Wearing the Wire


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A thin film of phase-change material sandwiched between indium tin oxide electrodes creates a display technology flexible enough to wear. Image: University of Oxford

Wearable electronics are all the rage: From the Google Glass and watches from Pebble or Apple to the footwarming Digitsole, companies have been trying to colonize our bodies head to foot with computers. But electronic clothing is hanging in no one’s closet. Why is there no Samsung Shirt or Microsoft Mitten?

The holdup is twofold: Advanced electronics aren’t flexible enough and they aren’t cheap enough. Prof. Harish Bhaskaran of the University of Oxford is working to solve that. “What we are trying to do is something a little bit crazy, if you will,” he said. “We want to use chip bag making technology to make advanced materials.”

By “chip bag,” Bhaskaran does not mean some kind of high-tech sheath for a microprocessor. He means the sharp, shiny, flexible, and cheap containers that hold crunchy junk food.

They owe their low cost and attractiveness to the state of roll-to-roll manufacturing—the same technology used for making newspapers. Roll-to-roll is already done at micrometer scales, sometimes with resolutions of 500 nanometers. “They do it at ridiculous speeds and at very low cost, so why can’t we do that for electronics?” Bhaskaran asked.

These lengths of yarn sport light-emitting diodes. Image: Nottingham Trent University

 

 

The United Kingdom’s Engineering and Physical Sciences Research Council has issued a grant of 3.1 million pounds (about $4.7 million) for him to do just that.

One of the challenges that his team must overcome is combining multiple printed layers. For instance, imagine a semiconductor or an insulator that has to be sandwiched between two conductors—all these must be aligned with exacting precision.
“We want them to be just a few nanometers thick,” Bhaskaran said. “So how do you ensure that these are controlled over large areas without any shorts?”

Then there’s the fact that different components are processed at different temperatures. How, for instance, do you integrate an organic sensor and an organic photovoltaic cell with an inorganic photo display? The silicon requires a higher temperature than the organic components can tolerate.

To attack some of these problems, Bhaskaran is working with several disparate labs, and is backed by seven industrial partners, including Sharp Labs, Oxford Instruments, and BASF.
Already, his lab has produced an ultra-thin, flexible display technology. The display uses a 7-nm thin film of the phase-change material germanium-antimony-tellurium sandwiched between electrode layers made of indium tin oxide. The whole thing can sit on a flexible Mylar sheet. The technology may find uses in roll-up display screens or even synthetic retinas.

Another project Bhaskaran is working on would be a wearable device that could warn children in war-torn countries of land mines. In addition to saving lives, such a first product would show the world that wearable electronics could finally be made on the cheap.

“I think everyone is frustrated at having had the technology demonstrated in a lab so long ago and not being able to manufacture it,” Bhaskaran said. “A lot of the physics behind these technologies are well known. There are lots of papers that you can read on wearable this and wearable that, flexible this and flexible that, but we haven’t seen them in real life,” he said. “Our vision is to demonstrate a viable manufacturing technology. Once we’ve done that we would disseminate our technology to everyone who’s been working in all wearable fields so they can go on and make everything they want to make.”

View the current and past issues of Mechanical Engineering.

I think everyone is frustrated at having had the technology demonstrated in a lab so long ago and not being able to manufacture it.

Prof. Harish Bhaskaran, University of Oxford

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May 2015

by Michael Abrams, ASME.org