The solar cells undergo photosynthesis
Benny Ran and Avi Blizovsky
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Spinach leaves and sunlight extend the life of batteries
Spinach. For the first time, scientists succeeded in producing a sustained electric current from the process of photosynthesis
Parents and doctors have been praising the virtues of spinach for years. Now a surprising group has joined the chorus: researchers who want to "put life into batteries". Scientists from the Massachusetts Institute of Technology (MIT), the University of Tennessee, the US Naval Research Laboratory, and the Defense Advanced Research Projects Agency have discovered a way to harness the energy that plants use during photosynthesis to create light. The scientists are applying the process to extend the life of batteries in cell phones, laptops and portable electronic devices. Mark Baldo, an electrical engineering professor at MIT who worked on the project, hopes to use the chips in radios and memory units as well. But the research is still in its infancy, and many more years will pass before the technology enters commercial use.
The discovery blurs the barriers between nature and technology, the scientists claim. "This shows that there is a way to use biologically generated molecules and connect them directly to applied electronic circuits," says Barry Bruce, professor of biochemistry and cellular and molecular biology at the University of Tennessee-Knoxville. "This opens the door to applications, whether you want to produce DNA cables, or enzyme-based reactive cells."
This is the first time that scientists have succeeded in producing "something as basic as an electric current" from the photosynthesis process, says Prof. Bruce. In previous attempts, the researchers managed to create a current for only a few hours, but this time the group of scientists managed to produce an electric current that lasted for three weeks. Previous attempts to generate electricity from photosynthesis failed because the proteins that capture energy from sunlight died without water. The breakthrough was achieved after Shuguang Zhang, deputy director of the Center for Biomedical Engineering at MIT, was able to create a protein detergent that stabilized the protein and allowed it to transfer energy.
Spinach was chosen for the task for two reasons: both because of its high chlorophyll concentration, evident in its dark green color, and because of its low price. Earlier, the scientists considered using green peas, but spinach's low price and availability made it the winning candidate. If in order to obtain fresh peas the scientists had to grow them themselves, said Prof. Bruce, then spinach "can be bought in quantities all year round".
Prof. Zhang said that the researchers melted the spinach in a centrifuge, extracted the protein from it and placed it upside down, with a space between each of the proteins, on the chip. The proteinaceous detergent was inserted in intervals, and in a process of "self-assembly", the two parts were connected like interlocking fingers. The mixture was placed between layers of plastic, gold and indium tin oxide - a semi-conducting transparent material. At the end of the process, the chips became durable and easy to repair: if one protein stops working, it can be replaced with another.
The device, which looks like a square microchip XNUMX cm long with a green liquid inside, will not activate electronic devices by itself, but will wrap a battery from the outside and use the power of light to extend its life.
So far, only one layer of spinach solution has been added to the chips, which allows only a small amount of electricity to be produced. In the future, the scientists plan to add more layers to add strength. "It's like erecting a building," said Prof. Zhang. "It becomes more complete with each additional floor." Prof. Zhang is in no rush to get excited; In his opinion, a decade will pass before he can use the discovery for commercial purposes. But it is possible that in the end it will be vegetables that will power the electronics. "It will take some time," said Prof. Zhang, "but the first barrier has already been broken."
Can laptops run on spinach?
First published on the science website on 07/9/2004. Update later
Avi Blizovsky and Beni Ran
Not only Popeye eats spinach - computers can also digest it, believe American researchers who have built electric cells powered by plant proteins. The biological solar cells convert the rays of light into electrical energy, and should be efficient and cheap to manufacture - says researcher Mark Baldo from the Massachusetts Institute of Technology, who took part in the development. The discovery was published in Nano Letters.
Baldo's team isolated some photosynthetic proteins from spinach leaves and sandwiched them between two layers of conductive material. As soon as the tiny cell was exposed to light, an electric current was produced. However, extracting the proteins was not easy. The molecules are delicate and tend to stop working as soon as they are separated from their natural environment. The researchers preserved them by mixing them with more resistant molecules, which protect the energy-producing proteins and make them behave as if they were still attached to the plant.
The proteins were attached to a thin gold plate, which was connected to a sheet of transparent and electrically conductive metal, on top of which was another layer of an organic conductor. The development of the system has not yet been completed, partly because at the moment it operates for only 21 days and then its operation ends. Now the researchers are looking for alternatives that are able to work for a longer time. In addition to this, the cells currently convert only about 12 percent of the energy absorbed in them into electricity. However, the researchers believe that it is possible to improve this value and reach a utilization of about twenty percent - a better rate than that of conventional solar cells, which are made of silicon.
Vegetable battery
14/10/2004
Remember the spinach-loving Popeye from Walt Disney's animated films? Soon, so scientists at the laboratory of the Massachusetts Institute of Technology, MIT, promise, the green spinach leaves will not only "add strength" to Popeye's arm muscles - they will be used to generate electrical energy, to operate portable computers and cell phones. In other words: the day is coming when we will see "biological" batteries. More correctly: a solar cell that produces electricity using a technology reminiscent of the photosynthesis process.
The idea of the American team therefore joins the idea of British engineers to produce oil from sunflowers - not only for seasoning salad and cooking, but also as fuel for engines. Both ideas are undoubtedly of extensive economic significance, for the future.
The innovation achieved in the innovative research at MIT, is that for the first time the ability of plants to convert energy derived from sunlight - into electricity, or more correctly into an electronic device (chip) now known as the "spinach sandwich" was harnessed.
The core of the device is a complex of photosynthetic proteins derived from the chloroplasts of spinach, the same plant organ system in which photosynthesis is carried out. The width of the protein system is 10 to 20 nanometers (nanometer = billionth of a meter). About 100 thousand of them "fit" into the head of a pin.
The development team headed by Prof. Mark Baldo includes other engineers from the University of Tennessee and the Central Research Laboratory of the US Navy, including experts in electronics, computers, biomedical engineering, biologists and nanotechnologists.
In a report to the scientific bulletin "Nano-Letters" published by the American Chemical Society - the largest scientific society in the world - the researchers emphasized: "We have already overcome the first obstacle in which we had to combine and integrate a complex of photosynthetic proteins inside a solid electronic device, that is, inside a chip."
Prof. Baldo said that the ability of plants to produce energy has been perfected over millions of years of evolution and it turned out that spinach leaves are exceptionally effective for this purpose. The amount of energy that the chlorophylls in the spinach leaves produce is huge relative to its dimensions and weight. The quest to combine biological and non-biological materials in one device has long fascinated scientists - except that until now biological materials required water and salts to survive - and these two components are not good for electronics.
But the development team created a peptide membrane, i.e. based on small protein molecules, extremely thin and reminiscent of a central component in soap - and it is this that stabilized the photosynthetic complex and thus made it possible to create a suitable electronic circuit. By the way, inside the "spinach sandwich" there are also layers of gold metal - a particularly excellent electrical conductor.
