down the price and allow market accessibility. [1] Conceptually, large area flexible displays would transform any surface into an interactive medium that could conform to any underlying substrate. In such case, the flexible display would revolutionize our surroundings by driving the development of novel display form factors, through which leading to a human-machine interface revolution. To achieve this practically, TFT-AMs, a core technology for displays, should be manufactured without cost and size limitations. [1][2][3] The solution can be found in roll-to-roll (R2R) additive manufacturing, such as R2R gravure printing, which has been used as a low-cost manufacturing technology for newspapers, magazines, packaging, and wallpaper for over 100 years. [4] If this technology can be adopted to manufacture TFT-AMs for displays, a variety of flexible displays can be realized by simply laminating electrophoretic or organic light-emitting diode (OLED) sheets on R2R printed TFT-AMs (Figure 1a). To attain R2R-printed TFT-AMs with a comparable device yield and electrical performance to amorphous Si-based TFT-AMs, a rapidly curable (<5 s) semiconducting ink that yields a semiconducting thin film with an appropriate Fermi level to meet the work function of printed silver drain/source electrodes 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 cm 2 V −1 s −1 , average on-off ratio of 10 4.1 , 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.
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