TechFront Research and Development in Manufacturing and Technology Researchers Develop a Muscular Micro Material V
anadium dioxide, already known for its ability to change size, shape and physical identity, could add super strength in a tiny package to its list of impressive attributes. A team of researchers at the US Department of En- ergy’s (DOE) Lawrence Berkeley National Laboratory (Berke- ley Lab) recently demonstrated how a micro-sized torsional muscle motor constructed of vanadium dioxide is thousands of times stronger than a human muscle. The researchers showed that the micro mate- rial was able to catapult objects 50 times heavier than itself over a distance five times its length within 60 milliseconds, or faster than the blink of an eye. “We’ve created a micro-bimorph dual coil that functions as a powerful torsional muscle, driven thermally or electro-thermally by the phase transi- tion of vanadium dioxide,” said the leader of this work, Junqiao Wu. “Using a simple design and in- organic materials, we achieve superior performance in power density and speed over the motors and actuators now used in integrated micro-systems.” Wu, a physicist who holds joint appointments with Berkeley Lab’s Materials Sciences Division and the University of California-Berkeley’s Department of Materials Science and Engineering, is the author of a paper describing the research in the journal Advanced Materials. The paper, entitled “Powerful, Multifunctional Torsional Micro Muscles Activated by Phase Transition,” was co-authored by Kai Liu, Chun Cheng, Joonki Suh, Robert Tang-Kong, Deyi Fu, Sangwook Lee, Jian Zhou and Leon Chua. The vanadium dioxide discovery is key for electronics industry researchers because it is one of the few known materials that’s an insulator at low temperatures, but abruptly becomes a conductor at 67° C. The temperature-driven phase transition from insulator-to-metal is expected to one day yield faster, more energy-efficient electronic and optical devices. Vanadium dioxide crystals also undergo a temperature-driven structural phase transition whereby when warmed they rapidly contract along one dimension while expanding along the other
two, making them an ideal material for miniaturized, multi- functional motors and artificial muscles.
“Miniaturizing rotary motors is important for integrated micro-systems and has been intensively pursued over the past decades,” Wu said. “The power density of our micro-muscle in combination with its multifunctionality distinguishes it from all current macro- or micro-torsional actuators/motors.”
A research team led by Junqiao Wu at the US Department of Energy’s (DOE) Lawrence Berkeley National Laboratory demonstrated how a micro-sized torsional muscle motor constructed of vanadium dioxide its thousands of times stronger than a human muscle.
The researchers fabricated a micro-muscle on a silicon substrate from a long “V-shaped” bimorph ribbon comprised of chromium and vanadium dioxide. When the V-shaped rib- bon is released from the substrate it forms a helix consisting of a dual coil that is connected at either end to chromium electrode pads. Heating the coil actuates it, turning it into either a micro-catapult, in which an object held in the coil is hurled when the coil is actuated, or a proximity sensor, in which remote sensing of an object (without touching it)
March 2014 |
ManufacturingEngineeringMedia.com 37
Image courtesy Lawrence Berkeley National Laboratory
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