Atsuko Nagataki

Static Friction Force of Carbon Nanotube Surfaces

To elucidate forces providing high mechanical strength during formation of carbon nanotube (CNT) yarns and sheets, internanotube static friction force was investigated using a transmission electron microscope with a nanomanipulation system. Results show that the static friction force depends strongly on the CNT surface state. That force between two as-grown CNTs grown by chemical vapor deposition is much larger than that for highly crystalline CNTs. The as-grown CNT surfaces generally have amorphous carbon and defects. For CNT yarns and sheets, the frictional force attributable to surface roughness, rather than the van der Waals force, affects interactions among CNTs.

Current-induced curing of defective carbon nanotubes

Defective carbon nanotubes (CNTs) were cured using current-induced thermal excitation. The original straight position of a CNT with an artificially induced plastic bend was restored using an applied current of 2.4μA∕nm. That current is nearly equivalent to the current causing sublimation of CNTs. Thermal excitation cures CNTs with defects of pentagons and heptagons. Such cured CNTs have high crystallinity, as confirmed by applying the second process to them to induce an artificial plastic bend and to recover their straight position. That curing phenomenon was also confirmed using a sample of a one-turn coiled CNT with pentagons and heptagons.

Covalent attachment of protein to the tip of a multiwalled carbon nanotube without sidewall decoration

We have demonstrated covalent bonding of protein molecules to an oxidized multiwall carbon nanotube (MWCNT) in an aqueous buffer solution. A chemical reaction using carbodi-imide forms chemical bonds between open-ended tips of MWCNTs and protein molecules. The statistical examination indicated that proteins were attached at the open-ended tip of MWCNT at a probability as high as 50% although proteins attached to the sidewall of the MWCNT were washed out after rinsing with running water.

Energy Barrier for Disappearance of Buckling to Form a Plastic Bend in Carbon Nanotubes

We have investigated the current-induced transformation from elastically buckled carbon nanotubes into plastically bent nanotubes with a large bending angle. For this study, C60-encapsulated single wall nanotubes were used, enabling the estimation of energy barriers in the process from the well known coalescence reactions. Increasing the current caused a sequential change: (a) coalescence of C60 molecules to form tube structures; (b) merging of the newly formed tubes with the original nanotube; (c) disappearance of buckling to form a plastic bend; and finally (d) sublimation of the nanotube. The order of the energy barriers for (a), (b), and (d) is consistent with the experimental results, which suggests that the observed structural change is caused by thermally activated reactions. The barrier for the disappearance of buckling to form the plastic bend is between 6.0 and 6.9 eV.

Release and nonvolatile operation of carbon nanotube nanorelay by resonant vibration

We investigated the release of a stuck carbon nanotube (CNT) cantilever beam in nanorelay applications using a nano-manipulator. Even with strong adhesion induced by electrostatic attraction that is 100 times stronger than the van der Waals interaction, successful release of a nanotube arm from a stuck state was realized by the application of a resonant vibration to the stuck CNT arm. Furthermore, nonvolatile operation of the nanotube nanorelay was demonstrated by the application of the resonant vibration to the stuck CNT arm.

Carbon nanotube mechanical resonator in potential well induced by van der Waals interaction with graphene

We demonstrate the control of a cantilever-type carbon-nanotube mechanical resonator in a potential well induced by van der Waals interaction with a graphene flake using molecular dynamics simulations. The energy potential profile for the resonator is successfully modulated by changing the graphene width. As a result of the potential profile modification, the resonance frequency can be markedly changed from the original value of 18.2 to 55 GHz by reducing the graphene width. Additionally, the nonlinear effect is easily developed even under the small amplitude regime around thermal vibration using a narrow graphene layer with a width of 10 A.

Release of Stuck Carbon Nanotube Arm by Resonant Vibration toward Nanorelay Application

We successfully demonstrated to release a stuck carbon nanotube (CNT) arm from a counter electrode toward the application of mechanical nano-relay by applying resonant vibration to the CNT arm. This paper experimentally proves the advantage of the use of resonant vibration.