Fig. 1

Schematic diagram and structural characterization of microswimmers. a, c Schematic diagram of silicon nanowire microswimmer without and with polyelectrolyte coating. The SPS layer was chemically grafted onto the core–shell silicon nanowire. Upon illumination, the surface electrochemical reaction driven by the nanowire solar cell produces OH⁻ and H⁺ ions on the n-type silicon shell and exposed p-type silicon core, respectively. The electric field built by the unbalanced ions propel the negatively charged nanowire. b, d The equivalent circuits of nanowire microswimmer operation without and with polyelectrolyte coating. e False-colored scanning electron microscopy image of silicon nanowire array grown by the VLS method. f Scanning transmission electron microscopy (STEM) image of SPS-grafted silicon nanowire. Inset is high-resolution TEM image of SPS-modified silicon nanowire. (Scale bars in e, f, and f inset are 10 μm, 200 nm, and 5 nm, respectively)