Fully roll-to-roll gravure printed 4-bit code generator based on p-type SWCNT thin-film transistors

Abstract

Current Si-based technologies have reached their intrinsic limits in meeting the demands of flexible electronics where free-form factors and low cost are critical for successful applications. For this reason, roll-to-roll (R2R) gravure printing has been considered a way to achieve the free-form factor and the low cost. However, the R2R gravure systems (servomechanism, electronic ink, printing process, and device design) could not integrate a number of thin-film transistors (TFTs) with small threshold voltage (V th) variations. Therefore, we designed a 4-bit code generator by combining one ring oscillator, six NAND gates, and one OR gate based on 37 p-type single-walled carbon nanotube (SWCNT) TFTs as a concept devices to test the R2R gravure system. First, ring oscillators with different physical dimensions were printed on a poly (ethylene terephthalate) roll using the R2R gravure. Then, we extracted important factors (channel length, channel width, and SWCNT network density) to optimize the V th variation and demonstrated a 4-bit code generator integrated with 37 p-type TFTs. This work will be further extended in the near future to develop R2R gravure printed near-field communication labels for smart packaging.