Fig. 1. Structural diagrams and parameters of simulation models. (a) Structural diagram of silicon-based double nanoballs; (b) structural diagram of gold-based double nanoballs; (c) parameters of silicon-based double nanoballs; (d) parameters of gold-based double nanoballs

Fig. 2. Enhanced electric field (|E/E0|) distributions. (a) Cross-section of silicon-based double nanoballs at z=100 nm; (b) cross-section of silicon-based double nanoballs at y=0; (c) cross-section of gold-based double nanoballs at z=100 nm; (d) cross-section of gold-based double nanoballs at y=0

Fig. 3. Heat loss density distributions under light intensity of 6.67 mW/μm2. (a) Heat loss density distribution of cross-section of silicon-based double nanoballs at z=100 nm; (b) cross-section of gold-based double nanoballs at z=100 nm

Fig. 4. Trapping ability of double nanoball structure under light intensity of 6.67 mW/μm2. (a) Functional relationship between z coordinate of polystyrene sphere and trapping force Fz in silicon-based structure (x=y=0); (b) functional relationship between z coordinate of polystyrene sphere and trapping potential energy Uz in silicon-based structure (x=y=0); (c) functional relationship between z coordinate of polystyrene sphere and trapping force Fz in gold-based structure (x=y=0); (d) functional relati

Fig. 5. Temperature distributions and convection velocity fields. (a) Temperature distribution of silicon-based structure (z=100 nm); (b) convection velocity field of silicon-based structure (x=0); (c) temperature distribution of gold-based structure (z=100 nm); (d) convection velocity field of gold-based structure (x=0)

Fig. 6. Brownian motion of polystyrene spheres after 5 s under different temperatures. (a) 293.15 K; (b) 364.95 K

Fig. 7. Trapping force of nanoparticles in optical tweezer structure with silicon-based double nanoballs. (a) Trapping forces (Fz and Fx) of nanoparticle at z=50 nm and z=150 nm; (b) trapping force of nanoparticles in x direction; (c) trapping force of nanoparticles in y direction; (d) absolute value of trapping stiffness in x and y direction