What if you could build a machine that runs on light. Plants do it just fine -- think photosynthesis -- with 100 percent efficiency. Solar cells use silicon conductors to capture sunlight, but only have efficiency rates from 6 to 25 percent.
Now a team of researchers have drawn a blueprint on how to harness light energy just like plants -- and they hope to use it to make new kinds of computers, storage devices or even engines.
"Plants are machines that have all the sophistication of a Boeing 777," said Greg Scholes, professor of chemistry at the University of Toronto. "They have thousands of feedback control loops making adjustments every second. That's the kind of machine we would aspire to make."
The plant-inspired devices "would be something that does not exist right now," explained Scholes. "We do a lot with electricity, we do a lot with optical light, we don't do anything in between where the energy of light is converted into the excitation of matter."
At the heart of Scholes' plan -- outlined in a review paper published today in Nature Chemistry -- is making a biological-based circuit that uses the quantum mechanical effects of light as it excites molecules of pigments and colors found in nature. Harnessing this ephemeral form of energy could lead to new kinds of energy sources, storage devices and electronic circuits.
In their paper, Scholes and co-author Alexandra Olaya-Castro at the University College of London, review the past few years of research into how plants collect and transport light into energy. Recently, there have been some surprises.
When a plant's light-gathering molecules get excited by photons from the sun, they start vibrating and pass the energy along to other cells like a wave propagating across a pond.
Previously it was thought that this energy moved by "hopping" from one place to another. That bit of understanding could be key in designing new kinds of artificial light harvesting systems.
"You could use these circuits to write information and to read from computers we have now," he said.
Other experts say the paper raises some interesting questions. Chris Bardeen, professor of chemistry at the University of California, Riverside, said the engineering challenge will be to capture energy from different wavelengths of light, rather than just the visible light used by plants or solar panels.
"The task now is to use the design principles outlined in this paper to build a better artificial system that harvests more of the solar spectrum," Bardeen said via-email.
"Biology has provided the guidelines, but not the specific molecules or materials that could be used -- that job is now up to the chemists. Fortunately, this paper provides specific instructions as to what properties we should look for in chemical systems for light harvesting."
Some companies such as Lowell, Mass.-based Konarka, are already manufacturing "organic" solar panels that are made of a flexible plastic material.
Alan Aspuru-Guzik, a Harvard chemistry professor, has been working on deconstructing how photosynthesis works in plants with the idea of making more efficient solar cells in the future. He notes that many engineering obstacles remain, and that bio-mimicry doesn’t always work.
"Plants have a repair mechanism that we won't be able to replicate," Aspuru-Guzik said. "The big challenge on the engineering side is how to cope with material that will need to be in the sun for 20 years without degrading. We're working on this."