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Microrobots filter microplastic from water

Czech 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, in a swarm, to remove microplastic from seas and other waters. The microrobots are controlled by magnetic fields and can, according to the research team, be cleaned and reused after taking up the microplastic. They see the microrobots as a highly promising approach for the cleaning and purifying of water.
 

 

According to the study "Magnetic Microrobot Swarms with Polymeric Hands Catching Bacteria and Microplastics in Water", which was published in the journal ACS Nano by the American Chemistry Society, the scientists used tiny robot systems with a diameter of 2.8 micrometres to remove microplastic and bacteria from water. Because microplastic can bind bacteria, which can cause many illnesses, the researchers also wanted at the same time to test the removal of microbes. According to the study, the small robots are barely larger than a bacteria cell, and consist of several components, which can work together and imitate natural swarms such as swarms of fish. The major component of the microrobots are strands of a positively charged polymer, which was combined with magnetic microparticles in order to be able to steer them in any desired direction from the outside through the use of magnets. The positively charged polymer strands served to attract plastics and microbes in the water. Via a rotating magnetic field, it was then possible to combine the microrobots into clusters, which acted together in a swarm. In the laboratory, the research team worked with a sample of water contaminated with microplastic and pathogenic agents. For this, they mixed water together with fluorescent polystyrene beads having a diameter of one micrometre. In addition, they added bacteria to the water. The microrobots placed in a water tank in various concentrations were controlled for 30 minutes by a rotating magnetic field. In order to visually confirm the simultaneous removal of microplastic and bacteria, the team performed analyses of the microrobots on the scanning electron microscope (SEM). The SEM images show, according to the study, that the microrobots have effectively interacted with the impurities and have captured them. This is also confirmed by the visually recorded reduction of microplastic at the various points in time, which was established using a fluorescence microscope and the fluorescein isothiocyanate filter (FITC). Images that were taken at intervals of 0.15 and 30 minutes confirm according to the study the progressive reduction of microplastic in the water medium. Afterwards, the microrobots were fetched back with a permanent magnet. The team carried out various physico-chemical analyses of the cleaned water and the collected microrobots. Subsequently, the microrobots were cleaned and disinfected with an ultrasonic process in order to be able to use them again. According to the research group, the study shows an effective method for cleaning water. The team hopes that it will be possible, through further improvements to the process, to increase the efficiency and practical application of such technologies. The researchers consider their approach to freeing water of microplastic and bacteria with the help of microrobots as highly promising.
 
Further information: Video of the research team that shows how the microrobots join up together and then "collect" microplastic and bacteria
 
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