Tech Front: Researchers Develop a Muscular Micro Material
Vanadium 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 Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley 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 material 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 transition of vanadium dioxide,” said the leader of this work, Junqiao Wu. “Using a simple design and inorganic 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, multifunctional 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.”
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 ribbon 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) causes a “micro-explosion,” a rapid change in the micro-muscle’s resistance and shape that pushes the object away.
“Multiple micro-muscles can be assembled into a micro-robotic system that simulates an active neuromuscular system,” Wu said. “The naturally combined functions of proximity sensing and torsional motion allow the device to remotely detect a target and respond by reconfiguring itself to a different shape. This simulates living bodies where neurons sense and deliver stimuli to the muscles and the muscles provide motion.”
The vanadium dioxide micro-muscles demonstrated reversible torsional motion over one million cycles with no degradation, according to the researchers. They also showed a rotational speed of up to approximately 200,000 rpm, amplitude of 500–2000 degrees per millimeters in length, and an energy power density up to approximately 39 kilowatts/kilogram.
This work was supported by a DOE Office of Science Early Career Award to the University of California, Berkeley. For more information on the Berkeley Lab, see www.lbl.gov. ME
New Study Shows EVs Have Little Impact on US Pollutant Emissions
New research from North Carolina State University (Raleigh, NC) contends that even a sharp increase in electric-drive passenger vehicles (EDVs), including hybrid, plug-in hybrid and battery electric vehicles, would not significantly lower emissions of the air pollutants carbon dioxide, sulfur dioxide or nitrogen oxides by 2050.
“We wanted to see how important EDVs may be over the next 40 years in terms of their ability to reduce emissions,” says Joseph DeCarolis, an assistant professor of civil, construction and environmental engineering at NC State and senior author of a paper on the model. “We found that increasing use of EDVs is not an effective way to produce large emissions reductions.”
The NC State researchers ran 108 different scenarios in a powerful energy systems model to determine the impact of EDV use on emissions between now and 2050. Their conclusion: Even if EDVs made up 42% of passenger vehicles in the US, there would be little or no reduction in the emission of key air pollutants. The researchers’ energy systems model also showed that key factors in encouraging use of EDVs are oil price and battery cost. If batteries are cheap and oil is expensive, DeCarolis said, EDVs become more attractive.
For more information, see “How Much Do Electric Drive Vehicles Matter to Future US Emissions?” (see http://tinyurl.com/EDVstudy), published in Environmental Science & Technology. The research was supported by a National Science Foundation grant. ME
Additive Manufacturing n the News
The Jan. 21 announcement by the National Additive Manufacturing Innovation Institute (NAMII; Youngstown, OH; www.americamakes.us) of 15 second-call award selections reflects the continued advancement of the state of the art and technical teaming involving 75 individual academic, corporate and government partners.
Ongoing NAMII projects along with the new awards represent nearly $30 million of public and private funds invested for innovation in additive manufacturing (AM) in the US. Added to the defined program of NAMII is a phenomenal flow of transformative ideas—ranging from customizing military parts on-site to creating instructional lab equipment to documenting a child’s vaccinations in a developing country—that show the capability of 3D printing to meet unique needs piece by piece and person by person.
With thousands of open-source designs (many by free download, such as from www.Thingiverse.com) and replicating rapid prototyping (Rep-Rap) machines, including do-it-yourself kits such as those by MakerBot Industries (Brooklyn, NY; www.makerbot.com), even an average homeowner, with a moderate level of technical skill, can conceivably make a needed snowblower or solar panel part.
Some of the recently announced NAMII projects:
- A team led by the McGowan Institute for Regenerative Medicine at the University of Pittsburgh (www.mirm.pitt.edu), partnering with ExOne and Magnesium Elektron Powders, will work to develop AM methods to convert magnesium and iron-based alloys into biomedical devices produced by a binder jet printing shape-making approach.
- The goal of a project led by North Carolina State University (Raleigh, NC; www.engr.ncsu.edu) with Advanced Machining, CalRAM Inc., FineLine Prototyping Inc., Iowa State University, John Deere, Kennametal and Productivity Inc., is to create a hybrid additive-then-subtractive system that can digitally manufacture mechanical products that meet required final geometric accuracy.
- Michigan Technological University (Houghton, MI; www.mse.mtu.edu), working with Aleph Objects Inc., ASM International, Miller/ITW, ThermoAnalytics Inc. and The Timken Co., will focus on commercialization steps for an ultra-low-cost 3D metal printer and development of new 3D printable aluminum alloys.
- The 3D metal printer idea by Michigan Tech associate professor Joshua Pearce and colleagues has also received coverage in the popular media and is described in an IEEE Access article (http://tinyurl.com/otb3eut). Pearce champions 3D printing as a benefit to people in the developing world, who have limited access to manufactured goods, and to researchers and instructors with limited scientific equipment budgets.
- Focusing on the assessment of a laser-assisted, wire-based additive process developed by the Lincoln Electric Co. (Cleveland; www.lincolnelectric.com) for different high-throughput functional material deposition applications, and benchmarking it against a laser/powder-based AM process, is a team led by Case Western Reserve University (Cleveland; www.cwru.edu) and partners Aquilex Corporate Technology Center, Lincoln Electric, rp+m Inc. and RTI International Metals.
Related Technical Papers
More than 100 SME Technical Papers cover additive manufacturing topics, including TP13PUB82, which describes three open-source machines built or redesigned at Robert Morris University (Moon Twp, PA; www.sems.rmu.edu/engineering )—two based on fused filament fabrication (FFF) and digital light processing (DLP) technologies, and another on the modification of a numerically controlled (NC) router into an extruder based on FFF. The project costs varied within a range of $200–$1000, and future work will include experimenting with additional biologically friendly materials for biomedical engineering and with composite materials for various applications. ME
TechFront is edited by Senior Editors Patrick Waurzyniak, firstname.lastname@example.org, and Ellen Kehoe, email@example.com.
This article was first published in the March 2014 edition of Manufacturing Engineering magazine. Click here for PDF.
Published Date : 3/1/2014