Microrobots tested as clean-up crew for polluted waters

Microrobots are at the forefront of addressing a significant environmental challenge. Microplastics – tiny fragments measuring 5 millimeters or less – not only contaminate our oceans and waterways but also pose substantial threats to wildlife and human health.

In a new study from the American Chemical Society, researchers have pioneered the use of innovative microrobots designed to tackle and effectively manage microplastic pollution.

“These particles are pervasive in aquatic environments, posing ecological risks due to their potential ingestion by marine organisms and the subsequent entry to the food chain, possibly impacting marine ecosystems and human health,” wrote the study authors. 

Coexistence of bacteria and microplastics

Originating from decomposed consumer products like old food packaging and children’s toys, microplastics break down and attract harmful bacteria, including disease-causing pathogens. This complicates the cleanup process and intensifies the pollution problem.

“The coexistence of bacteria and microplastics complicates the task of their complete removal, exacerbating their impacts and posing a compounded threat to the environment and human well-being,” wrote the researchers.

“Despite the most recent advancements, the complex challenge of concurrently addressing the presence of free-swimming bacteria and microplastics remains largely unexplored, and ideas to reduce or prevent their interaction are yet to be discussed.”

Harnessing the power of microrobots

Under the guidance of Martin Pumera and his team, the creation of these microrobots marks a significant breakthrough in environmental technology. The team engineered the robots by fusing magnetic microparticles with positively charged polymer strands.

These polymers, emanating from the microparticles’ surface, allow the robots to attract both microplastics and microbial contaminants effectively. Remarkably, each microrobot is minuscule, measuring only 2.8 micrometers in diameter.

Swarm dynamics and functionality of microrobots

What’s captivating about these microrobots is their swarming capability. When exposed to a rotating magnetic field, the robots cluster together in a manner similar to schools of fish.

The swarming behavior can be manipulated by varying the number of robots, which in turn affects the swarm’s movement and speed. This innovative method was demonstrated in a video by the researchers, emphasizing the robots’ efficiency in cleaning water.

Field testing and results

The practical application of these microrobots was evaluated in a controlled laboratory environment. The team introduced fluorescent polystyrene beads and Pseudomonas aeruginosa bacteria, which are known to cause infections such as pneumonia, into a water tank.

After adding the microrobots to the contaminated water and activating them with a rotating magnetic field, the results were encouraging. At a concentration of 7.5 milligrams per milliliter, the robots successfully captured about 80% of the bacteria.

Furthermore, the amount of microplastics in the water significantly decreased over time as they were drawn to the swarming robots.

Reusability and sustainability

Following the capture of microplastics and bacteria, the microrobots were collected using a permanent magnet.

The contaminants attached to the robots were then removed using ultrasound and exposed to ultraviolet radiation to ensure thorough disinfection. Remarkably, these cleaned microrobots could be reused.

Although they captured slightly lesser amounts during subsequent uses, their ability to be recycled highlights the sustainable potential of this technology.

The future of microrobots in environmental cleanup

This microrobotic system offers a promising avenue for mitigating the impacts of plastic and bacterial pollution in water bodies.

According to the study authors, the technology not only addresses current environmental challenges but also opens up new possibilities for future advancements in robotic environmental cleaning solutions.

“In summary, this multifaceted experiment demonstrated the ability of the self-propelled rotating microrobotic planes to capture bacterial contaminants and microplastics from water,” noted the researchers.

“The integration of qualitative and quantitative assessments emphasizes their robust performance and potential as materials for treating various environmental pollutants simultaneously.”

“This approach can stimulate the development of more sophisticated materials, including hybrid systems capable of capturing both positively and negatively charged contaminants at the same time. This is especially attractive for real-world water purification applications where contaminated water samples usually contain several types of pollutants.”

The study is published in the journal ACS Nano.

Video Credit: American Chemical Society

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