Scientists have developed energy efficient, ultra-thin light-emitting diodes (LEDs) for next-generation communication technologies.

Light sources that reliably convert electrical to optical signals are of fundamental importance to information processing technologies. Energy-efficient and high-speed LEDs that can be integrated onto a microchip and transmit information are one of the key elements in enabling high volume data communication.

Two-dimensional (2D) semiconductors, graphene-like, atomically thin materials, have recently attracted significant interest due to their size (just a few atoms thick), well-defined light emission properties, and their prospects for on-chip integration. While, in recent years, researchers have succeeded in fabricating LEDs based on these materials, realizing efficient light emission has remained a challenge.

An efficient LED device converts most of its electrical power input into light emission (i.e., with minimal losses due to conversion into other forms of energy such as heat). Previous studies on LEDs based on 2D semiconductors reported that a large amount of electrical current is needed to trigger light emission. This means that a substantial fraction of the input electrical power is dissipated as heat instead of generating light.

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TransistorIncorporating organic electronic materials in the field of bioelectronics has indicated promising potential in interfacing with biological systems, including neuroscience applications. Researchers from Linköping University are taking a major step forward in that work with their development of the world’s first complementary electrochemical logic circuits that can function for long periods of time in water.

While the first printable organic electrochemical sensors appeared as early as 2002, significant advancements have developed in a few years. Organic components such as light-emitting diodes and electrochemical displays are already commercially available.

This from Linköping University:

The dominating material used until now has been PEDOT:PSS, which is a p-type material, in which the charge carriers are holes. In order to construct effective electron components, a complementary material, n-type, is required, in which the charge carriers are electrons.

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GrapheneAdding a little ultrathin hexagonal boron nitride to ceramics could give them outstanding properties, according to new research.

Rouzbeh Shahsavari, an assistant professor of civil and environmental engineering at Rice University, suggests the incorporation of ultrathin hBN sheets between layers of calcium-silicates would make an interesting bilayer crystal with multifunctional properties.

These could be suitable for construction and refractory materials and applications in the nuclear industry, oil and gas, aerospace, and other areas that require high-performance composites.

Combining the materials would make a ceramic that’s not only tough and durable but resistant to heat and radiation. By Shahsavari’s calculations, calcium-silicates with inserted layers of two-dimensional hBN could be hardened enough to serve as shielding in nuclear applications like power plants.

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Quantum dotsResearchers have found an explanation for why a certain class of quantum dots shines with such incredibly bright colors.

The nanocrystals in question contain caesium lead halide compounds arranged in a perovskite lattice structure. Three years ago, Maksym Kovalenko, a professor at ETH Zurich and the Swiss Federal Laboratories for Materials Science and Technology (Empa), succeeded in creating nanocrystals from the same semiconductor material.

“These tiny crystals have proved to be extremely bright and fast emitting light sources, brighter and faster than any other type of quantum dot studied so far,” says Kovalenko.

By varying the composition of the chemical elements and the size of the nanoparticles, Kovalenko also  produced a variety of nanocrystals that light up with the colors of the entire visible spectrum. These quantum dots could be used as components for future light-emitting diodes (LEDs) and displays.

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PlantSensors on tape that attach to plants yield new kinds of data about water use for researchers and farmers.

“With a tool like this, we can begin to breed plants that are more efficient in using water,” says Patrick Schnable, plant scientist at Iowa State University. “That’s exciting. We couldn’t do this before. But, once we can measure something, we can begin to understand it.”

The tool making these water measurements possible is a tiny graphene sensor that can be taped to plants—researchers call it a “plant tattoo sensor.” Graphene is an atom-thick carbon honeycomb. It’s great at conducting electricity and heat, and is strong and stable. The graphene-on-tape technology in this study has also gone into wearable strain and pressure sensors, including sensors for a “smart glove” that measures hand movements.

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By: Srikanth Saripalli, Texas A&M University

Autonomous driverless carIn early November, a self-driving shuttle and a delivery truck collided in Las Vegas. The event, in which no one was injured and no property was seriously damaged, attracted media and public attention in part because one of the vehicles was driving itself – and because that shuttle had been operating for only less than an hour before the crash.

It’s not the first collision involving a self-driving vehicle. Other crashes have involved Ubers in Arizona, a Tesla in “autopilot” mode in Florida and several others in California. But in nearly every case, it was human error, not the self-driving car, that caused the problem.

In Las Vegas, the self-driving shuttle noticed a truck up ahead was backing up, and stopped and waited for it to get out of the shuttle’s way. But the human truck driver didn’t see the shuttle, and kept backing up. As the truck got closer, the shuttle didn’t move – forward or back – so the truck grazed the shuttle’s front bumper.

As a researcher working on autonomous systems for the past decade, I find that this event raises a number of questions: Why didn’t the shuttle honk, or back up to avoid the approaching truck? Was stopping and not moving the safest procedure? If self-driving cars are to make the roads safer, the bigger question is: What should these vehicles do to reduce mishaps? In my lab, we are developing self-driving cars and shuttles. We’d like to solve the underlying safety challenge: Even when autonomous vehicles are doing everything they’re supposed to, the drivers of nearby cars and trucks are still flawed, error-prone humans.

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By: Jeremy Straub, North Dakota State University

Driverless carIn the wake of car- and truck-based attacks around the world, most recently in New York City, cities are scrambling to protect busy pedestrian areas and popular events. It’s extremely difficult to prevent vehicles from being used as weapons, but technology can help.

Right now, cities are trying to determine where and how to place statues, spike strip nets and other barriers to protect crowds. Police departments are trying to gather better advance intelligence about potential threats, and training officers to respond – while regular people are seeking advice for surviving vehicle attacks.

These solutions aren’t enough: It’s impractical to put up physical barriers everywhere, and all but impossible to prevent would-be attackers from getting a vehicle. As a researcher of technologies for self-driving vehicles, I see that potential solutions already exist, and are built into many vehicles on the road today. There are, however, ethical questions to weigh about who should control the vehicle – the driver behind the wheel or the computer system that perceives potential danger in the human’s actions.

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Engineers have developed a flexible sensor “skin” that can stretch over any part of a robot’s body or prosthetic to accurately convey information about shear forces and vibration—information critical to grasping and manipulating objects.

If a robot sets out to disable a roadside bomb—or delicately handle an egg while cooking you an omelet—it needs to be able to sense when objects are slipping out of its grasp. Yet, to date, it’s been difficult or impossible for most robotic and prosthetic hands to accurately sense the vibrations and shear forces that occur, for example, when a finger is sliding along a tabletop or when an object begins to fall.

To solve that issue, the bio-inspired robot sensor skin mimics the way a human finger experiences tension and compression as it slides along a surface or distinguishes among different textures. It measures this tactile information with similar precision and sensitivity as human skin, and could vastly improve the ability of robots to perform everything from surgical and industrial procedures to cleaning a kitchen.

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PaperA new flexible, paper-based supercapacitor could power wearable electronics.

The device uses metallic nanoparticles to coat cellulose fibers in the paper, creating supercapacitor electrodes with high energy and power densities—and the best performance so far in a textile-based supercapacitor.

By implanting conductive and charge storage materials in the paper, the researchers’ layer-by-layer technique creates large surface areas that function as current collectors and nanoparticle reservoirs for the electrodes. Testing shows that devices fabricated with the technique can be folded thousands of times without affecting conductivity.

“This type of flexible energy storage device could provide unique opportunities for connectivity among wearable and internet of things devices,” says Seung Woo Lee, an assistant professor in the Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. “We could support an evolution of the most advanced portable electronics. We also have an opportunity to combine this supercapacitor with energy-harvesting devices that could power biomedical sensors, consumer and military electronics, and similar applications.”

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The development of prosthetics has changed many lives, providing mobility options and allowing for more active lives. But all artificial limbs aren’t perfect. Some can be painful, difficult to use, and lead to possible skin infections. The Office of Naval Research is looking to change that, providing new options for those in need of artificial limbs.

By teaming up with the Walter Reed National Military Medical Center, the Office of Naval Research has developed a “smart” artificial leg, using sensor technology to monitor walking, alter the way the user wears the prosthetic to aid in comfortability and reduce wear and tear, and warn of potential infection risks. They’re referring to this development as Monitoring Ossolntegrated Prosthesis (MOIP).

“This new class of intelligent prostheses could potentially have a profound impact on warfighters with limb loss,” says Liming Salvino, a program officer in ONR’s Warfighter Performance Department. “MOIP not only can improve quality of life, but also usher in the next generation of prosthetic limbs.”

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