Researchers at Leiden University have developed microrobots capable of movement, navigation, and adaptation without a brain, sensors, or software. Their behaviour is driven entirely by physical structure and interaction with the environment.
These microrobots are only a few tens of micrometres long, making them approximately 10 times thinner than a human hair. Despite their minute size, they can swim and respond to obstacles in a manner that appears life-like.
The team, led by Professor Daniela Kraft and researcher Mengshi Wei, constructed the robots as flexible chains of connected segments. When exposed to an electric field, these structures begin moving autonomously.
The robots generate motion and adjust to their surroundings in real time by utilising their shape and flexibility, rather than relying on electronics. This concept draws inspiration from how animals like worms and snakes move by continuously changing their body shape to navigate complex spaces.
Professor Kraft noted the challenge in creating these tiny, flexible robots. "Animals like worms and snakes constantly adapt their shape as they move, which helps them to navigate their environments," Kraft said. "Macroscopic robots similarly use flexibility for their function. However, until now, microrobots were either small and rigid, or large and flexible. We wondered if we could realise small and flexible microrobots in our lab."
To create these devices, the team employed a high-precision 3D microprinter. Each element measures about 5 micrometres in size, with joints as small as 0.5 micrometres connecting them.
The structures are built as chains of self-propelling elements that collectively generate motion. Once activated, the robots move at speeds of around 7 micrometres per second.
The fabrication process uses advanced microprinting systems operating at the limits of current manufacturing capabilities. This allows for both flexibility and structural precision at extremely small scales.
When activated, the robots move with a wave-like motion. Their flexible design enables them to bend and propel forward without programmed instructions.
Researchers discovered continuous feedback between the robot’s movement and shape. This interaction allows them to adjust automatically as conditions change.
Kraft added, "We discovered there's continuous feedback between the shape and motion of the robot: the shape influences how it moves, and its movements in turn alters its shape. This microrobot therefore senses how the environment changes its body and reacts to it, making it appear life-like. This means that we don't need microscopic electronics for integrating smart abilities."
The robots can avoid obstacles and change direction without any control system. They are also able to move through crowded environments and push objects out of their path.
"When the robot is slowed down or even stopped, it starts to wave its tail as if it wants to break free," Wei said.
Researchers suggest that this technology could support applications such as targeted drug delivery and minimally invasive procedures. The next step involves better understanding how such behaviour emerges from simple physical interactions. The study was published in the journal *PNAS*.
Leiden University researchers developed microrobots that move and adapt without a brain or code.
These robots are tens of micrometres long and utilise shape and flexibility for navigation.
They are created using a high-precision 3D microprinter, with elements measuring 5 micrometres and joints 0.5 micrometres.
Source: INTERESTING ENGINEERING
