Discover the light-driven toroidal micro-robot that autonomously navigates viscous liquids

Researchers from the University of Tampere in Finland and Anhui Jianzhu University in China have achieved a significant breakthrough in the field of soft robotics. Their study presents the first light-powered toroidal micro-robot capable of moving autonomously in viscous liquids, such as mucus. This innovation marks a major advance in the development of microrobots capable of navigating complex environments, with promising applications in areas such as medicine and environmental monitoring.

Their paper, titled “Light-steerable locomotion using zero-elastic-energy modes,” was recently published in Natural materials.

A glance through the optical microscope reveals a hidden universe teeming with life. Nature has developed ingenious methods for microorganisms to navigate their viscous environments: for example, E. coli bacteria use corkscrew movements, cilia move in coordinated waves, and flagella press against with a whip-like beat to propel itself forward. However, swimming on a microscopic scale is akin to a human trying to swim in honey, due to the overwhelming viscous forces.

Inspired by nature, scientists specializing in cutting-edge micro-robotic technologies are now looking for a solution. At the heart of the University of Tampere’s pioneering research is a synthetic material called liquid crystalline elastomer. This elastomer reacts to stimuli like lasers. When heated, it rotates on its own through a special zero elastic energy mode (ZEEM), caused by the interaction of static and dynamic forces.

According to Zixuan Deng, a doctoral researcher at the University of Tampere and first author of the study, this discovery not only represents a significant leap forward in soft robotics, but also paves the way for the development of micro-robots capable of navigating in complex environments.

“The implications of this research extend beyond robotics and could impact fields such as medicine and environmental monitoring. For example, this innovation could be used for the transport of drugs through physiological mucus and to unblock blood vessels after miniaturization of the device,” he says.

Donut shape simplifies control of swimming robots

For decades, scientists have been fascinated by the unique challenges of swimming at the microscopic scale, a concept introduced by physicist Edward Purcell in 1977. He was the first to imagine the toroidal (doughnut-shaped) topology for its potential to improve the navigation of microscopic objects. organisms in environments where viscous forces are dominant and inertial forces are negligible. This is called the Stokes regime or the lower limit of the Reynolds number. Although this seemed promising, no such toroidal swimmer had been demonstrated.

Now, a major advancement in toroidal design has simplified the control of swimming robots, eliminating the need for complex architectures. Using a single beam of light to trigger non-reciprocal movement, these robots leverage ZEEM to autonomously determine their movements.

“Our innovation enables three-dimensional free swimming in the Stokes regime and opens new possibilities for exploring confined spaces, such as microfluidic environments. Additionally, these toroidal robots can switch between rolling and rolling modes. self-propulsion to adapt to their environment.” adds Deng.

Deng believes future research will explore the interactions and collective dynamics of multiple tori, potentially leading to new methods of communication between these intelligent microrobots.

Highlight of light-driven soft robotics development

This latest study represents the culmination of results from two major research projects.

The first project, STORM-BOTS, aims to train a new generation of researchers in the field of soft robotics, with a specific focus on liquid crystal elastomers. As part of this project, Deng’s doctoral thesis research focuses on the development of light-driven soft robots capable of moving efficiently through air and water. His work is co-supervised by Professor Arri Priimagi and Professor Hao Zeng from the University of Tampere.

The second project, ONLINE, explores non-equilibrium soft actuator systems. This project aims to achieve autonomous movement, enabling new robotic functions such as locomotion, interaction and communication.