Scientists at Queen Mary University of London have developed an artificial muscle that can change from soft to hard in response to a voltage change. The technology aims to mimic human muscles in both its movements and in its ability to sense forces and deformation. The muscle is made using carbon nanotubes that have been coated with silicone to form a cathode that can also sense forces, and an anode made from a soft metal mesh, forming an actuation layer between the anode and cathode. The resulting artificial muscle can seamlessly transition from soft to hard, contracting as it does so, while sensing its own deformation. The researchers hope that the technology will be invaluable for medical soft robots, such as in components of robotic prostheses or rehabilitation equipment.
Soft robotics have enormous potential in the medical field. The flexible and compliant nature of these robotic components means that they are well suited for interaction with soft tissues without causing damage, unlike more rigid electrical components. However, to date, many soft robotic systems have used pneumatic-style actuators, where compressive forces acting on enclosed gases or liquids produce movement.
This has its uses, but does not accurately mimic our muscles, which function completely differently through the action of muscle fibers, transitioning the muscle from soft to hard seamlessly as it contracts. Moreover, simple actuators have a limited capacity to sense their own environment and measure the force they are exerting and the forces that are acting on them.
This latest artificial muscle takes soft robotic actuation to the next level. It has similar flexibility and stretchability as natural muscle, withstanding 200% stretch along its length, and can transition from soft to hard, a stiffness change of 30-fold, as it contracts under the influence of electrical voltage. Its electrical responsiveness also means that it can actuate more quickly than conventional soft actuators.
“Empowering robots, especially those made from flexible materials, with self-sensing capabilities is a pivotal step towards true bionic intelligence,” said Ketao Zhang, a researcher involved in the study. “While there are still challenges to be addressed before these medical robots can be deployed in clinical settings, this research represents a crucial stride towards human-machine integration. It provides a blueprint for the future development of soft and wearable robots.”
Study in journal Advanced Intelligent Systems: An Electric Self‐Sensing and Variable‐Stiffness Artificial Muscle