Bendy silicon

 

Wearable systems have stretched to new lengths.

Researchers have extended the possibilities that stretchable silicon can bring to personal health monitoring, therapeutics and even aircraft wing and fuselage design.

In 2005, University of Illinois material scientists and engineers reported on the development of a one-dimensional, stretchable form of single-crystal silicon with micron-sized, wave-like geometries. However, that configuration only allowed for stretching in one direction without altering the electrical properties.

Now the team in collaboration with the Institute of High Performance Computing in Singapore, have reported that they have brought the same concept into two dimensions at a much more sophisticated level.

“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 John Rogers, a Founder Professor of Materials Science and Engineering at the University of Illinois.

Optimised mechanical designs

“The wavy concept now incorporates optimised 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.”

Achieving high degrees of mechanical flexibility, or foldability, is important to sustaining the wavy shapes, Rogers said. “The more robust the circuits are under bending, the more easily they will adopt the wavy shapes which, in turn, allow overall system stretchability. For this purpose, we use ultrathin circuit sheets designed to locate the most fragile materials in a neutral plane that minimises their exposure to mechanical strains during bending.”

Fully stretchable silicon circuits could wrap around complex shapes such as spheres, body parts and aircraft wings without a reduction in electrical performance.

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