Two antenna-like feelers turn unicellular microalgae into fantastic swimmers. Two researchers from the Max Planck Institute for Intelligent Systems have harnessed this ability. They transformed the organisms into mini-robots that could be used as drug transporters in medicine, for example.

Magnetic microalgae as microrobots

As part of the study, researchers Birgül Akolpoglu and Saadet Fatma Baltaci wanted to find out whether the microalgae could also swim through confined spaces and viscous fluids such as those found in the human body. Their aim was to functionalize the surface of the unicellular organisms with a magnetic material so that the cells could be steered in any desired direction like a micro-robot. To do this, they coated algae with the biopolymer chitosan and magnetic nanoparticles. The magnetic coating worked without any problems in nine out of ten microalgae. These biohybrid mini-robots were then tested in both a water-like and a viscous liquid. In both cases, the magnetic microalgae were controlled using external magnetic fields and maneuvered along tiny 3D-printed tubes.

Magnetic control works

As the team reports in the journal Matter, the microalgae's swimming ability was “largely unaffected” by the magnetic coating, whereas without the coating they either got stuck or moved backwards. “With magnetic control, however, they moved more smoothly and avoided obstacles,” says co-first author of the publication, Birgül Akolpoglu. “Magnetic steering helped the microswimmers to align themselves with the direction of the field. They showed real potential for navigation in confined spaces - as if they were equipped with a kind of tiny GPS.”

Potential not only in biomedicine

According to the study, however, the viscosity has an influence on the buoyancy of the coated microalgae. Only when the magnetic field was applied did the swimmers move. “This shows how fine-tuning viscosity and magnetic orientation can optimize the navigation of microrobots in complex environments,” says Saadet Fatma Baltaci. The researchers are convinced that the mini-robots made from algae “open doors for applications such as targeted drug delivery” and offer “exciting potential for future innovations in biomedicine and beyond”.

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