Researchers have developed a pioneering robotic gripper that uses gecko-inspired sticky pads to clear up space debris.
Developed at Stanford University and NASA’s Jet Propulsion Laboratory (JPL), and detailed today in the journal Science Robotics, the gripper has been tested both on the ground and on the International Space Station, demonstrating that it can successfully operate in zero-gravity environments.
With around 500,000 pieces of man-made debris littering orbit, there is a growing need to successfully clear much of it so that humanity can safely increase its operations in low-Earth orbit. Each piece of space junk is whizzing around at up to 17,500 miles per hour, meaning a collision with a satellite, spacecraft or even astronaut would be extremely expensive and potentially very dangerous.
However, many conventional junk removal methods don’t work particularly well. Suction cups rely on creating a difference in air pressure, meaning they don’t work in a vacuum; magnets only work on a limited number of materials and debris harpoons risk missing and knocking the objects off in unpredictable directions.
Sticky solutions, then are preferred, however most tape-like solutions fail because the chemicals they rely on to make them sticky can’t cope with the massive temperature changes objects in space are subjected to. Which is where the gecko-inspired gripper comes in.
“What we’ve developed is a gripper that uses gecko-inspired adhesives,” said study senior author Mark Cutkosky, professor of mechanical engineering at Stanford. “It’s an outgrowth of work we started about 10 years ago on climbing robots that used adhesives inspired by how geckos stick to walls.”
Geckos are able to scale vertical surfaces because they have microscopic flaps that create weak intermolecular forces between the feet and the wall’s surface, allowing them to grip on. The researchers have simply replicated these flaps, albeit on a larger scale; while each flap on a gecko’s foot is around 200 nanometers long, on the robotic gripper it is only 40 micrometers across.
However, it works in the same way, allowing an object to be gripped in a zero-g environment without needing to apply force.
“If I came in and tried to push a pressure-sensitive adhesive onto a floating object, it would drift away,” said study co-author Dr Elliot Hawkes, a visiting assistant professor from the University of California, Santa Barbara. “Instead, I can touch the adhesive pads very gently to a floating object, squeeze the pads toward each other so that they’re locked and then I’m able to move the object around.”
The gripper has already undergone extensive testing, including in JPL’s Robodome, which has a floor like a giant air hockey table that is designed to simulate a 2D zero-G environment.
“We had one robot chase the other, catch it and then pull it back toward where we wanted it to go,” said Hawkes. “I think that was definitely an eye-opener, to see how a relatively small patch of our adhesive could pull around a 300kg robot.”
Now it has been tested on the International Space Station, the next step is to test a version outside the space station, in the radiation-filled reality of space. Cutkosky also plans to commercialise the gecko-inspired adhesive here on Earth.