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Running hamsters, tapping fingers tapped for energy

Feb. 17, 2009
Courtesy Georgia Tech
and World Science staff

Could ham­sters solve the world’s en­er­gy cri­sis? Probably not, but a ham­ster wear­ing a pow­er-generating jack­et may be do­ing its own small part to pro­vide a new and re­new­able source of elec­tricity.

Geor­gia In­sti­tute of Tech­nol­o­gy re­search­ers re­port that they have gen­er­at­ed elec­trical cur­rent from the ham­ster’s move­ments as well as from a tap­ping fin­ger. Both se­tups rely on nan­otech­nol­ogy, or molecular-scale ma­chin­ery, to gen­er­ate ti­ny amounts of cur­rent.

A ham­ster wear­ing a jack­et at­tached to nano­gen­er­a­tor that pro­duces elec­tric­i­ty as the an­i­mal runs and scratch­es. (Cour­te­sy Zhong Lin Wang)

Al­though thou­sands of these sin­gle-wire gen­er­a­tors would have to be com­bined to pow­er even one hand­held elec­tron­ic de­vice, the de­vel­op­ers say their work moves users of Black­Ber­ries, cell phones and oth­er gad­gets clos­er to pow­ering them with their own typ­ing.

“We have dem­on­strat­ed ways to con­vert even ir­reg­u­lar” an­i­mal move­ments into elec­tricity, said Zhong Lin Wang, of Geor­gia Tech’s School of Ma­te­ri­als Sci­ence and En­gi­neer­ing. “This tech­nol­o­gy can con­vert any me­chan­i­cal dis­turb­ance in­to elec­trical en­er­gy.” The find­ings were re­ported Feb. 11 on­line in the re­search jour­nal Nano Let­ters.

Scav­eng­ing en­er­gy from ir­reg­u­lar mo­tion is im­por­tant be­cause much en­er­gy from ani­mals is var­i­a­ble, un­like the reg­u­lar me­chan­i­cal mo­tion used to gen­er­ate most large-scale elec­tricity, Wang said.

The minuscule devices Wang and colleagues designed rely on the piezoe­lec­tric ef­fect, a phe­nom­e­non in which cer­tain ma­te­ri­als pro­duce elec­trical charges when they are bent and then re­laxed.

To make their gen­er­a­tors, Wang’s re­search team en­cap­su­lat­ed sin­gle zinc ox­ide wires no more than eight hundred-millionths of a mil­li­me­ter wide and half a mil­li­me­ter long in a flex­i­ble ma­te­ri­al. The wires were an­chored at each end with an elec­trical con­tact, and a de­vice to con­trol cur­rent flow placed at one end. 

The de­vel­op­ers at­tached one of these sin­gle-wire gen­er­a­tors to the joint ar­ea of an in­dex fin­ger, or com­bined four of the sin­gle-wire de­vices on a small jack­et worn by the ham­ster. The ro­den­t’s run­ning and scratch­ing – and the fin­ger-tap­ping – flexed the ma­te­ri­al around the wires, pro­duc­ing al­ter­nat­ing elec­trical cur­rent, the group re­ported.

At the sug­ges­tion of Wang’s daugh­ter, the re­search­ers found that ham­sters are more ac­tive af­ter 11 p.m. They had to ex­pe­ri­ment with a jack­et tight enough to stay on and wrin­kle the flex­ible ma­ter­ial – but not so tight as to hamp­er move­ment. “This study shows that we really can har­ness hu­man or an­i­mal mo­tion to gen­er­ate cur­rent,” Wang said.

* * *

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Could hamsters solve the world’s energy crisis? Probably not, but a hamster wearing a power-generating jacket may be doing its own small part to provide a new and renewable source of electricity. Georgia Institute of Technology researchers report that they have generated electrical current from the hamster’s movements as well as from a tapping finger. Both setups rely on nanotechnology, or molecular-scale machinery, to generate tiny amounts of current. Although thousands of these single-wire generators would have to be combined to power even one handheld electronic device, the developers say their work moves users of BlackBerries, cell phones and other gadgets closer to powering them with their own typing. “We have demonstrated ways to convert even irregular biomechanical energy into electricity,” said Zhong Lin Wang, of Georgia Tech’s School of Materials Science and Engineering. “This technology can convert any mechanical disturbance into electrical energy.” The findings were reported Feb. 11 online in the research journal Nano Letters. Scavenging energy from irregular motion is important because much biomechanical energy is variable, unlike the regular mechanical motion used to generate most large-scale electricity today, Wang said. The nanogenerator power is produced by the piezoelectric effect, a phenomenon in which certain materials produce electrical charges when they are bent and then relaxed. The wires are no more than eight hundred-millionths of a millimeter wide, and half a millimeter long. To make their generators, Wang’s research team encapsulated single zinc oxide wires in a flexible material. The wires were anchored at each end with an electrical contact, and a device to control current flow placed at one end. The developers attached one of these single-wire generators to the joint area of an index finger, or combined four of the single-wire devices on a small jacket worn by the hamster. The rodent’s running and scratching – and the finger-tapping – flexed the material encapsulating the tiny wires, producing alternating electrical current, the group reported. At the suggestion of Wang’s daughter, the researchers found that hamsters are more active creatures – but only after 11 p.m. They had to experiment with a jacket configuration that was tight enough to stay on and to wrinkle the nanogenerator substrate – but not so tight as to make the hamster uncomfortable. “This study shows that we really can harness human or animal motion to generate current,” Wang said.