Conductive CNT wire and CNT sensor open potential for new composite functionality
12/23/2019
Graphite, one of the typical forms of carbon, includes graphene and carbon nanotubes (CNT)
depending on the nanoscale form, which are also called nanocarbon. Graphene is a protective
material offering flexibility and impact resistance properties while CNT provide improved fracture
toughness and thermal conductivity properties obtained through epoxy resin addition.
To diversify nanocarbon applications, new functionality is now required in addition to conventional
properties. Sensing technology is attracting attention as one of these new functionalities.
Thanks to recent technological developments, nanocarbon has been included as one of the LeadingEdge Industry Design Projects in Saitama Prefecture since 2014. As part of Saitama Prefecture's
initiatives in nanocarbon fields , the composite industry consortium formed by Saitama Industrial
Promotion Public Corporation and Ishizue Magnet Wire Works Ltd. is leading research anddevelopment on conductive CNT wire. In addition to being conductive because they have a πconjugated system throughout the planar macromolecule, CNT also has fewer eddy currents, adensity of 1.3-1.4g/cm3 and lightweight properties. Although it is said to show excellent conductivity
due to the ballistic transport in CNT, the problem remains that the conductivity is not increased
because of the shape heterogeneity, the lack of long fibre CNT and its insufficient synthesis.
The objective of research and development on conductive CNT wire is to obtain a level ofconductivity equivalent to or higher than copper wire using CNT, thanks to a new concept of applying
metal plating after putting CNT into a wire state. The conductivity of CNT wire has been steadily
improved by reviewing its form and plating conditions. In addition to LED lighting, Ishizue Magnet
Wire Works succeeded in producing coils for use in motors.

Fig. 1: Energized plated CNT wire

Fig. 2: Pre-plated CNT wire assembled as a coilAmong CNT, single-wall carbon nanotubes (SWNT) offer metallic and semiconducting properties
depending on the arrangement of the carbon atoms. Since these CNTs can be separated on an
agarose gel column for example, they can be used to produce temperature sensors. Specifically, it ispossible to create a Seebeck element that measures temperature by applying the difference in
Seebeck coefficient that generates voltage due to the temperature difference between metal CNTand semiconductor CNT. A gas sensor with a field effect transistor (FET) structure using
semiconductor SWCNT is also a promising future application.
The CNT sensor made this way and the conductive CNT wire described above are different fromthose made of conventional metals. In addition to their low weight, there is less risk of electricalcorrosion in CFRP and they are not brittle like ceramic materials.
Seeing CNT through their potential to bring sensing functions to composite materials is an approachthat opens many expectations.

For more information
FRP Consultant Corporation.：

https://www.frp-consultant.com/en/

Ishizue Magnet Wire Works Ltd. ：http://www.ishizuedensen.com/company-en/

Saitama Industrial Promotion Public Corporation :https://www.saitama-j.or.jp/english-aboutus/
Saitama Prefectural Government Leading-Edge Industries Division, Department of Industry and Labor:

https://www.saitama-leading-edge-project.jp/nanocarbon/