In a study published in ACS Nano, researchers discuss the challenges of cleaning up microplastics from oceans and waterways, as well as the potential health risks associated with these tiny plastic particles. These microplastics can attract bacteria, including pathogens that cause disease, making them an even greater concern. To address this issue, researchers developed microscale robots, or microrobots, that are capable of capturing both microplastics and bacteria from water and can be decontaminated and reused.
One of the main concerns with microplastics, which are 5 millimeters or smaller in size, is that animals can ingest them, potentially passing the particles along the food chain and eventually reaching humans. The health effects of microplastics on humans are not fully understood, but the presence of bacteria on these particles poses an additional risk. To tackle this problem, the researchers developed microscale robotic systems that mimic natural swarms to remove both microbes and plastic from water simultaneously, providing a promising solution to this environmental issue.
To create these microrobots, the research team linked strands of a positively charged polymer to magnetic microparticles that only move when exposed to a magnetic field. These polymer strands attract both plastics and microbes, resulting in the formation of individual robots measuring 2.8 micrometers in diameter. When exposed to a rotating magnetic field, the robots swarmed together, with the researchers able to adjust the movement and speed of the swarm by controlling the number of robots in each cluster.
In lab experiments, the researchers demonstrated the effectiveness of the microrobots in capturing both microplastics and bacteria. By adding fluorescent polystyrene beads and actively swimming Pseudomonas aeruginosa bacteria to a water tank, the researchers were able to show that the microrobots captured approximately 80% of the bacteria at a concentration of 7.5 milligrams per milliliter. The microrobots also attracted and removed free plastic beads from the water, providing a dual cleaning function for water contaminated with microplastics and bacteria.
After capturing the bacteria and plastic particles, the researchers were able to decontaminate the microrobots using ultrasound and ultraviolet radiation, allowing them to be reused for further cleaning. The researchers note that this microrobotic system shows promise for removing plastic and bacteria from water and could be a valuable tool in addressing plastic pollution in oceans and waterways. The study was funded by the European Regional Development Fund/European Social Fund project TECHSCALE, the REFRESH program of the European Union, and CzechNanoLab.
