Copper wires are fundamental to modern electrical systems, underpinning everything from household wiring to advanced industrial networks. Copper has developed this monopoly over other metals due to its high electrical and thermal conductivity, enabling efficient power transmission while dissipating heat to reduce the risk of overheating. Copper also provides relatively high mechanical strength while retaining ductility and malleability. 

The use of copper in wires dates back to the 19th century, when they were used in telegraph systems, and has continued ever since. However, with the modern transformation and expansion of electrical devices, an alternative to copper wires is being sought out. Modern devices require lightweight and highly efficient wires – introducing… carbon nanotube (CNT) wires. 

With the increasing attention on CNT wires as a potential replacement for copper wires, we have decided to delve into the long history of carbon wires, extending back surprisingly far.

Early History of Carbon Wires

The use of carbon as a conductor dates back over 150 years. In 1860, Joseph Swan created carbon fibres for use in his new invention, the incandescent filament electric lamp (precursor to Edison’s lightbulb). These early carbon wires were produced from cellulose filaments and were used to form filaments in the lamps. Thomas Edison advanced Swan’s technology, producing carbon wires by heating bamboo strips in an inert atmosphere (in a process called pyrolysis) and using the resulting carbon-rich wire for the filament in his lightbulbs. The key properties of these carbon wires for use in filaments were their high resistance and ability to withstand high temperatures. 

Despite carbon wires dominating early electric lighting, their use waned with the introduction of tungsten for use in filaments. 

Modern Carbon Fibres and Nanotube Wires

Mild interest in carbon wires was rekindled in the 1950s with the first production of carbon fibres. However, it was the development of CNTs that truly increased the excitement surrounding carbon wires. CNTs were first discovered and characterised in 1991 by Sumio Iijima, who subsequently developed methods to produce single-walled CNTs. Further investigation and experimentation identified CNTs as having excellent electrical, thermal, and mechanical properties, with their high electrical conductivity and electron emission properties sparking interest in their use to replace copper. However, it wasn’t until breakthroughs in CNT fibre technology that the potential for CNT wires was truly unlocked.

CNT use in wires requires the alignment of the CNTs as opposed to dispersal (a technique often used for different applications where the CNTs end up in a randomly orientated matrix). To achieve this, CNTs must be transformed into fibres. Dr Richard Smalley and Dr Wade Adams are credited with the idea for using the wet spinning technique to produce CNT fibres. Wet-spinning is a manufacturing process already popular in the production of the manmade cellulose fibre, viscose. When applied to CNTs, the technique successfully spun the CNTs into fibres, aligning the nanotubes. The CNT fibres retained the electrical and mechanical properties of the CNTs, dramatically increasing the conductivity and strength compared to mixed CNT composites – mixed CNT composites only have a conductivity of 0.00001 MS/m, whereas CNT fibres have a conductivity of 10 MS/m.

With the production of CNT fibres, the door was opened to using CNT fibres to produce CNT wires. Improvements in manufacturing techniques have produced stronger CNT wires with enhanced conductivity. With this came the potential for CNT wire use in a wide range of applications.

How are CNT Wires Changing the World?

CNT wires now provide conductivity at a similar level to copper, but with greater strength and lower weight. While not yet replacing copper in general wiring, CNT wires are gaining popularity and are already being used for specific applications. Their lightweight properties make them ideal for aerospace and satellite applications, where their use can reduce the overall weight of the aeroplane, spacecraft, or satellite, improving fuel efficiency and potentially enabling travel at longer distances. 

CNT wires could also revolutionise electric cars. Electric cars can have thousands of metres of wiring; reducing the weight of wiring by using CNT instead of copper wiring improves fuel efficiency and range. CNT wires are also increasingly being incorporated into wearable devices, where lightweight properties are amongst the most important.

With ever-improving manufacturing methods, CNT wires ultimately have the potential to replace copper wiring in a wide range of applications, improving weight, efficiency, and durability.

Conclusion

Carbon wires have a long history, dating back to the invention of the first electric lamps. Despite copper wiring forming a monopoly on wiring for the past 150 years, many fields are once again looking to carbon wires as a potential solution to copper wire’s limitations. CNT wires offer comparable conductivity with significantly lower weight and enhanced strength, transforming high-performance industries, such as aerospace, automotive, and wearable technologies. As advances in CNT wires and manufacturing optimisation continue, CNT wires have the potential to redefine modern electrical systems – pushing the boundaries of efficiency, sustainability, and innovation.

For more information on the history of carbon fibres, check out this article:

A Misconception that Obscures the Real Progress of Solid Carbon