Fundamental Limits of Optical Tweezer Nanoparticle Manipulation Speeds

Abstract

Optical tweezers are a noncontact method of 3D positioning applicable to the fields of micro- and nanomanipulation and assembly, among others. In these applications, the ability to manipulate particles over relatively long distances at high speed is essential in determining overall process efficiency and throughput. In order to maximize manipulation speeds, it is necessary to increase the trapping laser power, which is often accompanied by undesirable heating effects due to material absorption. As such, the majority of previous studies focus primarily on trapping large dielectric microspheres using slow movement speeds at low laser powers, over relatively short translation distances. In contrast, we push nanoparticle manipulation beyond the region in which maximum lateral movement speed is linearly proportional to laser power, and investigate the fundamental limits imposed by material absorption, thus quantifying maximum possible speeds attainable with optical tweezers. We find that gold and silver nanospheres of diameter 100 nm are limited to manipulation speeds of ∼0.15 mm/s, while polystyrene spheres of diameter 160 nm can reach speeds up to ∼0.17 mm/s, over distances ranging from 0.1 to 1 mm. When the laser power is increased beyond the values used for these maximum manipulation speeds, the nanoparticles are no longer stably trapped in 3D due to weak confinement as a result of material absorption, heating, microbubble formation, and enhanced Brownian motion. We compared this result to our theoretical model, incorporating optical forces in the Rayleigh regime, Stokes' drag, and absorption effects, and found good agreement. These results show that optical tweezers can be fast enough to compete with other common, serial rapid prototyping and nanofabrication approaches.

All optical dynamic nanomanipulation with active colloidal tweezers

“…Various alternate approaches have relied on combining plasmonic tweezers with additional forcing schemes, such as direct mechanical manipulation of tethered nano-patterned optical fibers 50 , integration with magnetic nanorobots 51 , electro-kinetic flows 14,52 , thermal forces in conjunction with specific chemical moieties 29–31,53 , etc. The ACTs discussed here could be operated remotely to trap and maneuver subwavelength colloidal cargo, using lower optical power than conventional gaussian beam tweezers 5,54 . They are mass-produced and thereafter can be integrated seamlessly to standard lab-on-chip devices as well as existing optical tweezer systems, such as to carry out colloidal manipulation of micron and submicron cargos.…”

“…Conventional optical traps are built using highly focussed laser beams where the focal spot can be positioned accurately within the fluidic chamber through external optical assembly, allowing multiple 3 tweezers to carry out micromanipulation tasks in parallel, leading to many important breakthroughs in biology, materials science, and soft condensed matter physics 4 . While performance of conventional optical tweezers is limited 5 by diffraction, alternate newer strategies rely on strong near-field concentration of plasmonic nanostructures under resonant optical illumination 6 . These near-field based tweezers 7,8 can generate stronger optical potentials around them, and thereby able to trap smaller colloids 9–12 at lower illuminations intensities, compared to traditional optical tweezers.…”

Dark mode plasmonic optical microcavity biochemical sensor

“…Compared to the existing single-rod plasmonic hybrid WGM system, the trimer system exhibits higher enhancement, stability, and greater contact area for particle detection. In future work, we plan to use high-precision optical tweezers [39,40] to position trimer microresonator systems for biological sensing experiments.…”

Massively Multiplexed Submicron Particle Patterning in Acoustically Driven Oscillating Nanocavities

“…[ 38 ] Furthermore, most of these manipulation methods are constrained by their dependence on particle polarizability, the need for low conductivity medium (which is often not biocompatible), and heating of the surrounding fluid. Optical tweezers [ 39,40 ] provide the highest degree of spatial resolution but they are usually applied in static fluids, owing to the relatively small forces that can be generated, [ 41 ] and only small numbers of nanoparticles can be manipulated at any one time (those within the field of a focused optical beam [ 42–44 ] ). Acoustic fields have been widely used for micron‐scale particle manipulation, employing either bulk acoustic waves (BAWs, where a resonance mode of a rigid microchannel is excited) or surface acoustic waves (SAWs, where an acoustic wave travels along the surface of a piezoelectric substrate and couples into an adjoining microchannel), to produce a nonzero time‐averaged pressure field in the channel which affects an acoustic radiation force on suspended particles.…”