Charged Paper Moves on Its Own

By | June 26, 2006

Charged Paper Moves on Its Own

Gold-coated cellophane that bends when charged could work as the tiny wing-flexing muscles in paper surveillance planes, insect robots or even serve as smart wallpaper that emits sound like a speaker.The electroactive paper, being developed by Jaehwan Kim of Inha?University in South Korea, contains the same cellulose fibers found in paper, making the material an ultra-lightweight, inexpensive and biodegradable option that has been largely overlooked.

“It has been estimated that the yearly biomass production of cellulose is 1.5 trillion tons, making it an inexhaustible source of raw material for environmentally friendly and biocompatible products,” said Kim. …

In the past, other researchers had discovered an unusual characteristic of cellulose: that it produces a charge when put under pressure.

But the so-called piezoelectric charge was too small to produce the force necessary to bend paper, that its potential as a sensor or an actuator was not explored.

Kim and his team found that they could enhance the piezoelectric property by capitalizing on positively charged particles, called ions, already present in cellulose-based paper such as cellophane.

To make the paper muscle, they coated each side of a 40 millimeter length of cellophane in a layer of gold thinner than the transparent cellophane.

When they applied a voltage, the gold coating on one side of the paper became positively charged, while the other side became negatively charged.

The positively charged ions, which are bond to water molecules, became attracted to the negative side of the paper. As they migrated over, they pulled the water molecules with them, creating a strain on one side of the paper that made it bend.

The combination of ion movement and the piezoelectric effect helped the paper to bend faster even when a low voltage was applied.

The cellophane bent 10 millimeters in one direction with a force enough to lift about 1 gram.

The muscle power from a piece of paper, however great, may not be enough to prove useful in a range of devices, though, said professor Paul Calvert, an expert in biomimetic materials at the University of Massachusetts, Dartmouth. – discovery

Advertisements on corporate sites like discovery are so annoying! Bunch of clueless jerks. If I want to *buy* something, I’ll go looking for it. Stay out my FACE when I’m not shopping. When I was trying to read this article, for example, an ad actually flew in and blocked the content so I had to click close to read the story. That should be mandatory jail time for the idiot who created it. Anyway, this paper is pretty cool. Heheh.

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