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Electronics Get a New Vanishing Act

09/28/2012
Ashley Yeager

Engineers have designed electronics that degrade in their environment, including the body.


New electronics are disappearing faster than ever—and not because they are being stolen. The cameras and biosensors are designed to disintegrate on command. The technology, which is described in the September 28 issue of Science (1), could be useful in biomedical implants to help treat surgical infections or stimulate bone growth.

A resorbable electronic circuit begins to dissolve. Credit: Fiorenzo Omenetto, Tufts.





"Our ability to use silicon is unique, and very important for future development work because it aligns this technology with existing commercial integrated circuits," said John Rogers, an engineer at University of Illinois at Urbana-Champaign and leader of the study.

Since the electronics industry started, engineers have built devices from silicon and designed them to perform consistently over time and last forever. For the past few years, Rogers and his collaborators have been making tiny, yet high-performance electronics out of ultrathin sheets of silicon. Now, however, the group has flipped the most important design goal for the electronics industry—durability—on its head.

"To our knowledge, nobody has ever demonstrated a fully transient form of electronics before," said Rogers.

In the study, the team, which included researchers from Tufts and Northwestern, made the silicon components from silicic acid and the magnesium electrodes from magnesium hydroxide and then wrapped the entire electronic system in cocoon silk. The structure of the silk determines how fast the device begins to dissolve, and scientists can control the rate of degradation, making the product last minutes, days, weeks, or years.

To test the techniques, the researchers designed an implantable device to monitor and prevent bacterial infection at surgical incisions and tested the biomedical device in rats. The team programmed the parts of the monitor to absorb or degrade after a certain amount of exposure to biofluids and then made incisions in the animals and placed the electronic system nearby. After three weeks, the incision sites showed only a small amount of residue from the implant and fewer signs of infection at the wound site.

The next step in the project is to further develop the devices so that it not only responds to heat, electrical potential, and drug release, but that it also can do sensing.

But the electronics' vanishing act isn’t necessarily limited to medical applications. From the same materials, the team created a 64-pixel digital camera and demonstrated it worked with 58 fully functioning pixels. The experiment suggests that consumer electronics, and their waste could become a major part of transient electronics research.

"Consumer electronics are more challenging, in a technical sense, than the kind of implantable devices and environmental monitors that we are currently pursuing," said Rogers, "but we’re optimistic that transient versions of consumer electronics will be possible, at least for certain parts and sub-components."

Reference

1. Hwang, S. et al. 2012. A Physically Transient Form of Silicon Electronics. Science 337: 1640-1644.

Keywords:  biosensors