PRL 100, 035503 (2008)  Jianyu Huang, Feng Ding, Boris I. Yakobson  

Since the early 1990s, when quantum dots and quantum wires began to attract the attention of physicists, and when carbon nanotubes were discovered, mechanics related issues have begun to emerge as important in understanding properties of nanostructures.  These structures were first considered useful mostly for their electronic or optical applications, yet deformation has been seen to play an important role in their functional characteristics.  Advances in modeling also have begun to link electronic structure with mechanical properties of materials at larger length scales, particularly when microstructural or crystallographic effects influence bulk behavior.

The effect of van der Waals-based interface cohesive law on carbonnanotube-reinforced composite materials

H. Tan, L. Y. Jiang, Y. Huang, B. Liu, and K. C. Hwang
Composite Science and Technology, 2007, accepted.

We report in detail that unlike other materials, carbon nanotubes are so small that changes in structure can affect the Young's modulus. The variation in modulus is attributed to differences in torsional strain, which is the dominant component of the total strain energy. Torsional strain, and correspondingly Young's modulus, increases significantly with decreasing tube diameter and increases slightly with decreasing tube helicity.  Journal of Applied Physics 84, 1939 (1998).

Dr. John Hart from MIT is giving a carbon nanotube (CNT) tutorial at the International Symposoum on Nanomanufacturing (ISNM) at MIT on November 1st, Wednesday. Please see the following if you are interested.

A material less sticky than Teflon has been created by covering a surface with a "forest" of carbon nanotubes. Newscients.com has a very interesting report. Read more...

Last year, I attended the course ES139/239 in Division of Engineering and Applied Sciences, Harvard University, the innovation in science and technology. The final project of my group was about carbon nanotube (CNT). In the stage of popping up ideas, we did not consider any feasibility issues, and just used our imagination to create fancy ideas. I was inspired by other guys a lot, felt too excited after the evening brainstorm session, and wrote down the ideas I coined up. Some of them are not nonsense, e.g. replacing Cu by CNT as conductor in integrated circuit (IC). Later on, I find a piece of news in nanotoday (Dec. 2005) that the company Arrowhead Research was to provide $680,000 over two years to Duke University to develop technology for IC based on CNTs. Of course, I am not the first one to come up with this idea. But this means the random imaginative idea is very helpful and sometimes feasible. Another point I learned from this course is to write down at least one idea per day. Keep doing this, then you have a large pool of ideas. One year later, you have 365 ideas. Don’t expect every idea to be useful. Even if just one or two of them are great, it is worthy doing. Imagine that if the future technology originated from one of your ideas, you will contribute the society and feel fullness of ecstasy. If you can realize your idea, you can be a millionaire or billionaire, and then lie on the beach of Caribbean to enjoy the sunshine.

Carbon nanotube has been widely investigated and perceived as having great potential in nanomechanical and nanoelectronic devices due to uniqe combination of mechanical, electrical and chemical properties. The carbon nanotubes may be applied (a) as light-weight structural materials with extraordinary mechanical properties such as stiffness and strength; (b) in nano-electronic components as the next-generation of semi-conductors and nanowires; (c) as probes in scanning probe microscopy and atomic force microscopy with the added advantage of a chemically-functionalized tip; (d) as high-sensitivity microbalances; (e) as gas and molecule sensors; (f) in hydrogen storage devices thanks to its high surface-volume ratio; (g) as field-emission type displays; (h) as electrodes in organic light-emitting diodes and (i) as tiny tweezers for nanoscale manipulation, to name a few.

As a postdoc in Xi Chen's group, my current research in the mechanics of carbon nanotubes concentrates in the following areas: a) thermal vibration and application as strain/mass/specie sensors; b) buckling of nanotubes caused by compression, bending, torsion, and indentation; c) mechanical properties of carbon nanotubes in axial and radial directions, and effective continuum modeling; d) fluid conduction in nanotubes. I have published 14 journal papers since 2005 in these areas. I will introduce more details in my blog later.

In theory, carbon nanotubes are 100 times stronger than steel at one-sixth the weight, but in practice, scientists have struggled make nanotubes that live up to those predictions. This is partly because there are still many unanswered questions about how nanotubes break and under what conditions.

Recently, Prof. Boris I. Yakobson at Rice University, his former postdoc Traian Dumitrica (now assistant professor at University of Minnesota), and his doctoral student Ming Hua, have developed a new computer modeling approach to create a “strength map” that plots the likelihood or probability that a carbon nanotube will break—and how it’s likely to break. Four critical variables are considered in the model: load level, load duration, temperature, and chirality. This work was published in the Proceedings of the National Adacemy of Sciences (Apr. 18, 2006 Cover feature). Full text pdf file of this paper is available here.