In-Place Printing of Carbon Nanotube Transistors at Low Temperature

Interest in flexible, stretchable, and wearable electronics has motivated the development of additive printing to fabricate customizable devices and systems directly onto virtually any surface. However, progress has been limited by the relatively high temperatures (>200 °C) required to sinter metallic inks and time-consuming process steps, many of which require removal of the substrate from the printer for coating, washing, or sintering. In this work, we addressed these challenges and demonstrate carbon nanotube thin-film transistors (CNT-TFTs) that are fabricated by aerosol jet printing with the substrate never leaving the printer. The full in-place printing approach, from first step to last, used a maximum process temperature of only 80 °C on the printer platen. Silver nanowire (Ag NW) ink was found to be most viable for low-temperature, in-place sintering while still yielding good electrical interfaces to the CNT thin-film channels. These aerosol-jet printed Ag NW films were conductive immediately after fabrication, which is the key component enabling rapid and sequential in-place printing. The devices exhibit on-currents as high as 80 μA/mm, effective mobilities of 12 cm2/(V·s), and on/off current ratios exceeding 105. These findings provide a promising path forward toward the additive manufacture of flexible and stretchable electronics in a low-cost, highly customizable, and agile manner.