In the field of robotics, researchers are constantly looking for the fastest, most powerful, most efficient, and cheapest ways to operate robots or enable them to perform the movements necessary to perform their intended functions.
The search for new and better actuation technologies and “soft” robotics is often based on principles of biomimetics, in which machine components mimic – and ideally exceed – the movement of human muscles. Despite the power of actuators such as electric motors and hydraulic pistons, their rigid shape limits their use. As robots move to more biological forms and humans ask for more biomimetic prostheses, actuators need to evolve.
Associate Professor (and alum) Michael Shafer and Professor Heidi Feigenbaum of the Department of Mechanical Engineering at Northern Arizona University, along with graduate student Diego Higueras-Ruiz, published an article in Science Robotics that introduced a new, powerful artificial muscle technology in from which they were developed. The paper, titled “Cavatappi Artificial Muscles by Pulling, Twisting, and Coiling Polymer Tubing” describes how the new technology allows for more human movement due to its flexibility and adaptability, but outperforms human skeletal muscles in several metrics.
We call these new linear actuators Cavatappi artificial muscles based on their similarity to Italian pasta. “
Michael Shafer, Associate Professor in the Department of Mechanical Engineering at Northern Arizona University
Because of their coiled or spiral structure, the actuators can generate more electricity, making them an ideal technology for bioengineering and robotic applications. In the team’s first work, they demonstrated that artificial Cavatappi muscles have specific work and performance metrics that are ten and five times higher, respectively, than those of human skeletal muscles. As they develop, they expect an even higher level of performance.
“Cavatappi artificial muscles are based on twisted polymer actuators (TPAs) which were quite revolutionary when they first appeared because they were powerful, light, and cheap. But they were very inefficient and slow to operate because you heat them up and cool them down In addition, their efficiency is only about two percent, “said Shafer. “For the Cavatappi, we get around this by using pressurized fluid to actuate it. So we believe these devices are more likely to be used. These devices respond about as quickly as we can pump the fluid. The big advantage is their efficiency. We have demonstrated a contractile efficiency of up to 45 percent, which is a very high number in the area of soft actuation. “
The engineers believe that this technology can be used in soft robotics applications, traditional robotic actuators (e.g. for walking robots) or even possibly in assistive technologies such as exoskeletons or prostheses.
“We anticipate that future work will include the use of artificial Cavatappi muscles in many applications because of their simplicity, low cost, light weight, flexibility, efficiency, and stretch energy recovery properties,” said Shafer.
Technology is available for licenses and partnering opportunities
In collaboration with the NAU innovation team, the inventors have taken steps to protect their intellectual property. The technology has entered the protection and early commercialization phase and is available for licensing and partnering opportunities. For more information, please contact NAU Innovations.
Shafer came to NAU in 2013. His other research interests relate to energy generation, wildlife telemetry systems and unmanned aerial systems. Feigenbaum came to NAU in 2007. Her other research interests include ratcheting metals and smart materials. The PhD student on this project, Diego Higueras-Ruiz, received his MS in mechanical engineering from the NAU in 2018 and will do his PhD in bioengineering in autumn 2021. This work was supported by a grant from the NAU’s pre-study program for research and development.
Source:
Northern Arizona University
Journal reference:
Higueras-Ruiz, DR, et al. (2021) Artificial Cavatappi Muscles When Pulling, Twisting, and Coiling Polymer Tubes. Science robotics. doi.org/10.1126/scirobotics.abd5383.
