If you've already designed a soft-bodied robot, it kind of defeats the purpose if you just go and stick a rigid motor inside of it. That's why Swiss scientists have created a motor that takes the form of a thin, flexible fiber.

Known as the FiberMotor, the device was developed by a team of researchers at the EPFL (École Polytechnique Fédérale de Lausanne) university in Switzerland. It builds upon a previous EPFL innovation, which incorporates liquid-pumping tubular fibers into clothing.

Ranging in diameter from 1 to 3 millimeters, each FiberMotor is in fact composed of two concentric hollow polymer fibers – a wider one on the outside, with a narrower one nested inside of it. Thin copper wire is tightly wound around each of the fibers, serving as an electrode on each fiber.

When an electrical current is applied to these electrodes, electrostatic forces repeatedly pull the fibers into alignment with one another, causing the inner fiber to slide within the outer one.

Utilizing that pulling force in lab tests, individual FiberMotors were able to support stationary loads equivalent to about 75 g (2.6 oz), while four of the motors bundled together could lift a 46-g (1.6-oz) chocolate bar and flex a tendon-driven robotic finger.

And importantly, because there are no gears or transmissions, the FiberMotor is back-driveable. This means that if it's pushed by an external opposing force, it won't lock up.

The scientists are now working on boosting the durability and performance of the technology via spinoff company Elecsyor, and hope to integrate the FiberMotors into items such as mobility-assisting clothing, VR haptic feedback systems, and lightweight prosthetic devices.

“Our FiberMotor is the first fiber-format, sliding motor,” says Herbert Shea, head of EPFL's Soft Transducers Lab. “It produces enough force to actuate devices for soft robotic applications, while remaining silent, flexible, and bidirectional.”

A paper on the research was recently published in the journal Advanced Materials.

Source: EPFL