Bend, Spin, Swim

Abstract

Engineering Nanostructures that undergo directional propulsion (“nanoswimmers”) have recently been powered by catalytic chemical reactions (such as hydrogen peroxide disproportionation) or electric fields. Gao et al. now show that flexible nanowires powered by external magnetic fields can swim in a manner analogous to bacterial flagella. After sequential electrodeposition of gold-silver-nickel nanowires (6 µm long and 200 nm in diameter), the silver section was thinned via hydrogen peroxide oxidation to create a flexible linker. In solution, the nanowires respond to a rotating magnetic field, but the nickel head rotates through a greater solid angle than does the gold tail. This broken symmetry, along with tailoring of the segment lengths and magnetic field modulation, allows the structure to swim at speeds of up to 6 µm/s, even in high-salt media. J. Am. Chem. Soc. 132 , 10.1021/ja1072349 (2010).