This grant supports research that will advance the fundamental understanding of the manufacturing process of multifunctional composite fibers through thermal drawing to enable energy storage textiles for next-generation wearable electronics and smart textiles. Thermal drawing, a manufacturing process that pulls fibers out of melts, is the most commonly used fiber production method in the textile industry. Its capability of manufacturing multifunctional composite fibers has been limited due to its susceptibility to melt fracture. This research will fill the knowledge gap on how the composition and nanostructures of the composites affect the failure mechanisms during the thermal drawing process. With the new fundamental knowledge, composites containing nanostructured carbon electrodes as the filler and polymer electrolytes as the matrix will be designed and processed into wearable fibers. Such composite fibers can be woven into energy storage textiles to serve as the power source for wearable electronics and smart textiles in many consumer, medical, and military applications. This research will promote US manufacturing science and technology and help preserve US technological and economic dominance in wearable and smart electronics. The research tasks will be used to train highly skilled engineers and scientists in STEM fields for the US manufacturing workforce. The outreach activities associated with this research will promote the early exposure of K-12 students, especially those from women and underrepresented minority groups, to STEM.<br/><br/>While thermal drawing is a versatile tool capable of scalable manufacturing of multimaterial multifunctional fibers, it has yet to achieve its full potential in manufacturing composite fibers due to the limited understanding of its failure mechanism. This research designs and experiments on new electrode-electrolyte composites with one-dimensional carbon nanomaterials and solid polymer electrolytes and seeks to understand the fundamental failure mechanisms during the thermal drawing of such composites. The failure mechanism will be elucidated using transport phenomena modeling and in-process rheological measurements. As a result, the research will elucidate 1) the currently unknown structural effects of one-dimensional nanofillers on the rate-limiting failure mechanisms during the thermal drawing processing of composite fibers, and 2) the widely observed but unexplained process effect of thermal drawing on the alignment and dispersion of the nanofillers in the produced composite textile fibers. This better understanding of the failure, alignment, and dispersion mechanisms will provide a new solution to produce supercapacitor-type energy storage textiles and enable the continuous manufacturing of new functional materials and devices using thermal drawing from a preform.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.