Plasmonic Optical Tweezers for Particle Manipulation: Principles, Methods, and Applications

Abstract

Inspired by the idea of combining conventional optical tweezers with plasmonic nanostructures, a technique named plasmonic optical tweezers (POT) has been widely explored from fundamental principles to applications. With the ability to break the diffraction barrier and enhance the localized electromagnetic field, POT techniques are especially effective for high spatial-resolution manipulation of nanoscale or even subnanoscale objects, from small bioparticles to atoms. In addition, POT can be easily integrated with other techniques such as lab-on-chip devices, which results in a very promising alternative technique for high-throughput single-bioparticle sensing or imaging. Despite its label-free, high-precision, and high-spatial-resolution nature, it also suffers from some limitations. One of the main obstacles is that the plasmonic nanostructures are located over the surfaces of a substrate, which makes the manipulation of bioparticles turn from a three-dimensional problem to a nearly two-dimensional problem. Meanwhile, the operation zone is limited to a predefined area. Therefore, the target objects must be delivered to the operation zone near the plasmonic structures. This review summarizes the state-of-the-art target delivery methods for the POT-based particle manipulating technique, along with its applications in single-bioparticle analysis/imaging, high-throughput bioparticle purifying, and single-atom manipulation. Future developmental perspectives of POT techniques are also discussed.

Single Photon Source from a Nanoantenna-Trapped Single Quantum Dot

“…Many approaches have been explored, relying on random dispersion, − two-step electron-beam lithography, , two-step nanofabrication, , DNA origami, , DNA self-assembly, , or atomic force microscopy . However, none of these techniques offer the simplicity and flexibility of plasmonic nano-optical tweezers where the trapped object is automatically positioned at the antenna hot spot. − Using the intense field gradients in plasmonic nanoantennas, − it becomes possible to manipulate single quantum emitters such as NV centers, , quantum dots, − erbium-doped nanocrystals, , or even a single atom . For a source to be considered into the quantum regime with single photon emission, it must verify the antibunching condition stating that its second-order intensity correlation at zero lag time must not exceed the 0.5 threshold. , Despite intense research, photon antibunching with , which gives the clear quantum signature of single photon emission, has remained elusive for a trapped quantum nano-object.…”

3D Optical Heterostructure Patterning by Spatially Allocating Nanoblocks on a Printed Matrix

“…As an important form of heterostructure application, optical heterostructure patterning with microscale or nanoscale materials has attracted immense attention in material science − and plays a key role in a variety of fields including display, , coding, , anticounterfeiting, , optical multiplexing, , and multiwavelength lasers. , In addition to size, composition, and morphology of the material, the spatial arrangement of the component units has a great influence on the property and function of the optical heterostructures. − Thus, various nanofabrication technologies, such as optical tweezers, , high-precision deposition, , lithography, , and field control, , have been applied to arrange the micro- and nanomaterials into morphology-controlled optical heterostructures. However, these techniques often suffer from the disadvantages of expensive instruments, complex processes, and limited materials, which largely restrict the large-area preparation and extensive application of the optical heterostructure.…”

Optical Archimedes Screw Along Arbitrary Trajectories

“…These are the intensity gradient force and the scattering force in the direction of beam propagation, which together create a stable optical trap, allowing for particle guiding, separation, and stable 3D trapping. [5] For manipulating nano-sized particles with these forces, plasmonic-based trapping is usually required, [6] where recent progress has allowed to realize conveyor functionality at those scales. [7][8][9] Another relevant medium is air [10] where a different force dominates the interaction with absorbing particles, namely, the photophoretic force which is thermal in nature.…”