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

Abstract

Abstract 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.

Keywords

• additive manufacturing
• carbon nanotubes
• e‐paper
• flexible TFTs
• active matrices
• roll‐to‐roll gravure