Meet DARPA's New Militarized Earthworm 83
derekmead writes "Meshworm is a toughened, robotic earthworm that can crawl virtually silently at a speed of about 5 millimeters per second. DARPA wants to send it into battle. Believe it or not, the Pentagon's been working on building a robotic earthworm for a while. They tried putting one together with gears. They tried with air-powered and pneumatic pumps, but the results were bulky and untenable. Then, researchers at Harvard, MIT and Seoul National University in Korea put their heads together and designed an 'artificial muscle.' It's essentially a polymer mesh that's wrapped with nickel and titanium wire designed to stretch and contract with heat. When an electric current is applied, the mesh mimics the circular muscle system of an earthworm to scoot forward."
Nitinol power consumption too high (Score:5, Interesting)
This "earthworm" device [harvard.edu] uses Nitinol shape-memory alloy [wikipedia.org] as an actuator. That's been tried many times before, going back to the 1980s.
As an actuator, Nitinol can produce significant power in small package, but it's a very inefficient device. The metal will change crystal structure when heated, and return to the original shape when cooled. Heating is usually accomplished by running electricity through the Nitinol wire. Most of the energy goes into waste heat; only a small fraction comes out of the actuator as useful work.
So a battery-powered earthworm isn't likely. As a cabled device, it has potential. A great application would be short run cable-laying for fibre optics. A machine that could get a fibre optic cable underground from street to house without digging up sidewalks and lawns would be very useful.