Flexible electronics enable applications where circuits need to be repeatedly bent or stretched without a deterioration in electrical performance. Carbon nanotubes are excellent candidates for flexible electronics thanks to their unique electrical and mechanical properties. By using networks of nanotubes that are randomly deposited over a substrate, device makers can compensate for variations in the individual nanomaterials.

Despite the current interest and numerous potential advantages of these nanotube networks, patterning them onto polymeric substrates is in its infancy and often requires complicated processing steps including transfer printing. This presents a major technological barrier to the proliferation of nanotube-based devices and their applications.

Fluidic self-assembly
Researchers at Northeastern University, Boston, US, have developed a new technique for fabricating nanotube-polymer architectures that can be used for making low-cost sensors and other flexible electronics. The group utilized a plasma treatment to modify the surface energy of the polymeric surface to facilitate fluidic self-assembly of carbon nanotubes into high-density networks. They have fabricated electrically continuous nanotube micro-arrays with fine pitch over a large scale. A pattern of SWNT structures on a wafer-level flexible substrate can be seen in the image above.

Highly organized nanotube patterns were formed directly on the flexible substrate without the need for any printing, transfer or chemical functionalization techniques. The self-assembled nanotube structures are highly dense with exceptional electrical conductivity. The mechanical and electrical testing of the fabricated nanotube structures on the polymer substrate in both static and dynamic modes indicates that they can handle a high degree of both compressive and tensile deformations with no hysteresis. This bottom-up chemical-free patterning technology is versatile and scalable and has direct applications in the realization of nanotube-polymer based sensors, field effect transistors (FETs) and interconnects for next-generation flexible electronics.

This work has been published in Nanotechnology.