14 DAY TRIAL // Ever since they were first obtained, carbon nanotubes (CNT) were hailed as a potential wonder material for producing long sought for flexible electronic circuits and devices. Once graphene was synthesized, back in 2004, CNT have fallen out of favor with scientists, but not with a team of researchers at the Stanford University, which recently figured out how to solve two issues plaguing this field.
Stanford researcher Zhenan Bao and colleague Yi Cui, an assistant professor at the university, continued to work with CNT even as most other groups of materials scientists moved on to studying graphene, a 2D pure carbon compound. In their latest study, the team explains how they were able to solve the two most important problems preventing the use of nanotubes in flexible electronics.
The first issue was that scientists at the time had no way of regulating the outcome of the CNT synthesis process. Conducting nanotubes were very difficult to separate from semi-conducting ones. A few years ago, the same Stanford team came up with a solution to this problem by developing a new sorting process. Now, the flow and composition of CNT can be easily controlled in the lab.
The second problem was that scientists used to find it very difficult to produce homogeneous nanotubes in bulk. This is absolutely necessary if experts are to ensure stable electrical responses in any electronics using CNT as a foundation material, IEEE Spectrum. Thanks to the new research, nanotube circuits can endure power fluctuations passing through flexible electronic devices.
The investigation is detailed in a paper entitled “Tuning the threshold voltage of carbon nanotube transistors by n-type molecular doping for robust and flexible complementary circuits,” which appears in the latest issue of the esteemed journal Proceedings of the National Academy of Sciences (PNAS).
“This is the first time anyone has designed flexible CNT circuits that have both high immunity to electrical noise and low power consumption,” Bao explains in an accompanying press release. With this study, CNT-based circuits are both more reliable, and more power-efficient, than their predecessors.
In order to achieve this significant breakthrough, the investigators had to use a dopant chemical called DMBI to turn carbon nanotubes into a mix of P-type and N-type semiconductors, as opposed to the standard P-type in use until now. A similar doping technique is also used on silicon, the material that underlines all modern-day electronics.
The team explains that this P-N mix is able to operate consistently and reliably even if power fluctuations move through the circuit. At the same time, these semiconductors require much lower amounts of energy to operate than previous versions. This is the first time CNT with such properties were developed.