Fabrication of multilayered polymer composite fibers for enhanced functionalities

Carbon nanoparticles-based polymer composites have wide applications across different fields for their unique functional properties, durability, and chemical stability. When combining nanoparticle morphologies with micro- or macro-scale morphologies, the hierarchal structure often would greatly enhance the composites' functionalities. Here in this work, a thermoplastic polyurethane (TPU) and graphene nanoplatelets (GnPs) based multilayered fiber is fabricated through the combination of dry-jet-wet spinning, based on an in-house designed spinneret which accommodates three layers spinning solution, and hot isostatic pressing (HIP), at 220 °C. The multilayered spinneret enables the spinnability of a high GnPs loaded spinning dope, highly elastic, with great mechanical strength, elongation, and flexibility. The HIP process resulted in superior electrical properties as well as a newly emerged fourth hollow layer. Together, such a scalable fabrication method promotes a piezoresistive sensor that is sensitive to uniaxial strain and radial air pressure. The hollow fiber is characterized based on surface morphologies, layer formation, percolation threshold, piezoresistive gauge factor, mechanical stability and reversibility, and air-pressure sensitivity and reversibility. Such facile fabrication methods and unique structures have combined the mechanically robust outer shell with a highly conductive middle sensing layer for a new sensor with great potentials in wearable, robotics, biomedical, and other areas.