Legions of animal-inspired robots are being created to improve military missions and disaster response efforts—from crawling cockroach-like RHex bots to leaping Sand Flea robots and the speeding Cheetah machines. Now, a squishier source for smart robo-tech has joined the ranks: octopuses.

Teams of researchers are already developing soft-bodied, octopus-esque robots for search and rescue. These endeavors include the European Union-funded OCTOPUS Integrating Project based in Livorno, Italy (home of the famous disembodied grasping robot octopus arm) and Harvard's four-legged, compressed-air driven bot.

But a new effort is underway to borrow just a part of the octopus's anatomy: its suckers.

Octopuses have dozens to hundreds of flexible suckers on each of their arms. These handy cups can generate substantial amounts of force for grabbing tasty crabs or hanging onto the rocky walls of a den.

Robotics researchers have been trying to mimic this ability for decades. Early robotic suckers used a central air pump connected to multiple suction cups. This technique, however, presented a problem if not all of the suckers were fully attached to the desired object: unattached suckers would mean lost air and suction ability for the whole device.

But a real octopus's sucker can activate individually when they come into contact with an object—adhering to or releasing it independently of suckers elsewhere on the arm.

So a collaboration of researchers at the U.S. Army Research Laboratory, the Edgewood Chemical Biological Center and the University of Maryland are taking a lesson from the animals and are creating individually activated robotic suckers. These suckers, made on multi-material 3-D printers, could adorn more traditional robots to give them an extra tool for more complex handling capabilities.

"Manipulation of unknown objects is a very difficult task for a robot," said Chad Kessens, a graduate robotic manipulation researcher at the Army Research Laboratory and lead developer of the robot-ready suction cups, in a prepared statement.

Often, robots are programed (or learn) to pick up or work with a specific type of object. But this sort of programming or training is often impossible in a disaster situation. "When something like Fukushima happens, it would be very useful if the robots that are sent in could perform some sort of manipulation activity like closing a valve, recovering an object or operating a tool in a contaminated area," Kessens noted. But traditional robots often have rigid digits that do not grasp well on other hard surfaces.

Actual octopus suckers are strong but are also super-sensitive to touch and under a high degree of muscular control. This allows them to hold onto an object they cannot see.

Rather than attempt to replicate the octopus's very keen sense and control, the researchers designed a self-sealing sucker. Still activated by a central vacuum, these suckers are outfitted with individual movable plugs. The plug automatically seals the suction cup closed if it is not touching anything, and it opens when the suction cup comes into contact with an object, allowing pump-driven suction to start. By focusing the suction action on only those cups that are in direct contact with the desired object, this approach also increases the pressure each of those active cups receives.

To get just the right combination of strength and precision, the researchers have been building their prototypes with the help of a multi-material 3-D printer. "With 3-D printing, you're getting a working ensemble of suction cups right off of the machine" in a matter of minutes, said Brad Ruprecht, a collaborator at the Edgewood Chemical Biological Center's Advanced Design and Manufacturing Division, in a prepared statement. He helped develop a combination of sturdy nylon and a liquid photo polymer that hardens when blasted with ultraviolet light.

Kessens and his colleagues have demonstrated that the suckers work quite well on land—and even at home; just four of the smallest suction cups—each about the size of a fingertip—can hold a full bottle of wine. But the researchers are hopeful that the suckers, like those of the octopus's, will work even better underwater. "When you're operating in the atmosphere using air, you're limited to the atmospheric pressure for how much force you can generate from the suction cup," Kessens said. "But when you go underwater, you have all of the extra pressure from the depths of the sea, so that gives you more force to utilize for the effectiveness of the cups."

Once the team takes these strong suckers into the deep, however, they will likely need to reassess the materials. "You probably wouldn't use the same materials," Ruprecht said. "You'd want something that is going to hold up to salt water, like a thermal plastic," which would be more cost-effective to create with traditional injection molds if these robotic octopus suckers ever take off in large quantities, he noted.

In the meantime, the researchers are continuing to test out different printed prototypes to find out which ones truly suck.

Illustration courtesy of Ivan Phillipsen