EPFL researchers develop wire-shaped motor for future robotic suits

A motor just 1 to 3 millimetres wide could help Swiss researchers rethink how wearable robots move. Engineers at the École Polytechnique Fédérale de Lausanne, EPFL, have developed a wire-shaped actuator designed to support human movement without the bulky gears used in conventional motors. The team calls the device the FiberMotor.

The technology could eventually be woven into clothing for people who need assistance walking or controlling a limb. EPFL researchers have already built the motors into a pair of trousers, testing whether slim actuators can help with actions such as bending or straightening the leg.

The work, described in the journal Advanced Materials, comes as Swiss laboratories and companies seek practical uses for robotics beyond industrial production. A wearable machine must follow the body, fit beneath or inside clothing, and respond safely when a user changes direction. Conventional mechanical transmissions can add weight and stiffness to that equation.

The FiberMotor offers a different engineering route. Its small size allows researchers to consider many actuators distributed through fabric rather than one large motor mounted near a joint. The prototype remains an early-stage device, and the team is now focused on increasing its power and durability.

The FiberMotor works through electrostatic attraction, not a conventional gear train. The device contains two hollow fibres, with one positioned inside the other. Thin copper wires wrap around both structures. When researchers apply a voltage, electrostatic forces pull the fibres closer together. That interaction drives the inner fibre back and forth inside the outer one.

This arrangement turns a linear movement into a compact motor function. Because the design has no gears or mechanical transmission system, it can remain flexible and can be moved externally. That feature matters for wearable robotics, where the user and the machine constantly influence each other.

A rigid geared mechanism can resist an unexpected movement. The EPFL design is intended to avoid locking when a person moves an arm or leg against the direction generated by the motor. Such compliance could help make future assistive devices more comfortable and safer during ordinary movement.

The source material does not provide a detailed power rating, operating voltage or endurance figure. Those limits will shape the technology’s route to market. For now, EPFL’s researchers are working to make the motor more powerful and durable while preserving its thread-like form.

Four prototype motors lifted a 46-gram chocolate bar. The demonstration gives a clear indication of the device’s current capability, while also showing why practical wearable systems may need many actuators working together.

A single small motor will not power an entire robotic suit. Researchers could distribute large numbers of FiberMotors through trousers, sleeves or support garments, with each thread contributing to a joint movement. The combined force could assist actions that place repeated demands on the muscles, including raising a leg, standing or climbing stairs. The source does not establish that the prototype can yet perform those tasks on a person.

The testing in trousers marks an important step because wearable robotics must operate in fabric, around joints and alongside natural body movement. The motors need to deliver force without creating uncomfortable pressure points or restricting the wearer’s range of motion. They also need to withstand repeated bending and the stresses of washing, dressing and daily use.

EPFL has not announced a finished medical device or a deployment timetable. The current results are a research demonstration. Power, durability, control systems and user safety will determine whether the concept can move from a laboratory garment to clinical or consumer applications.