Researchers have demonstrated a light-driven micro-robot that can move autonomously in viscous liquids, such as mucus.
The innovation - a culmination of two major EU-funded projects - marks a major step forward in developing micro robots capable of navigating complex environments, with promising applications in fields such as medicine and environmental monitoring.
Microorganisms rife in viscous environments
Nature has devised ingenious methods for microorganisms to navigate their viscous environment. For example, E. coli bacteria employ corkscrew motions, cilia move in coordinated waves, and flagella rely on a whip-like beating to propel themselves forward.
However, swimming at the microscale is akin to a human attempting to swim through honey, due to the overwhelming viscous forces.
In their research, scientists from Tampere University in Finland and Anhui Jianzhu University in China use a liquid crystalline elastomer that reacts to stimuli like lasers. When heated, it rotates on its own due to a special zero-elastic-energy mode (ZEEM), caused by the interaction of static and dynamic forces.
The material’s toroidal – or doughnut shaped – design is key to the control of swimming robots. The potential of toroidal topology to improve the navigation of microscopic organisms in viscous environments was first highlighted by physicist Edward Purcell in 1977. The effect is a result of the dominant viscous forces and negilible inertial forces in these types of liquid.
Although the concept – known as the Stokes regime or the low Reynolds number limit – seemed promising, no such toroidal swimmer had been demonstrated until now.
By using a single beam of light to trigger non-reciprocal motion, the Finnish/Chinese developed robots can autonomously determine their movements.
“Our innovation enables three-dimensional free swimming in the Stokes regime and opens up new possibilities for exploring confined spaces, such as microfluidic environments. In addition, these toroidal robots can switch between rolling and self-propulsion modes to adapt to their environment,” said Zixuan Deng, a Doctoral Researcher at Tampere University and the first author of a study published in Nature Materials.
Deng believes that future research will explore the interactions and collective dynamics of multiple tori, potentially leading to new methods of communication between these intelligent microrobots.
“The implications of this research extend beyond robotics, potentially impacting fields such as medicine and environmental monitoring. For instance, this innovation could be used for drug transportation through physiological mucus and unblocking blood vessels after the miniaturisation of the device,” he said.
The research was recently published in Nature Materials.
Credit for main image: KinoMasterskaya/Shutterstock
