Flexible self-assembly carbon nanotube/polyimide thermal film endowed adjustable temperature coefficient of resistance

The development of multi-role flexible thermal films embedded with single-walled carbon nanotubes (SWCNTs) exhibiting an adjustable temperature coefficient of resistance (TCR) is presented. The composite film is prepared by an alternating electric field to assembling CNTs on Ni conductive layer and polyimide. Modified vacuum thermal treatment is then conducted to adjust the TCR behavior of films, thereby gaining the positive, negative and near-zero TCR ranging from-1.5% °C-1 to nearly 1.0% °C-1 at different annealing conditions, respectively. The changes of morphologies, tube crystallinity and chemical elements in films are investigated. The enhanced intertube couplings in bundles of CNTs, formations of chemical bonds and recrystallization in heat-treated films, resulting in the change of charge transport, play a dominant role in the evolution of the TCR behavior. Heat-treated films also exhibit linear temperature dependence and high stability while operating at wide ambient temperature, leading to broad prospects in flexible electronic thermal applications.