Researchers at ETH Zurich have developed a new approach to building robots with living muscles that can produce movements visible to the naked eye. The breakthrough comes from designing muscle tissue and its supporting scaffold together as a single integrated system, rather than developing them separately.
This research is published in Nature Communications.
Computer-driven design beats trial and error
The team created what they call bioactuators - devices about 1.5 centimetres long that combine living skeletal muscle tissue grown from mouse cells with a soft hydrogel scaffold. Hydrogel is a water-rich material that bends and stretches like living tissue. The researchers used computer simulations to determine where to place muscle tissue and what properties the scaffold should have. An algorithm searched for configurations that would produce the greatest movement when the muscle contracted.
The scaffolds were manufactured using xolography, a 3D printing technique that uses light and takes about one minute per scaffold. The researchers then built and tested the computer-designed actuators in the laboratory, feeding information about material properties back into the simulation to refine the designs. They describe this iterative process as essential to the approach.
The result is a dramatic improvement over previous systems. These bioactuators achieve a range of motion up to eleven times greater than earlier designs with comparable amounts of muscle tissue. With single contractions, the devices can lift themselves approximately five millimetres off the surface - about a third of their body length. A walking version moves at 6.2 millimetres per second, which is faster relative to body length than any walking biohybrid robot reported to date.
The strong performance depends on more than just muscle tissue. Fine grooves in the hydrogel scaffold help anchor the tissue firmly and align muscle fibres, ensuring minimal loss of strength between muscle and scaffold.
This research matters because it demonstrates a practical path forward for biohybrid robotics. Living muscles offer advantages that conventional motors cannot match: they can change shape, adapt to their environment, and operate with soft, flexible structures. By treating muscle and scaffold as a unified system from the start, the ETH team shows how engineers can design biohybrid devices with genuinely useful capabilities.