Microrobots can clean up microplastics and bacteria

Researchers designed a swarm of tiny spherical robots to collect bacteria and small pieces of plastic. Image credit: American Chemical Society

When old food packaging, discarded children's toys and other mismanaged plastic waste break down into microplastics, they become more difficult to remove. In a study published in the latest issue of ACS Nano, a journal of the American Chemical Society, Czech researchers describe a swarm of microscopic robots that can capture plastic fragments and bacteria from water. The robots can then be purified and reused.

Microplastics are 5 mm or smaller in size, and animals can easily ingest them and be harmed. These animals then pass the particles into the human food chain. At the same time, microplastic fragments can also attract various bacteria, including pathogens, posing a greater threat to organisms.

In order to remove microorganisms and microplastics from water at the same time, the Brno University of Technology in the Czech Republic has developed a micro-robotic system composed of many small parts working in collaboration to mimic biological groups in nature, such as schools of fish.

The team attached positively charged polymers to magnetic microparticles that move only when exposed to a magnetic field. Polymer threads extending from the surface of the beads attract microplastics and microorganisms. The finished individual robots are 2.8 micrometers in diameter. When exposed to a rotating magnetic field, the robots cluster together. By adjusting the robots, which self-organize into flat clusters, the movement and speed of the robot group can be changed.

The team used Pseudomonas aeruginosa, which can cause pneumonia and other infections, to replicate microplastics and bacteria in the environment. The results showed that the microrobots successfully captured about 80% of the bacteria, and free plastic beads were also captured by the microrobots. The researchers then collected the robots and separated the bacteria using ultrasound, and then exposed them to ultraviolet light for disinfection, allowing them to be reused.