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Aerogel fibers are an emerging class of ultralightweight materials, which, compared to conventional bulk monolithic and aerogel films, provide better flexibility and extensibility. Despite the recent advancements in this field, due to their highly porous structure, their mechanical properties can be deteriorated. Inspired by the textile industry, we report the development of aerogel fiber bundles with twisted structures as a promising strategy to enhance the mechanical performance and practicality of aerogel fibers. Polyimide (PI) aerogel fibers were prepared via the sol-gel confined transition method. The fibers showed a unique nanostructured assembly with high specific surface area, excellent optical transparency, outstanding flexibility at diverse extreme conditions, self-extinguishing behavior, and superior thermal insulation performance. Using PI aerogel fibers as the backbone, aerogel fiber bundles in various configurations were designed and fabricated. A systematic study was performed to analyze the effect of design parameters on the mechanical performance of the bundles. Results revealed an optimal twist level for bundles, leading to a peak in mechanical properties across various bundle configurations. The observed improvement in mechanical properties was attributed to increased fiber-to-fiber binding strength, enhanced friction, and interlocking mechanism of fibers, underscoring the potential of the optimized twist level for enhancing the performance of aerogel fiber bundles. Overall, the development of aerogel fiber bundles holds great promise in revolutionizing the production of high-performance ultralightweight materials for thermal management applications.

Polyimide (PI) aerogels are promising in various fields of application, ranging from thermal insulators to aerospace. However, they are typically in the form of a bulk monolith, which suffers from a lack of conformability and drapability. Moreover, their electrical conductivity is limited, and they mainly display an insulative behavior. These shortcomings can limit the applications of PI aerogels in energy storage systems, which require ultralightweight flexible conductive films, which at the same time offer high thermal stability, ultralow density, and high surface area. To overcome these obstacles, the present study reports the fabrication of PI-carbon nanotube (PI-CNT) aerogel composite films with varying CNT content prepared through a sol-gel preparation method, followed by a supercritical drying procedure. Compared to pristine PI aerogels, which displayed a large shrinkage and density of 18.3% and 0.12 g cm -3 , respectively, the incorporation of only 5 wt % CNTs resulted in a significant reduction of both shrinkage and density to only 11.5% and 0.10 g cm -3 , respectively. This suggests the importance of CNTs in improving the dimensional stability of aerogels and creating a robust network. Further characterizations showed that incorporation of 5 wt % CNTs also resulted in the highest pore volume (1.25 cm 3 g -1 ), highest surface area (324 m 2 g -1 ), highest real permittivity (80), highest electrical conductivity (3 × 10 -1 S m -1 ), and ultrahigh service temperature (575 °C). It was also shown that the aerogel films can withstand a large degree of bending, can be twisted, and can be fully rolled with no obvious cracks propagated in the structure. The combined outstanding properties of the developed aerogel composite films make them promising potential candidates for supercapacitor electrodes. Therefore, the electrochemical performance of the devices based on aerogel electrodes was further studied. The device demonstrated a high energy density of 2.6 Wh kg -1 at a power density of 303.8 W kg -1 . The total capacitance after 5000 cycles was 91.8% of the initial capacitance, which indicated excellent stability and durability of the device. Overall, this work provides a facile yet effective methodology for the development of high-performance aerogel materials for energy storage applications.