Researchers from the Johns Hopkins University have built electronic circuits which exhibit a rubbery behavior. The flexible circuits, built by using gold springs, can stretch like rubber. And Nature says that these stretchy wires can be used to create artificial nerves bending inside our bodies, wearable electronics or rubbery electrodes to monitor heart beatings.
Vigorous twisting and stretching destroys traditional electronics made from metals or silicon. And earlier versions of bendy electronics tended to break down if they were deformed too much.
Christopher Chen at Johns Hopkins University, Baltimore, and his co-workers built rubbery circuits out of several squashed but extendable gold wires. These are 20 times thinner than a human hair and wrapped in a springy polymer. The wires can be stretched by over half their initial length without loss of electrical conductivity.
Here is an image showing how these curved wires can stretch (Credit: Darren Gray, Chen Lab, Johns Hopkins University).
You can find a larger version on his website (1,056 x 1,056 pixels, 533 KB).
Now, how did they create these flexible wires starting from gold springs?
Instead of fashioning the gold wires into helical springs, however, they gave them a flat, oscillating shape, like a meandering river, since this is easier to make. They manufactured them by electroplating gold onto a sheet of silver, surrounding the wires with polymer and then stripping the silver away.
The researchers refined the wires to avoid buckling and breaking at the peaks of the bend. Thin wires break less easily than fat ones, they found, so the electrical current is carried in several parallel thin wires rather than one wide one. And small wiggles work better than broad ones.
The researchers think that many applications will use these wires.
Wiring like this could be woven into stretchy sports clothing and used to connect up sensors that monitor athletic performance. Rubbery electrodes made from biocompatible materials might be attached to a beating heart and used to sense impending problems.
Flexible electronics might also make rubbery needles, suggests Chen. These could be safer and more reliable than the needles currently used in the brains of Parkinson's disease patients, whose tremors are soothed by electrical stimulation.
The research work has been published by Advanced Materials (No. 5, 2004), under the title "High-Conductivity Elastomeric Electronics." If you are a registered user, the full text is available from this page.
Source: Philip Ball, Nature, March 15, 2004
12:41:03 PM
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