Comparison of resonance frequencies between normal and tangential vibration modes of graphene-nanoribbon-resonators.

We investigate tunable graphene-nanoribbon (GNR)-resonators actuated in the tangential direction, and their properties are compared to those actuated in the normal direction, via classical molecular dynamics simulations. These GNR-resonators can be tuned both by the initial strain and the gate. The relationships between the frequency-versus-gate and the initial strain in this work are in good agreement with those in previous experimental works. With increasing initial strain, the resonance frequencies are greatly upshifted, whereas the tunable ranges in frequency are greatly decreased. The tunability in the dynamic operating range decreases with increasing initial strain. For very small strains, the GNR-resonators have large dynamic operating ranges in the normal vibration mode, and for large strains, the GNR-resonators have higher operating frequencies in the tangential vibration mode. The resonance frequencies are estimated by a classical continuum model, with tension acting on the GNR-resonators consisting of both initial tension by initial strain and induced tension by gate actuating.

Effect of number and length of outerwalls on cantilevered-carbon-nanotube resonators.

In this paper, we investigated the resonant frequencies of multi-walled carbon nanotube (MWCNT) resonators with short outertubes according to the classical molecular dynamics approach. The resonant frequencies of the MWCNT resonators with short outertubes were influenced in both the wall number and the length of the short outertubes. The resonance frequencies of MWCNTs with short outertubes could be modeled by Gaussian distribution functions. Both the bandwidth and the sensitivity increased with increasing the wall number of the outertubes. The maximum frequency increased with increasing the diameter and with increasing the wall number of the outertubes for MWCNTs. So the effects of increasing the wall number of the outertubes were very important factors for understanding the vibrational frequency changes of MWCNTs with short outertubes as well as the effect of increasing the lengths of the outertubes.

Linear nanomotor based on electromigration of a nanoparticle encapsulated in a carbon nanotube.

We investigated a linear nanomotor based on the telescoping carbon nanotube motion induced by electromigration of an encapsulated nanoparticle. The nanoparticle motion induced by the electric current makes the inner nanotube linearly telescope or retreat. Theoretical results using a kinetic Monte Carlo method were in good agreement with previous experiments. The telescoping speed of the linear nanomotor exponentially decreased with increasing mass of the inner nanotube.

Resonant frequencies of cantilevered (8,8)(3,3) double-walled carbon nanotube Resonator with short outer wall.

Resonant frequencies of cantilevered (8,8)(3,3) double-walled carbon nanotube (DWCNT) resonators are investigated via classical molecular dynamics simulation. The interwall van der Walls forces as a nonlinear function had a great effect on noncoaxial vibration of DWCNT resonators. Bandwidths of DWCNT resonators with short outer walls were similar with each other irregardless to the structural difference. The frequency trends of DWCNT resonators with short outer wall were affected by the outer wall length. The vibration of the DWCNT resonator with short outer wall was very closely related to the vibration of the inner CNT in the stripped region.

Molecular dynamics study of nano mass transfer in a vibrating cantilevered carbon-nanotube.

We investigate the nano mass transfer in an ultrahigh frequency carbon-nanotube-resonator encapsulating a nanocluster via classical molecular dynamics simulations. When the carbon-nanotube-resonator vibrated, the encapsulated copper nanocluster more rapidly approached the end of the cantilevered carbon-nanotube-resonator. Such phenomena were due to the migration of the encapsulated copper nanocluster due to the centrifugal force induced by the vibrating nanotube resonator. So the resonance frequency change could be time-dependently found. For the movable copper nanocluster in carbon nanotube resonator, the vibrational spectra when the copper nanocluster inside the carbon nanotube resonator rapidly settled at the capped edge were different from those obtained when the copper nanocluster continuously oscillated inside the carbon nanotube resonator. Such results showed that the frequency of the carbon-nanotube-resonator encapsulating the movable copper nanocluster could be adjusted by controlling the mean position of the oscillating copper nanocluster. The movable nanocluster inside a carbon-nanotube can be applied to a nanotube-based data storage media by sensing the position of the nanocluster.

Study on electromigratively-telescoping carbon-nanotube-based reversible-tuner.

We conceptually investigated a carbon-nanotube-based tuner operated by the telescoping nanotube motion in a multi-walled carbon-nanotube induced by electromigration of an encapsulated nanoparticle. The telescoping lengths in the proposed carbon-nanotube-based tuner could be achieved from the electromigration phenomena of the nanoparticle embedded in the carbon nanotube. So the core part is the nanoparticle shuttle and a multi-walled carbon-nanotube with ultra-low interlayer friction. The tuning of this telescoping carbon-nanotube-based tuner is achieved from the electric current flow. The properties of operation were investigated via classical molecular dynamics simulations and then the parameters of the continuum model were then calibrated to fit the results of the molecular dynamics simulations. Since the effective boundary considered as the movable clamp affected the vibration of the telescoping nanotube, the calibrated Young's modulus of this work were lower than the those of the previous works. Presented tuners are controllable in a few nanometers, and their operations are robust and reliable.

Molecular Dynamics Study on Graphene-Nanoflake Sensor Sandwiched Between Crossed Graphene-Nanoribbon Junctions.

We present a design of a nanoscale inertial measurement unit or a data archive using a graphene-nanoflake (GNF) sandwiched between crossed graphene-nanoribbon (GNR) junctions. When an external force applied is below the retracting force, the inertial force exerted on the movable GNF can telescope it. Then, the self-restoring force increases as the attractive van der Waals force between the GNF and the GNRs, which enables the GNF to automatically and fully retract back into the sandwich position immediately after the externally applied force is released. When the external force exceeds the retracting force, the GNF escapes from the crossed GNR junctions, which enables the device to be used as non-volatile memory. The heterostructure of GNR/h-BN/GNR can be considered as an advanced structure in the proposed scheme.

Molecular Dynamics Study of Graphene Nanoflake Shuttle Device on Graphene Nanoribbon with Carbon Nanotube Blocks.

Superlubric motions of graphene nanoflakes (GNFs) on graphene have opened up more applications of graphene for micromachines and nanomachines. Here, we investigate the dynamic behavior of a GNF shuttle on a graphene nanoribbon (GNR) with carbon nanotube (CNT) blocks via molecular dynamics simulations. The GNF moves on a GNR superlubrically, and the CNTs as building blocks induce bistable potential wells so that the GNF is stabilized. MD simulation results indicate that when a GNF shuttle approaches the CNTs, a potential well is created by an increase in the attractive van der Waals energy between the GNF and CNTs, and bistability at the local energy minima positions can be achieved near the CNTs. In order for the GNF shuttle to escape the local energy minima positions, a high external force must be applied to overcome the potential energy barrier. However, after the GNF shuttle escapes from one of the bistable positions, only a low external force is required to stabilize the GNF shuttle. This work explicitly demonstrates that a GNF-GNR/CNT system could be applied to alternative nonvolatile memory and high-speed mass storage by using GNR-CNT arrays.

Molecular Dynamics Simulation Study on Energy Exchange Between Vibration Modes of a Square Graphene Nanoflake Oscillator.

Superlubricity in nanoscale graphene structures has been of interest for developing graphene-based nanoelectromechanical systems, as well as for the study of basic mechanical properties. Here, we investigated the translational and rotational motions of a square graphene nanoflake with retracting motions by performing classical molecular dynamics simulations. Our results show that the kinetic energy of the translational motion was exchanged into the kinetic energy of the rotational motion. Thus, square graphene nanoflake oscillators have very low quality factors in translational motions. We discuss that square graphene nanoflakes have great potential to be a core component in nanoelectromechanical systems by detecting their motions with ultrahigh sensitivity to facilitate the development of sensor, memory, and quantum computing.

Molecular Dynamics Simulations of a C60 Molecule Adsorbed on Sinusoidal Graphene Nanoflake.

We have investigated the motion of a C60 molecule absorbed on sinusoidal graphene nanoflake (GNF) via molecular dynamics simulations. Since C60 deposited on sinusoidal GNF is favorable on energetic grounds, the C60 molecule moved toward one of the valleys of sinusoidal GNF without energy barrier. So no sooner the C60 molecule was deposited on the sinusoidal GNF, then the C60 molecule immediately began to move toward the valley of the sinusoidal GNF Since the position of the C60 molecule can be changed by externally applied force fields and has a binding energy of 0.754 eV in the valley of sinusoidal GNF, the sinusoidal C60/GNF can be applied to a switchable nonvolatile memory device. This work provides the probability of alternative 'bucky shuttle' memory based on the sinusoidal C60/GNF hybrid nanostructure.

Bistability of C60 Fullerene in Partially Side-Opened Carbon Nanopeapod.

Partially side-opened carbon nanopeapods show great potential for various applications. Here, we investigated the schematics and energetics of a nonvolatile nanomemory element, based on a C60 fullerene encapsulated in a partially opened carbon nanopeapod, using empirical interatomic interaction potential functions. Bistability of the van der Waals potential energy is achieved from the positional change of the encapsulated C60 fullerene, and the encapsulated C60 fullerene can shuttle between bistable positions, under alternatively applied force fields. Since the C60 fullerene can retain its position without recharging, the proposed system can operate as a nonvolatile memory device. These results can be useful for the understanding of new molecular machines.

The frequency of cantilevered double-wall carbon nanotube resonators as a function of outer wall length.

Analysis of vibrational characteristics of cantilevered double-walled carbon nanotube (DWCNT) resonators is carried out based on classical molecular dynamics simulation. Vibrational frequencies of DWCNTs are less than those of single-walled carbon nanotubes (SWCNTs) with the same length and the same diameter because of van der Waals intertube interaction. For DWCNTs with short outer walls, the resonance frequency initially increases with increasing outer nanotube length and then decreases after a peak, and thus the result can be modeled by a Gaussian distribution. The frequency of DWCNT resonators with short outer walls is a maximum when the length of the outer wall is about 72.5% of the length of the inner wall.