soft actuator

“Give a kid a hammer, and the whole world looks like a nail.” It’s natural to try to solve problems using familiar tools, which explains why engineers turn to gears and pulleys and wheels and hinges when trying to create a robot that simulates human activity. But humans don’t rely on these components to move and interact with their world; we have muscles that are flexible and soft and can exert a force by contracting.

That’s what researchers were trying to create at Harvard’s Wyss Institute for Biologically Inspired Engineering. They wanted to make a mechanical actuator that works like human skeletal muscle. And they have succeeded by creating soft rubber “beams” that are powered by a vacuum. The simple shape is cast in a mold, and then two halves are combined to create a rectangular beam. When a vacuum is applied, the air spaces in the beam collapse causing the beam to contract. It remains flexible throughout the process, just like real muscle. It responds quickly, and can extend back to its original length just as rapidly. Twist it, bend it, and it still works. And it’s self-healing; if you poke a hole through it, it still works.

Since the actuator relies on a vacuum instead of pressure (like hydraulics) or electricity (like most motors), it is much safer for use with humans. This is an important step toward building “soft” robots and more natural prosthetics.