When the Dragon spacecraft is propelled into space atop a Falcon 9 rocket this week on a resupply mission to the International Space Station (ISS), it will be carrying an artificial muscle material developed by Lenore Rasmussen and her company RasLabs. In addition to better prosthetic devices, it is hoped the material could find applications in robots on deep space missions.
The Synthetic Muscle is a gel-like material known as an electroactive polymer (EAP), which means it changes size or shape in response to an electric field. Its ability to contract or expand at low voltages gives it the potential to mimic human muscle movement and find applications in prosthetics and robotics.
"We can’t explore space without robots," Rasmussen said. "Humans can only withstand a certain amount of radiation so that limits the time that people can be in space, whereas robots particularly if they’re radiation-resistant can be up there for long periods of time without being replaced."
But to realize this potential, there were a number of problems that needed to be overcome. Firstly, a way to make the gel adhere to metal electrodes made of steel or titanium needed to be found. With the help of a team at the US Department of Energy’s Princeton Plasma Physics Laboratory (PPPL), this was accomplished by treating the metal with a plasma, which altered its surface and allowed the gel to more closely adhere to it.
Then, to examine whether the material would be suitable for use in robots intended for extended periods in space, such as deep space missions, last year the researchers exposed the material to more than 300,000 RADs of gamma radiation. This is the equivalent to a return trip to Mars and 20 times the lethal dose in humans. A second test lasting 45 hours was also conducted, which would be equivalent to the radiation received on a trip to Jupiter and beyond.
The researchers say the material showed no change in strength, electroactivity, or durability in response to the radiation, with the only effect being a slight change in color. Extreme temperature tests were also carried out on samples of the material, which was found to be unaffected by temperatures as low as -271° C (-456° F).
For the upcoming tests aboard the ISS, the material will be kept in a zero gravity storage rack for a period of 90 days and be photographed every three weeks. After it is returned to Earth in July, it will be tested against identical materials that remained on Earth.
"Based on the good results we had on planet Earth, the next step is to see how it behaves in a space environment," said Charles Gentile, an engineer at PPPL who has worked closely with Rasmussen. "From there the next step might be to use it on a mission to Mars."