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3D-printed soft robot muscles 'three times stronger than natural tissue'

Joseph Flaig

The artificial muscle moves a skeleton forearm by contracting (Credit: Aslan Miriyev/ Columbia Engineering)
The artificial muscle moves a skeleton forearm by contracting (Credit: Aslan Miriyev/ Columbia Engineering)

Robotic 'muscles' that lift 1,000 times their own weight could enable powerful exoskeletons, an expert has said – if they start moving a bit faster.

Researchers from Columbia University in New York created the synthetic muscles, which they claimed are three times as powerful as natural tissue and could “revolutionise” soft robots.

The team, led by mechanical engineer Hod Lipson, 3D-printed silicone rubber matrixes with ethanol distributed throughout in “micro-bubbles”. The resulting material is elastic and changes volume when exposed to electrical current and high temperatures, and can be shaped to perform different movements.

The muscles – known as actuators – have more abilities than others currently in research, said Helge Wurdemann from University College London, who was not involved in the research.

“People are looking for actuators that are smaller, can lift more, that don’t need so much power,” Wurdemann said to Professional Engineering. “There is always a trade-off, you can have heavy actuators that can lift a lot of force, you can have actuators lift a lot of force when you have a lot of power or voltage.”

The Columbia actuators use voltages of just 8-30V. Their small size, relative to their strength, could also make them attractive alternatives for pneumatic systems in exoskeletons or lifting aids, said Wurdemann.

The US research team released a video showing devices with the muscles completing several different tasks, including raising the forearm of an artificial skeleton and lifting a 1kg weight. Other tools also “wormed” along surfaces, while another delicately picked up an egg.

“We've been making great strides toward making robot minds, but robot bodies are still primitive,” said Lipson. “This is a big piece of the puzzle and, like biology, the new actuator can be shaped and reshaped a thousand ways. We've overcome one of the final barriers to making lifelike robots.”

The actuators’ low power requirements and adaptability could enable miniaturisation of existing technologies and enable more independent robots, the team said. Soft robots are also promising for areas with human interaction, such as manufacturing and healthcare.

The work’s main drawback is the time currently needed for the muscles to expand and contract, said Wurdemann – the team’s video shows processes sped up by as much as 32 times. “In minimally invasive surgery, they probably have more time,” he said. “But if you think of applications of humans carrying, movements are quite quick.”

The team said it will continue working on the muscles, aiming to remove wires, improve response time and increase shelf life. In the long term, the researchers also hope to introduce artificial intelligence control for "natural motion".

The research, which was funded by Columbia University and a grant from the Israeli Ministry of Defence, was published in Nature Communications

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