Fig. 1. Experimental setup for particle capture based on photothermal effect

Fig. 2. Diagrams of optical manipulation for SiO2 sphere based on thermal convection effect. (a) Fiber being stationary; (b) fiber moving along z axis; (c) fiber moving along y axis; (d) fiber moving along x axis

Fig. 3. Optical microscope images of lateral movement of SiO2 sphere by vertical movement of fiber (top view). (a) t=0 s, fiber is located at z=500 μm; (b) t=3.2 s, fiber is located at z=300 μm; (c) t=5.8 s, fiber is located at z=150 μm; (d) t=6.1 s, fiber is located at z=80 μm; (e) t=9.6 s, fiber is located at z=350 μm; (f) t=11.3 s, fiber is located at z=550 μm

Fig. 4. Simulation results of heat transfer field (HT) and convective velocity field (FM) at different heights of fiber. (a) Temperature field distribution of fiber at z=50 μm; (b) temperature field distribution of fiber at z=550 μm; (c) convective velocity field distribution of fiber at z=50 μm; (d) convective velocity field distribution of fiber at z=550 μm

Fig. 5. Trajectories of silica sphere at z=50 μm at different times. (a) t=1.2 s; (b) t=4.3 s; (c) t=8.2 s; (d) t=12.7 s

Fig. 6. Trajectories of silica sphere at z=550 μm at different time. (a) t=1.2 s; (b) t=8.1 s; (c) t=16.5 s; (d) t=23.3 s

Fig. 7. Electromagnetic field (EM) distributions of fiber and optical trapping force distributions of SiO2 sphere. (a) EM distribution of optical fiber in suspension; (b) EM distribution of SiO2 sphere with chain structure; (c) axial optical force distribution of SiO2 sphere; (d) transverse optical force distribution of SiO2 sphere