Researchers are continually looking for the fastest, strongest, and least expensive ways to enable robots to move efficiently. This quest is often based on biomimetics principles, with machine components that mimic the movement of human muscles and ideally, outperform them. Despite the performance of electric motor and hydraulic piston actuators, their rigid form limits how they can be deployed. As robots transition to more biological forms as people ask for more biomimetic prostheses, actuators must evolve.
Associate Professor and alumnus Michael Shafer and Professor Heidi Feigenbaum of Northern Arizona University’s (NAU) Department of Mechanical Engineering, along with graduate student researcher Diego Higueras-Ruiz, published their paper, “Cavatappi artificial muscles from drawing, twisting, and coiling polymer tubes,” in Science Robotics. Their research presents a new, high-performance artificial muscle technology, developed in NAU’s Dynamic Active Systems Laboratory, that enables more human-like motion due to its flexibility and adaptability, while outperforming human skeletal muscle.
“We call these new linear actuators cavatappi artificial muscles based on their resemblance to the Italian pasta,” Shafer says.
Because of their coiled, or helical, structure, the actuators can generate more power, making them an ideal technology for bioengineering and robotics applications. The team’s initial work demonstrated that cavatappi artificial muscles exhibit specific work and power metrics 10x and 5x higher than human skeletal muscles, respectively. 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%,” Shafer says. “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 nearly 45%, 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 such as exoskeletons or prostheses.
Working with the NAU Innovations team, the inventors have taken steps to protect their intellectual property (IP). The technology is in protection and early commercialization stages and is available for licensing and partnering opportunities.
Northern Arizona University