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: News, Electronics, Power Management, Metals, Antennas


Engineers Prepare Battery Module Swapping Approach for Electric Cars

Imagine being able to switch out the batteries in electric cars just like you switch out batteries in a photo camera or flashlight. A team of engineers at the University of California, San Diego, are trying to accomplish just that, in partnership with a local San Diego engineering company.Rather than swapping out the whole battery, which is cumbersome and requires large, heavy equipment, engineers plan to swap out and recharge smaller units within the battery, known as modules.Swapping battery modules could also have far-reaching implications for mobile and decentralized electrical energy storage systems such as solar backup and portable generators. The technology can make energy storage more configurable, promote safety, simplify maintenance and eventually eliminate the use of fossil fuels for these applications.Engineers not only believe that their approach is viable, but also plan to prove it. They will embark on a cross-country trip with a car powered by the removable, rechargeable M-BEAM, or Modular Battery Exchange and Active Management, battery modules.  They plan to drive from coast to coast only taking breaks that are a few minutes long to swap out the modules that will be recharged in a chase vehicle. They believe they can drive from San Diego to the coast of South Carolina less than 60 hours — without going over the speed limit.SourceAlso: Learn about a Full-Cell Evaluation/Screening Technique for New Battery Chemistries.

Posted in: News, Batteries, Power Management, Renewable Energy, Solar Power


'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: News, Displays/Monitors/HMIs


New Algorithm Lets Cheetah Robot Run

Speed and agility are hallmarks of the cheetah: The big predator is the fastest land animal on Earth, able to accelerate to 60 mph in just a few seconds. As it ramps up to top speed, a cheetah pumps its legs in tandem, bounding until it reaches a full gallop.Now MIT researchers have developed an algorithm for bounding that they’ve successfully implemented in a robotic cheetah — a sleek, four-legged assemblage of gears, batteries, and electric motors that weighs about as much as its feline counterpart. The team recently took the robot for a test run on MIT’s Killian Court, where it bounded across the grass at a steady clip. In experiments on an indoor track, the robot sprinted up to 10 mph, even continuing to run after clearing a hurdle. The MIT researchers estimate that the current version of the robot may eventually reach speeds of up to 30 mph.The key to the bounding algorithm is in programming each of the robot’s legs to exert a certain amount of force in the split second during which it hits the ground, in order to maintain a given speed: In general, the faster the desired speed, the more force must be applied to propel the robot forward. In experiments, the team ran the robot at progressively smaller duty cycles, finding that, following the algorithm’s force prescriptions, the robot was able to run at higher speeds without falling. Sangbae Kim, an associate professor of mechanical engineering at MIT, says the team’s algorithm enables precise control over the forces a robot can exert while running. SourceAlso: Learn about Hall Thrusters for Robotic Solar System Exploration.

Posted in: News, Motors & Drives, Machinery & Automation, Robotics


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: News, Composites, Motors & Drives, Machinery & Automation, Robotics


Unmanned "Urban Beat Cop" Surveillance System Protects Soldiers

In a non-combat environment, information is typically collected by local law enforcement officers who are "walking their beat." Air Force expeditionary forces in Afghanistan requested a system that would give them similar situational awareness in Afghan villages and other remote areas, but without human participation or requiring them to "walk a beat." So, the Air Force and a small business partner recently developed and tested in the field a small, unmanned aircraft system (SUAS) that allows U.S. military forces to perform strategic reconnaissance while staying out of harm's way.

Posted in: News, Aviation, Video


Testing Electric Propulsion

Could this be the future — a plane with many electric motors that can hover like a helicopter and fly like a plane, and that could revolutionize air travel?

Posted in: News


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