Temperature effects on a motion transmission device made from carbon nanotubes: a molecular dynamics study

Abstract

A motion transmission system made from coaxial carbon nanotubes (CNTs) is introduced. In the system, the motor is built from a single-walled carbon nanotube (SWCNT) and the converter is made from triple-walled carbon nanotubes (TWCNTs). The outer shell acts as a stator with two fixed tube ends. The inner tube (rotor 1) and the middle tube (rotor 2) can move freely in the stator. When the axial gaps between the motor and the TWCNTs are small enough and the motor has a relatively high rotational speed, the two rotors have either stable rotation or oscillation, which can be considered as output signals. To investigate the effects of such factors as the length of rotor 2, the rotational speed of the motor, and the environmental temperature on the dynamic response of the two rotors, numerical simulations using molecular dynamics (MD) are presented on a device model having a (5, 5) motor and a (5, 5)/(10, 10)/(1, 15) converter. Numerical results show that the two inner tubes can act as both rotor(s) and oscillator, simultaneously if the middle tube is longer than the inner tube. In particular, we find a new phenomenon, mode conversion of the rotation of rotor 1 by changing the environmental temperature. Briefly, rotor 1 rotates synchronously with the high-speed motor at a higher temperature or with rotor 2 at a lower temperature. The effect of radii difference among the three tubes in the bearing are also discussed by replacing the middle tube (10, 10) with different zigzag tubes.