[Editors] MIT moves toward vehicles that morph

[Elizabeth Thomson]

MIT News Office
Massachusetts Institute of Technology
Room 11-400
77 Massachusetts Avenue
Cambridge, MA  02139-4307
Phone: 617-253-2700
http://web.mit.edu/newsoffice/www

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MIT makes move toward vehicles that morph
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For Immediate Release
WEDNESDAY, MAR. 22, 2006
Contact: Elizabeth A. Thomson, MIT News Office
Phone: 617-258-5402
Email: thomson at mit.edu

--PHOTO AVAILABLE--

CAMBRIDGE, Mass.--Picture a bird, effortlessly adjusting its wings to 
catch every current of air. Airplanes that could do the same would 
have many advantages over today's flying machines, including 
increased fuel efficiency.

Now MIT engineers report they may have found a way for structures -- 
and materials -- to move in this way, essentially morphing from one 
shape into another.

The discovery could lead to an airplane that morphs on demand from 
the shape that is most energy efficient to another better suited to 
agility, or to a boat whose hull changes shape to allow more 
efficient movement in choppy, calm or shallow waters.

This science-fiction outcome, in the works for 20 years, has been 
unobtainable with such conventional devices as hydraulics, which 
aren't practical for a variety of reasons -- from cost to weight to 
ease of movement.

MIT's work involves a new application of a familiar device: the 
rechargeable battery. Papers describing the team's progress appeared 
earlier this year in Advanced Functional Materials and 
Electrochemical and Solid-State Letters.

Batteries expand and contract as they are charged and recharged. 
"This has generally been thought to be something detrimental to 
batteries. But I thought we could use this behavior to another end: 
the actuation, or movement, of large-scale structures," said Yet-Ming 
Chiang, the Kyocera Professor in the Department of Materials Science 
and Engineering (MSE).

Chiang and Professor Steven R. Hall of the Department of Aeronautics 
and Astronautics led a team that also includes MSE graduate student 
Timothy E. Chin and postdoctoral associate Yukinori Koyama, 
aero-astro graduate student Fernando Tubilla and postdoctoral 
associate Kyung Yeol Song, and three visiting students, Urs Rhyner 
(from the Swiss Federal Institute of Technology, ETH-Zurich) and 
Dimitrios Sapnaras and Georg Baetz (University of Karlsruhe, Germany).

Several types of "active" materials are already used to move devices 
ranging from miniature motors to micropositioners. None, however, 
"can enable the large-scale structural morphing we've been working 
toward," Hall said.

For example, some "smart materials" called piezoelectrics can change 
shape in less than the blink of an eye, but they do so on almost a 
microscopic level. They wouldn't be capable of moving a wing the 
distance necessary to affect flight.

Similarly, shape-memory alloys have characteristics useful to 
large-scale actuation, but they require temperature control to work. 
"So to make them work you've got to keep them warm and insulate them. 
And if you insulate them, it takes a long time to cool them down if 
you want them to return to their original shape," Hall said. Those 
are not exactly optimum conditions for seamless morphing.

In the quest for materials that would allow such morphing, engineers 
have recently focused on nature's approach to the problem. A plant 
that bends toward the light, quickly furls its leaves when touched, 
or pushes a concrete sidewalk aloft with its roots is essentially 
moving fluids between cells.

Chiang realized that the solid compounds used to store electrical 
energy in lithium rechargeable batteries could be made to work in a 
similar way. The movement of ions to and from these materials during 
charging and recharging, he thought, was analogous to the moving 
fluids in plants. Could this be a synthetic counterpart to nature's 
solution?

To find out, Chiang and Hall began testing commercially available 
rechargeable batteries of a prismatic form, then designed their own 
devices composed of graphite posts surrounded by a lithium source. 
The results were promising.

Among other things, they found that the batteries continued to expand 
and contract under tremendous stresses, a must for devices that will 
be changing the shape of, say, a stiff helicopter rotor that's also 
exposed to aerodynamic forces.

Other key advantages of the approach: The electrically activated 
batteries can operate at low voltages (less than five volts) as 
compared to the hundreds of volts required by piezoelectrics. The 
materials that make up the batteries are also inherently light. "For 
things that fly, weight is important," Hall said.

The researchers have already demonstrated basic battery-based 
actuators that can pull and push with large force. Later this year, 
they hope to demonstrate the shape-morphing of a helicopter rotor 
blade. The morphing capability should allow for a more efficient 
design, ultimately making it possible for a vehicle to carry heavier 
loads. Team members say that other applications, including 
miniaturized devices for Micro-Electrical-Mechanical Systems (MEMS), 
may flow from these initial demonstrations.

The researchers emphasize that much work remains to be done, such as 
refining the design of the battery for optimal operation in a 
morphing vehicle. Chiang notes, however, that "we've been able to 
demonstrate the potential of this approach even using these very 
unoptimized off-the-shelf batteries."

This work was funded by the Defense Advanced Research Projects Agency (DARPA).

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Elizabeth A. Thomson
Assistant Director, Science & Engineering News
Massachusetts Institute of Technology
News Office, Room 11-400
77 Massachusetts Ave.
Cambridge, MA  02139-4307
617-258-5402 (ph); 617-258-8762 (fax)
<thomson at mit.edu>

<http://web.mit.edu/newsoffice/www>
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