Magazine article Science News

Spot On: Printing Flexible Electronics One Nanodot at a Time

Magazine article Science News

Spot On: Printing Flexible Electronics One Nanodot at a Time

Article excerpt

Plastic displays, solar cells, and other kinds of gadgets are attractive for their flexibility and potential low cost. But they rely on materials--polymers, nanoparticles, and carbon nanotubes--that are incompatible with manufacturing processes designed for silicon-based devices. Now, researchers have developed a printing process that could make possible mass production of plastic electronic devices.

Many companies are experimenting with ink-jet systems to create flexible printed electronics, usually by adapting standard ink-jet printers to dispense fluids with useful electronic properties. But such systems generally can only print features down to 20 microns in diameter--too large for many applications.

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John Rogers of the University of Illinois at Urbana-Champaign and his colleagues have devised an alternative strategy called electrohydrodynamic, or e-jet, printing. In contrast to conventional ink-jet printing, which relies on either heat or vibration to push ink droplets out of a nozzle, e-jet printing uses electric fields to pull droplets from the nozzle's tip.

The system consists of a glass nozzle coated with a thin, conducting layer of gold. The coating extends to the tip of the nozzle, where it makes contact with the emerging ink.

The researchers bring the nozzle close to a surface on which they wish to print a pattern, in this case a silicon wafer sitting on a conducting plate. Applying a voltage between the nozzle and the plate produces an intense electric field at the nozzle's tip. As the field draws the ink out of the nozzle, a cone-shaped meniscus forms at the tip and pinches off droplets of fluid.

"Those droplets then travel like bullets down to the substrate," says Rogers. …

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