MIT creates bendable artificial muscle fibers from nylon

Scientists have been trying to create fibers that could flex like human muscles for a long time with varying degrees of success. MIT scientists have created materials that are able to contract and expand in a manner similar to human muscle fibers that have many potential applications. These nylon fibers could find use in robotics, automotive, and aviation industries. The MIT breakthrough is on of the simplest and cheapest systems developed so far.

The key ingredient in the MIT breakthrough is common nylon fiber. MIT shapes and heats the fibers in a particular way and scientists Seyed Mirvakili, a doctoral candidate, and Ian Hunter, the George N. Hatsopoulos Professor in the Department of Mechanical Engineering describe their process in a paper published in "Advanced Materials". In The past, scientists had been able to use a twisted coil of nylon filament to mimic basic muscle activity, but making the synthetic fibers extend and retract like natural muscle was much more complicated.

Allowing the artificial muscles to bend and flex to mimic the movement of human fingers and limbs hadn't been achieved using these same cheap and simple systems until the recent MIT breakthrough. The new nylon-based system at MIT requires simple manufacturing processes and has very good cycling longevity. Mirvakili says that one key property of the nylon used on the project is that the nylon is able to "... shrink in length but expand in diameter" when heated.

One limitation that the scientists had to overcome was the fact that heating causes the actuators to bend, but the cooling process to relax the fibers took a long time to complete. "The cooling rate can be a limiting factor," Mirvakili says. "But I realized it could be used to an advantage." The scientists heat one side of the fiber leading to that side contracting faster than heat is able to penetrate the other side producing a bending motion. The team used fishing line and shaped it in rectangle of square via compression and then heated one side to create a bending motion. In tests, the nylon was able to survive 100,000 bending cycles and could bend at a rate of 17 cycles per second.