Foldable and stretchable, silicon circuits conform to many shapes

CHAMPAIGN, Ill. — Scientists have developed a new form of stretchable silicon integrated circuit that can wrap around complex shapes such as spheres, body parts and aircraft wings, and can operate during stretching, compressing, folding and other types of extreme mechanical deformations, without a reduction in electrical performance.

“The notion that silicon cannot be used in such applications because it is intrinsically brittle and rigid has been tossed out the window,” said John Rogers, a Founder Professor of Materials Science and Engineering at the University of Illinois.

“Through carefully optimized mechanical layouts and structural configurations, we can use silicon in integrated circuits that are fully foldable and stretchable,” said Rogers, who is a corresponding author of a paper accepted for publication in the journal Science, and posted on its Science Express Web site.

The new designs and fabrication strategies could produce wearable systems for personal health monitoring and therapeutics, or systems that wrap around mechanical parts such as aircraft wings and fuselages to monitor structural properties.

In December 2005, Rogers and his U. of I. research group reported the development of a one-dimensional, stretchable form of single-crystal silicon with micron-sized, wave-like geometries. That configuration allows reversible stretching in one direction without significantly altering the electrical properties, but only at the level of individual material elements and devices.

Now, Rogers and collaborators at the U. of I., Northwestern University, and the Institute of High Performance Computing in Singapore report an extension of this basic wavy concept to two dimensions, and at a much more sophisticated level to yield fully functional integrated circuit systems.

“We’ve gone way beyond just isolated material elements and individual devices to complete, fully integrated circuits in a manner that is applicable to systems with nearly arbitrary levels of complexity,” said Rogers, who also is a researcher at the Beckman Institute and at the university’s Frederick Seitz Materials Research Laboratory.

“The wavy concept now incorporates optimized mechanical designs and diverse sets of materials, all integrated together in systems that involve spatially varying thicknesses and material types,” Rogers said. “The overall buckling process yields wavy shapes that vary from place to place on the integrated circuit, in a complex but theoretically predictable fashion.”