Hair-thin actuator fiber can help make robots, body-conforming wearables

Researchers from Tohoku University, in collaboration with international partners, have developed ultrafine "soft yarn" actuator fibers using a thermal drawing technique adapted from optical fiber manufacturing. These hair-thin fibers, made primarily from thermoplastic polyurethane—a flexible dielectric elastomer—can bend, contract, and perform complex three-dimensional movements when electrically stimulated. Unlike conventional actuators that often rely on stiff metallic materials like shape-memory alloys and require complex activation methods, these new fibers are soft, flexible, and thread-like, allowing easy integration into textiles and flexible structures such as wearable devices and soft robots. The key innovation lies in combining fiber manufacturing with soft electroactive materials to produce actuators with enhanced mechanical compliance and greater degrees of freedom in motion. The fibers maintain a low Young’s modulus of 37 MPa, enabling diverse actuation modes including bending, compression, and swirling motions with an estimated compression strain of 1.59%. Their thread-like form factor allows them to be wound, knitted, or woven into