In their search for eco-friendly energy sources, scientists have learned how to harness power from ever smaller living things: first corn, then algae, now bacteria. By figuring out how to generate electricity using the M13 bacteriophage, a virus that infects bacteria, engineers at the University of California, Berkeley, have gone smaller still. Although the virus-powered device produces only a tiny bit of energy, it may one day pave the way for cell phones that can be charged while you walk.
The device relies on a property known as piezoelectricity, which can translate mechanical energy, say, a finger tap, into electrical energy. Most cell-phone microphones are piezoelectric and convert the energy from sound waves into electrical output that is transmitted and translated back into sound waves in the recipient's phone. The problem with these piezoelectric devices, Berkeley bioengineer Seung-Wuk Lee says, is that they are made out of heavy metals such as lead and cadmium. Many biomolecules such as proteins and nucleic acids are also piezoelectric—they generate electricity when compressed—but lack the toxicity of traditional devices.
Lee and his colleagues found that the pencil-shaped M13 phage fits all their requirements. Because the virus infects only bacteria, it is safe for humans. And it is cheap and easy to create: scientists can get trillions of viruses from a single flask of infected bacteria. The shape of the virus is also important because M13 can easily self-assemble into thin sheets. To improve the electricity-generating power of M13, Lee's team tweaked the amino acid content of the virus's outer protein coat by adding four negatively charged glutamate molecules. The researchers stacked sheets of viruses on top of one another to amplify the piezoelectric effect.
When the scientists attached the one-square-centimeter virus film to a pair of gold electrodes and pressed firmly on one of those electrodes, the film produced enough electricity to light up a liquid-crystal display of the numeral 1. Although it generated only a small amount of power—400 millivolts, or about one quarter of the energy of a AAA battery—the study shows that biomaterial piezoelectrics are feasible, Lee says.
“This will bring a lot of excitement to the field,” says Zhong Lin Wang, an engineer at the Georgia Institute of Technology who was not involved in the study. “By utilizing the properties of these biomaterials, we can find unique applications in the future,” such as a pacemaker powered by the beating of one's heart.
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10 Comments
Add CommentInformative article but the sentence
Reply | Report Abuse | Link to this"Although it generated only a small amount of power—400 millivolts, or about one quarter of the energy of a AAA battery—the study shows that biomaterial piezoelectrics are feasible, Lee says." has problems.
millivolts is a unit of potential not power, nor is power the same thing as energy. Scientific American ought to do better.
Fascinating article, but lots of technical confusion when discussing power, energy, etc. "Although it generated only a small amount of power - 400 millivolts, or about one quarter of the energy of a (sic) AAA battery..." Volts (or millivolts)are not units of power. Electrical power is expressed in Watts = Volts x Amps. So if you want to inform on power, you needed to state the watts (or milliwatts). Further the comparison to an AAA Battery is technical gibberish. The energy of a battery is expressed in units of energy - watt-hours - the time integral of the power in watts. (I think the intention was to compare the 400 millivolts to the approx. 1500 millivolts of an AAA battery (or AA or B or C, they are all the same Voltage). That is a comparison of electrical potential - Volts - not power or energy. So, in summary, Volts are Potential, Volts x Amps = Watts is Power, and Watts x Time = Watt-Hours is Energy.
Reply | Report Abuse | Link to thisI think someone needs some remedial basic Physics.
You may think this is being picky. To me it is as informative as saying that Judy's age is 14 inches more than Bob's weight.
This is a field (energy, power, etc.) I understand. Can I trust the Scientific American articles on fields that I don't understand?
"Although it generated only a small amount of power—400 millivolts, or about one quarter of the energy of a AAA battery.." WHAT!! Volts as the unit of power (and energy). From other publications I have gathered that kilowatts per hour is the unit for power (and energy). That would explain my high electric bill, though. I can unplug everything, and my line voltage stays at 120 volts. Or maybe that should be 120 volts per hour.
Reply | Report Abuse | Link to thisBill,
Reply | Report Abuse | Link to thisYou are on the right track, but not quite...
Kilowatt-hours are the units of energy, not per hour. (Multiply the KW times the hours, not Divide), Kilowatts alone are the units of Power. Power and Energy are not the same thing. Energy is the time integral of Power. Your electrical meter is tracking how much you use the toaster, for example. The toaster draws about 2KW of power, and runs for about 3 minutes (2x3/60=0.1 KWH.) You pay for that at the rate of about 10c per KWH, or 1 cent to make toast. Hope that helps.
I was going to point out the incorrect units used in this article, but I see others have already done so. I must say that it is disconcerting to see such errors appear in a respected scientific journal. I'm a physicist, and noticed it right away, but in another science discipline such as biology I might be mislead by such errors. In the past, Scientific American had mostly articles written by the scientists actually working in the field, which was it's great advantage over other "popular" magazines. Now that the Sci Am staff writes much more of the content, it seems that the scientific quality has suffered. I hope that there can be better vetting of the scientific quality of staff-written articles.
Reply | Report Abuse | Link to thisThis carelessness regarding dimensions of power, energy, and electrical potential is so egregious in a respected scientific magazine that it deserves more than the five online remarks of chastisement it has so far garnered. So I'll add my voice to the fray. The problem may go deeper, however, than befuddled dimensionality. Considerations of both power and energy are far more likely to limit the suitable applications of the new device than is its voltage, so the inclusion of actual information on power and or energy capabilities, if available, would have been far more relevant than its output voltage. Better yet would be information on specific power and specific energy -- key figures of merit for battery technology.
Reply | Report Abuse | Link to this"Lee and his colleagues found that the pencil-shaped M13 phage fits all their requirements. Because the virus infects only bacteria, it is safe for humans."
Reply | Report Abuse | Link to thisI thought humans contained million or billions of bacteria?
Isn't it like saying guns don't kill people bullets do?
Aside from the obvious confusion between voltage, power and energy that throws serious doubt upon the legitimacy of this article. This article is so far fetched it is ridiculous. Let's see now, the virus infects bacteria, a living organism. The virus in turn will generate a voltage when placed under mechanical force. And somehow this mechanism can be used to power small devices like cell phones? Wait a minute; does this effect still work when the bacteria expire? If not, how will the bacteria be kept alive and how will its numbers be controlled? Too many bacteria and the container may explode. And what about these pencil viruses? They infected only bacteria before getting ginned up with that amino acid bath. Are they as stable and predictable now? Since viruses have been known to mutate, is it wise to be messing around with them at all? I say lets stick with Lithium technology. After all its good enough for Captain Kirk.
Reply | Report Abuse | Link to thisDon't be confused, Bacteriophages (such as M13) are *Only* capable of infecting bacteria.
Reply | Report Abuse | Link to thisTheir mechanism of action is to float around until a very specific protein on their tail binds to a receptor on a bacteria. They then contract, butting up against the bacterial cell wall, and shoot their RNA into the bacteria like a hypodermic needle.
There's extensive research into using bacteriophages as an alternative to antibiotics, but the problem researchers keep having is that they are very species and strain selective. A single strain or species of phage can't infect more than a few different bacteria, much less a eukariotic cell. For all intents and purposes bacteriophages are as safe to humans as water or saline solution. Don't worry, any engineering done to them would be astronomically more likely to hobble the bacteriophages and make them incapable of reproduction within a host, than to make them mankillers.
ldobehardcore: You are forgetting evolution. Phages may be species specific, but they too evolve, billions will die from starvation from lack of a host, but ever so often one learns to make do with another.
Reply | Report Abuse | Link to thisIt wont be a catastrophe, in fact in my opinion it is desirable; a phage mutates to infect a bacterium vital for the survival of the Homo sapien. What a wonderful solution to the Homo spaien plague on planet earth.