Torsion Fracture Testing of Carbon Nanocoils (CNCs)

Interview conducted by Will SoutterApr 26 2013

In this Thought Leader interview, Dr. Yoshiyuki Suda, Associate Professor in the Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Japan, talksAZoNano about his recent work on the synthesis and characterization of carbon nanocoils, particularly in terms of their use in NEMS (nano electro-mechanical systems).

What areas of research have you been focusing on recently?

We have been doing a large amount of research on carbon nanocoils (CNCs). Our work has covered a variety of areas such as CNC synthesis, applications for energy devices, and investigation of physical properties.

Can you summarize you recently published findings?

Our main finding involved the mechanical properties of CNCs. We investigated the CNC’s responses to tensile load and fracture mechanism, and found that they behave in a very similar way to normal-sized industrial coil springs, such as those used in automobiles—proving that carbon nanocoils can be used as springs in Nano-Electromechanical Systems (NEMS).

What makes carbon nanocoils such interesting structures to study? What are their potential applications?

We are fascinated by CNCs because of their beautiful structure. Many helical structures occur in natural materials, from DNA to fibrovascular bundles, and even conch shells.

We expect that the nanoscale helical structure of CNCs will prove to be useful in a wide range of novel industrial fields. They have already been shown to have a number of interesting applications – most famously as an electromagnetic absorption material.

What were the main challenges you had to overcome to perform precise mechanical tests on such a tiny scale?

We did have a number of difficulties with the measurements. CNCs are grown with random orientations on a substrate. For each test, we had to pick up a single CNC using a focused ion beam (FIB) probe, and move it into the vicinity of a second substrate to make the measurements.

We had to find a vertically-oriented CNC from the random as-grown sample, because the FIB probe we were using had a limited range of motion – it wasn’t possible to angle the probe to pick up horizontal CNCs. Finding and extracting the vertical CNC alone can take up to a few hours.  On extraction, the CNCs sometimes trailed a bunch of other CNCs behind them, which had to be cut off using a second FIB beam. Finally, even when the CNC was approaching the test substrate, we lost the CNC from the imaging area of the scanning ion microscope we were using to track the experiment!

I would like to give credit to my colleague Mr. Taiichiro Yonemura, who performed all the experiments in this study and did a great job overcoming these problems.

Scanning ion microscope image of a carbon nanocoil, showing the beginning of a fracture forming under tensile load.

How will your results affect potential development of NEMS based around carbon nanocoils?

Our results prove that carbon nanocoils behave like ordinary springs. Springs are a crucial component to many fundamental NEMS devices such as actuators and generators, and this result means that we can confidently use CNCs in these devices and be able to predict their mechanical behaviour and tolerances.

What are the main technological hurdles for the creation of NEMS components on a larger, more commercial scale?

For the creation NEMS components on a commercial scale, we have to develop a synthesis technique for CNC which aligns them in a more regular fashion. This technique will enable us to apply CNC into NEMS components easily.

However, even though the technique hasn’t developed, we think we can apply CNCs in NEMS in the first instance using the installation technique as described in this research. This is the reason we have been trying to develop our CNC installation technique – finding any problems with the method, and trying to make it more repeatable.

MEMS are already beginning to be commercialized – what are the main practical differences between MEMS and NEMS? Are there any capabilities which NEMS will bring which MEMS cannot provide?

The interesting features in NEMS are mostly because of their scale – obviously NEMS are a lot smaller then MEMS, which brings certain quantum effects into play. The applications developed for NEMS are likely to take advantage of these effects in their electronic design. There are also potential applications for NEMS in biotechnology, again due to their small size.

Are there any other potential NEMS components which have a similar lack of physical data, that you might consider studying?

We will be focusing on carbon nanocoils for the time being. We have synthesized a variation on CNCs called multi-walled CNCs (MWCNCs) – these are made up of multiple layers, much like multi-walled carbon nanotubes. The smallest fiber and coil diameters we have seen are respectively 10 and 20 nm. We expect that MWCNCs also behave like a springs, which will make for an interesting range of properties for NEMS applications.

What research do you have planned for the next year or so?

We plan to measure the spring constant of CNCs. This measurement will be done in a scanning electron microscope using a nano-manipulator and spring table which has quite a small spring constant.

Where can we find more information about your work?

You can find all the information about our research on our group website.

About Yoshiyuki Suda

Yoshiyuki Suda was born in Nagoya, Japan in 1971. He received his B.E. and M.E. degrees in Electrical Engineering from Hokkaido University, Sapporo, Japan, in 1994 and 1997, respectively. Then, he was involved in the electronics division at Paloma Industrues, Ltd. from Apr. 1997 to May 1998. From 1998 to 2008, He worked for the Department of Electronic Information Engineering, Hokkaido University as a Research Associate and received Dr. Eng. degree in 2006. He is currently an Associate Professor in the Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Aichi, Japan.

His majors are carbon nano-materials processing and plasma technology. His group has conducted research works, synthesis and application of carbon nanocoils (CNCs), plasma-enhanced chemical vapor deposition of vertically-aligned carbon nanotubes (CNTs) and its plasma analysis with computer modelling, X-ray photoelectron spectroscopy of catalyst nanopartciles for CNT growth, and CNT gas sensor. His current research interests include:

• basic property of CNCs,
• developments of energy devices using carbon nano-materials
• synthesis of multi-walled carbon nanocoils (CNCs)
• surface treatment of living cell model by dielectric barrier discharge for fundamental understanding plasma-biological body interaction
• surface treatment of carbon nanofibers by dielectric barrier discharge for the application of electron field emitters.

Dr. Suda is a member of The Japan Society of Applied Physics, The Fullerenes and Nanotubes Research Society, The Electrochemical Society of Japan, and The IEE of Japan.