Fig. 1. (a) and (b) Sketches and SEM images of NMPs and AuNMPs; scale bars 2 μm; (c) and (d) TEM images of thin central sections of different AuNMPs; scale bars 2 μm; (e) TEM image of a section near to the edge of an AuNMP; note the AuNPs’ distribution on the surface; scale bar 1 μm. (f) AuNPs located at the NMP surface, magnification of (c); scale bar 200 nm.

Fig. 2. (a) Optical microscope transmission image of an NMP between crossed polarizers; scale bar 5 μm. In the inset, the bipolar configuration scheme is shown. (b) Optical tweezers scheme. L, laser source; BE, beam expander; CCD, camera; DM, dichroic mirror; λ/4, quarter-wave plate, 60× objective; S, sample, LAMP illumination. In the enlargement, the propagation directions details of the wave vectors k and the gradient optical force f. The scheme is not to scale. Reflectance spectra of (c) NMPs and (d) AuNMPs. In the insets, the optical microscopy reflection images of NMPs and AuNMPs; scale bar 2 μm.

Fig. 3. (a) Sequence of snapshots for a spinning bare NMP when irradiated by a left circularly polarized beam. The blue line represents the long axis of the ellipsoidal NMP. The yellow scale bar is 3 μm. (b) Track of the central position of a bare NMP which undergoes five full spinning rotations. (c) Spin frequency dependence of a bare NMP (average radius 2.8 μm) versus beam intensity, at 514 nm (magenta) and 1064 nm (black).

Fig. 4. (a) Sequence of snapshots for a spinning AuNMP when irradiated by a left circularly polarized beam. The red line represents the long axis of the ellipsoidal AuNMP. The yellow scale bar is 3 μm. (b) Track of the central position of the AuNMP, which undergoes five full spinning rotations. (c) Spin frequency dependence versus beam intensity of 3.2±0.2  μm and 2.8±0.2  μm radius AuNMPs, at 514 nm (magenta) and 1064 nm (black), respectively.

Fig. 5. (a) Rotational kinetic energy of the bare NMPs (blue solid squares) and AuNMPs (red solid squares) as a function of the light intensity at 1064 nm. Rotational frequencies versus particle radius for (b) NMPs and (c) AuNMPs irradiated at 1064 nm and 1.7  mW/μm2; (d) rotational kinetic energy of the bare NMPs (blue solid squares) and AuNMPs (red solid squares) as a function of the light intensity at 514 nm; rotational frequencies versus particle radius for (e) NMPs and (f) AuNMPs irradiated at 514 nm and 1.7  mW/μm2; solid lines represent curve fitting according to Eq. (3). The fit parameters used are the following: (b) P=50  mW; σin=0.90; αeff=100  m−1; Δn=0.13; (c) P=50  mW; σin=0.90; αeff=230  m−1; Δn=0.13; (e) P=87  mW; σin=0.90; αeff=120  m−1; Δn=0.16.