Predicting better photonic devices.
Understanding precisely how light behaves as it moves through devices such as solar cells or optical chips will lead to more efficient devices–and reveal new physical phenomena that engineers can exploit. To this end, theoretical physicist Michelle Povinelli is creating models of how photons interact with complex materials.
In one surprising finding, Povinelli correctly predicted that light being guided down a strip of silicon would exert a mechanical force on an adjacent strip. If moving parts driven by light were incorporated into optical circuits and used to reroute light signals, the light might not have to be converted into electricity for processing and then back to light again.
Making better solar cells may sound very different from optical communications, but understanding how light interacts with a device is equally important in this context. Povinelli is working on models to predict the efficiency of solar cells that have different nanostructures. Finding the ultimate efficiency for these cells will set a boundary on what researchers can hope to achieve and guide them toward photovoltaics that are less expensive but much better at generating electricity.
Simulating chemistry with quantum computers.
In theory, quantum mechanics should offer perfect understanding of some of the most interesting events in chemistry–for example, the behavior of excited electrons, which controls such things as photosynthesis in plants. In practice, however, the necessary calculations are far too difficult for even the most powerful computers. So approximations must be made, especially when larger molecules such as proteins are involved.
Alán Aspuru-Guzik, a theoretical chemist at Harvard, is developing methods that could one day do away with the need for approximations altogether–and lead to better drugs or solar cells.
He has created an algorithm that allows quantum computers to simulate chemistry with a level of accuracy that traditional computers will never be able to match. Although quantum computers are not yet powerful enough to simulate the behavior of large molecules, Aspuru-Guzik and collaborators in Australia, working with an experimental quantum computer, successfully used the algorithm to compute the energy of the hydrogen molecule.
Aspuru-Guzik is also probing the quantum effects at the heart of photosynthesis in the hopes of developing cheaper and more efficient organic photovoltaics.
Bringing down the price of OLED displays.
Television displays based on organic light-emitting diodes are brighter, crisper, and more energy efficient than liquid-crystal displays. But they’re very expensive, especially for large-screen models. Conor Madigan is working to drive down the cost of these displays as the CEO and cofounder of a Silicon Valley startup called Kateeva, which is developing efficient machinery for printing pixels over large areas. The technology makes it possible to manufacture OLED screens at 60 percent of the cost of LCD screens.
Kateeva is sending out a beta version of its OLED-display printers to customers for evaluation in the first half of 2011 and hopes to have its first production tools on the market in 2012. If OLEDs replace LCDs, Kateeva could tap into a $10-billion-a-year market for display-manufacturing equipment.
Powering electronics with human motion.
Michael McAlpine has developed a flexible material that produces record amounts of energy when subjected to mechanical pressure. It could turn the action of a patient’s lungs into enough energy to power an implanted medical device; forces produced by walking around could be sufficient to drive portable electronics.
In 2008, as a new assistant professor at Princeton, McAlpine started thinking about pacemakers: was there a way to harvest power from the lungs as people inhaled and exhaled, so that the batteries wouldn’t need to be surgically replaced every few years? Drawing on previous experience in making nanowire electronics and sensors on sheets of plastic, McAlpine began experimenting with PZT, a well-known material that is piezoelectric–able to convert physical stress into electricity. To make a flexible device, he deposits the PZT onto a hard substrate before carving the material into tiny ribbons. Then he uses chemicals to release the ribbons of PZT from the substrate and transfers them to a piece of silicone. A second piece of silicone seals the PZT in, creating a pliable, biocompatible material that’s four times as efficient as previous flexible piezoelectrics. So far McAlpine has made only small pieces of the material, but he is now scaling up the process to make larger wafers suitable for use in implanted electronics.