Monday, May 28, 2012

Scientists Generate Electricity from Viruses

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 scientists describe their work in a May 13 advance online publication of the journal Nature Nanotechnology.
"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 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.
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."

Artificial Leaf Device Produces Hydrogen in Water Using Only Sunlight

Scientists and researchers from the Photovoltaic and Optoelectronic Devices group from the Universitat Jaume I, led by Professor Juan Bisquert, have developed, using nanotechnology, a device with semiconductor materials which generate hydrogen independently in water using only sunlight.

This technology, which has been named artificial photosynthesis, was inspired by photosynthesis which occurs naturally (a process in which plants use sunlight to transform organic material into organic compounds, freeing chemical energy stored in the bonds of the molecule adenosine triphosphate-ATP, and obtaining energetic compounds such as sugars or carbohydrates).
The efficient production of hydrogen using semiconductor materials and sunlight constitutes a crucial challenge to make a paradigm shift towards sustainable energy technology, using inexhaustible resources that are environmentally friendly. "Although the energy efficiency of the device is still not sufficient enough for us to consider marketing it, we are exploring various ways to improve its efficiency and to show that this technology represents a real alternative to meet the energy demands of the 21st century," comments Sixto Giménez, one of the researchers responsible for the investigation.
Hydrogen is an extremely abundant element on Earth's surface, but in combination with oxygen: water (H20). The hydrogen molecule (H2) contains a great amount of energy that can be released when burned due to the reaction with atmospheric oxygen, creating water as the result of this combustion process. In order to convert water into fuel (H2), the H2O must be broken down into its separate components and so that the process can be carried out in a renewable way (without using subsoil fossil fuels), it is necessary to use a device which relies on solar power, and with no other assistance, to provoke the chemical reactions to break the water and form hydrogen in a way similar to leaves on plants. For this reason these devices are named artificial leaves.
The device is submerged in an aqueous solution which, when illuminated with a light source, forms hydrogen gas bubbles. Firstly, the research group used a solution with an oxidizing agent and studied the evolution of hydrogen produced by photons. "Now the biggest challenge," comments Iván Mora, member of the team developing the solution, "is to understand the physical-chemical process which is produced by the semiconductor material and its interface with the aqueous medium in order to streamline the device process."
The development of the artificial leaf is a great scientific challenge due to the difficulty posed by the selection of materials that will be used in the process, working continuously and not decomposing. Currently, the Photovoltaic and Optoelectronic Devices group from the Universitat Jaume I is one of the few research groups on an international level that has shown the viability of a device with these characteristics, together with the North American laboratories from MIT in Boston or NREL in Denver. The research group leader, Juan Bisquert, comments that "in comparison to other devices, that which has been developed by the UJI has the advantage of low production costs and a large collection of incident photons of light, used in the production of hydrogen photons in the infrared spectrum."