Golden waves make stretchy microcircuits

More and more, sensors and other electronic gadgets are riddling the world—even our clothing and bodies. People developing this technology find themselves in need of circuitry that can conform to the changeable shapes of fabrics, tissues, and other soft materials (SN: 8/31/02, p. 133: Available to subscribers at Electronics in the Round: Mixing plastic and silicon yields form-fitting circuitry).

HELPFUL HUMPS. Sinuous gold microwires (above) flatten and lengthen when tugged (below). Scale bars represent 100 micrometers. Gray, et al./Advanced Materials

Gray, et al./Advanced Materials

Now, Darren S. Gray of Johns Hopkins University in Baltimore and his colleagues have embedded into a plastic film fine, flat wires that can stretch and contract much like telephone cords do. When pulled, the wires increase in length by more than 50 percent with no loss of conductivity. The researchers created the elastic wires by sandwiching wiggly, two-dimensional micropatterns of gold between layers of a rubbery polymer. Gray likens the process to “microfabricating a spring.”

In previous work, other researchers made stretchy microwires using conductive elastic polymers or by wrinkling conductive strips that then could unfold. However, those wires didn’t stretch as far as the new ones do, while still maintaining full conductivity.

The stretchy conductors described in the March 5 Advanced Materials may lead to implantable biomedical devices, including artificial nerves that can elongate as muscles extend, Gray says. The wires may also prove useful in circuitry incorporated into textiles, such as a shirt that monitors its wearer’s vital signs, and in electronic systems such as instruments launched into space, which must remain reliable despite much vibration.

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