Jul 8, 2009
Fluidic self-assembly adds nano-architecture to flexible substrates
High-density single-walled carbon nanotube (SWNT) networks with microscale structures and controllable dimensions have been directly assembled on to flexible parylene-C substrates using dip coating. The integration of nanostructured materials onto polymeric substrates provides a framework for making functional devices and sensors that are low cost, high performance and suitable for large area applications, while being mechanically flexible for widespread use.
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.
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.
About the author
This research was conducted at the George J Kostas Nanoscale Technology and Manufacturing Research Center at Northeastern University, Boston, US. Dr Xugang Xiong was working as a postdoctoral researcher at the National Science Foundation Nanoscale Science and Engineering Center (NSEC) for High-rate Nanomanufacturing and is now based at the University of Washington, Seattle. Chia-Ling Chen is a PhD student studying in the Electrical and Computer Engineering Department at Northeastern University. She was financially supported by the NSF NSEC for High-rate Nanomanufacturing. Peter Ryan is a PhD student studying in the Mechanical and Industrial Engineering Department at Northeastern University. He was financially supported by the NSF NSEC for High-rate Nanomanufacturing. Prof. Ahmed A Busnaina is director of the NSF NSEC for High-rate Nanomanufacturing and he is also the W L Smith Professor in the Mechanical and Industrial Engineering Department at Northeastern University. Yung Joon Jung is an Assistant Professor in the Department of Mechanical and Industrial Engineering at Northeastern University. Prof. Mehmet R Dokmeci is an assistant professor in the Department of Electrical and Computer Engineering at Northeastern University.