Electrically powered artificial muscle fibers: The new power for soft actuation

In the dynamic landscape of intelligent technology, electrically powered artificial muscle fibers (EAMFs) are emerging as a revolutionary power source for advanced robotics and wearable devices. Renowned for their exceptional mechanical properties, integration flexibility, and functional versatility, EAMFs are at the forefront of cutting-edge innovation. A recent review article titled “Emerging Innovations in Electrically Powered Artificial Muscle Fibers”, was published online in the National Science Review (NSR).

A New Chapter in Intelligent Materials: Fiber Morphology

Fiber-shaped materials have demonstrated remarkable advantages in the field of smart materials and functional devices, becoming a focal point of scientific innovation. The high molecular orientation of fibers endows them with significant axial mechanical strength and toughness, laying a solid foundation for high-performance applications. Advanced manufacturing techniques such as wet spinning, electrospinning, and chemical vapor deposition provide reliable processes for engineering fiber devices. Moreover, multi-dimensional weaving techniques in modern textiles support the high-degree integration of functional fibers, catering to complex structures and multifunctional designs. Specific in the realm of artificial muscles, the rotational and extensible actuation of fibers mimics biological muscle movements, showcasing exceptional biomimicry with vast potential in soft robotics and other pioneering technologies (as shown in Figure 1).

Operating Mechanisms: Three Major Driving Mechanisms

EAMFs utilize three primary driving mechanisms, each with its unique characteristics and advancements. Thermoelectric actuation leverages Joule heating to drive the expansion and contraction of active materials, with significant research dedicated to optimizing high-activity thermoresponsive base materials and innovative Joule heating electrodes, including electrode-active material blends, core-shell structures, and interwoven fiber structures. Electrochemical actuation involves the directional movement of ions under an electric field, leading to material expansion or contraction. This method predominantly uses conductive polymers and nanomaterials, where conductive polymers facilitate rapid electron and ion exchange through reversible redox reactions, and carbon nanomaterials enhance charge-discharge cycles due to their high surface area. Innovations in this area focus on developing new electrochemically responsive materials and ion injection mechanisms. Dielectric actuation achieves movement through the deformation of dielectric elastomers under 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 various applications, from soft robotics to wearable technology.

Challenges and Opportunities

While foundational research in EAMFs has progressed significantly, scaling for broader applications poses numerous challenges. These include optimizing thermal management systems in thermoelectric mechanisms and enhancing the performance of electrochemical muscles with solid-state electrolytes. Dielectric actuation requires advancements in fiber production methods to overcome its inherent technical challenges.

As Professor Jiuke Mu concludes “While addressing these challenges is crucial, it is equally important to leverage the unique characteristics of different artificial muscle fibers to ensure they are well-suited for specific applications”. Looking ahead, the rapid development of flexible electronics andefficient energy storage technologies will likely propel EAMFs into widespread use in responsive wearable fields, soft robotics, and medical rehabilitation devices.