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Robots intended to work alongside people or operate in confined, unpredictable environments need actuators that can bend, twist, and conform in ways that traditional motors cannot. Conventional artificial muscles—based on pneumatics, electroactive polymers, or shape-memory alloys—have made progress toward that goal, but many remain bulky, inefficient, or difficult to control. As a result, engineers have continued searching for mechanisms that capture the adaptability of biological muscle without inheriting its limitations.
A new review highlights a class of actuators that is beginning to fill that gap: fiber-type artificial muscles. Built from twisted, coiled, or layered fibers, these actuators imitate the hierarchical structure of natural muscle tissue and can produce several types of motion—bending, torsion, tension, and isometric contraction—within a compact form factor. Their behavior is governed by internal changes in the fibers when exposed to external stimuli such as heat, light, electrical signals, chemicals, or vapor.
For defense and homeland security applications, this kind of versatility has clear advantages. Soft robotic systems powered by fiber-based muscles could navigate rubble, manipulate hazardous materials with precision, or operate quietly in sensitive environments. Unlike rigid actuators, these fibers can deform safely around people, making them suitable for medical evacuation robotics, wearable exoskeletons, or autonomous systems that must adapt to complex terrain without heavy mechanical joints.
According to TechXplore, the review outlines several performance milestones that exceed biological benchmarks. Vapor-driven systems have produced torsional speeds above 11,000 rpm. Tensile actuation has reached extreme strains—up to 8,600%—in coiled yarn configurations. Isometric contraction stresses far surpass human muscle, with some electrochemically actuated fibers generating more than 28 MPa, compared to roughly 0.35 MPa for mammalian skeletal muscle. Bending actuation is equally promising, with laser-driven fibers capable of complex, multi-directional movement.
These capabilities enable a wide range of emerging applications: adaptive textiles, soft grippers, micro-surgical tools, automated wound-closure devices, and robots that crawl, swim, or climb by exploiting naturalistic motion patterns. Still, challenges remain. Current systems face constraints related to durability, material cost, and integration with sensors and power sources. Researchers are now exploring self-healing materials, embedded sensing, and sustainable fiber production—using sources such as cotton or lotus fibers—to make these actuators more practical for real-world deployment.
As materials science advances, fiber-type artificial muscles are moving from laboratory demonstrations toward systems that can outperform natural muscle in strength, speed, and adaptability—opening the door to next-generation soft robotics and human-machine integration.
The research was published here.
