VIRUS GENERATES ELECTRICITY when SQUISHED
by Mellisae Fellet / May 15 2012
“Squishing a stack of virus sheets generates enough electricity to power a small liquid crystal display. With increased power output, these virus films might one day use the beating of your heart to power a pacemaker, the researchers behind them say. Piezoelectric materials build up charge when pushed or squeezed. These materials may be familiar to you: they generate the spark in a gas lighter, and motors powered by such materials vibrate some cell phones. Piezoelectric materials made of metals or polymers require large inputs of energy to build up a charge. Bone, DNA, and protein fibers are weakly piezoelectric, but it’s hard to efficiently organize these materials on a large scale to yield electricity.To handle this organizational issue, Seung-Wuk Lee, of the University of California in Berkeley and the Lawrence Berkeley National Laboratory, and his colleagues looked for a biomaterial that had intrinsic order and was easy to make. They settled on the M13 bacteriophage, a rod-shaped virus that only infects bacteria. One bacterium can produce one million copies of the virus within four hours, so starting material isn’t a problem. And the virus neatly arranges itself in stacked rows when spread on a surface.
The researchers first tested the virus to see if it was piezoelectric. Instead of pushing on the virus and measuring a current, they looked for the opposite effect. They electrified a film made with the virus and watched for mechanical motion. The scientists saw the helical proteins covering the virus twist. To understand why the virus is piezoelectric, we need to look at its structure. About 2700 copies of a helical protein stretch along the length of the virus, tipping out from that central axis about 20°. Each helix has a positively charged end and a negatively charged end. The amount of this charge difference and the distance between the two charged areas sets up an electric dipole, which runs along each helix.
A closeup of the virus’ coat proteins. The red end is the positively charged end of the protein. The negatively-charged blue end was engineered to contain four extra negative charges. The M13 bacteriophage has a length of 880 nanometers and a diameter of 6.6 nanometers. It’s coated with approximately 2700 charged proteins that enable scientists to use the virus as a piezoelectric nanofiber.
Normally these dipoles cancel each other out because the proteins are symmetrically arranged around the outside of the virus—the amount of negative charge around the virus surface balances out the amount of positive charge. But when the virus is squished from above, its rod shape elongates into an oval, and the dipole moments become uneven. One area of the virus coat can now hold negative charges while another builds positive charge. Establishing that charge difference causes current to flow along the virus. Since the structure of the coat proteins is well known, the researchers engineered the virus to increase its piezoelectric properties. They added four extra negatively charged amino acids, specifically a string of glutamates, to one end of the helical surface protein. That increased the charge difference between the positive and negative ends of the helix, thus raising the amount of electrical energy it produced when squished. Next, the scientists sandwiched sheets of engineered virus between two gold electrodes about the size of a postage stamp. When pushed with a thumb, the virus stack produces 6 nA of current with 400 mV of potential. That’s about one-quarter the voltage of an AAA battery. Combining two of these stacks provides enough energy to bring up a “1” on a small liquid crystal display.
Lee is working to increase the amount of current that these viral particles can produce by tweaking the viral coat proteins and playing with their arrangement on the electrode surface. In five to ten years, he estimates, viral piezoelectric films in your shoes could be personal electricity generators to power your iPod as you run. Or they could use the thumping of your heart to power a pacemaker, Lee says. Though the current produced now is small because only a thin layer of the virus deforms, virus-based devices could still be useful for small scale applications, writes S. Michael Yu, of Johns Hopkins University, in the News and Views article accompanying the paper. This flexible film has a “self-assembling capability that no other piezoelectric materials can even dream about,” he writes. That reliable self-organization forms tidy structures gives the material its piezoelectric activity, Yu writes.”
Nature Nanotechnology, 2012. DOI: 10.1038/nnano.2012.69
“Pressing a virus-filled device can generate power. The gloves protect the virus, which only infects bacteria, from us.”
Berkeley Lab Scientists Generate Electricity From Squeezing Viruses
by Dan Krotz / May 13, 2012
“Imagine charging your phone as you walk, thanks to a paper-thin generator embedded in the sole of your shoe. This futuristic scenario is now a little closer to reality. Scientists from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a way to generate power using harmless viruses that convert mechanical energy into electricity. The scientists tested their approach by creating a generator that produces enough current to operate a small liquid-crystal display. 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. Their generator is the first to produce electricity by harnessing the piezoelectric properties of a biological material. Piezoelectricity is the accumulation of a charge in a solid in response to mechanical stress. The milestone could lead to tiny devices that harvest electrical energy from the vibrations of everyday tasks such as shutting a door or climbing stairs.
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. The first part of the video shows how Berkeley Lab scientists harness the piezoelectric properties of a virus to convert the force of a finger tap into electricity. The second part shows the “viral-electric” generators in action, first by pressing only one of the generators, then by pressing two at the same time, which produces more current. “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,” says Seung-Wuk Lee, a faculty scientist in Berkeley Lab’s Physical Biosciences Division and a UC Berkeley associate professor of bioengineering. He conducted the research with a team that includes Ramamoorthy Ramesh, a scientist in Berkeley Lab’s Materials Sciences Division and a professor of materials sciences, engineering, and physics at UC Berkeley; and Byung Yang Lee of Berkeley Lab’s Physical Biosciences Division.
The first part of the video shows how Berkeley Lab scientists harness the piezoelectric properties of a virus to convert the force of a finger tap into electricity. The second part shows the “viral-electric” generators in action, first by pressing only one of the generators, then by pressing two at the same time, which produces more current.
The piezoelectric effect was discovered in 1880 and has since been found in crystals, ceramics, bone, proteins, and DNA. It’s also been put to use. Electric cigarette lighters and scanning probe microscopes couldn’t work without it, to name a few applications. But the materials used to make piezoelectric devices are toxic and very difficult to work with, which limits the widespread use of the technology. Lee and colleagues wondered if a virus studied in labs worldwide offered a better way. The M13 bacteriophage only attacks bacteria and is benign to people. Being a virus, it replicates itself by the millions within hours, so there’s always a steady supply. It’s easy to genetically engineer. And large numbers of the rod-shaped viruses naturally orient themselves into well-ordered films, much the way that chopsticks align themselves in a box. These are the traits that scientists look for in a nano building block. But the Berkeley Lab researchers first had to determine if the M13 virus is piezoelectric. Lee turned to Ramesh, an expert in studying the electrical properties of thin films at the nanoscale. They 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.
The bottom 3-D atomic force microscopy image shows how the viruses align themselves side-by-side in a film. The top image maps the film’s structure-dependent piezoelectric properties, with higher voltages a lighter color.
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. 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. The only thing remaining to do was a demonstration test, so the scientists fabricated a virus-based piezoelectric energy generator. They created the conditions for genetically engineered viruses to spontaneously organize into a multilayered film that measures about one square centimeter. This film was then sandwiched between two gold-plated electrodes, which were connected by wires to a liquid-crystal display. When pressure is applied to the generator, it produces up to six nanoamperes of current and 400 millivolts of potential. That’s enough current to flash the number “1” on the display, and about a quarter the voltage of a triple A battery. “We’re now working on ways to improve on this proof-of-principle demonstration,” says Lee. “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.”
MICROBIAL FUEL CELLS
by Phil McKenna / March 2012
“A fuel cell powered by naturally occurring bacteria has successfully converted 13 per cent of the energy in sewage to electricity – and cleaned the waste water at the same time. It’s hoped genetic engineering could make this much more efficient. Treating sewage and other liquid waste uses roughly 2 per cent of the US energy supply, at a cost of $25 billion a year, yet this carbon-rich material harbours nine times the energy needed to render it environmentally benign. Microbiologists believe they can drastically cut the cost and power consumption by using genetically modified bugs to treat the waste and produce electricity. “It’s a substantial energy resource that we just end up landfilling,” saysOrianna Bretschger, of the J. Craig Venter Institute in San Diego, California. “If we could recover the energy we could do waste water treatment for free.” Bretschger described a 380-litre microbial fuel cell at a meeting of the American Chemical Society in San Diego this week. It uses naturally occurring microbes to break down organic waste and produce electrons and protons. The electrons are collected by an anode while the protons pass through a permeable membrane to a cathode. The resulting voltage between the two electrodes enables the fuel cell to produce an electric current.
The announcement represents a significant improvement over the institute’s earlier fuel cell, a 75-litre device able to harvest only 2 per cent of the waste’s potential energy. Further improvements will be needed, however, for the technology to compete with conventional waste water treatment techniques, which can rapidly process huge volumes of water. By genetically modifying microbes to enhance their ability to consume organic waste, and better shuttling electrons to an electrode, Bretschger hopes to harvest 30 to 40 per cent of the available energy. Genetically modified organisms aren’t currently used in either municipal or commercial waste water treatment facilities. Their potential use in a fuel cell would be regulated in the US by the Environmental Protection Agency (EPA), which has yet to determine how to govern such applications.
Conventional waste water treatment, however, already has ways of killing microbes before water gets back into the environment, including the use of chlorine, ozone and ultraviolet light. The EPA also recently granted permission for a pilot study in which genetically modified microbes were used as tracers to find leaks from sewers. Roland Cusick, an environmental engineer at Pennsylvania State University in University Park, says genetically engineered microbes may boost efficiency, but it may be difficult to control the bug population. “Waste water has millions of microbes in it. Any time you are adding waste water, you are adding competition to your system,” Cusick says.”