DARPA, the U.S. Defense Advanced Projects Research Agency, is the financial force behind a new biomimicry robotics project from MIT. The end result is Meshworm, a small, soft robot that looks like a moldy lint sock, moves like an earthworm, and holds its own under various stressors, even when “bludgeoned with a hammer.” The question is, why?
Resilient Robots for the U.S. Military
Meshworm has the ability to survive a frightening degree of misuse, and that provides one clue into DARPA’s interest in the new technology.
As described by writer Jennifer Chu, the field of soft robotics is of growing interest to engineers. With little or no need for bulky hardware, soft robots are more durable and lend themselves to miniaturization more easily than their mechanical counterparts.
In terms of military purpose, soft robots like Meshworm could be air-dropped, launched or thrown over relatively long distances, land without damage, and set about crawling silently around, squeezing through tight openings and conducting surveillance.
That kind of unobtrusive mobile robot could also be useful in environmental monitoring, among other applications in the civilian world.
The Inner Workings of a Robotic Worm
One particular challenge for soft robots is developing a means of propulsion that adds little or no bulk. The MIT team overcame this by integrating propulsion into the infrastructure of the robot.
Earthworms provided the inspiration because they move along by teaming longitudinal muscles with another set of muscles that wrap around their bodies in circles.
To mimic these muscles, the team developed a springy mesh tube (yes, just like a link sock) and wrapped it with wires made of a “very bizarre material,” a nickel-titanium alloy.
“Depending on the ratio of nickel to titanium, the alloy changes phase with heat. Above a certain temperature, the alloy remains in a phase called austenite — a regularly aligned structure that springs back to its original shape, even after significant bending, much like flexible eyeglass frames. Below a certain temperature, the alloy shifts to a martensite phase — a more pliable structure that, like a paperclip, stays in the shape in which it’s bent.”
A miniature battery and circuit board provided the juice to heat and cool the alloy, and a series of stress tests (the aforementioned hammer, plus a stomping) proved its durability.
The Future of Soft Robotics
Phase-changing material like MIT’s alloy fall into the programmable matter category, so look for many more Meshworm-type devices to make an appearance as this field develops apace with soft robotics.
It’s also worth noting that one key advantage of small robots, soft or hard, is their ability to perform tasks while using a minimal amount of energy.
Along those lines, engineers at Virginia Tech have been working with the U.S. Navy to develop Robojelly, a robot that swims like a jellyfish. Energy is provided by a fuel cell that scavenges power from seawater, with an assist from a platinum catalyst.
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