Scientists at EPFL in Switzerland have unveiled the FiberMotor, a novel actuator designed to replicate the fluid motion of biological muscles. This technology aims to replace the rigid joints common in current robotics with a flexible, telescope-like mechanism for use in assistive wearables.
Copper wires and electrostatic forces power the FiberMotor
The FiberMotor consists of two hollow fibers wrapped in insulated copper wire that is only slightly thicker than a human hair. According to the research, the system operates by applying voltage to these fibers,which creates electrostatic forces that pull the components into alignment. This process causes the inner fiber to slide through the outer one , mimicking the contraction and relaxation of a muscle.
Unlike traditional motors that are limited by their physical housing, the range of motion for the FiberMotor is determined solely by the length of the fibers. This means that EPFL researchers can theoretically increase the distance a motor moves simply by extnding the fiber length, rather than redesigning the entire motor architecture.
Lifting 46-gram chocolate bars with bundled fibers
Initial performance tests demonstrate that while a single FiberMotor can hold approximatelly 75 grams in place, its true utility emerges when bundled. As reported by the source , a cluster of four FiberMotors was capable of lifting a 46-gram chocolate bar and successfully bending a tendon-driven robotic finger.
These results highlight a shift in robotic design toward "soft" actuation. While traditional robotics rely on heavy, rigid motors at every joint—which often results in the jerky, stiff movements associated with humanoid machines—the FiberMotor's ability to produce fluid motion suggests a path toward more naturalistic robotic behavior.
Integrating FiberMotor into knee garments and prosthetics
The EPFL team has already tested the technology within a prototype garment designed for a human knee. Because the FiberMotor can follow curved paths as effectively as straight ones, it is uniquely suited for integration into clothing and lightweight prosthetics that must bend in tandem with the human body.
This development is part of a broader trend toward wearable assistive devices and soft exosuits. By embedding these actuators directly into fabric, developers can create mobility aids that provide support without the bulk and rigidity of traditional mechanical braces, potentially improving the quality of life for users with mobility impairments.
How "backdriveable" fibers prevent robotic locking
A critical safety feature of the FiberMotor is that it is "backdriveable," a term used by the EPFL staff to describe the motor's reaction to external pressure. If a force pushes against the motor with enough strength, the fibers simply slide past one another instead of locking up, which is a common failure point in rigid gear-based motors.
The researchers' paper emphasizes that this characteristic is essential for safe human-robot interaction.. In environments where robots and people work in close proximity, a motor that yields under pressure is far less likely to cause injury than one that remains rigid during a collision.
Scaling modest force for full humanoid movement
Despite the promising demos, the FiberMotor currently produces only modest force on its own.. This raises a significant technical question: how many thousands of fibers would need to be bundled to move a full-sized humanoid limb or support a human's full body weight in an exosuit?
Furthermore, the research has yet to prove the durability of these hair-thin copper wires over millions of cycles in real-world environments. While the prototype knee garment shows conceptual promise, the transition from lifting a chocolate bar to supporting a human patient remains a steep engineering challenge.
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