3D-printed synthetic muscle opens door to lifelike robots

A ‘soft actuator’ with an intrinsic expansion ability and three times the strength of natural muscle has been developed by researchers at Columbia Engineering – signalling a major breakthrough in the push for lifelike robots.

I recently reported on the unveiling of a robot with flexible sensor ‘skin’, noting that bio-inspiration is enhancing the physical fidelity of robots and helping their mechanical attributes catch up with their AI capabilities. Now, natural muscle has provided the framework for the latest advancement in soft robotics.

Imagine the aforementioned sensor skin placed over synthetic muscle that can expand and contract without external compressors or high-voltage equipment. A group in the Creative Machines lab at Columbia Engineering, led by professor of mechanical engineering Hod Lipson, have made this possible.

“We’ve been making great strides toward making robot minds, but robot bodies are still primitive,” said Hod 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 hard road to soft robotics

One of the long-standing hurdles in robotics has been the lack of easily processed soft actuators with the ability to bear high levels of strain. Previous solutions have required high voltages or external compressors and pressure-regulating components.

This latest method combines the elastic nature of silicone rubber with the extreme volume change of the ethanol distributed throughout it. A thin resistive wire provides a small electric current that heats the 3D-printed muscle up to 80°C, causing it to expand by as much as 900 percent. It is also incredibly strong – boasting a strain density 15 times larger than natural muscle and the ability to lift 1,000 times its own weight.

“Our soft functional material may serve as robust soft muscle, possibly revolutionizing the way that soft robotic solutions are engineered today,” said lead author of the study Aslan Miriyev. “It can push, pull, bend, twist, and lift weight. It’s the closest artificial material equivalent we have to a natural muscle.”

What’s next for lifelike robots?

Along with its extremely low cost (about 3 cents per gram), simple fabrication process and environmental-friendliness, its capabilities could enable new kinds of electrically-driven, entirely soft robots.

By mimicking living organisms, soft robotics has enormous potential in areas where robots need to contact and interact with humans, such as manufacturing and healthcare. Soft robots are better suited to replicating the intricacies and dynamic nature of natural motion, such as grasping and object manipulation. In other words, the sorts of delicate tasks performed every day in manufacturing and healthcare.

The researchers aren’t content to settle for the results revealed in their study, titled Soft Material for Soft Actuators. Going forward, they hope to replace the embedded wire by incorporating conductive materials into the muscle, as well as increasing its response time and shelf life.

Beyond that, if natural motion in robots is to be realized, they will need to develop the artificial intelligence required to control the synthetic muscles – brains to match the brawn.