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New technology focuses on low-cost, implantable sensors

Posted: 13 Jun 2013 ?? ?Print Version ?Bookmark and Share

Keywords:implantable sensor? organ transplant rejection. silicon?

A team of researchers at the Ohio State University has created a technology that paves the way for low-cost electronic devices that work in direct contact with living tissue inside the body. According to them, the first planned use of the technology is a sensor that can detect the very early stages of organ transplant rejection.

Paul Berger, professor of electrical and computer engineering and physics at Ohio State, explained that one barrier to the development of implantable sensors is that most existing electronics are based on silicon, and electrolytes in the body interfere with the electrical signals in silicon circuits. Other, more exotic semiconductors might work in the body, but they are more expensive and harder to manufacture.

"Silicon is relatively cheap... it's non-toxic," Berger said. "The challenge is to bridge the gap between the affordable, silicon-based electronics we already know how to build, and the electrochemical systems of the human body." Berger and his colleagues have also revealed a new, patent-pending coating that that they believe will bridge that gap.

In tests, silicon circuits that had been coated with the technology continued to function, even after 24 hours of immersion in a solution that mimicked typical body chemistry.

Silicon circuit coated with a protective layer and immersed in fluid

Silicon circuit coated with a protective layer and immersed in fluid that mimics human body chemistry. Source: Ohio State University.

The project began when Berger talked to researchers in Ohio State's department of biomedical engineering, who wanted to build an insertable sensor to detect the presence of proteins that mark the first signs of organ rejection in the body. They were struggling to make a working protein sensor from gallium nitride.

"We already have sensors that would do a great job at detecting these proteins, but they're made out of silicon. So I wondered if we could come up with a coating that would protect silicon and allow it to function while it directly touched blood, bodily fluids or living tissue," Berger said.

In the body, electrolytes such as sodium and potassium control nerves and muscles and maintain hydration. They do this by carrying a positive or negative electric charge that spurs important chemical reactions. But those same charges make the electrolytes attractive to silicon, which will readily absorb them. Once inside, the charges alter the electronic behaviour of the silicon so that the readings of a sensor can't be trusted.

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