Scientists Built Tiny Robots Using Living Mouse Muscles — They Can Jump, Swim and Walk!

Scientists have developed tiny biohybrid robots powered by lab-grown mouse muscle cells that can jump, swim, walk across surfaces and even grasp objects. The breakthrough, achieved by researchers at ETH Zurich, Switzerland, could open new possibilities for building robots that move more naturally by combining living tissues with artificial materials.

The most interesting part of the research is not simply the use of living muscles. Instead, the scientists discovered that the way muscle tissue connects and interacts with a soft artificial structure plays a major role in determining how much movement a robot can produce.

By designing these two components together using computer simulations, the researchers created muscle-powered devices capable of producing much larger movements than earlier systems containing comparable amounts of muscle tissue.

The findings were published in the journal Nature Communications in a study titled Co-optimized volumetric muscle design for large dynamic deformations in versatile biohybrid robots.

How Do Robots Powered by Living Muscles Work?

Traditional robots generally rely on electric motors, gears and mechanical components to produce movement. Biohybrid robots take a different approach by combining living biological materials with artificial structures.

In this case, the researchers used skeletal muscle tissue grown from mouse muscle cells. Skeletal muscles naturally contract and relax, allowing animals to move their bodies. Scientists can grow similar muscle tissues in laboratories and use their contractions to generate movement in small robotic devices.

However, getting these muscles to produce useful movement has been challenging. Although lab-grown muscle tissue can contract, the resulting movement is often too small to see clearly without a microscope.

This limits the practical capabilities of biohybrid robots.

To overcome this problem, the ETH Zurich team combined living muscle tissue with a soft, water-rich material called hydrogel. This material acts as an artificial scaffold that supports the muscle and changes shape as the muscle contracts.

The researchers found that simply adding more muscle tissue was not necessarily the best solution. Instead, they focused on designing the muscle and hydrogel scaffold as one integrated system.

Computer Simulations Help Design Stronger Movements

The research team developed a new approach in which the shape and arrangement of the muscle tissue and the properties of the artificial scaffold were optimized together.

Aiste Balciunaite and Mike Y. Michelis, the study's co-lead authors, helped develop this method. Balciunaite is a doctoral researcher in the Soft Robotics Lab led by ETH Zurich professor Robert Katzschmann.

Rather than starting with a fixed robotic structure and adding muscle tissue afterward, the researchers designed the entire system from scratch on a computer.

An algorithm examined different possible configurations to identify arrangements in which muscle contraction would produce the greatest movement of the overall device. It also helped determine where the muscle should be positioned and how the hydrogel scaffold should behave.

Once the designs were ready, the team built and tested the muscle-powered actuators in the laboratory.

The artificial scaffolds were produced using a light-based 3D-printing technique called xolography. According to the researchers, printing each scaffold took approximately one minute.

The process involved repeated cycles of computer modelling, fabrication and testing. Results from laboratory experiments helped the researchers improve their simulations and refine the material properties and manufacturing conditions.

This combination of computer-aided design, biological engineering and soft robotics allowed the team to create much more effective muscle-powered devices.

Muscle-Powered Devices Show Movement Visible to the Naked Eye

The resulting bioactuators were approximately 1.5 centimetres long. Each device combined living skeletal muscle tissue with a specially designed hydrogel scaffold.

Unlike earlier systems, in which muscle contractions could be difficult to observe, these devices produced substantial movements visible to the naked eye.

The researchers reported a range of motion up to 11 times greater than that of earlier systems containing a comparable amount of muscle tissue.

This improvement highlights how the arrangement of muscle tissue and its connection to an artificial structure can influence performance.

The scaffold is not merely a support that holds the muscle in place. It is an active part of the overall mechanical design, helping convert the muscle's contraction into useful movement.

Fine grooves built into the scaffold help the muscle tissue attach firmly and align its fibres. This strong connection allows the force generated by the muscle to transfer more effectively into the artificial structure.

When the connection is poorly designed, some of the muscle's force may be lost instead of producing movement. By improving this interaction, the researchers made better use of the force generated by the living tissue.

Tiny Robots Can Jump, Swim, Walk and Grasp Objects

One of the most striking achievements was the ability of the bioactuators to perform several different types of movement.

A jumping version of the device can lift itself approximately 5 millimetres off the bottom of a dish with a single muscle contraction. That distance is about one-third of the actuator's body length.

Although the jump appears small in absolute terms, it represents a significant movement for a device measuring only 1.5 centimetres.

The researchers also developed a walking version that moves at approximately 6.2 millimetres per second. According to the study, this was the fastest walking speed relative to body length reported for a biohybrid walking robot at the time.

Other configurations demonstrated the ability to swim, travel across a surface and grasp objects.

Jumping was particularly impressive because it requires a rapid and substantial change in body shape. The result demonstrated that the interaction between living muscle and the soft scaffold could produce more than simple bending.

Different arrangements of muscle tissue and artificial material can create different movements, suggesting that the design approach could be adapted for a range of small robotic applications.

Why Use Living Muscle Instead of Electric Motors?

Living muscles offer several interesting properties for robotics. They naturally generate force through contraction and can change their shape, potentially allowing robotic systems to move in ways that are difficult to achieve with conventional rigid components.

By combining biological tissue with soft artificial materials, researchers hope to develop machines that are more flexible and capable of interacting with their surroundings in a natural manner.

The new study also changes how engineers can approach muscle-powered robots. Instead of treating muscle geometry as a limitation, they can design the muscle's shape and arrangement to help determine how the entire robot moves.

This approach could eventually support the development of small, flexible robotic devices for specialized tasks. However, practical applications remain a long-term possibility rather than an immediate outcome of the research.

Major Challenges Still Remain

Despite the impressive results, the technology is not yet ready for widespread real-world use.

One major challenge is keeping the living muscle tissue alive. At present, these biohybrid robots depend on a nutrient solution that supplies the substances needed to maintain the tissue.

Larger devices would require a more sophisticated system capable of delivering oxygen and nutrients throughout the tissue while removing waste products. An artificial vascular network, similar in function to blood vessels, could be necessary to achieve this.

Another difficulty is the natural variability of living tissue. Unlike industrially manufactured motors and gears, lab-grown muscles do not always develop or behave identically. Differences in tissue growth and maturation can affect the performance of individual devices.

Researchers must therefore find better ways to control how muscle tissue develops and ensure that biohybrid robots behave more consistently.

These challenges will need to be addressed before the technology can move beyond laboratory experiments and become suitable for long-term operation.

A New Direction for the Future of Robotics

The ETH Zurich study demonstrates that combining living muscle with carefully designed artificial structures can produce significantly greater movement without simply increasing the amount of muscle tissue.

By bringing together cell biology, materials science, computer simulations and robotics, the researchers have shown how biological and artificial components can be engineered as a single system.

In the future, this approach could help scientists build small robotic devices that take advantage of the natural properties of living tissue. Such machines might eventually find uses in specialized medical technologies, delicate manipulation tasks or other applications where flexibility and controlled movement are important.

For now, the technology remains experimental, and significant challenges involving tissue maintenance, reliability and scaling must still be solved.

Nevertheless, these tiny muscle-powered robots offer a glimpse of a different approach to engineering: one in which machines do not rely exclusively on conventional motors, but instead combine artificial structures with the movement capabilities of living cells.

Reference: Aiste Balciunaite et al., “Co-optimized volumetric muscle design for large dynamic deformations in versatile biohybrid robots,” Nature Communications (2026). DOI: 10.1038/s41467-026-77655-1.