Abstract
Laser traps provide contactless manipulation of plasmonic nanoparticles (NPs) boosting the development of numerous applications in science and technology. The known trapping configurations allow immobilizing and moving single NPs or assembling them, but they are not suitable for massive optical transport of NPs along arbitrary trajectories. Here, we address this challenging problem and demonstrate that it can be handled by exploiting phase gradients forces to both confine and propel the NPs. The developed optical manipulation tool allows for programmable transport routing of NPs to around, surround or impact on objects in the host environment. An additional advantage is that the proposed confinement mechanism works for off-resonant but also resonant NPs paving the way for transport with simultaneous heating, which is of interest for targeted drug delivery and nanolithography. These findings are highly relevant to many technological applications including micro/nano-fabrication, micro-robotics and biomedicine.
Highlights
Trajectory can be open or closed, here, as an example, we have considered several closed loop trajectories allowing for continuous transportation of the NPs
The laser wavelength was 532 nm, which is on the blue-detuned side near the localized surface plasmon resonance (LSPR) of gold NPs
The corresponding distributions of the transverse forces F⊥ + F, displayed in the bottom panel of Fig. 2(a1–c1), have been numerically calculated to confirm the experimental results. Note that such a NP confinement mechanism cannot be exploited in the case of a Gaussian vortex trap because the dominant repulsive forces F⊥ are oriented towards its dark center, where the rotation of NPs has been observed[24]
Summary
Trajectory can be open or closed, here, as an example, we have considered several closed loop trajectories allowing for continuous transportation of the NPs. In contrast to other laser traps, the proposed confinement mechanism exploits transverse phase gradient forces[14,15,17] that allows working with resonant and off-resonant wavelengths on both red/blue-detuned sides of the LSPR.
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