PREVIEW

Robots may be the technology of the future - but did you know they rely on technology that’s 200 years old to power them?

Even the most advanced walking robots are driven by motors rather than muscles, which explains why they lack the agility seen in humans and animals.

However, researchers at ETH Zurich and the Max Planck Institute for Intelligent Systems (MPI-IS) have developed a revolutionary muscle-powered robotic leg.

It may not look like much now, but the robotic leg could pave the way for far more advanced human-like robots than we have today - like those seen in The Terminator films, or Steven Spielberg's A.I. Artificial Intelligence.

That's because the new leg, designed by the Max Planck ETH Centre for Learning Systems (CLS), is more energy-efficient than conventional motor-powered legs and capable of performing high jumps, fast movements, and adapting to obstacles without the need for complex sensors.

The research team, led by Robert Katzschmann from ETH Zurich’s Soft Robotics Lab and Christoph Keplinger from MPI-IS, has modelled the robotic leg on the human musculoskeletal system.

Their animal-inspired design uses electro-hydraulic actuators, known as HASELs, which mimic the flexor and extensor muscles in living organisms. These actuators are oil-filled plastic bags, with conductive electrodes that are drawn together when a voltage is applied, creating a shortening effect similar to muscle contraction.
Thomas Buchner, one of the co-authors, likens the mechanism to static electricity, and says it’s also much more energy efficient than existing motorised systems - as less energy is converted into heat.

“On the infrared image, it’s easy to see that the motorised leg consumes much more energy if, say, it has to hold a bent position,” Buchner explains.

The temperature in the electro-hydraulic leg, in contrast, remains the same. This is because the artificial muscle is electrostatic.

“It’s like the example with the balloon and the hair, where the hair stays stuck to the balloon for quite a long time,” Buchner adds.

“Typically, electric motor driven robots need heat management which requires additional heat sinks or fans for diffusing the heat to the air. Our system doesn’t require them,” co-author Toshihiko Fukushima continues.

This technology allows the robotic leg to contract and extend just like natural muscles, with paired movements that give it remarkable agility.
The greater efficiency of the new musculoskeletal leg also removes another problem conventional motors have - cooling.

Conventional motors generate heat and require cooling systems like fans or heat sinks, while the electrostatic artificial muscles remain cool, even under a constant load. This makes the robotic leg not only energy-efficient but also adaptable to varied and uneven terrain.

The researchers demonstrated the leg’s ability to jump and its adaptability, which is crucial for soft robotics. As with living creatures, the robotic leg’s flexibility allows it to navigate uneven surfaces, making it an exciting advancement in the field of robotics.