Empa researchers develop artificial muscles using 3D printing processes

A team of researchers at the Swiss Federal Laboratories for Materials Science and Technology (Empa) has developed a process that allows artificial muscles to be produced from soft and elastic materials using 3D printing. In the future, these actuators could be used not only in robotics, but also in medicine and industrial applications.

Artificial muscles pose a technical challenge as they need to be both powerful and flexible. Conventional mechanical actuators, which convert electrical impulses into movement, often consist of hard components and their functionality is very different from that of biological muscles. Empa researchers are therefore working on so-called dielectric elastomer actuators (DEA), which consist of two different silicone-based materials: an electrically conductive electrode and a non-conductive dielectric material. These layers are closely interwoven and contract when an electrical voltage is applied, similar to natural muscles.

Printing these structures places high demands on the material properties. The two materials used must clearly separate from each other during the printing process, but still form a stable structure. They must also retain their shape after extrusion from the printer nozzle, which requires precise coordination of the viscosity. “These properties are often in direct contradiction,” explains Empa researcher Patrick Danner. “If you optimize one of them, three others change … usually for the worse.”

In collaboration with ETH Zurich, Danner and Dorina Opris, who heads the research group for functional polymer materials, have developed special inks for the 3D printing of actuators. This project is part of the Manufhaptics initiative, which is driving forward the development of a glove for virtual reality applications. In future, the artificial muscles could simulate resistance and thus enable a more realistic gripping sensation.

Soft actuators also offer potential for numerous other applications. They work almost silently, are lightweight and can be flexibly adapted to different requirements thanks to additive manufacturing. In addition to their integration into machines or vehicles, they could also be used for medical purposes in the long term. The research team is already working on printing elongated, elastic fibers using the new process. If they succeed in miniaturizing them further, they could replicate the functioning of natural muscle fibres even better. “If we manage to make them just a little thinner, we can get pretty close to how real muscle fibers work,” says Opris. However, there is still a lot of research work to be done before this is achieved.