May 14, 2012
Portable, Virus-Powered Recharging Source On The Horizon?
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Researchers from the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) report that they have found a way to convert mechanical energy into electricity using viruses.
"The scientists tested their approach by creating a generator that produces enough current to operate a small liquid-crystal display," officials from the Berkeley Lab reported in their media advisory. "It works by tapping a finger on a postage stamp-sized electrode coated with specially engineered viruses. The viruses convert the force of the tap into an electric charge."
This generator is believed to be the first capable of producing electricity by capturing the accumulated charge in solid, biological material, which occurs as a response to mechanical stress. This is known as piezoelectricity, and the researchers believe that it could lead to units that could charge electrical devices simply through daily living tasks, such as going up stairs or entering and exiting through a doorway.
"It also points to a simpler way to make microelectronic devices. That's because the viruses arrange themselves into an orderly film that enables the generator to work. Self-assembly is a much sought after goal in the finicky world of nanotechnology," they added.
"More research is needed, but our work is a promising first step toward the development of personal power generators, actuators for use in nano-devices, and other devices based on viral electronics," University of California-Berkeley Associate Bioengineering Professor Seung-Wuk Lee said in a statement.
According to the Berkeley Lab, the so-called piezoelectric effect was discovered in 1880 and has been used in devices such as electric cigarette lighters and scanning probe microscopes, among others. However, the materials needed to develop such devices are toxic and difficult to work with, limiting their uses -- a problem that Lee and colleagues hope that their work will help solve.
Their solution involves a virus known as the M13 bacteriophage, which is harmless to people and replicates itself rapidly, producing millions of particles in mere hours. It is also easy to genetically engineer, they say, and the naturally orient themselves, making them an ideal nano-building block. However, they first had to ensure that M13 virus was piezoelectric in nature.
Lee's team "applied an electrical field to a film of M13 viruses and watched what happened using a special microscope. Helical proteins that coat the viruses twisted and turned in response -- a sure sign of the piezoelectric effect at work“¦ Next, the scientists increased the virus's piezoelectric strength. They used genetic engineering to add four negatively charged amino acid residues to one end of the helical proteins that coat the virus."
"These residues increase the charge difference between the proteins' positive and negative ends, which boosts the voltage of the virus," they added. "The scientists further enhanced the system by stacking films composed of single layers of the virus on top of each other. They found that a stack about 20 layers thick exhibited the strongest piezoelectric effect."
They then conducted a demonstration test, creating a virus-based piezoelectric energy generator and simulating conditions that allowed them to spontaneously form a multilayered film approximately one square centimeter.
It was then placed between a pair of gold-plated electrodes, which were then, in turn, connected via wires to an LCD display. When pressure was applied to the generator, it produced up to six nanoamperes of current and 400 millivolts of potential -- enough power to flash a number on the screen, and approximately one-fourth of the voltage of a triple A battery, according to the Berkeley researchers.
A paper detailing their research was published online Sunday in the journal Nature Nanotechnology.