Fully R2R‐Printed Carbon‐Nanotube‐Based Limitless Length of Flexible Active‐Matrix for Electrophoretic Display Application

Author(s): Sun, J; Sapkota, A; Park, H; Wesley, P; Jung, Y; Maskey, BB; Kim, Y; Majima, Y; Ding, J; Ouyang, J; Guo, C; Lefebvre, J; Li, Z; Malenfant, PRL; Javey, A; Cho, G | Abstract: © 2020 WILEY-VCH Verlag GmbH a Co. KGaA, Weinheim A limitless-length flexible active-matrix implies that virtually any surface can be rendered into an interactive medium when laminated with electrophoretic or organic light-emitting diode sheets. However, performance, cost, and size limitations of current fabrication technologies and semiconducting materials, typically utilized in thin film transistor (TFT) active matrices (TFT-AMs), have hindered progress, thus preventing the realization of fully printed TFT-AMs on a plastic roll. A new high-purity semiconducting single-walled carbon nanotube (s-SWCNT) ink is prepared by first isolating 99.9% pure s-SWCNTs via conjugated polymer extraction, and then utilizing a ligand-exchange method to formulate a novel hydrophilic gravure-compatible semiconducting ink. Based on the s-SWCNT ink, a fully additive manufacturing process using roll-to-roll (R2R) gravure printing enables the fabrication of a flexible TFT-AM, overcoming performance, cost, and size limitations. TFT-AMs with 10 to 40 PPI resolution where average mobility of 0.23 ± 0.12 cm2 V−1 s−1, average on–off ratio of 104.1, and threshold voltage variation of ±13% are attained. As a proof of concept, an inexpensive and flexible electrophoretic display is demonstrated by simply laminating an electrophoretic sheet onto the R2R gravure-printed s-SWCNT-based TFT-AM.