Fig. 2: Opto-thermoelectric swimming of PS/Au Janus particles under a defocused laser beam.

a Schematic illustration of the swimming mechanism. The velocity is directed from the PS hemisphere to the Au-coated hemisphere. b Swimming velocity as a function of the optical power for 5 µm PS/Au Janus particles. A 660 nm laser beam with a beam size of 31 µm was applied to drive the swimming. c Time-resolved images of a swimming 2.1 µm PS/Au particle. A 1064 nm laser beam with a beam size of 31 µm and a power of 32 mW was applied to drive the swimming. d Swimming velocity as a function of the optical power for 2.1 µm PS/Au Janus particles. Two different laser beams, i.e., a 1064 nm laser beam with a beam size of 45 µm and a 660 nm laser beam with a beam size of 45 µm, were applied to drive the swimming. The insets of b, d show a PS/Au Janus particle driven to swim under a defocused laser beam. All the aforementioned beam sizes were obtained by experimental measurement