Electrofluidic Fiber Muscles (EFM), a new class of artificial muscles for robots and wearable devices.

Each fiber is less than 2 millimeters in diameter and can deliver power comparable to human skeletal muscle, around 50 W/kg. Unlike the rigid servo motors used in most robots today, these fiber-shaped muscles are soft and flexible, and they can be bundled or arranged in different ways to increase force and response speed while remaining compliant. This performance is achieved by integrating electrohydrodynamic (EHD) fiber pumps — slender tubes that move liquid using electric fields and generate pressure silently, with no moving parts — with fluid-filled fiber actuators. The result is a long, thin, soft artificial muscle fiber that contracts by 20% in 0.3 seconds when a DC voltage is applied. We discovered that biasing the fiber pumps and actuators to an optimal internal pressure allows the system to operate in a fully sealed loop. Before use, the fibers are filled with a dielectric liquid and slightly overfilled to reach the desired pressure. The filling valve is then closed, allowing the muscles to operate completely untethered and powered only by electrical input. This removes bulky external equipment — such as pumps, compressors, and tubing — that has long limited the portability and practical use of fluidic soft robots. These artificial muscles could enable more agile robots and wearable assistive systems in which actuation is integrated directly into textiles.

Authors:

Ozgun Kilic Afsar, PhD Student at MIT and lead author.

Vito Cacucciolo, professor at Politecnico di Bari and Principal Investigator.

Gabriele Pupillo and Gennaro Vitucci, Politecnico di Bari

Wedyan Babatain and Hiroshi Ishii, MIT

Funding:

The European Union, through the European Research Council (ERC) Starting Grant RoboFluid, and the Media Lab’s multi-sponsored consortium.

Article published on Science Robotics: https://doi.org/10.1126/scirobotics.ady6438