ElectronicsA new process for growing wafer-scale 2D crystals could enable future super-thin electronics.

Since the discovery of the remarkable properties of graphene, scientists have increasingly focused research on the many other two-dimensional materials possible, both those found in nature and those concocted in the lab.

Growing high-quality, crystalline 2D materials at scale, however, has proven a significant challenge.

Researchers led by Joan Redwing, director of the National Science Foundation-sponsored Two-Dimensional Crystal Consortium—Materials Innovation Platform, and professor of materials science and engineering and electrical engineering at Penn State, developed a multistep process to make single crystal, atomically thin films of tungsten diselenide across large-area sapphire substrates.

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Flexible materialStress a muscle and it gets stronger. Mechanically stress a new rubbery material—say with a twist or a bend—and it automatically stiffens by up to 300 percent, the engineers say.

In lab tests, mechanical stresses transformed a flexible strip of the material into a hard composite that can support 50 times its own weight.

This new composite material doesn’t need outside energy sources such as heat, light, or electricity to change its properties. And it could be used in a variety of ways, including applications in medicine and industry.

The researchers found a simple, low-cost way to produce particles of undercooled metal—that’s metal that remains liquid even below its melting temperature. Researchers created the tiny particles (they’re just 1 to 20 millionths of a meter across) by exposing droplets of melted metal to oxygen, creating an oxidation layer that coats the droplets and stops the liquid metal from turning solid. They also found ways to mix the liquid-metal particles with a rubbery elastomer material without breaking the particles.

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Scientists who introduced laser-induced graphene (LIG) enhanced their technique to produce what may become a new class of edible electronics.

The chemists, who once turned Girl Scout cookies into graphene, are investigating ways to write graphene patterns onto food and other materials to quickly embed conductive identification tags and sensors into the products themselves.

“This is not ink,” says James Tour, chair of chemistry and professor of computer science and of materials science and nanoengineering at Rice University. “This is taking the material itself and converting it into graphene.”

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ElectronsWhile tracking electrons moving through exotic materials, researchers have discovered intriguing properties not found in conventional, silicon-based semiconductors.

Unlike current silicon-based electronics, which shed most of the energy they consume as waste heat, the future is all about low-power computing. Known as spintronics, this technology relies on a quantum physical property of electrons—up or down spin—to process and store information, rather than moving them around with electricity as conventional computing does.

On the quest to making spintronic devices a reality, scientists at the University of Arizona are studying an exotic crop of materials known as transition metal dichalcogenides, or TMDs. TMDs have exciting properties lending themselves to new ways of processing and storing information and could provide the basis of future transistors and photovoltaics—and potentially even offer an avenue toward quantum computing.

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GrapheneNew graphene printing technology can produce electronic circuits that are low-cost, flexible, highly conductive and water repellent, researchers report.

The nanotechnology “would lend enormous value to self-cleaning wearable/washable electronics that are resistant to stains, or ice and biofilm formation,” according to the new paper.

“We’re taking low-cost, inkjet-printed graphene and tuning it with a laser to make functional materials,” says Jonathan Claussen, an assistant professor of mechanical engineering at Iowa State University, an associate of the US Department of Energy’s Ames Laboratory, and the corresponding author of the paper in the journal Nanoscale.

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Carbon dioxide Scientists have found a way to make their asphalt-based sorbents better at capturing carbon dioxide from gas wells: Adding water.

The lab of chemist James Tour, a chair in chemistry as well as a professor of computer science and of materials science and nanoengineering at Rice University, discovered that treating grains of inexpensive Gilsonite asphalt with water allows the material to adsorb more than two times its weight in the greenhouse gas. The treated asphalt selects carbon dioxide over valuable methane at a ratio of more than 200-to-1.

The material performs well at ambient temperatures and under the pressures typically found at wellheads. When the pressure abates, the material releases the carbon dioxide, which can then be stored, sold for other industrial uses, or pumped back downhole.

Natural gas at the wellhead typically contains between 3 and 7 percent carbon dioxide, but at some locations may contain up to 70 percent. Oil and gas producers traditionally use one of two strategies to sequester carbon dioxide: physically through the use of membranes or solid sorbents like zeolites or porous carbons, or chemically through filtering with liquid amine, a derivative of ammonia.

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GraphenePillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, report engineers.

Materials scientist Rouzbeh Shahsavari of Rice University and alumnus Navid Sakhavand first built atom-level computer models of pillared graphene—sheets of graphene connected by covalently bonded carbon nanotubes—to discover their strength and electrical properties as well as their thermal conductivity.

In a new study, they found that manipulating the joints between the nanotubes and graphene has a significant impact on the material’s ability to direct heat. That could be important as electronic devices shrink and require more sophisticated heat sinks.

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A reversible fabric keeps skin a comfortable temperature whatever the weather—and could save energy by keeping us away from the thermostat.

As reported in Science Advances, the double-sided fabric is based on the same material as everyday kitchen wrap and can offer warmth or cooling depending on which side faces out.

“Why do you need to cool and heat the whole building? Why don’t you cool and heat individual people?” says Yi Cui, professor of materials science and engineering at Stanford University, who thought if people could be more comfortable in a range of temperatures, they could save energy on air conditioning and central heating.

Thirteen percent of all of the energy consumed in the United States is due to indoor temperature control. But for every 1 degree Celsius (1.8 degrees Fahrenheit) that a thermostat is turned down, a building can save a whopping 10 percent of its heating energy—and the reverse is true for cooling. So adjusting temperature controls by just a few degrees could have major effects on energy consumption.

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Researchers have developed a type of “smart paper” that can conduct electricity and detect water.

The paper, laced with conductive nanomaterials, can be employed as a switch, turning on or off an LED light, or as an alarm system indicating the absence or presence of water.

In cities and large-scale manufacturing plants, a water leak in a complicated network of pipes can take tremendous time and effort to detect, as technicians must disassemble many pieces to locate the problem.

The American Water Works Association indicates that nearly a quarter-million water line breaks occur each year in the United States, costing public water utilities about $2.8 billion annually.

The smart paper could simplify the process for discovering detrimental leaks.

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GrapheneScientists have learned how to tame the unruly electrons in graphene.

Graphene is a nano-thin layer of the carbon-based graphite in pencils. It is far stronger than steel and a great conductor. But when electrons move through it, they do so in straight lines and their high velocity does not change. “If they hit a barrier, they can’t turn back, so they have to go through it,” says Eva Y. Andrei, professor in the Rutgers University-New Brunswick department of physics and astronomy and the study’s senior author.

“People have been looking at how to control or tame these electrons.”

Graphene is a better conductor than copper and is very promising for electronic devices.

The new research “shows we can electrically control the electrons in graphene,” says Andrei. “In the past, we couldn’t do it. This is the reason people thought that one could not make devices like transistors that require switching with graphene, because their electrons run wild.”

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