Interest in emulating the properties of biological muscles that allow for fast adaptability and control in unstructured environments has motivated researchers to develop new soft actuators, often referred to as 'artificial muscles'. The field of soft robotics is evolving rapidly as new soft actuator designs are published every year. In parallel, recent studies have also provided new insights for understanding biological muscles as 'active' materials whose tunable properties allow them to adapt rapidly to external perturbations. This work presents a comparative study of biological muscles and soft actuators, focusing on those properties that make biological muscles highly adaptable systems. In doing so, we briefly review the latest soft actuation technologies, their actuation mechanisms, and advantages and disadvantages from an operational perspective. Next, we review the latest advances in understanding biological muscles. This presents insight into muscle architecture, the actuation mechanism, and modeling, but more importantly, it provides an understanding of the properties that contribute to adaptability and control. Finally, we conduct a comparative study of biological muscles and soft actuators. Here, we present the accomplishments of each soft actuation technology, the remaining challenges, and future directions. Additionally, this comparative study contributes to providing further insight on soft robotic terms, such as biomimetic actuators, artificial muscles, and conceptualizing a higher level of performance actuator named artificial supermuscle. In conclusion, while soft actuators often have performance metrics such as specific power, efficiency, response time, and others similar to those in muscles, significant challenges remain when finding suitable substitutes for biological muscles, in terms of other factors such as control strategies, onboard energy integration, and thermoregulation.
Special Issue on Artificial Muscle Actuators for Bioinspired Mechanisms
Guest Editors
Yoseph Bar-Cohen, Jet Propulsion Laboratory, California Institute of Technology, USA
Iain Anderson, University of Auckland, New Zealand
Edwin Jager, Linköpings Universitet, Sweden
Scope
For about 3.5 billion years, nature, through natural selection has been actively experimenting with mechanisms for locomotion, energy harvesting, thermal control, and manipulation. Today, we share a planet with substantially more than 8.7 million species, each inhabiting an ecological niche made possible through proven and robust materials and mechanisms.
Biology's incredible capabilities have always served as a model for inspiration to and mimicking by humans in efforts to improve their life and augment their abilities. Mimicking these capabilities have benefited humans in new materials, structures, systems, mechanisms, processes, algorithms, methods, and tools. There are no gearboxes in nature and many natural mechanisms are soft and flexible too. For instance, the emergence of electroactive polymers (EAP) and their capability to operate as artificial muscles have enabled new possibilities to make devices without gearboxes with soft electroactive actuators making e.g. gear change unnecessary. They are inspiring other biomimetic technologies too in soft energy harvesting and sensing.
This Special Issue focuses on the various aspects of artificial muscles, including EAP, and their applications to bioinspired mechanisms. The Guess Editors are seeking to publish an issue that provides a snapshot of the current state of the field. Contributions are sought to cover the fundamental aspects of artificial muscles, ionic and field activated EAP, methods of fabrication, databases, sensors, applications and others.