Fig. 5. Particle vertical migration properties of TOTs by DFLs.

a Schematic illustration of the vertical migration of a single particle through two parallel moving DFLs. b The trapping force distributions of TOT with DFLs on double-track PTWs. The color bar indicates the amplitude, and the arrows show the directions of the trapping force. The optical power of each laser is 12.0 mW. c Experimental results of the vertical migration of TOT particles. The red arrow indicates the movement direction of the lasers. Red and blue dotted circles mark the positions of the lasers. The yellow dotted circles represent the positions of the PS particles at 0 s, 48.8 s, and 81.1 s. d The moving trajectories of the PS and DFLs over time on the x‒y plane. e Schematic diagram of vertical particle migration by DFLs along a single PTW. f The trapping force distribution of TOTs with DFLs on a single-heeled PTW. The white dotted circles indicate PS particles trapped in the force potential wells. g PS particle and laser change curves with time along the y-direction. h Experimental results of particles moving in the y-direction. The optical power of each laser is 11.1 mW. Scale bar: 25 μm