[Engineering Feature]
Military R&D 101
Many of the military’s newest and most sophisticated technologies lie behind ivy-covered walls on the nation’s campuses.
SHAPE SHIFTER When Yet-Ming Chiang looks at a flying bird, he admires its beauty and grace. But as an engineer, he also marvels at how the creature can quickly change its shape to fly faster and more efficiently.
Inspired by birds and DARPA funding, the Massachusetts Institute of Technology (MIT) materials science and engineering professor is working to boost the performance of aircraft and ships by enabling them to morph from one shape into another. Strangely enough, Chiang's research is based on a detrimental battery property, the fact that power cells expand and contract as they're charged and recharged.
"We looked at this behavior and thought we could use it for another purpose: the actuation of large-scale structures," says Chiang. The approach could lead to an airplane that morphs on demand from a shape designed for agility to one that aims for maximum fuel efficiency. Likewise, a ship or submarine could be designed with a hull that changes its shape in response to speed, steering, and water conditions.
To test the concept, Chiang and co-researcher Steven Hall, an MIT aeronautics and astronautics professor, started evaluating commercially available lithium rechargeable batteries (Fig. 2). They confirmed that the batteries continued to expand and contract under tremendous stresses—a must for devices that will change the shape of structures like airplane wings, helicopter rotors, and ship hulls. The researchers also discovered that the batteries can be used as actuators at low voltages (under 5 V) and that the materials that make up the batteries are also inherently light—an important consideration for aircraft use.
Later this year, Chiang and Hall hope to demonstrate a shape-morphing helicopter rotor blade. Yet even if that test proves successful, Chiang notes that much work remains to be done before shape-shifting military or commercial vehicles become a reality. Still, he's optimistic that the research will eventually lead to a practical technology. "The fact that we've been able to demonstrate the potential of this approach using unoptimized off-the-shelf batteries is a hopeful sign," he says.
DATA EXPRESS Taking advantage of $9.5 million in DARPA funding, S.J. Ben Yoo, an electrical and computer engineering professor at the University of California, Davis, plans to develop a technology that will push optical data transmission speeds through the roof. Working in cooperation with researchers at MIT and several commercial partners, Yoo's team plans to design, build, and test thumbnail-sized chips that can potentially encode data at rates of up to 100 THz, some 10,000 times faster than currently available devices (Fig. 3).
"We will be prototyping a compact optical waveform generator capable of communicating at unprecedented bandwidth," says Yoo, who is director of the UC Davis Center for Information Technology Research in the Interest of Society.
Over the next three years, Yoo's research team will be prototyping a new microsystem capable of manipulating and encoding mid-infrared light carrier comb frequencies. Besides ultra-high capacity communications, the improved technology could lead to the development of high-resolution light-based radars (ladars), enhanced medical imaging systems, and even electrical signal synthesizers capable of extremely rich electronic tones.
Yoo says the military envisions several future applications, including ultra-high resolution surveillance capabilities.
"They have a very keen interest in remote sensing and imaging," he says. The military would most like to nullify the enemy's ability to hide inside complex mountain terrains and cityscapes. A very compact ultra-high-resolution imaging system installed on an unmanned air vehicle (UAV), such as a Predator, could eliminate the need to send troops on reconnaissance missions into hostile areas.
"The military says they can image a tennis or soccer ball on a field from a satellite, but they want to do much better than that," says Yoo. "If they use our technology, they can make the resolution a thousand times better." That would allow the military to not only image a ball from space, but closely examine its surface texture—or the beads of sweat on an enemy combatant's forehead. Potential commercial applications include speedier optical data networks and higher-resolution, more realistic maps for personal navigation devices.
SMALL-SCALE RESEARCH Nanotechnology has emerged over the past several years as a key defense-funded research area. Military planners are tantalized by the potential of using molecularsized machines to virtually invisibly treat and monitor injuries and diseases, provide hands-free communications systems, sense hazardous materials, and accomplish a variety of other important tasks.
Chris Phoenix, research director of the Center for Responsible Nanotechnology, a non-profit research and advocacy organization, expects many military-funded nanotechnology projects to eventually find commercial applications.
"Molecular manufacturing, the mature general-purpose form of nanotechnology, will have a significant impact on almost all parts of society," he says. "Personal nanofactories, working rapidly and directly from blueprints, may offer advanced products for a wide range of applications including home, medicine, and industry."
Like conventional technologies, nanodevices require a steady and reliable power source. Zhong Lin Wang, a materials science and engineering professor at the Georgia Institute of Technology, wants to convert mechanical energy from body movement, flowing water, structural vibrations, and other everyday sources into electricity.
His goal is to create a nanogenerator that can power a wide range of nanodevices without bulky energy sources such as batteries. "The nanogenerator could be the foundation for exploring new self-powering technologies for in-situ, real-time, and implantable biosensing, biomedical monitoring, and biodetection [devices], with great potential for defense and civil applications," says Wang.
With funding from DARPA, NSF, and the NASA Vehicle Systems Program, Wang is building nanogenerators that create tiny piezoelectric discharges when zinc-oxide nanowires are bent and then released. Ideal for use inside the body, because zinc oxide is non-toxic, the nanogenerators could also be used wherever mechanical energy is available. The nanowires can be grown on crystal substrates, as well as polymer-based films. Flexible polymer substrates could one day allow portable devices to be powered by the movement of their users.
"You might even place nanogenerators in your shoes to produce electricity as you walk," says Wang. That could help soldiers in the field, who now require batteries to power an ever-growing assortment of radios and other electrical equipment. "As long as the soldiers were moving, they could generate electricity," he says.
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