Tag Archives: University of Rochester

Next Generation of AR/VR Headsets (Quantglasses)

“Image” is everything in the $20 billion market for AR/VR glasses (Quantglasses). Consumers are looking for glasses that are compact and easy to wear, delivering high-quality imagery with socially acceptable optics that don’t look like “bug eyes.”

University of Rochester researchers at the Institute of Optics have come up with a novel technology to deliver those attributes with maximum effect. In a paper in Science Advances, they describe imprinting freeform optics with a nanophotonic optical element called “a metasurface.”

The metasurface is a veritable forest of tiny, silver, nanoscale structures on a thin metallic film that conforms, in this advance, to the freeform shape of the optics—realizing a new optical component the researchers call a metaform. The metaform is able to defy the conventional laws of reflection, gathering the visible light rays entering an AR/VR eyepiece from all directions, and redirecting them directly into the human eye.

 

Freeform optics is an emerging technology that uses lenses and mirrors with surfaces that lack an axis of symmetry within or outside the optics diameter to create optical devices that are lighter, more compact, and more effective than ever before.

Nick Vamivakas, a professor of quantum optics and quantum physics, likened the nanoscale structures to small-scale radio antennas.  “When we actuate the device and illuminate it with the right wavelength, all of these antennas start oscillating, radiating a new light that delivers the image we want downstream.

Metasurfaces are also called ‘flat optics’ so writing metasurfaces on freeform optics is creating an entirely new type of optical component,” says Jannick Rolland, the Brian J. Thompson Professor of Optical Engineering and director of the Center for Freeform Optics.

Adds Rolland, “This kind of optical component can be applied to any mirrors or lenses, so we are already finding applications in other types of components” such as sensors and mobile cameras.

The first demonstration required many years to complete.

The goal is to direct the visible light entering the AR/VR glasses to the eye. The new device uses a freespace optical combiner to help do that. However, when the combiner is part of freeform optics that curve around the head to conform to an eyeglass format, not all of the light is directed to the eye. Freeform optics alone cannot solve this specific challenge. That’s why the researchers had to leverage a metasurface to build a new optical component.

Integrating these two technologies, freeform and metasurfaces, understanding how both of them interact with light, and leveraging that to get a good image was a major challenge,” says lead author Daniel Nikolov, an optical engineer in Rolland’s research group.

Source: https://www.rochester.edu/

How To Turn Seawater Into Fuel

For the first time, Rochester chemical engineers have demonstrated a ‘potassium-promotedcatalyst’s potential for use on an industrial scale. Now, the Navy’s quest to power its ships by converting seawater into fuel is nearer fruition.

University of Rochester chemical engineers—in collaboration with researchers at the Naval Research Laboratory, the University of Pittsburgh, and OxEon Energy—have demonstrated that a potassium-promoted molybdenum carbide catalyst efficiently and reliably converts carbon dioxide to carbon monoxide, a critical step in turning seawater into fuel.

Gulf of Aden, April 27, 2011- The Military Sealift Command fleet replenishment oiler USNS Joshua Humphreys (T-AO 188), left, refuels the amphibious assault ship USS Boxer (LHD 4) during a replenishment at sea. Boxer is underway supporting maritime security operations and theater security cooperation efforts in the U.S. 5th Fleet area of responsibility.

This is the first demonstration that this type of molybdenum carbide catalyst can be used on an industrial scale,” says Marc Porosoff, assistant professor in the Department of Chemical Engineering at Rochester. In a paper in the journal Energy & Environmental Science, the researchers describe an exhaustive series of experiments they conducted at molecular, laboratory, and pilot scales to document the catalyst’s suitability for scale-up.

If navy ships could create their own fuel from the seawater they travel through, they could remain in continuous operation. Other than a few nuclear-powered aircraft carriers and submarines, most navy ships must periodically align themselves alongside tanker ships to replenish their fuel oil, which can be difficult in rough weather.

In 2014, a Naval Research Laboratory team led by Heather Willauer announced it had used a catalytic converter to extract carbon dioxide and hydrogen from seawater and then converted the gases into liquid hydrocarbons at a 92 percent efficiency rate.

Since then, the focus has been on increasing the efficiency of the process and scaling it up to produce fuel in sufficient quantities.
The carbon dioxide extracted from seawater is extremely difficult to convert directly into liquid hydrocarbons with existing methods. So, it is necessary to first convert carbon dioxide into carbon monoxide via the reverse water-gas shift (RWGS) reaction. The carbon monoxide can then be converted into liquid hydrocarbons via Fischer-Tropsch synthesis.
Typically, catalysts for RWGS contain expensive precious metals and deactivate rapidly under reaction conditions. However, the potassium-modified molybdenum carbide catalyst is synthesized from low-cost components and did not show any signs of deactivation during continuous operation of the 10-day pilot-scale study. That’s why this demonstration of the molybdenum carbide catalyst is important.

Source: https://www.rochester.edu/

How To Purify Water Without Wasting Energy

Amid the coronavirus pandemic, people in developed countries are assured of ample supplies of clean water to wash their hands as often as needed to protect themselves from the virus. And yet, nearly a third of the world’s population is not even assured of clean water for drinking. University of Rochester researchers have now found a way to address this problem by using sunlight—a resource that everyone can access—to evaporate and purify contaminated water with greater than 100 percent efficiency.

How is this possible? In a paper in Nature Sustainability, researchers in the laboratory of Chunlei Guo, professor of optics, demonstrate how a burst of femtosecond laser pulses etch the surface of a normal sheet of aluminum into a superwicking (water-attracting), super energyabsorbing material. Using sunlight to boil has long been recognized as a way to eliminate microbial pathogens and reduce deaths from diarrheal infections. But boiling water does not eliminate heavy metals and other contaminants. Experiments by the lab show that their new method reduces the presence of all common contaminants, such as detergent, dyes, urine, heavy metals, and glycerin, to safe levels for drinking.

Solar-based water purification can greatly reduce contaminants because nearly all the impurities are left behind when the evaporating water becomes gaseous and then condenses and gets collected. The most common method of solar-based water evaporation is volume heating, in which a large volume of water is heated but only the top layer can evaporate. This is obviously inefficient, Guo says, because only a small fraction of the heating energy gets used. A more efficient approach, called interfacial heating, places floating, multilayered absorbing and wicking materials on top of the water, so that only water near the surface needs to be heated. But the available materials all have to float horizontally on top of the water and cannot face the sun directly. Furthermore, the available wicking materials become quickly clogged with contaminants left behind after evaporation, requiring frequent replacement of the materials.

The panel developed by the Guo lab avoids these inefficiencies by pulling a thin layer of water out of the reservoir and directly onto the solar absorber surface for heating and evaporation. “Moreover, because we use an open-grooved surface, it is very easy to clean by simply spraying it,” Guo says.

The biggest advantage,” he adds, “is that the angle of the panels can be continuously adjusted to directly face the sun as it rises and then moves across the sky before setting” —maximizing energy absorption. “There was simply nothing else resembling what we can do here,” Guo says.

Source: https://www.rochester.edu/

How To Etch A ‘Perfect’ Solar Energy Absorber

The University of Rochester research lab that recently used lasers to create unsinkable metallic structures has now demonstrated how the same technology could be used to create highly efficient solar power generators.

In a paper in Light: Science & Applications, the lab of Chunlei Guo, professor of optics also affiliated with the Department of Physics and Astronomy and the Material Sciences Program, describes using powerful femto-second laser pulses to etch metal surfaces with nanoscale structures that selectively absorb light only at the solar wavelengths, but not elsewhere.

A regular metal surface is shiny and highly reflective. Years ago, the Guo lab developed a black metal technology that turned shiny metals pitch black.

 

But to make a perfect solar absorber,” Guo says, “We need more than a black metal and the result is this selective absorber.”

This surface not only enhances the energy absorption from sunlight, but also reduces heat dissipation at other wavelengths, in effect, “making a perfect metallic solar absorber for the first time,” Guo says. “We also demonstrate solar energy harnessing with a thermal electric generator device.

This will be useful for any thermal solar energy absorber or harvesting device,” particularly in  places with abundant sunlight, he adds.

The researchers experimented with aluminum, copper, steel, and tungsten, and found that tungsten, commonly used as a thermal solar absorber, had the highest solar absorption efficiency when treated with the new nanoscale structures. This improved the efficiency of thermal electrical generation by 130 percent compared to untreated tungsten.

Co-authors include Sohail Jalil, Bo Lai, Mohamed Elkabbash, Jihua Zhang, Erik M. Garcell, and Subhash Singh of the Guo lab.

Source: https://www.rochester.edu/