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Researchers Control Surface Tension of Liquid Metals

Researchers from North Carolina State University have developed a technique for controlling the surface tension of liquid metals by applying very low voltages, opening the door to a new generation of reconfigurable electronic circuits, antennas and other technologies. The technique hinges on the fact that the oxide “skin” of the metal – which can be deposited or removed – acts as a surfactant, lowering the surface tension between the metal and the surrounding fluid.The researchers used a liquid metal alloy of gallium and indium. In base, the bare alloy has a remarkably high surface tension of about 500 millinewtons (mN)/meter, which causes the metal to bead up into a spherical blob. “But we discovered that applying a small, positive charge – less than 1 volt – causes an electrochemical reaction that creates an oxide layer on the surface of the metal, dramatically lowering the surface tension from 500 mN/meter to around 2 mN/meter,” says Dr. Michael Dickey, an associate professor of chemical and biomolecular engineering at NC State and senior author of a paper describing the work. “This change allows the liquid metal to spread out like a pancake, due to gravity.”The researchers also showed that the change in surface tension is reversible. If researchers flip the polarity of the charge from positive to negative, the oxide is eliminated and high surface tension is restored.  The surface tension can be tuned between these two extremes by varying the voltage in small steps.SourceAlso: Learn about Gradient Metal Alloys Fabricated Using Additive Manufacturing.

Posted in: Electronics & Computers, Electronics, Power Management, Materials, Metals, RF & Microwave Electronics, Antennas, News

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'Squid Skin' Metamaterial Yields Vivid Color Display

The quest to create artificial "squid skin" — camouflaging metamaterials that can "see" colors and automatically blend into the background — is one step closer to reality, thanks to a color-display technology by Rice University's Laboratory for Nanophotonics (LANP).The new full-color display technology uses aluminum nanoparticles to create the vivid red, blue, and green hues found in today's top-of-the-line LCD televisions and monitors.The breakthrough is the latest in a string of recent discoveries by a Rice-led team that set out in 2010 to create metamaterials capable of mimicking the camouflage abilities of cephalopods — the family of marine creatures that includes squid, octopus, and cuttlefish.LANP's new color display technology delivers bright red, blue, and green hues from five-micron-square pixels that each contains several hundred aluminum nanorods. By varying the length of the nanorods and the spacing between them, LANP researchers Stephan Link and Jana Olson showed they could create pixels that produced dozens of colors, including rich tones of red, green, and blue that are comparable to those found in high-definition LCD displays.

Posted in: Imaging, Displays/Monitors/HMIs, Materials, Nanotechnology, News

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Untethered Soft Robot Walks Through Flames

Developers from Harvard’s School of Engineering and Applied Sciences and the Wyss Institute for Biologically Inspired Engineering have produced the first untethered soft robot — a quadruped that can stand up and walk away from its designers.The researchers were able to scale up earlier soft-robot designs, enabling a single robot to carry on its back all the equipment it needs to operate — micro-compressors, control systems, and batteries.Compared with earlier soft robots, which were typically no larger than a steno pad, the system is huge, measuring more than a half-meter in length and capable of carrying as much as 7½ pounds on its back.Giving the untethered robot the strength needed to carry mechanical components meant air pressures as high as 16 pounds per square inch, more than double the seven psi used by many earlier robot designs. To deal with the increased pressure, the robot had to be made of tougher stuff.The material settled on was a “composite” silicone rubber made from stiff rubber impregnated with hollow glass microspheres to reduce the robot’s weight. The robot’s bottom was made from Kevlar fabric to ensure it was tough and lightweight. The result was a robot that can stand up to a host of extreme conditions.SourceAlso: Learn about a Field-Reconfigurable Manipulator for Rovers.

Posted in: Materials, Composites, Mechanical Components, Motion Control, Motors & Drives, Machinery & Automation, Robotics, News

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Researchers Create See-Through Solar Concentrator

A team of researchers at Michigan State University has developed a new type of solar concentrator that when placed over a window creates solar energy.The device is called a transparent luminescent solar concentrator and can be used on buildings, cell phones, and any other device that has a clear surface.And, according to Richard Lunt of MSU’s College of Engineering, the key word is “transparent.”The solar harvesting system uses small organic molecules developed by Lunt and his team to absorb specific nonvisible wavelengths of sunlight.The “glowing” infrared light is guided to the edge of the plastic where it is converted to electricity by thin strips of photovoltaic solar cells.“Because the materials do not absorb or emit light in the visible spectrum, they look exceptionally transparent to the human eye,” said Richard Lunt of MSU’s College of Engineering.SourceAlso: Learn about High-Efficiency Nested Hall Thrusters for Robotic Solar System Exploration.

Posted in: Materials, Plastics, Solar Power, Renewable Energy, Energy, Semiconductors & ICs, News

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Water Splitter Runs on AAA Battery

Scientists at Stanford University have developed a low-cost, emissions-free device that uses an ordinary AAA battery to produce hydrogen by water electrolysis.  The battery sends an electric current through two electrodes that split liquid water into hydrogen and oxygen gas. Unlike other water splitters that use precious-metal catalysts, the electrodes in the Stanford device are made of inexpensive and abundant nickel and iron.In addition to producing hydrogen, the novel water splitter could be used to make chlorine gas and sodium hydroxide, an important industrial chemical. Splitting water to make hydrogen requires no fossil fuels and emits no greenhouse gases. But scientists have yet to develop an affordable, active water splitter with catalysts capable of working at industrial scales."It's been a constant pursuit for decades to make low-cost electrocatalysts with high activity and long durability," said Stanford University Professor Hongjie Dai. "When we found out that a nickel-based catalyst is as effective as platinum, it came as a complete surprise."SourceAlso: Learn about a Proton Exchange Membrane Fuel Cell.

Posted in: Batteries, Electronics & Computers, Power Management, Alternative Fuels, Green Design & Manufacturing, Materials, Metals, Energy, News

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Researchers Create Energy-Absorbing Material

Materials like solid gels and porous foams are used for padding and cushioning, but each has its own advantages and limitations.A team of engineers and scientists at Lawrence Livermore National Laboratory (LLNL) has found a way to design and fabricate, at the microscale, new cushioning materials with a broad range of programmable properties and behaviors that exceed the limitations of the material's composition, through additive manufacturing, also known as 3D printing. Livermore researchers, led by engineer Eric Duoss and scientist Tom Wilson, focused on creating a micro-architected cushion using a silicone-based ink that cures to form a rubber-like material after printing. During the printing process, the ink is deposited as a series of horizontally aligned filaments (which can be fine as a human hair) in a single layer. The second layer of filaments is then placed in the vertical direction. This process repeats itself until the desired height and pore structure is reached.The researchers envision using their novel energy-absorbing materials in many applications, including shoe and helmet inserts, protective materials for sensitive instrumentation, and in aerospace applications to combat the effects of temperature fluctuations and vibration.SourceAlso: Read more Materials tech briefs.

Posted in: Manufacturing & Prototyping, Rapid Prototyping & Tooling, Materials, Aerospace, Defense, News

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NASA 3D Printing Technique Creates Metal Spacecraft Parts

Researchers at NASA's Jet Propulsion Laboratory are implementing a printing process that transitions from one metal or alloy to another in a single object. JPL scientists have been developing a technique to address this problem since 2010. An effort to improve the methods of combining parts made of different materials in NASA's Mars Science Laboratory mission inspired a project to 3D print components with multiple alloy compositions.

Posted in: Manufacturing & Prototyping, Rapid Prototyping & Tooling, Materials, Metals, Aerospace, News

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