Compliant Robotic Arm Image
NAU mechanical engineer Michael Shafer and graduate student Diego Higueras-Ruiz conducting a visual inspection of their new compliant robotic arm actuated with cavatappi artificial muscles. (Credit: NAU)

Researchers have devleoped a new, high-performance artificial muscle technology that enables more human-like motion due to its flexibility and adaptability but outperforms human skeletal muscle in several metrics. Because of their coiled, or helical, structure, the actuators can generate more power, making them an ideal technology for bioengineering and robotics applications.

In the team’s initial work, they demonstrated that cavatappi artificial muscles exhibit specific work and power metrics ten and five times higher than human skeletal muscles, respectively, and as they continue development, they expect to produce even higher levels of performance.

“The cavatappi artificial muscles are based on twisted polymer actuators (TPAs), which were pretty revolutionary when they first came out because they were powerful, lightweight and cheap. But they were very inefficient and slow to actuate because you had to heat and cool them. Additionally, their efficiency is only about 2 percent,” says Michael Shafer, associate professor at Northern Arizona University. “For the cavatappi, we get around this by using pressurized fluid to actuate, so we think these devices are far more likely to be adopted. These devices respond about as fast as we can pump the fluid. The big advantage is their efficiency. We have demonstrated contractile efficiency of up to about 45 percent, which is a very high number in the field of soft actuation.”

The engineers think this technology could be used in soft robotics applications, conventional robotic actuators such as walking robots, or potentially in assistive technologies like exoskeletons or prostheses.