Ultrahigh-Ratio Drawing During Spinning Produces Strong, Thermally Conductive Graphene Fibres

Graphene has long been celebrated as one of the most extraordinary materials ever discovered, combining exceptional mechanical strength, electrical conductivity and the ability to transport heat rapidly. Yet turning isolated sheets of graphene into a useful, macroscopic fibre has proved far more difficult than demonstrating the properties of a single nanoscale layer. A new study reports a processing strategy that may overcome this long-standing obstacle, producing graphene fibres with a tensile strength of 5.9 gigapascals, a Young modulus of 963 gigapascals and thermal conductivity reaching 1,720 watts per metre-kelvin. The fibres also achieved an electrical conductivity of 1.3 million siemens per metre. The results, published in Nature Materials, suggest that carefully stretching graphene during fibre formation can force its sheets into a more compact and orderly architecture, allowing the finished material to retain far more of graphene’s remarkable intrinsic performance.

The challenge arises because graphene’s celebrated properties are easiest to observe in individual sheets or very small, highly controlled structures. A macroscopic fibre must contain vast numbers of those sheets, and the interfaces between them determine how efficiently forces, heat and electrical charges move through the material. In conventional assemblies, graphene layers can become misaligned, folded or separated by nanoscale voids. Regions of disordered stacking act as barriers: under mechanical loading, they can concentrate stress and trigger failure; for heat flow, they scatter or interrupt the movement of energy; and for electrical transport, they increase resistance. These multiscale defects mean that the collective material often performs far below the theoretical potential of its individual building blocks. The researchers behind the new work addressed the problem by treating graphene sheets not simply as particles to be gathered into a thread, but as two-dimensional components that can be manipulated while suspended in a viscous liquid.

Their method is called ultrahigh-ratio draw spinning. In a spinning process, a graphene-containing solution is first shaped into a continuous filament. The critical step is then to draw, or stretch, that filament substantially as it forms. The drawing ratio describes how much the material is elongated during processing; in this study, the researchers reached a ratio of up to 11. Stretching a fibre in this way can orient its internal constituents along the direction of the fibre axis. For graphene, that alignment is particularly important because the sheets conduct heat and electricity far more effectively within their planes than across their thickness. If the sheets lie in a disordered arrangement, transport pathways are repeatedly interrupted. If they become aligned and densely packed, heat and charge can travel through a more continuous network. The drawing process therefore changes not only the shape of the fibre, but also the organization of its internal nanoscale structure.

The success of the approach depends on a physical behaviour that graphene sheets display when dispersed in viscous solvents. Although graphene is not a conventional polymer, the researchers describe the suspension as having polymer-like viscoelasticity. Viscoelastic materials combine the characteristics of liquids and solids: they can flow under one set of conditions but resist deformation and transmit stress under another. In the graphene suspension, interactions among the large, thin sheets allow the material to be continuously processed while maintaining enough internal cohesion for the sheets to respond collectively to stretching. As the newly formed filament is drawn, the sheets can rotate and slide into greater alignment rather than remaining randomly stacked. This behaviour gives the researchers a route to impose order during spinning, when the fibre is still sufficiently mobile for its internal architecture to be reorganized.

The researchers then combined the high-ratio drawing step with high-temperature annealing. Annealing involves heating a material under controlled conditions to allow structural imperfections to relax or disappear. In a graphene fibre, heat treatment can help remove residual disorder, improve contact between neighbouring sheets and consolidate regions that remain loosely connected after spinning. The study reports that the combination of drawing and annealing efficiently removed defects and produced fibres that were densely packed and highly ordered. This matters because alignment alone is not enough: a fibre could contain well-oriented sheets but still perform poorly if gaps, discontinuities or weak interfaces remain between them. The two-stage strategy addresses both problems. Drawing organizes the graphene over larger distances, while annealing refines the contacts and reduces the nanoscale interruptions that limit the transfer of stress, heat and electrical charge.

The resulting mechanical properties are striking. A tensile strength of 5.9 gigapascals means the fibre can withstand an extremely large pulling force relative to its cross-sectional area before breaking. Its Young modulus of 963 gigapascals indicates a very high resistance to elastic deformation: when a load is applied, the fibre stretches comparatively little. These are related but distinct properties. Strength describes the point at which a material fails, whereas modulus describes its stiffness during reversible deformation. Achieving both simultaneously is difficult because structural features that make a material stiff can sometimes make it brittle, while mechanisms that improve toughness can reduce rigidity. In the graphene fibres, the ordered sheet arrangement appears to create efficient load-bearing pathways along the fibre axis. Stress can be distributed through densely connected layers rather than being concentrated at large voids or badly misaligned regions, helping the material combine high stiffness with exceptional strength.

The thermal results could be especially important for technologies that must move heat away from compact or powerful components. The fibres reached a thermal conductivity of up to 1,720 watts per metre-kelvin, a measure of how readily heat travels through a material when a temperature difference is applied. Graphene’s carbon lattice supports rapid energy transport, but in a macroscopic assembly, phonons—the collective vibrations that carry much of the heat through a solid—can be scattered by defects, interfaces and disorder. The fibre architecture developed in the study is designed to reduce those obstacles by creating longer, more direct pathways along aligned graphene sheets. At the same time, the reported electrical conductivity of 1.3 million siemens per metre shows that the fibres can transport charge as well as heat. This combination is unusual: materials optimized for mechanical performance do not necessarily conduct heat efficiently, and electrically conductive fibres may not possess the stiffness or strength needed for demanding structural applications.

The researchers say the properties surpass those of most existing fibres that combine high strength with high thermal conductivity, positioning the material as a candidate for multifunctional systems rather than a component with only one specialized role. Potential application areas include aerospace and automotive engineering, where low-dimensional materials may be attractive for structures that must carry loads while managing heat. The fibres could also be relevant to thermal-management systems and energy technologies, in which electrical pathways and heat dissipation may need to coexist in a lightweight form. However, the study establishes a materials-processing advance rather than demonstrating a finished device or commercial product. Questions about long-term durability, performance under repeated loading, environmental stability and manufacturing at industrial scale will determine how broadly the fibres can ultimately be used. Their reported properties nevertheless show that controlling structure during assembly can be as important as discovering a high-performance nanoscale material in the first place.

More broadly, the work offers a general strategy for converting two-dimensional materials into high-performance three-dimensional forms. Graphene sheets are powerful building blocks, but their advantages can be lost when they are assembled without sufficient control over orientation, density and interfaces. Ultrahigh-ratio drawing provides a way to use the flow behaviour of a viscous suspension to organize those sheets before high-temperature treatment locks in a more coherent structure. The approach may therefore extend beyond graphene if other two-dimensional materials can be processed with comparable viscoelastic behaviour. By linking processing conditions directly to nanoscale order and then to macroscopic strength, heat transport and electrical conductivity, the study illustrates a central principle of advanced materials science: extraordinary properties do not automatically survive assembly. They must be engineered into the architecture of the final material. In this case, stretching a graphene fibre far beyond ordinary spinning ratios may have brought the material significantly closer to the promise of graphene itself.