Researchers in the United States and Singapore have developed a fully functioning silicon integrated circuit that can be bent, stretched and folded.

Traditional circuits are made on thin, rigid silicon wafers, but building on the concept of accordion bellows, the researchers in Illinois and Singapore have transformed the technology into a stretchable form, opening the possibility of applications in medical monitoring.

Mechanically stretchable, wavy silicon integrated circuit embedded in transparent rubber, in a highly twisted configuration.
(Science)

"We've been able to show that silicon, which is intrinsically a brittle, fragile material, can be formed in such a way that allows integration into circuits that are fully stretchable, bendable, foldable and twistable," co-author John Rogers, a professor of materials science and engineering at the University of Illinois, told CBC News in an e-mail.

In 2005, Rogers and colleagues developed the first step to these new circuits, creating a one-way stretchable circuit using narrow strips of silicon.

Now, Rogers and colleagues at the University of Illinois, Northwestern University in Chicago and the Institute of High Performance Computing in Singapore report that they've pushed the concept into full-scale stretching in fully functional circuits.

To do so, the researchers made the silicon and the circuits as small as possible — roughly one-50th of the diameter of a human hair. They also had to design the materials in such a way that the silicon would experience minimal strain when the circuit is bent.

Then researchers bonded the ultrathin circuit sheet to a slab of prestretched rubber. With their design, when the rubber snaps back to its original size and shape it causes the circuit to form wavy patterns of relief.

"In this wavy state, the entire system can be stretched reversible and in any direction, with a physics that is similar to the motion of an accordion bellows," said Rogers. "The strain in the silicon and other critical and fragile components of the circuits remain small even during these extreme deformation."

The electrical performance "achieved in these stretchy systems is comparable to that of similar devices formed on conventional, rigid silicon wafers," Rogers said.

Applications in health monitoring

Rogers said he believes the findings "open up entirely new design opportunities, and associated applications, for silicon electronics."

He said the researchers are focusing first on biomedical devices, such as wearable health monitors, where "integration of electronics with the human body can have health benefits."

As an example, he said the researchers are collaborating with a professor at the University of Pennsylvania to produce stretchable electronic sheets that are suitable for wrapping the brains of people who suffer from epilepsy.

"Monitoring the electrical activity of the brain in this fashion might be able to predict the onset of seizures, and even prevent them entirely," he said. Another possibility could be the integration of electronics with surgical gloves, to provide sensing and other functions that could benefit surgeons.

The study was published Wednesday on the Science Express website of the journal Science.

With files from Jennifer Wilson