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.
what has demanded from practical applications for collecting the big data. Therefore, to resolve the cost issues, a R2R printing foundry has been highly attracted because the flexible passive components (such as sensor electrodes, capacitors, and antenna) are able to integrate with their flexible active components (such as display, processor, [3] transponder, [4] analogto-digital converter (ADC), [5] operation amplifier [6]) through a R2R inline printing system. [7] However, although sensor electrodes, [8] capacitors, [9] antenna, [10] and thin film transistor (TFT) active matrix-based display [11] have been successfully printed via R2R printing method, they cannot integrate with flexible active components yet through the R2R inline printing system so far. The major reason in difficulty of inline integration of R2R printed passive components with the flexible active components was mainly originated from the incompatibility between printing and vacuum deposition techniques, employed in manufacturing those flexible active components. Although a printing process was incorporated with the vacuum deposition methods in fabricating those flexible active components, it was limited to fabricating only the semiconducting layers, [12] and lacked the scalability required for practical mass production. Thus, those hybrid vacuum deposition and printing processes cannot be incorporated into the R2R printing foundry. To establish the R2R printing foundry concept, the design rule that encompasses physical dimensions and electrical parameters of the fully printed devices should be first established. The design rule in a semiconductor fabrication plant-referred to as the foundry-is a compromised rule between circuit design engineers and process engineers to provide the geometry of an integrated circuit layout with an acceptable cost. However, unlike the Si-chip foundry, the printed devices' physical dimensions and electrical parameters are variable to the rheological parameters of the electronic inks, the web tension, printing speed, and overlay printing registration accuracy (OPRA) of employed R2R printer. Therefore, the design rule of the R2R printing foundry (Figure 1a) should be always comprising characteristics of both employed ink and R2R printer to prove that the R2R printed complementary metal-oxide-semiconductor (CMOS)-based active
spanning almost the entire range of commercial products in industry, agriculture, and medicine. That is why the development of roll-to-roll (R2R) printed passive RFID tags is extremely attractive, due to perceived cost reduction achievableindeed, this has been the driving force for the realization of the penny RFID tag for the ID and the authentication without incorporating any encryption engine. SuchThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/admt.201900935.Printed electronics has been received a great deal of attention in the last two decades with a primary focus being on the use of organic semiconductors for the inexpensive and flexible electronic devices. [1][2][3][4][5][6][7][8] Applications such as flexible displays and passive radio frequency identification (RFID) tags have been widely touted in this regard. In particular, the roll-to-roll (R2R) printed passive 13.56 MHz RFID tag has a very competitive advantage for ID and authentication to prevent counterfeits over the traditional Si-chip based one because the low cost is always the first priority to be considered to authenticate genuine products
Organic semiconductor-based thin-film transistors’ (TFTs) charge-carrier mobility has been enhanced up to 25 cm 2 /V s through the improvement of fabrication methods and greater understanding of the microstructure charge-transport mechanism. To expand the practical feasibility of organic semiconductor-based TFTs, their electrical properties should be easily accessed from the fully printed devices through a scalable printing method, such as a roll-to-roll (R2R) gravure. In this study, four commercially available organic semiconductors were separately formulated into gravure inks. They were then employed in the R2R gravure system (silver ink for printing gate and drain–source electrodes and BaTiO 3 ink for printing dielectric layers) for printing 20 × 20 TFT-active matrix with the resolution of 10 pixels per inch on poly(ethylene terephthalate) (PET) foils to attain electrical properties of organic semiconductors a practical printing method. Electrical characteristics (mobility, on–off current ratio, threshold voltage, and transconductance) of the R2R gravure-printed 20 × 20 TFT-active matrices fabricated with organic semiconducting ink were analyzed statistically, and the results showed more than 98% device yield and 50 % electrical variations in the R2R gravure TFT-active matrices along the PET web.
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