Sunday, September 12, 2010

Be Flexible

Engineers have published in Nature Materials about artifical electronic skins that may help robots and/or prosthetic limbs to feel. These skins can detect the gentlest of touches by sensing pressure changes. How gentle? You may ask. Less than a kilopascal, about the pressure you use when typing for picking up a pen.

There is actually more than one paper published on this topic this week. The papers describe similar devices that work in different ways. One of the devices uses six square centimeters of an elastic polymer called ppolydimethylsiloxane (PDMS) that has pyramid-shaped chunks cut out of it at regular intervals. When the material is compressed the chunks, which were previously filled with air, become filled with PDMS and change the material's ability to hold an electric charge. Put this little square onto an organic transistor (reads differences as a change in current) and you can track pressure changes across the material. This little device can detect pressure changes as light as a fly or butterfly landing on it.

The other skin uses semiconductor nanowires pulled into the shape of a 7-centimeter-square grid using a method called contact printing. They then put this grid on a flexible pressure-sensitive rubber. The nanowires operate using low voltages while the rubber changes its electrical resistance under pressure. Because of the rubber this device is much bendier than the first one, allowing it to shape around various objects.

You look at these together and you see that they each have their pluses. The first detects very very small pressure differences while the second is very flexible. Obviously there is much more research to be done to get these skins working like actual skin. But it is definately a step, or a touch, closer.

Read the papers for more:
Mannsfeld, Stefan C. B., et al. (2010) Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers. Nature Materials: published online. (DOI: 10.1038/nmat2834)

Takei, Kuniharu. (2010) Nanowire active-matrix circuitry for low-voltage macroscale artificial skin. Nature Materials: published online. (DOI: 10.1038/nmat2835)

Boland, John J. (2010) Flexible electronics: Within touch of artificial skin. Nature Materials: published online. (DOI: 10.1038/nmat2861)

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(image credit Linda Cicero, Stanford University News Report)
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