantial limitations in dynamic biological environments. Their mechanical properties are fundamentally mismatched with those of soft human tissues. This mismatch not only compromises biocompatibility but also poses a real risk of damaging surrounding delicate tissues during implantation or physiological movement, restricting their potential for long-term or minimally invasive monitoring and therapeutic intervention. Elastic polymer optical fibers (EPOFs) have emerged as a promising solution to these critical challenges. Their exceptionally low Young’s modulus closely resembles that of biological tissues, significantly reducing the risk of mechanical irritation or damage. Moreover, EPOFs demonstrate excellent biocompatibility, minimizing adverse immune responses and enabling stable, long-term tissue integration. Most notably, they exhibit remarkable stretchability, allowing them to endure significant deformations—such as bending, twisting, and elongation—that occur in living, moving organisms without compromising optical performance. This mechanical adaptability enables them to conform to complex tissue geometries and accommodate physiological movements. In addition to their mechanical and biocompatible advantages, EPOFs provide considerable versatility through structural and functional tunability. Their composition, geometry, and dopants can be precisely engineered to tailor optical properties (e.g., light guiding, scattering, luminescence), sensitivity to specific stimuli (e.g., strain, pressure, biochemical analytes), and even therapeutic functions (e.g., light delivery for photodynamic therapy, optogenetics, or localized heating).Leveraging these distinctive features, EPOFs have rapidly evolved from novel materials into key enablers of cutting-edge biomedical technologies. They are increasingly utilized in diverse applications such as minimally invasive signal transmission pathways for deep-tissue light delivery or sensing, and highly sensitive in vivo biosensors capable of continuously monitoring physiological parameters (e.g., pressure, strain, pH, specific biomarkers) or drug release kinetics. Their flexibility and biocompatibility make them particularly well-suited for interfacing with dynamic organs such as the heart, muscles, and brain.This article presents a comprehensive review of the emerging field of elastic polymer optical fiber materials. It begins by defining their core characteristics and differentiating them from conventional optical fibers. The review systematically classifies EPOFs based on their constituent polymers (e.g., silicones, hydrogels), fabrication methodologies, structural designs, and functional mechanisms. The central focus of the discussion lies in the expanding range of applications for EPOFs, particularly their transformative role in biomedical sensing, including various sensing principles (intensity-based, interferometric, spectroscopic, luminescent) and target analytes. While highlighting the significant progress and distinct advantages offered by EPOFs, the review evaluates current challenges impeding their widespread clinical adoption. Finally, the review synthesizes the current state of research and outlines potential future directions. By consolidating this knowledge, it aims to serve as a valuable reference and provide strategic insights to accelerate the development, optimization, and practical implementation of elastic polymer optical fibers in next-generation sensing technologies.