Nanoscale Continuous Motion Driven By Cyclic Temperature Gradients

Directional motion is indispensable,from the evolution of nature to the life activities of human beings.The motion of direction is realized by driving,which makes the mass move in a certain way.In the process of driving,all kinds of machines are often accompanied by energy conversion,power transfer or material transportation.A new driving technology may completely change the way of human production and life.With the development of nanotechnology,the design of nano devices has become a hot research field and the demand for motion's diversity of nano machines is increasing.Therefore,it is necessary to explore a new directional driving mechanism of nano machines.At present,numerous studies have shown that the directional motion of nano devices can be realized by applying external fields such as heating,electricity,light or magnetic field,and the motor driving the target object to move or rotate in nano scale can be constructed.When these nano-devices work,they are usually required to drive the target object continuously in a directional and controllable way.However,the existing nanomotors can't move continuously,controllably for long distances in a stable field.In this paper,we design a kind of nanostructure unit,which can keep continuous motion in periodic stable thermal field,and use the molecular dynamics method to carry out the calculation simulation,and then put forward the corresponding analytical model to further verify the rationality of the design.The main research contents are as follows:The nanostructure unit is composed of a carbon nanotube and a carbon/boron nitride heterojunction concentric outer nanotube.Thus,three asymmetric temperature gradient fields are respectively imposed on the carbon boundary,on the heterojunction and on the boron nitride boundary of the heterojunction.The simulation results show that carbon nanotubes can produce three kinds of continuous directional motion under three stable temperature fields.The mechanism of different directional motion is based on the thermophoresis of solid surface under the temperature distribution of three kinds of heterojunction external tubes.In order to study the controllability of the motion,we propose the relevant analytical model.Results show that the speed and direction of the nanostructure unit can be controlled by the temperature gradient and the geometric structure parameters of the heterojunction nanotube.The simulation results are in good agreement with the analytical prediction,which further verifies the rationality of the model.