Communications of the ACM
All the Electronics That's Fit to Print
A shift register circuit built on an inkjet printer.
Credit: T. Ng / PARC
New technology that allows the printing of electronic devices has been used by researchers at Palo Alto Research Center to build a portable X-ray imager and small mechanical devices.
"It's a demonstration of how far this technology can go," says Tina Ng of the Palo Alto Research Center, a Xerox company. Ng describes these devices in "Organic Sensors and Actuators Patterned by Inkjet Printing," to be presented at the AVS 61st International Symposium & Exhibition in Baltimore, Md.
Making electronics on conventional silicon wafers can be costly and time consuming. Traditional photolithography methods are complex. They involve first depositing layers of material, placing a stencil-like mask on it, and then shining ultraviolet light to etch away the exposed material. This process is repeated to create the patterns needed to form electronic circuits and devices.
But in the last ten years, researchers have been developing ways to deposit patterns of metals, semiconductors, and other material directly, just like how a printer deposits patterns of ink. The materials are dissolved in a liquid solution, which can then be printed on a variety of substrates, such as plastic, paper, and even fabric. When the "ink" dries, the material remains.
As a demonstration of this technology, Ng and her colleagues built a digital X-ray sensor. Using printing techniques, the researchers fabricated flexible X-ray imager arrays on plastic films that are much more portable than the behemoths at a dentist's office. Such a device could be used by doctors in the field, serve as small security scanners, or even help soldiers in the field identify bombs.
The researchers are also working on printing an actuator, a simple mechanical device. Unlike typical silicon actuators, the printable actuator is based on solution-processed organic materials and behaves like "artificial muscles." While they haven't developed specific applications for such an actuator, Ng says, it could be used in conjunction with photo imagers to make adaptive optical parts that tune focal distance, or to make moving mirrors that redirect light beams.
This printing technique won't work for producing the high-end silicon chips in computers and phones, Ng says. Instead, "we're going for more high-volume, simple but useful systems." In the future, for example, users might be able to print sensors onto clothing or some other device attached to the skin to monitor vital signs — and alert a doctor in case of emergency. Some researchers have also been printing devices to make flexible solar cells; imagine wearing a jacket that doubles as a solar panel. Another possibility, Ng says, is to print flexible antennae for wireless communication.
The authors of "Organic Sensors and Actuators Patterned by Inkjet Printing," — Ng, J. Kim, W.S. Kim, and K.S. Kwon — are affiliated with Palo Alto Research Center in California; Simon Fraser University in Canada; and Soonchunhyang University in South Korea.
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