New power for soft activation

August 2, 2024

(Nanowerk News) Electrically powered artificial muscle fibers (EAMFs) are emerging as a revolutionary power source for advanced robotics and wearable devices. Known for their exceptional mechanical properties, flexible integration, and functional versatility, EAMFs are at the forefront of cutting-edge innovation.

A review article on this topic was recently published online National Scientific Review (“New Innovations in Electrically Powered Artificial Muscle Fibers”). Schematic diagram of electrically powered artificial muscle fibers, classified by mechanism, material components and configuration, as well as their application areas. (Graphic: Science China Press)

A New Chapter in Smart Materials: Fiber Morphology

Fiber-shaped materials have shown remarkable advantages in the field of intelligent materials and functional devices, becoming a focal point of scientific innovation. The high molecular orientation of fibers gives them significant mechanical strength and axial strength, which provides a solid foundation for high-performance applications.

Advanced manufacturing techniques such as wet spinning, electrospinning, and chemical vapor deposition provide reliable processes for designing textile devices. In addition, multidimensional weaving techniques in modern textiles support a high degree of functional fiber integration, supporting complex structures and multifunctional designs.

Particularly in the field of artificial muscles, rotational and extensible movement of fibers mimics the movements of biological muscles, an example of unique biomimicry with enormous potential in soft robotics and other pioneering technologies.

Operating Mechanisms: Three Main Driving Mechanisms

EAMFs utilize three main drive mechanisms, each with its own unique features and refinements: Thermoelectric control uses Joule heating to drive the expansion and contraction of active materials. Considerable research is being conducted to optimize highly active, thermosensitive base materials and innovative Joule heating electrodes, including active material blends, core-shell structures, and interwoven fiber structures.

Electrochemical control involves the directional movement of ions under an electric field, which leads to the expansion or contraction of the material. This method mainly uses conductive polymers and nanomaterials, where conductive polymers facilitate rapid exchange of electrons and ions through reversible redox reactions, and carbon nanomaterials enhance charge and discharge cycles due to their large surface area. Innovation in this field is focused on the development of new electrochemically sensitive materials and ion injection mechanisms.

Dielectric action achieves motion by deforming dielectric elastomers under the influence of an applied electric field, causing the material to compress along the field direction and expand perpendicularly due to charge accumulation. Together, these mechanisms illustrate the robust and versatile nature of EAMFs in a variety of applications from soft robotics to wearable technology.

Challenges and opportunities

While fundamental research at EAMF has made significant progress, scaling up to broader applications poses numerous challenges. These include optimizing thermal management systems in thermoelectric mechanisms and improving the performance of electrochemical muscles using solid-state electrolytes. Dielectric control requires improved fiber manufacturing methods to overcome the inherent technical challenges.

As Professor Jiuke Mu summarises: ‘While addressing these challenges is crucial, it is equally important to exploit the unique characteristics of different artificial muscle fibres to ensure that they are well suited to specific applications.’ Looking to the future, the rapid development of flexible electronics and efficient energy storage technologies is likely to bring EAMF into widespread use in sensitive wearables, soft robotics and medical rehabilitation devices.