COMMUNICATION Adv. Mater. 2012, 24, 3065-3069 using an Agilent 4156C semiconductor parameter analyzer. A standard f T measurement setup was used with a high impedance active probe, Picoprobe Model 18C with 20 fF input capacitance by GGB Industries Inc. to minimize coupling.

Printed electronics promises the realization of low-cost electronic systems on flexible substrates over large areas. In order to achieve this, high quality patterns need to be printed at high speeds. Gravure printing is a particularly promising technique that is both scalable and offers micron-scale resolution. Here, we review the tremendous progress that has recently been made to push gravure printing beyond its traditional limitations in the graphic arts. Rolls with far greater precision than traditional rolls and with sub-5 μm resolution can be fabricated utilizing techniques leveraging the precision of silicon microfabrication. Physical understanding of the sub-processes that constitute the gravure process is required to fully utilize the potential of gravure. We review the state-of-the-art of this understanding both for single cells and patterns of multiple cells to print high-resolution features as well as highlyuniform layers. Finally, we review recent progress on gravure printed transistors as an important technology driver. Fully high-speed printed transistors with sub-5 μm channel length and sub-5 V operation can be printed with gravure.

Pattern printing techniques have advanced rapidly in the past decade, driven by their potential applications in printed electronics. Several printing techniques have realized printed features of 10 μm or smaller, but unfortunately, they suffer from disadvantages that prevent their deployment in real applications; in particular, process throughput is a significant concern. Direct gravure printing is promising in this regard. Gravure printing delivers high throughput and has a proven history of being manufacturing worthy. Unfortunately, it suffers from scalability challenges because of limitations in roll manufacturing and limited understanding of the relevant printing mechanisms. Gravure printing involves interactions between the ink, the patterned cylinder master, the doctor blade that wipes excess ink, and the substrate to which the pattern is transferred. As gravure-printed features are scaled, the associated complexities are increased, and a detailed study of the various processes involved is lacking. In this work, we report on various gravure-related fluidic mechanisms using a novel highly scaled inverse direct gravure printer. The printer allows the overall pattern formation process to be studied in detail by separating the entire printing process into three sequential steps: filling, wiping, and transferring. We found that pattern formation by highly scaled gravure printing is governed by the wettability of the ink to the printing plate, doctor blade, and substrate. These individual functions are linked by the apparent capillary number (Ca); the printed volume fraction (φ(p)) of a feature can be constructed by incorporating these basis functions. By relating Ca and φ(p), an optimized operating point can be specified, and the associated limiting phenomena can be identified. We used this relationship to find the optimized ink viscosity and printing speed to achieve printed polymer lines and line spacings as small as 2 μm at printing speeds as high as ∼1 m/s.

This work employs novel SnO(2) gel-like precursors in conjunction with sol-gel deposited ZrO(2) gate dielectrics to realize high-performance transparent transistors. Representative devices show excellent performance and transparency, and deliver mobility of 103 cm(2) V(-1) s(-1) in saturation at operation voltages as low as 2 V, a sub-threshold swing of only 0.3 V/decade, and /(on) //(off) of 10(4) ~10(5) .