Thermal management for purification of aligned arrays of single-walled carbon nanotubes based on thermocapillary flow by pulsed heating

Semiconducting single-walled carbon nanotube (s-SWNT) arrays attract much attention due to the ideal configuration for high performance electronics. A recent approach based on the nanoscale thermocapillary flow enabled the achievement of aligned arrays of highly purified s-SWNTs by removing the metallic SWNTs (m-SWNTs) in as-grown arrays by direct pulsed current injection. Thermal management of this process is critically important since the cumulative heating from the m-SWNT array yields a high temperature increase to cause the difficult control of thermocapillary flow. In this paper, an analytical heat transfer model combining a two-dimensional transient thermal model and a three-dimensional steady state thermal model is established for predicting the temperature increase of the SWNT array under a pulsed current injection with a period step function. The analytical predictions agree well with three-dimensional finite element analysis. Effects of parameters (such as duty cycle, period, spacing, etc.) on the temperature distributions and the maximum temperature increase are investigated systematically. These results can help guide the purification process to reduce the adverse thermal effects to obtain highly purified s-SWNTs.