 Synthetic muscles, presented by science at NASA. Muscles are a miracle of nature. They convert energy into motion more efficiently than any gasoline engine or electric motor. They're extremely resilient and even heal themselves. Instead of degrading with use, our muscles become stronger the more we work them. Researchers have long sought a way to recreate that miracle in prosthetics. So far, no one has succeeded. But Lenore Rasmussen, principal investigator for the US National Lab-sponsored Synthetic Muscle Investigation on the International Space Station, is getting closer. Rasmussen has been focusing her efforts on creating a new type of material for making lifelike, flexible, strong prosthetic devices that are appealing in both form and function. Her quest has led her to a class of smart materials called electroactive polymers. Rasmussen has explained that smart materials react to external stimuli such as light, temperature, and electricity. Like real muscles, electroactive polymers react to electricity, bending in response to an electrical impulse, while real muscles contract. She wanted to find a material that would contract and also expand to affect movement. To develop it, she took any possible candidate and zapped it. She has a personal reason for her quest. When she was in graduate school, one of her cousins almost lost his foot in an accident with a hay spreader as he worked on his family farm. My cousin lost a lot of tissue in the accident, and our family feared he would lose part of his leg and foot. As a resident scientist in the family, I was put in charge of researching prosthetics. This was back in the 1980s, so I was pretty disappointed with the selection of prosthetic devices that I found. The ones that looked more lifelike moved awkwardly, and those that moved well looked artificial. Even with the robotic arms of today, this is still true. I want the best of both worlds for people who have lost limbs, so I've been working to create a material that both looks natural and moves naturally. As it turned out, her cousin's foot and leg were saved, no prosthetics required, but the whole experience resonated with her deeply. Now she's finally found the right stuff. Her creation, synthetic muscle, behaves a lot like human muscle, converting electrical potential energy into mechanical motion. Synthetic muscle contracts in response to electricity, and by flipping the electric polarity applied, making the positive negative and negative positive, I can also get expansion, which human muscles can't do. The result is this material can bend, stretch and contract or expand in any direction. What does all this have to do with space travel? The synthetic muscle she has created could also be used to create humanoid robots that can go where people can't or don't want to go. With ability to mimic human dexterity and mobility, such robots could serve as human assistants in space, nuclear plants, or the military. In fact, synthetic muscle samples are being tested for radiation resistance in the synthetic muscle investigation on the station, where the environment allows the samples to be exposed to a wide variety of radiation all at the same time. Variations of the material, with different additives and coatings, were sent to the space station and attached to lesser protected areas of its interior in April. The samples are being photographed every five to six weeks during exposure before returning to Earth in 2016, where they'll be examined to see how they held up. We are still in the early stages of working with synthetic muscle, but the future looks promising, both on Earth and in space. For more on investigations on the International Space Station, go to www.nasa.gov. Find more smart science news at science.nasa.gov.