MIT engineers craft spring device to enhance robotic muscles

Despite their size, muscle fibers are usually stronger and more accurate than most other synthetic actuators. They also have self-healing properties, making them attractive for robotic applications. 

Demonstrating “biohybrid” robots

So far, designs have usually lacked the ability to maximize muscle efficiency. This research tackles this challenge by designing a flexible skeleton-like structure for various robotic designs. 

The flexure is soft and flexible, particularly in one direction, while remaining stiff in other directions. This allows the efficient conversion of muscle contractions into movement.

As per MIT, designers “demonstrated a handful of “biohybrid” robots that use muscle-based actuators to power artificial skeletons that walk, swim, pump, and grip. 

“But for every bot, there’s a very different build and no general blueprint for how to get the most out of muscles for any given robot design.”

Stretches five times more than other designs

Upon testing a ring of muscle tissue on a device akin to how a rubber band extends to two posts, the muscle pulled on the spring repeatedly.

It also demonstrated stretching five times more in contrast to previous similar designs. 

This could potentially lay the foundation for developing other flexures to build any artificial skeletons. Engineers can subsequently equip the skeletons with muscle tissues to drive their motions.

“These flexures are like a skeleton that people can now use to turn muscle actuation into multiple degrees of freedom of motion in a very predictable way,” stated Ritu Raman, the Brit and Alex d’Arbeloff Career Development Professor in Engineering Design at MIT. 

“We are giving roboticists a new set of rules to make powerful and precise muscle-powered robots that do interesting things.”

The flexures forming the basis of this invention are often crafted from parallel beams that have the potential to flex and stretch with nanometer precision.

Raman said, “Depending on how thin and far apart the beams are, you can change how stiff the spring appears to be.”

The surgical robot

The flexure is actually 1/100th as stiff as muscle tissue. The device takes on the appearance of a small, accordion-like structure. Its corners are anchored to a base beneath a slender post. Adjacent to this post sits another, directly affixed to the base.

After this, they measured how close the posts were pulled together as the muscle band contracted.

“When the muscle contracts, all the force is converted into movement in that direction. It’s a huge magnification,” Raman added.

Now, scientists are working to advance flexures for precise, articulated, and reliable robots that are powered by natural muscles.

He stated, “An example of a robot we are trying to build in the future is a surgical robot that can perform minimally invasive procedures inside the body.” 

“Technically, muscles can power robots of any size, but we are particularly excited in making small robots, he said.

“This is where biological actuators excel in terms of strength, efficiency, and adaptability.”

The study was published in the journal–Advanced Intelligent Systems.