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Smart bridge: Iowa State engineers load new bridge with damage-detection gauges
(Newswise) The new bridge over the Iowa River near downtown Iowa Falls is a major upgrade over the 1928 concrete arch structure it replaced last fall, once the longest arch span bridge in the state. The new US Highway 65/Oak Street bridge is stronger. Its foundation is more secure. Its roadway is 18 feet wider. The steel arch maintains some of the aesthetics of the old bridge. And all over the new bridge are gauges, sensors and other technologies installed by Iowa State University researchers that will be used for continuous, real-time monitoring of the structural health, behavior and security of the structure. Those sensors will provide a tremendous amount of quantitative information about the bridge’s performance and condition, says Brent Phares, the interim director of the Bridge Engineering Center. It’s a model that could be used for other new bridges, including much larger ones. Those gauges take 100 readings a second for corrosion, strain, surface conditions, moisture within the steel arch and structure movements over time. The bridge is also equipped to monitor the security of the structure and to record surveillance video
USC researchers develop path to liquid solar cells
Scientists at USC have developed a potential pathway to cheap, stable solar cells made from nanocrystals so small they can exist as a liquid ink and be painted or printed onto clear surfaces. “Like you print a newspaper, you can print solar cells,” says Richard L. Brutchey, assistant professor of chemistry at the USC. Brutchey and USC postdoctoral researcher David H. Webber developed a new surface coating for the nanocrystals, which are made of the semiconductor cadmium selenide. Their research is featured as a “hot article” in Dalton Transactions. Liquid nanocrystal solar cells are cheaper to fabricate than available single-crystal silicon wafer solar cells but are not nearly as efficient at converting sunlight to electricity. Brutchey and Webber solved one of the key problems of liquid solar cells: how to create a stable liquid that also conducts electricity. In the past, organic ligand molecules were attached to the nanocrystals to keep them stable and to prevent them from sticking together. These molecules also insulated the crystals, making the whole thing terrible at conducting electricity.
Improving the efficiency of water splitting in dye-sensitized solar cells by using a biomimetic electron transfer mediator
(PNAS) Although water splitting using semiconductor photoelectrodes has been studied for more than 40 years, it has only recently been demonstrated using dye-sensitized electrodes. The quantum yield for water splitting in these dye-based systems has, so far, been very low because the charge recombination reaction is faster than the catalytic four-electron oxidation of water to oxygen. We show here that the quantum yield is more than doubled by incorporating an electron transfer mediator that is mimetic of the tyrosine-histidine mediator in Photosystem II. The mediator molecule is covalently bound to the water oxidation catalyst, a colloidal iridium oxide particle, and is coadsorbed onto a porous titanium dioxide electrode with a Ruthenium polypyridyl sensitizer. As in the natural photosynthetic system, this molecule mediates electron transfer between a relatively slow metal oxide catalyst that oxidizes water on the millisecond timescale and a dye molecule that is oxidized in a fast light-induced electron transfer reaction. The presence of the mediator molecule in the system results in photoelectrochemical water splitting with an internal quantum efficiency of approximately 2.3% using blue light.
Folding light: Wrinkles and twists boost power from solar panels
Taking their cue from the humble leaf, researchers have used microscopic folds on the surface of photovoltaic material to significantly increase the power output of flexible, low-cost solar cells. The team, led by scientists from Princeton University, reported online April 22 in the journal Nature Photonics that the folds resulted in a 47 percent increase in electricity generation. Yueh-Lin (Lynn) Loo, the principal investigator, said the finely calibrated folds on the surface of the panels channel light waves and increase the photovoltaic material’s exposure to light. “On a flat surface, the light either is absorbed or it bounces back,” said Loo, a professor of chemical and biological engineering at Princeton. “By adding these curves, we create a kind of wave guide. And that leads to a greater chance of the light’s being absorbed.”
NASA flexible aerogel, innovator inducted into Space Technology Hall of Fame
Pioneering work to manufacture composite blankets for space applications has yielded a number of Super-insulating flexible aerogel products for the commercial marketplace. The creation of low-density, light-weight flexible aerogel insulating material was saluted April 19 during Space Technology Hall of Fame ceremonies, held during the Space Foundation’s 28th National Space Symposium. Recognized for their leading aerogel work was James Fesmire, senior principal investigator of the Cryogenics Test Laboratory at NASA’s Kennedy Space Center, and the startup company, Aspen Systems of Marlborough, Mass. There were two key reasons why it has taken decades to realize the commercial potential of aerogel. “First it was so brittle that you could not really make it into a durable product,” said Kang Lee, President and CEO of Aspen Systems. “The second reason is that it was too expensive. My joke is, even if you look at aerogel, it breaks,” Lee said. In tackling those durability and cost issues, Lee said that he and his colleagues applied a multi-disciplinary approach to problem-solving — a mixture of thermal dynamics and acoustics, as well as chemical engineering. “We combined all kinds of disciplines and looked at it with a fresh set of eyes,” Lee said. Taking that approach led to the formation of his company, Aspen Aerogels, to utilize the firm’s patented method to establish an array of industrial, construction, refrigeration, automotive, medical and commercial applications.
Single nanomaterial yields many laser colors
Engineers at Brown University and QD Vision Inc. have created nanoscale single crystals that can produce the red, green, or blue laser light needed in digital displays. The size determines color, but all the pyramid-shaped quantum dots are made the same way of the same elements. In experiments, light amplification required much less power than previous attempts at the technology. The team’s prototypes are the first lasers of their kind. “Today in order to create a laser display with arbitrary colors, from white to shades of pink or teal, you’d need these three separate material systems to come together in the form of three distinct lasers that in no way shape or form would have anything in common,” said Arto Nurmikko, professor of engineering at Brown University and senior author of a paper describing the innovation in the journal Nature Nanotechnology. The materials in prototype lasers described in the paper are nanometer-sized semiconductor particles called colloidal quantum dots or nanocrystals with an inner core of cadmium and selenium alloy and a coating of zinc, cadmium, and sulfur alloy and a proprietary organic molecular glue. The cladding and the nanocrystal structure are critical advances beyond previous attempts to make lasers with colloidal quantum dots, said lead author Cuong Dang, a senior research associate and nanophotonics laboratory manager in Nurmikko’s group at Brown. Because of their improved quantum mechanical and electrical performance, he said, the coated pyramids require 10 times less pulsed energy or 1,000 times less power to produce laser light than previous attempts at the technology.