A paper-thin "viral" generator embedded in the sole of a shoe could charge a person's phone as they walk, scientists at the Lawrence Berkeley National Laboratory said.
The power would be generated by harmless viruses that convert mechanical energy into electricity by a phenomenon knows as piezoelectricity, which is the accumulation of a charge in a solid in response to mechanical stress.
The piezoelectric effect was discovered in 1880 and has been found in crystals, ceramics, bone, proteins and DNA.
Now scientists have made a thin film using a bacteriophage dubbed M13 that is benign to people but that has piezoelectric properties, the Berkeley lab reported.
This film was connected by wires to a liquid-crystal display, and when pressure was applied it produced up to six nanoamperes of current and 400 millivolts of potential -- about a quarter the voltage of a AAA battery -- enough current to flash the number "1" on the display.
"Because the tools of biotechnology enable large-scale production of genetically modified viruses, piezoelectric materials based on viruses could offer a simple route to novel microelectronics in the future," said Seung-Wuk Lee, a professor of bioengineering at the University of California, Berkeley.
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