Carbon nanotubes more conductive than copper, a breakthrough arrives. But they are still expensive

Carbon nanotube (CNT) wires are approaching the conductivity of copper, and a new study published in Science marks one of the most significant steps in this direction. The result, achieved through a chemical treatment applied to CNT fibers, brings the conductivity of individual nanotubes to levels comparable to those of the metal that has dominated the wiring industry for decades. The critical point, as usual, does not concern the single nanotube, which can transmit nearly a thousand times more current than copper, but rather the ability to replicate that property when millions of tubes are aggregated into a macroscopic fiber.

The 'bulk gap' problem

An isolated carbon nanotube is an exceptional conductor: its structural characteristics allow for nearly ballistic electron transport, with resistance close to zero under ideal conditions. The problem arises when one attempts to construct a real cable. When nanotubes are aggregated into fibers, the inter-tubular junctions introduce parasitic resistances that drastically reduce the overall conductivity. Until recently, the best CNT cables could only achieve a maximum of 13% of copper's volumetric conductivity, which equates to about 7.7 megasiemens per meter compared to the 59 MS/m of the orange metal. The result achieved in 2026 breaks this barrier thanks to a chemical approach that reduces contact resistances between nanotubes, improving the alignment and purity of the conductive structure.

The path to this result

The journey towards this outcome has been long. In 2024, researchers from the Chinese Academy of Sciences had already established a record by reaching 86% of copper's conductivity with CNT fibers, accompanied by a mechanical resistance of 1.65 GPa and a stability exceeding 5,000 bending cycles. In 2025, studies on hybrid CNT-conductive polymer fibers had pushed the specific mass conductivity up to 98% of that of copper, a significant figure especially in applications where weight matters more than physical size, such as in aerospace.

The chemical treatment and its stability

The new study published in Science introduces a chemical treatment that, applied to nanotube fibers, brings their conductivity to values that closely approach those of pure copper. The details of the substance used are not declared as definitive: the authors themselves acknowledge that the current compound may not be sufficiently stable for long-term commercial applications, but the mechanism identified paves the way for the search for an analogous molecule with better durability characteristics. In practice, the discovery is twofold: a conductivity result and a map for further optimization of it.

This approach reflects a broader trend in research on conductive CNTs. The LAST (Lyotropic Liquid Crystal-Assisted Surface Texturing) process developed by the Korea Institute of Science and Technology in 2025 used lyotropic liquid crystals to align and separate the nanotubes, increasing conductivity by 130% and reducing residual metallic impurities from the synthesis process. Each method addresses the same bottleneck: reducing the interface resistances between adjacent tubes, which represent the main obstacle to charge transport in bulk CNT fibers.

Specific conductivity and volumetric conductivity

It is worth distinguishing between two often-confused metrics in the debate over copper and nanotubes. The volumetric conductivity measures how much current passes per unit of cross-sectional area: here copper still decisively wins, with 59 MS/m compared to CNT values that, in the best recent cases, get close but do not exceed this threshold. The specific mass conductivity, which normalizes for the weight of the conductor, tells a different story: the density of copper (8.9 g/cm³) is much higher than that of CNT fibers, and this means that, for the same weight, the best nanotube cables can already carry more current than copper. Research from Rice University in 2014 showed that wet-spun CNT fibers could handle up to four times more current than a copper cable of the same mass.

This distinction determines where nanotubes are already ready to replace copper and where they are not. In weight-critical applications (such as aerospace motors, eVTOL aircraft, satellite wiring, and high-altitude drone motors), the mass advantage is already significant enough to justify the additional costs. KIST, testing a small 3.5-watt electric motor with CNT CSCEC windings, demonstrated that the conductive core weighs one-fifth of its copper counterpart, with a specific rotational speed (rpm per unit of weight) only 6% lower.

The knot of cost and scalability

Nevertheless, scientific advances remain constrained by a significant practical issue: the production cost of CNT cables hovers between $375 and $500 per kilogram, compared to $10-11 for copper. A gap of over thirty times that makes any large-scale replacement in the automotive, construction, or consumer electronics industries unthinkable at present. This is compounded by the fact that the synthesis processes for nanotubes largely depend on fossil hydrocarbons, generate toxic byproducts, and require a lot of energy, as is the case with the LAST process that uses chlorosulfonic acid and produces hydrochloric acid as waste.

Therefore, the path to commercialization requires not only further optimization of conductivity but also a drastic reduction in production costs and the development of more sustainable processes. The research published in 2026 in Science represents an important piece on the front of electrical performance, but replacing copper in mainstream wiring remains an engineering and industrial challenge that goes well beyond material chemistry. Meanwhile, niche applications with high added value remain the most realistic testing ground for this technology.

Impact on semiconductors and the electronics industry

There is another front where carbon nanotubes are gaining ground: interconnection structures in chips. The miniaturization of technology nodes has reduced the sizes of copper wires in processors to a level where resistivity increases drastically due to surface effects and grain boundaries. CNTs, thanks to their one-dimensional structure and ballistic transport, maintain good conductive properties even at nanometric diameters. This property is currently being explored by companies like TSMC, Intel, and IBM to understand if it is possible to create a partial or complementary alternative to copper in nodes below 3 nm. The findings highlighted by Science could therefore have implications that go beyond macroscopic wiring, opening a path toward next-generation interconnections in integrated circuits.