CNT Fiber Sensors Break Accuracy Barriers in Real‑Time Tracking of Nanocomposites
Scientists have demonstrated, for the first time, a quantitative accuracy assessment of carbon nanotube fiber (CNTF) sensors embedded in CNT/epoxy nanocomposites. The study shows that these fibers introduce virtually no measurement error and outperform standard sensing methods by one to two orders of magnitude, paving the way for advanced real‑time monitoring technologies.
A team of researchers from Skoltech working with collaborators in China and Iran has achieved a major advance in precision sensing for next‑generation composite materials. Their new study, published in iScience, provides the first quantitative evaluation of how accurately carbon nanotube fibers (CNTFs) can measure changes inside CNT‑reinforced epoxy nanocomposites. The findings confirm that these fibers offer exceptionally high fidelity, enabling real‑time monitoring during both the manufacturing process and the service life of the final material.
Polymer nanocomposites containing carbon nanotubes have long been considered promising for aerospace, automotive, energy, and structural applications due to their unique combination of strength, functionality, and low weight. Yet monitoring their behavior - especially during curing and in long‑term use - has remained a challenge. Traditional sensors such as fiber‑optic systems or piezoelectric devices cannot easily be embedded without compromising mechanical performance. In many cases, they add bulk, disturb the composite architecture, or cause local stress concentrations that reduce reliability.
CNTFs offer a fundamentally different approach. Unlike externally attached electrodes, they can be seamlessly incorporated into the composite structure during manufacturing through a single-step embedding process. Their nanoscale architecture allows them to interact directly with the conductive CNT network that forms within the polymer matrix. However, until now, there had been no rigorous quantification of how accurate these embedded fibers truly are under practical operating conditions.
The new study fills that gap with a detailed analysis of measurement fidelity. The researchers fabricated CNTFs using wet-pulling of thin films composed of single-walled carbon nanotubes - films with thicknesses of 18, 39, and 59 nanometers. These fibers were then embedded in epoxy matrices containing either 0.005 wt% or 0.5 wt% single-walled or multi-walled CNTs. The goal was to assess how embedding, processing conditions, and environmental factors affect electrical measurements collected through the fibers.
According to the experimental results, the measurement inaccuracy introduced by CNTFs is remarkably low. For multi-walled CNT (MWCNT) nanocomposites, the error does not exceed 10⁻⁶ percent, while for single-walled CNT (SWCNT) systems, the maximum error is around 10⁻¹ percent even in unfavorable conditions. These values are dramatically below the typical 2 percent (or higher) error seen in commercial sensors.
“This discovery elevates CNT fibers from a promising concept to a ready‑to‑use high‑precision sensing platform,” said Sergei Shadrov, a Skoltech Ph.D. student and lead author. “With this level of fidelity, we can not only track the curing kinetics of composite materials but also monitor the performance of the final product with confidence.”
One of the most significant findings is that CNTFs maintain their accuracy even when using a standard two‑point measurement configuration. Normally, precision measurements inside conductive materials require a more complex four‑point setup to eliminate contact resistance. Here, the fibers’ unique morphology inherently reduces the influence of contact effects. The CNTF surface forms an intimate electrical interface with the surrounding CNT-filled epoxy, enabling direct transfer of current without the typical losses found in metal electrodes.
“The outstanding accuracy comes from the morphology of the fibers themselves,” explained Hassaan Ahmad Butt, Assistant Professor at Skoltech and co-author of the study. “They create direct electrical contact with the CNT network inside the polymer, essentially removing the issue of contact resistance that limits many traditional sensing approaches.”
This improved electrical behavior not only boosts precision but also simplifies the equipment needed for monitoring. Because complex four‑point systems are no longer required, the overall sensing architecture becomes easier to use, more cost-effective, and more feasible for industrial-scale deployment. This opens the door to embedding CNTFs in a wide range of polymer composites used in manufacturing, infrastructure, and aerospace components - areas where real‑time structural health monitoring could significantly increase safety and extend service lifetimes.
Albert Nasibulin, director of the Skoltech Photonics Center and head of the Laboratory of Nanomaterials, emphasized the broader implications: “By achieving high-fidelity sensing using simple measurement tools, CNT fibers become a practical solution for industrial monitoring. They offer unprecedented insight into what is happening inside the material from the moment it begins to cure.”
Ultimately, the study positions CNTFs as highly accurate, low‑artifact sensors well suited for next-generation multifunctional composites. With their ability to deliver real-time feedback during fabrication as well as throughout the material’s operational life, they provide a powerful platform for intelligent materials and advanced manufacturing technologies.