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Engineers Develop High-Performance Artificial Muscle Technology

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Engineers at Northern Arizona University (NAU) have developed a new, high-performance artificial muscle technology that enables more human-like motion. The flexible and adaptable technology has demonstrated an ability to outperform human skeletal muscle in several metrics. 

Researchers often rely on principles of biomimetics to develop better actuation technologies and soft robotics. In biomimetics, machine components are designed to mimic the movement of human muscles, hopefully outperforming them. 

Robots in Biological Form

Actuators such as electric motors are rigid, which limits them in their abilities, so biomimetic prostheses and actuators must change as robots take on a more biological form. 

The new, high-performance artificial muscle technology was developed in NAU’s Dynamic Active Systems Laboratory. The paper, published in Science Robotics, is titled “Cavatappi artificial muscles from drawing, twisting, and coiling polymer tubes.”

The paper was authored by associate professor Michael Shafer and professor Heidi Feigenbaum of NAU’s Department of Mechanical Engineering. They were assisted by graduate student researcher Diego Higueras-Ruiz.

“We call these new linear actuators cavatappi artificial muscles based on their resemblance to the Italian pasta,” Shafer said.

Artificial Muscle vs. Human Skeletal Muscles

The actuators are fitting for bioengineering and robotics applications given their coiled structure, which generates more power. The engineers demonstrated that cavatappi artificial muscles exhibit work and power metrics ten and five times higher than human skeletal muscles, respectively. As they continue to develop, they are expected to raise even higher in 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 two percent,” Shafer said. “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.”

According to the engineers, this technology could be useful in soft robotics applications, conventional robotic actuators, and assistive technologies such as exoskeletons and prosthesis. 

“We expect that future work will include the use of cavatappi artificial muscles in many applications due to their simplicity, low-cost, lightweight, flexibility, efficiency and strain energy recovery properties, among other benefits,” Shafer said.

The new technology is available for licensing and partnering, and it is now in the protection and early commercialization stage. 

Compliant, biomimetic actuation technologies will have big implications as they continue to be developed. They are both efficient and powerful when used in robotic systems, and they can help enable them to interact, augment, and eventually integrate with humans.