Swarming Microrobots Prove Able to Grab Bacteria and Microplastics Right Out of Dirty Water

Researchers from the Brno University of Technology have come up with a novel approach to cleaning water of everything from microplastics to harmful bacteria — by sending in swarms of magnetic microrobots.

"This study introduces magnetically controlled microrobots that possess polymeric sequestrant 'hands' decorating a magnetic core," the researchers explain of their work. "Under the influence of external magnetic fields, the functionalized magnetic beads dynamically self-assemble from individual microparticles into well-defined rotating planes of diverse dimensions, allowing modulation of their propulsion speed, and exhibiting a collective motion."

Microrobots driven by external magnetic fields aren't new, but what the team has created is something with real purpose behind its movement: "These mobile microrobotic swarms can actively capture free-swimming bacteria and dispersed microplastics 'on-the-fly,'" the team explains, "thereby cleaning aquatic environments."

To prove the concept, the team flowed contaminated water through a chamber that was filled with the polymeric microrobots and surrounded by coils generating a rotating magnetic field. As the microrobots swarmed under the magnetic fields' control, they picked up the contaminants — and could be separated from what they'd picked up using ultrasound, depositing bacteria in a second tank for ultraviolet irradiation before being reused to clean yet more water.

"This multifaceted experiment demonstrated the ability of the self-propelled rotating microrobotic planes to capture bacterial contaminants and microplastics from water," the researchers conclude.

"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 team's work has been published in the journal ACS Nano under closed-access terms.