An electroadsorption technique similar to the ultrafast charging mechanism in supercapacitors is utilized to remove metals with different sizes and hydrophilicities from contaminated water using self-propelled microswimmers. The swimmers carry graphite fibre or bismuth with a layered crystal structure providing high electrostatic double-layer capacitances. Unlike previous methods, this electrochemical technique does not only utilize the surface of the swimmers, but due to the interlayer spacing of the graphite and bismuth, it is able to store metals in ≈400 layers, allowing removal and recovery of >50 ppm lithium in only 5 min. A larger interlayer distance between bismuth sheets allows the removal of bigger cations (sodium and calcium), expanding the application of this method to a large variety of natural elements. Finally, magnetic navigation of charged swimmers to an oxygen-saturated media causes oxidation and thus immediate release of the metal ions from the swimmers.

Center for the Advanced Functional Nanorobots Department of Inorganic Chemistry University of Chemistry and Technology Technická 5 Prague Czech Republic

Department of Chemical and Biomolecular Engineering Yonsei University 50 Yonsei ro Seodaemun gu Seoul 03722 Republic of Korea

Future Energy and Innovation Laboratory Central European Institute of Technology Brno University of Technology Purkyňova 656 123 616 00 Brno Czech Republic

Institute of Organic Chemistry and Biochemistry of the CAS Flemingovo nám 542 2 166 10 Prague Czech Republic

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Smart micro- and nanorobots for water purification