JAPAN NANONET BULLETIN - 49th Issue - July 21, 2005

Theory of nano-design - Mechanics of nano-machine, nano-fabrication, and nano-structure

I am theoretically studying mechanical nano-design from the viewpoints of nano-machine, nano-fabrication, and nano-structure.

Nano-machine: We have developed a “C₆₀ bearing,” which is a system with zero kinetic friction, and theoretically proposed its dynamical model. The sandwiched structure, which confines a C₆₀ monolayer between graphite plates [Fig.1(a)], exhibits ultralubrication, where kinetic friction becomes zero independent of the normal load [Fig.1(b)]. A “Step Rotation and Rolling Model,” considering the atomic structure of the C₆₀ molecule and graphite, can be used to explain the ultralubrication feature [Fig.1(c)]. This study is the first proposal of artificial nano-machine using fullerene, which is the smallest bearing in the world.

Nano-fabrication: We have predicted and quantitatively reproduced various experimental results of Si(111)√3×√3-Ag surface observed by noncontact AFM(NC-AFM), based on a first-principles electronic state calculation. For example, at room temperature, it was shown that an image, which does not reflect stable Ag atom positions, appears due to thermal fluctuation [Fig.2(a)]. However, at low temperature, each Ag atom can be resolved because thermal fluctuation is reduced [Fig.2(b)]. Furthermore, thermal fluctuation of Ag atoms can be controlled using a NC-AFM tip [Fig.2(c)].

In summary, I am doing theoretical research involving nano-design from several viewpoints, trying to act as go-between experiment and theory in nanotechnology, and trying to develop materials and devices useful for industrial applications.

Fig. 1 Large Image
(a) Ultralubricated system, which confines a C60 monolayer between graphite plates (b) Load dependence of the frictional force (c) "Step Rotation and Rolling Model"

Fig. 2  Large Image
(a) NC-AFM image at room temperature (theoretical simulation) (b) NC-AFM image at low temperature (theoretical simulation) (c) Schematic illustration of thermal fluctuation of Ag atoms controlled by a NC-AFM tip

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