Efficient carbon nanotube/polyimide composites exhibiting tunable temperature coefficient of resistance for multi-role thermal films

Thermal films based on carbon nanotube (CNT) composite film have attracted focus in practical applications. This paper develops a highly flexible and multi-role CNT/Polyimide (PI) composite film by employing the dielectrophoresis technique to incorporate bundles of SWCNT into patterned PI substrates. The CNT composite film with a nickel conductive layer exhibits a tunable temperature coefficient of resistivity (TCR) while vacuum thermally treated at diverse temperature. The evolution of the TCR could be controlled from the negative correlation (reached −15000 ppm/°C) to the positive (up to nearly 10000 ppm/°C), which is mainly determined by the reform of the tube connection and covalent bonds in composites due to accumulated thermal energy of annealing, resulting in the change of charge transport. Moreover, the transient response of film devices annealed at different temperature could remain on the order of microseconds proving the robustness of the technology. Demonstrations in human body temperature sensing and micro wind tunnel flow measuring represent excellent sensitivity and reproducibility. The proposed thermal film based on CNT/PI composite with a tunable resistance-temperature characteristic gives a great application potential in intelligent protection electronics, sensing elements and other related thermal applications.