MIT engineers 3D print multidirectional muscle tissue

According to MIT, researchers have developed a groundbreaking technique to 3D print artificial muscle tissue capable of contracting in multiple directions – paving the way for more versatile, muscle-powered biohybrid robots. Traditionally, lab-grown muscle fibers for robotics have only moved in a single direction, restricting range of motion. But this new approach, inspired by the human iris, allows engineered muscles to flex concentrically and radially – opening a new frontier for soft robotic applications.

The innovation centers around a 3D printed ‘stamp’ patterned with microscopic grooves, each as narrow as a single cell. When pressed into a hydrogel and seeded with genetically engineered muscle cells, the grooves act as a blueprint for muscle fiber orientation. “With the iris design, we believe we have demonstrated the first skeletal muscle-powered robot that generates force in more than one direction. That was uniquely enabled by this stamp approach,” said Ritu Raman, the Eugene Bell Career Development Professor of Tissue Engineering at MIT.

The stamped design mimics the layered muscle structure of the human iris, which allows the pupil to dilate and contract. When exposed to light, the artificial muscle contracts in a similar multidirectional fashion. Although the real human iris is made of smooth muscle, the researchers used skeletal muscle cells to show the flexibility of their method.

Beyond robotic applications, this stamping technique could enable the engineering of complex biological tissues like neurons and cardiac muscle. Importantly, the stamps can be made with standard desktop 3D printers – making the technology widely accessible.

“Natural muscle has multiple orientations in the tissue, but we haven’t been able to replicate that in our engineered muscles,” said Raman. Now, with this simple yet precise fabrication method, the team is one step closer to creating soft, biodegradable, energy-efficient robots that function in real-world environments – whether in the body or under the sea.

The research, published in Biomaterials Science, was supported by the US Office of Naval Research, Army Research Office, National Science Foundation, and National Institutes of Health.