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Robust rotation of rotor in a thermally driven nanomotor

View Article: PubMed Central - PubMed

ABSTRACT

In the fabrication of a thermally driven rotary nanomotor with the dimension of a few nanometers, fabrication and control precision may have great influence on rotor’s stability of rotational frequency (SRF). To investigate effects of uncertainty of some major factors including temperature, tube length, axial distance between tubes, diameter of tubes and the inward radial deviation (IRD) of atoms in stators on the frequency’s stability, theoretical analysis integrating with numerical experiments are carried out. From the results obtained via molecular dynamics simulation, some key points are illustrated for future fabrication of the thermal driven rotary nanomotor.

No MeSH data available.


Schematic of symmetrically geometric model of a thermal driven rotary nanomotor ((nR, mR)/(nS, mS)) formed by two stators (L- and R-Stator with the same chirality) and a rotor.All tubes are carbon nanotubes. (a) The initial distance between neighbor ends of L-Stator and rotor is a, whose value is ~0.248 nm in this model. The length of each stator is b, which is ~0.495 nm. GS is the gap between two stators. LR is the axial length of rotor, which could be different in different models. (b) To drive the rotation of rotor, we adjust the positions of some end carbon atoms on R-stator with “A-type” inward radial deviation28, which satisfies Δd = 2e × lc-c = 0.284 e (nm). Dimensionless parameter “e” is called relative radial deviation of IRD atom. All IRD atoms have the same value of e in (0, 0.6) in simulations. Δr is the radii difference between rotor and stator. N is the number of IRD atoms on each stator.
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f1: Schematic of symmetrically geometric model of a thermal driven rotary nanomotor ((nR, mR)/(nS, mS)) formed by two stators (L- and R-Stator with the same chirality) and a rotor.All tubes are carbon nanotubes. (a) The initial distance between neighbor ends of L-Stator and rotor is a, whose value is ~0.248 nm in this model. The length of each stator is b, which is ~0.495 nm. GS is the gap between two stators. LR is the axial length of rotor, which could be different in different models. (b) To drive the rotation of rotor, we adjust the positions of some end carbon atoms on R-stator with “A-type” inward radial deviation28, which satisfies Δd = 2e × lc-c = 0.284 e (nm). Dimensionless parameter “e” is called relative radial deviation of IRD atom. All IRD atoms have the same value of e in (0, 0.6) in simulations. Δr is the radii difference between rotor and stator. N is the number of IRD atoms on each stator.

Mentions: In recent year, device/machine fabrication tends to be miniaturized along with the rapid development of nanotechnology1. For example, the carbon nanotube (CNT) has been manufactured and fitted in a tip of atomic force microscopy which can interact with and physically measure a sample surface with ultrahigh resolution2. Due to their ultrahigh in-shell stiffness34 and ultralow friction between neighbor tubes56, CNTs are now excellent candidate material for the fabrication of such nanodevices as strain sensors789, oscillator1011, nanomotors12131415, and MEMS/NMES systems1617. Among these nanodevices, nanomotor is the simplest nanomachine, which can transform chemical or physical energy into kinetic energy1218192021. In particular, the CNT-based nanomotor attracted much attention in the past two decades. For example, Fennimore et al.22 developed a nanomotor experimentally. In the nanomotor, multi-walled carbon nanotubes (MWCNTs) acted as a rotary axis on which a metal strip was attached. The metal strip on the rotor can be actuated to rotate under the external periodic electric field. Soon after, Bourlon et al.23 proposed a similar work in 2004. In 2008, Barreiro et al.24 also built a nanomotor from MWCNTs. In their work, the inner tubes acted as a stator, on which a short outer tube attached to a cargo can be actuated to rotate and/or move along a stator when a thermal gradient exists along the axis of a stator. Frankly speaking, a successful fabrication of such nanomotors is still difficult even full advantage of the state-of-the-art in nanotechnology and advanced manufacturing technology is taken. Considering that most knowledge on nanodevices are expansive or difficult to achieve experimentally, many researchers use numerical experiments to estimate the relationship between outer filed and the output motion of those nanomotors. Besides fabrication experiment, Bourlon et al.23 provided numerical simulations for investigating the performance of their nanomotor. By mimics of hydroturbine, Kang and Hwang25 built a complicated model of nanomotor from nanotubes and nanofluid. In their nanomotor, the rotor made from a nanotube bonded with several blades can be driven to rotate by the collision from the nanofluid in the nano-volute. Within the framework of the Smoluchowski-Feynman ratchet, Tu and Hu26 built a rotary nanomotor from double-walled carbon nanotubes (DWCNTs). The long inner tube in the nanomotor is fixed as a stator, and the short outer tube as the rotor. When an axially varying electrical voltage is applied on the inner tube, the unidirectional rotation of rotor was triggered. Wang et al.27 proposed a rotary nanomotor from nanotubes and fullerenes. Their numerical experiment showed that the blades bonded on CNT-rotor have periodic charging and discharging, and the rotor can rotate in an external electric field. Recently, Cai et al.28 built a new type of nanomotor from DWCNTs, with the outer tube fixed as a stator and the inner tube as the rotor (Fig. 1a). The mechanism of the rotary nanomotor is that the atoms on rotor have drastic thermal vibration. Due to thermal vibration of the atoms, the rotor and the IRD atoms over stators collide. The rotation of the rotor is actuated when the collision provides the rotor a stable axial torque.


Robust rotation of rotor in a thermally driven nanomotor
Schematic of symmetrically geometric model of a thermal driven rotary nanomotor ((nR, mR)/(nS, mS)) formed by two stators (L- and R-Stator with the same chirality) and a rotor.All tubes are carbon nanotubes. (a) The initial distance between neighbor ends of L-Stator and rotor is a, whose value is ~0.248 nm in this model. The length of each stator is b, which is ~0.495 nm. GS is the gap between two stators. LR is the axial length of rotor, which could be different in different models. (b) To drive the rotation of rotor, we adjust the positions of some end carbon atoms on R-stator with “A-type” inward radial deviation28, which satisfies Δd = 2e × lc-c = 0.284 e (nm). Dimensionless parameter “e” is called relative radial deviation of IRD atom. All IRD atoms have the same value of e in (0, 0.6) in simulations. Δr is the radii difference between rotor and stator. N is the number of IRD atoms on each stator.
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Related In: Results  -  Collection

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f1: Schematic of symmetrically geometric model of a thermal driven rotary nanomotor ((nR, mR)/(nS, mS)) formed by two stators (L- and R-Stator with the same chirality) and a rotor.All tubes are carbon nanotubes. (a) The initial distance between neighbor ends of L-Stator and rotor is a, whose value is ~0.248 nm in this model. The length of each stator is b, which is ~0.495 nm. GS is the gap between two stators. LR is the axial length of rotor, which could be different in different models. (b) To drive the rotation of rotor, we adjust the positions of some end carbon atoms on R-stator with “A-type” inward radial deviation28, which satisfies Δd = 2e × lc-c = 0.284 e (nm). Dimensionless parameter “e” is called relative radial deviation of IRD atom. All IRD atoms have the same value of e in (0, 0.6) in simulations. Δr is the radii difference between rotor and stator. N is the number of IRD atoms on each stator.
Mentions: In recent year, device/machine fabrication tends to be miniaturized along with the rapid development of nanotechnology1. For example, the carbon nanotube (CNT) has been manufactured and fitted in a tip of atomic force microscopy which can interact with and physically measure a sample surface with ultrahigh resolution2. Due to their ultrahigh in-shell stiffness34 and ultralow friction between neighbor tubes56, CNTs are now excellent candidate material for the fabrication of such nanodevices as strain sensors789, oscillator1011, nanomotors12131415, and MEMS/NMES systems1617. Among these nanodevices, nanomotor is the simplest nanomachine, which can transform chemical or physical energy into kinetic energy1218192021. In particular, the CNT-based nanomotor attracted much attention in the past two decades. For example, Fennimore et al.22 developed a nanomotor experimentally. In the nanomotor, multi-walled carbon nanotubes (MWCNTs) acted as a rotary axis on which a metal strip was attached. The metal strip on the rotor can be actuated to rotate under the external periodic electric field. Soon after, Bourlon et al.23 proposed a similar work in 2004. In 2008, Barreiro et al.24 also built a nanomotor from MWCNTs. In their work, the inner tubes acted as a stator, on which a short outer tube attached to a cargo can be actuated to rotate and/or move along a stator when a thermal gradient exists along the axis of a stator. Frankly speaking, a successful fabrication of such nanomotors is still difficult even full advantage of the state-of-the-art in nanotechnology and advanced manufacturing technology is taken. Considering that most knowledge on nanodevices are expansive or difficult to achieve experimentally, many researchers use numerical experiments to estimate the relationship between outer filed and the output motion of those nanomotors. Besides fabrication experiment, Bourlon et al.23 provided numerical simulations for investigating the performance of their nanomotor. By mimics of hydroturbine, Kang and Hwang25 built a complicated model of nanomotor from nanotubes and nanofluid. In their nanomotor, the rotor made from a nanotube bonded with several blades can be driven to rotate by the collision from the nanofluid in the nano-volute. Within the framework of the Smoluchowski-Feynman ratchet, Tu and Hu26 built a rotary nanomotor from double-walled carbon nanotubes (DWCNTs). The long inner tube in the nanomotor is fixed as a stator, and the short outer tube as the rotor. When an axially varying electrical voltage is applied on the inner tube, the unidirectional rotation of rotor was triggered. Wang et al.27 proposed a rotary nanomotor from nanotubes and fullerenes. Their numerical experiment showed that the blades bonded on CNT-rotor have periodic charging and discharging, and the rotor can rotate in an external electric field. Recently, Cai et al.28 built a new type of nanomotor from DWCNTs, with the outer tube fixed as a stator and the inner tube as the rotor (Fig. 1a). The mechanism of the rotary nanomotor is that the atoms on rotor have drastic thermal vibration. Due to thermal vibration of the atoms, the rotor and the IRD atoms over stators collide. The rotation of the rotor is actuated when the collision provides the rotor a stable axial torque.

View Article: PubMed Central - PubMed

ABSTRACT

In the fabrication of a thermally driven rotary nanomotor with the dimension of a few nanometers, fabrication and control precision may have great influence on rotor’s stability of rotational frequency (SRF). To investigate effects of uncertainty of some major factors including temperature, tube length, axial distance between tubes, diameter of tubes and the inward radial deviation (IRD) of atoms in stators on the frequency’s stability, theoretical analysis integrating with numerical experiments are carried out. From the results obtained via molecular dynamics simulation, some key points are illustrated for future fabrication of the thermal driven rotary nanomotor.

No MeSH data available.