Researchers have unveiled the first-ever toroidal micro-robot powered by light, capable of moving on its own in thick liquids like mucus. This innovation represents a significant advancement in the development of micro-robots that can maneuver through intricate environments, with potential uses in healthcare and environmental monitoring.
A team of researchers from Tampere University in Finland and Anhui Jianzhu University in China has made a remarkable advancement in the field of soft robotics. Their pioneering study introduces a toroidal, light-driven micro-robot that can autonomously navigate viscous substances, such as mucus. This new technology is a significant step towards creating micro-robots capable of handling complex surroundings, which could be invaluable in areas like medicine and environmental supervision.
An examination under an optical microscope reveals a vibrant microcosm of life. Nature has equipped micro-organisms with clever tools to move through thick environments: for instance, E. coli bacteria twist and turn, cilia undulate in synchrony, and flagella utilize a whip-like action to move forward. Yet, swimming on the microscale resembles a human trying to swim through honey, due to the dominant viscous resistance encountered.
Drawing inspiration from nature, scientists focused on advanced micro-robotics are working towards a solution. Central to the research at Tampere University is a synthetic material called liquid crystalline elastomer, which reacts to stimuli like laser light. When it is heated, this material rotates automatically due to a unique zero-elastic-energy mode (ZEEM) resulting from the combination of static and dynamic forces.
As stated by Zixuan Deng, a Doctoral Researcher at Tampere University and lead author of the study, this achievement not only marks an important progression in soft robotics, but it also lays the groundwork for micro-robots that can navigate complex settings.
“The significance of this research spans beyond robotics and could influence fields such as medicine and environmental monitoring. For example, these devices could facilitate drug delivery through physiological mucus and assist in clearing blocked blood vessels once miniaturized,” he explains.
The doughnut shape enhances control of swimming robots
For years, scientists have been captivated by the unique hurdles associated with swimming at microscopic scales, a concept brought to light by physicist Edward Purcell in 1977. He was the first to propose the toroidal shape—resembling a doughnut—due to its potential in improving navigation for microscopic organisms in environments where viscous forces outweigh inertial forces. This scenario is referred to as the Stokes regime or low Reynolds number limit. Despite its promise, a toroidal swimmer had yet to be realized.
Now, a significant advancement in toroidal design has streamlined the control of swimming robots, removing the necessity for complex structures. By utilizing a single light beam to trigger non-reciprocal motion, these robots employ ZEEM to autonomously manage their navigation.
“Our breakthrough allows for three-dimensional free swimming within the Stokes regime and creates new opportunities for exploring confined areas, like microfluidic environments. Moreover, these toroidal robots can effortlessly switch between rolling and self-propelling actions based on their surroundings,” Deng adds.
Deng anticipates that future research will investigate the interactions and collective behavior of multiple toroidal robots, which could lead to new modes of communication among these intelligent micro entities.
Bringing together the evolution of light-driven soft robotics
The study titled “Light-steerable locomotion using zero-elastic-energy modes” has been published in Nature Materials. This report is the culmination of two significant research initiatives.
The first project, STORM-BOTS, focuses on training a new generation of scientists in the field of soft robotics, particularly with liquid crystal elastomers. As part of this initiative, Zixuan Deng’s doctoral research is dedicated to creating light-driven soft robots that can navigate effectively in both air and water, under the guidance of Professors Arri Priimagi and Hao Zeng from Tampere University.
The second project, ONLINE, investigates non-equilibrium soft actuator systems with the aim of achieving self-sustained movement, leading to innovative robotic capabilities such as locomotion, interaction, and communication.
