Engineers at Princeton University have developed a new way to manufacture electronic devices made of plastic that is translucent, malleable and able to conduct electricity.
Engineers have developed a new way to manufacture electronic devices made of plastic that is translucent, malleable and able to conduct electricity. They hope to open the door to broader use of conductive plastics in a wide range of products.
“Conductive polymers have been around for a long time, but processing them to make something useful degrades their ability to conduct electricity,” claims Yueh-Lin Loo, an associate professor of chemical engineering at Princeton University. “We have figured out how to avoid this trade-off. We can shape the plastics into a useful form while maintaining high conductivity.”
According to Loo, organic electronics holds promise for producing “new types of electronic devices and new ways of manufacturing existing technologies. However, until recently, it has been hampered by the mysterious loss of conductivity associated with moldable plastics.
“People didn’t understand what was happening,” Loo points out. “We discovered that in making the polymers moldable, their structures are trapped in a rigid form, which prevented electrical current from traveling through them.”
Once they understood the underlying problem, Loo and her colleagues developed a way to relax the structure of the plastics by treating them with an acid after they were processed into the desired form.
Using the method, the Princeton engineers were able to make a plastic transistor. They produced the electrodes of the transistor by printing the plastic onto a surface, a fast and cheap method similar to the way an ink-jet printer produces a pattern on a piece of paper.
Loo believes the technique could be scaled up for mass production presses similar to those used to print magazines and newspapers. “You could distribute the plastics in cartridges the way printer ink is sold, and you wouldn’t need exotic machines to print the patterns,” she explains.
By using the technique, plastics could represent a low-cost alternative to indium tin oxide (ITO), an expensive conducting material that’s currently used in solar panels. Traditionally, the electricity generated by plastic solar cells is collected by a transparent metal conductor made of ITO. The conductor must be transparent so that sunlight can pass through it to the materials in solar cells that absorb the light energy.
However, the cost of ITO is skyrocketing, because it’s in big demand for use in flat-screen televisions, mobile phones and other electronic devices with display screens. “To bring down the cost of plastic solar cells, we need to find a replacement for ITO,” says Loo. “Our conducting plastics allow sunlight to pass through them, making them a viable alternative.”
Loo also claims that the plastic could replace expensive metals used in other electronic devices, such as flexible displays. Another potential application is biomedical sensors that would display a certain color if a person had an infection. For instance, the plastics turn from yellow to green when exposed to nitric oxide, a chemical compound produced during ear infections in children.
“If the devices could be produced at a low cost, they might be useful in developing countries that lack advanced medical facilities,” says Loo. “You wouldn’t need any fancy machines or lab equipment to diagnose an infection. All you would need is your eyes to see the color change in the plastics.”
New Manufacturing Process Could Boost Demand for Conductive Plastic
December 17, 2010