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A partnership between IM2NP and carbon nanotube expert NAWAH
Nanomaterials for innovation
Carbon nanotubes with innovative properties
Carbon-based nanostructured materials are extremely interesting for industry, as they possess properties specific to this scale, enabling them to improve the performance of the devices in which they are integrated. By mastering the shape, structure and size of these carbon nanomaterials, it is possible to achieve unrivalled characteristics in many fields of physics (mechanics, electronics, thermics, etc.). For example, they can be integrated into composite parts to make them more mechanically resistant or lighter, or into electrodes to reduce the amount of material needed for their manufacture and enhance their performance (for reasons of cost, environmental footprint, availability or supply, harmfulness, etc.).
NAWAH has developed a process for producing Vertically Aligned Carbon Nanotubes (VACNT): this method organizes graphene molecules into a vertical tubular structure perpendicular to the surface. The resulting 3D nanocarbon is made up of almost 100 billion carbon nanotubes per square centimetre, all vertically aligned.
The advantages of the additive approach
NAWAH is able to grow carbon nanotubes vertically oriented with respect to the support (substrate) en masse, creating real "carpets" of large-area nanotubes at high production rates in roll-to-roll mode. The new challenge for NAWAH is to be able to deposit carbon nanotubes in specific places on the substrate to create patterns, instead of having surfaces entirely covered with nanotubes. A potential process had been identified by the company, which called on IM2NP's SPRINT platform to implement and test it.
The platform's expertise lies in inkjet printing, which is an additive and digital process. To highlight the advantages of such a process, let's take a look at what is usually done in microelectronics. On silicon wafers, a functional material (conductor, semiconductor, etc.) is deposited over the entire surface using sputtering and vacuum evaporation techniques. Then, using a subtractive process, material is removed from specific areas by means of masks, thus defining patterns. By repeating these steps, the desired components and integrated systems can be built. However, these processes are energy- and chemical-intensive, and the elements removed (precious metals, rare earths, etc.) are lost.
A technological alternative is to use printers, identical to those used in conventional printing, but using inks specially developed to perform electronic functions. There are various printing methods, such as screen printing, flexography and rotogravure. But the SPRINT platform has focused on the inkjet process to facilitate proof-of-concept and rapid prototyping. It is better suited to iterative R&D processes, with design, manufacturing and testing loops that are faster and less costly than with standard electronics. This process enables material to be deposited only where it is needed, in an ambient atmosphere, and with no material wastage. What's more, its additive nature makes it possible to do away with masks, which present constraints in terms of manufacturing, cost, lead times and the risk of design errors.
The SPRINT platform's expertise lies in mastering the triptych of ink, printer (or printhead) and substrate. It is necessary to ensure the compatibility of the ink with the printer, then to study its interaction with the substrate, and finally to define a printing strategy to produce the desired patterns and achieve the best possible resolutions.
Conclusive results open up new prospects
In the final analysis, the technological step developed by the SPRINT platform meets the criteria of reproducibility and pattern resolution expected by NAWAH.
In the future, it could be envisaged to achieve higher resolutions on larger surfaces at higher speeds, thanks to a higher-performance printer and printheads. We could also offer them support in transferring printing skills with a view to industrializing roll-to-roll production. A new win-win collaboration for both partners is currently under discussion.