3D-printed artificial muscles: soft silicone actuators for medicine

Artificial muscles have the potential to do more than power robotic systems. In the future, they could support walking, assist with physical work, or replace damaged muscle tissue. However, to match biological muscles, artificial versions must be both strong and flexible – a difficult combination to achieve technically. 

Artificial muscles function as actuators – components that transform electrical signals into motion. While actuators are already used in cars, industrial machinery, and household devices, conventional models are rigid and mechanical, far from the softness of natural muscles. 

Researchers at Empa’s Laboratory for Functional Polymers have developed dielectric elastic actuators (DEAs) from silicone. These are made up of two different silicone-based materials: a conductive electrode and a non-conductive dielectric. The two components interlock in alternating layers. 

“It's a bit like interlacing your fingers,” explains Empa researcher Patrick Danner. 

When voltage is applied, the actuator contracts like a biological muscle. Once the voltage is removed, it returns to its original shape. The challenge lies in printing these two materials together: though electrically different, they must behave similarly during printing, remain separate yet adhere well, and respond to pressure without losing their form. “These properties are often in direct contradiction,” says Danner. “If you optimize one of them, three others change … usually for the worse.” 

In collaboration with ETH Zurich researchers Tazio Pleij and Jan Vermant, the team led by Dorina Opris and Patrick Danner managed to overcome these material challenges. Using a special nozzle developed at ETH and custom inks developed at Empa, they succeeded in printing fully functional soft actuators. 

One of the goals is to develop a glove that allows users to “feel” virtual objects by providing resistance with artificial muscles. 

Beyond virtual reality, soft actuators offer many other potential applications: 

• They are lightweight and silent. 

• They can be formed into complex shapes thanks to 3D printing. 

• They may replace traditional actuators in vehicles, industrial automation, and robotics. 

The medical field also holds promise. Opris and Danner are exploring how their actuators could be adapted for healthcare technologies. Their method allows for the creation of long, elastic fibers. 

“If we manage to make them just a little thinner, we can get pretty close to how real muscle fibers work,” says Opris. 
COMPAMED-tradefair.com; Source: Empa