Swarms of microrobots remove microplastics and bacteria from water
In future, micro-robots will be able to filter out microplastics and bacteria from the sea that are harmful to humans and the environment.
Microrobots capture microplastics and bacteria.
(Image: Martin Pumera u. a.)
Researchers from the Future Energy and Innovation Laboratory, the Central European Institute of Technology and the Brno University of Technology have developed microrobots that are able to swarm and remove microplastics from oceans and other bodies of water. The microrobots are controlled by magnetic fields and can be cleaned and reused after ingesting microplastics.
Microplastics, i.e. pieces of plastic that are less than 5 mm in size, are a major problem. The plastic particles can also enter the human food chain via the ingestion of marine animals, for example. The health effects this can have are not yet fully understood. What is certain, however, is that microplastics attract bacteria, including pathogens, which are harmful to humans and animals and can have a direct impact on the organism.
To remove microplastics and pathogens from water, the scientists rely on microscale robotic systems with a diameter of 2.8 ÎĽm, as they write in their scientific paper "Magnetic Microrobot Swarms with Polymeric Hands Catching Bacteria and Microplastics in Water", published in ACS Nano. The small robots essentially consist of a positively charged polymer interspersed with magnetic microparticles. This allows the robots to be steered in any direction by means of a magnetic field. In addition, several of these robots can be combined into clusters via a rotating magnetic field so that they can act together in a swarm. They attract plastics and microbes via the positively charged polymer threads.
Ridding water of microplastics and bacteria
In the laboratory, the researchers recreated a body of water contaminated with microplastics and pathogens. To achieve this, they added fluorescent polystyrene beads with a diameter of one micrometer to the water. They also added actively floating Pseudomonas aeruginosa bacteria to the water. These bacteria can cause pneumonia and other infections.
The scientists then inserted microrobots into the water tank. They controlled them via a rotating magnetic field for 30 minutes, which they switched on and off every 10 seconds. They tested the robots in different concentrations. At the highest concentration of 7.5 mg per ml, around 80 percent of the bacteria were captured by the microrobots. They also attracted the polystrol beads, reducing their concentration in the water.
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Using a permanent magnet, the researchers collected the microrobots again and decontaminated them with ultrasound to remove the adhering bacteria. The microbes were then killed with ultraviolet radiation.
The scientists used the disinfected robots again to purify water. However, the robots were then no longer able to absorb the same number of bacteria and microplastics as before.
The researchers see their approach of using microrobots to remove microplastics and bacteria from water as promising.
(olb)