Significance With the rapid development of textile engineering and material science, intelligent fibers and related fabrics have become the preferred carriers for wearable electronics with their advantages in softness, lightness, and breathability. A variety of fiber manufacturing technologies has been developed, enabling conventional fibers with new capabilities such as environmental/physical/chemical sensing, logical computing, human-machine interaction, and so on. Among these manufacturing techniques, the thermal drawing process can be adopted to fabricate multimaterial optoelectronic fibers, providing an innovative research for intelligent fibers and fabrics. By enriching fiber structures, materials and post-treatment techniques, thermal-drawn fibers can be integrated with multiple functions such as multi-parameter sensing, temperature regulation, and information interaction, broadening the application scenarios of fibers.
Progress Thermal-drawn multimaterial optoelectronic fibers are generally drawn from fiber preforms with a fiber drawing tower. The external forms, internal structures, and materials of fiber preforms can all be designed with great flexibility according to the applications and functions. The diameters of fibers are typically in the micron range, and the structures of the fibers are consistent with the preform rods. In addition, fiber post-treatment techniques, such as thermal treatment and cold-drawing process, can further enrich and modify the structures, giving more ways to improve the functionalities of fibers.
With these advanced fiber drawing and processing technologies, micro- and nano-structured fibers can be achieved. For example, a low-loss CO2 laser-propagated photonic bandgap fiber has been achieved with a hollow core surrounded by a solid multilayer structure of high refractive-index contrast. The fiber has a large photonic bandgap and omnidirectional reflectivity. Nanowires, structural micro- and nanospheres, nanorods, and porous fibers have also been produced in a scalable way by the in-fiber fluid instability phenomena, cold-drawing deformation, and salt leaching techniques. Moreover, surface micro-nano imprinting technology has been utilized to construct specific fibers with micro/nano-surface patterns.
The richness of structures and materials gives fibers a variety of advanced functionalities, such as sensing, energy management, neural probing, and information interaction. For sensing, the thermal-drawn fibers have been achieved with acoustic, photoelectric, strain, and chemical sensing. For energy management, fiber-based devices are enabled with the functions of passive temperature regulation and energy generation/storage. Thermal-drawn fibers have also been widely used as neural probes because of their flexibility, small size, and conductive property. In addition, semiconductor diodes and integrated circuits have been integrated into thermal-drawn fibers successfully, which empowers the fibers with the abilities of logical computing and information interaction.
Conclusion and Prospect This work focuses on the research progress and application fields of thermal-drawn multimaterial fiber, reviews the regulation of the micro/nanostructures inside the fibers by thermal drawing, and discusses their applications in sensing, energy, biology and others with recent studies.
However, there are still some limitations to thermal-drawn multimaterial fiber optoelectronics. 1) Only a few of materials and structures are investigated and applied into the system. 2) The mechanical properties and comfort of wearing of thermal-drawn fibers need to be improved. 3) It is still difficult to integrate multiple functions into one fiber. 4) The abilities of logical calculation and data management of the thermal-drawn fibers should be enhanced.
The future research trends of thermal-drawn multimaterial optoelectronic fibers are discussed from five aspects: more material selection, complex fiber structure, textile processing, multi-function integration, and artificial intelligence. It is foreseen that current mono-functional thermal-drawn multimaterial optoelectronic fibers can be improved for higher integrations, better mechanical properties, and more intelligence. These advanced fibers can also be combined with conventional textiles to enable their functionalities, comfort of wearing, and applicability to scenarios.
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