The thermophoretic force, escaping velocity, and capture time of C
inside CNT. (a) Thermophoretic force as a function of the temperature gradient. The average system temperature is 400 K. An approximate linear relationship of the magnitude of the thermophoretic force and the thermal gradient was observed as . (b) The escaping velocity of C60 was evaluated by calculating the required energy of C60 from the cold bottom to the hot top according to the relationship of thermophoretic force and thermal gradient, which were clearly described in Additional file 1. (c) Velocity of C60 under the heat flux of 6.5 eV/ps. (d) Capture time of C60 as a function of heat flux.