A Novel Thermal Driving Force for Nanodevices

Design and construction of nanomotors are one of the most attractive fields in nanotechnology. Following the introduction of a novel concept of the thermomass, the relative mass of a phonon gas based on the Einstein’s energy–mass relation, the continuum and momentum conservation equations for the phonon gas are established to characterize the hydrodynamics of the phonon current in a solid. Like the gas flows in the porous mediums, the phonon current in a dielectric solid imposes a driving force on the solid framework atoms, which can be calculated quantitatively and can be applied to actuate nanomotors. We also predict the dynamic behavior of a nanomotor made up of multiwalled carbon nanotubes in terms of molecular dynamics simulations. A shorter single-walled carbon nanotube with a larger diameter, as a mobile part, surrounds a longer single-walled carbon nanotube with a smaller diameter working as a shaft. When a phonon current passes through the inner shaft, the outer nanotube will translate along and/or rotate around the shaft depending on the chiralities of the carbon nanotubes. The motion traces are found to depend on the chirality pair regularly. This type of nanomotor may be promising, because they are directly driven by thermal energy transport.