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July 05, 2007

Towards printing press electronics

One goal for the future of electronics is the ability to print large, flexible circuits using machines similar to printing presses. While great strides have been made in developing bendable and lightweight organic materials to use in this type of circuitry, methods to deposit those materials over large areas have not been as successful. Recently, a research group developed a circuit-printing technique that addresses some of the problems that have plagued other attempts.

One such problem, perhaps the biggest, is the inability of the other methods to produce high-resolution features – those down to the micron, or millionth-of-a-meter, scale.

Another issue is the rather low conductivity of the polymer materials used as electrodes in the circuits, which suggests a need for inorganic (metallic) electric contacts. An additional problem is the slight mixing of ink that occurs when ink is layered, which occurs during most types of printing. In conventional graphic-arts printing the end product isn't affected, but, in the case of “electronic inks,” mixing would compromise the electrical characteristics of the circuit.

“We envision that a new generation of high-resolution printing plates in combination with nano-based inks will provide the platform for manufacturing electronic devices very similarly to what you see in commercial printing houses today,” corresponding author Graciela Blanchet of DuPont told PhysOrg.com.

The researchers inked the plate with a solution of silver nanoparticles, which, after the solvent evaporated, left it coated with a dry film of silver (thereby avoiding any mixing issues). The group next pressed the plate onto a Mylar substrate, transferring the nanoparticles from the raised portions of the plate onto the Mylar without degrading the pattern's high-resolution features. At this point, the printed silver pattern can be sintered (a process in which heat is used to increase the conductivity of the film).

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