Long-range and rapid transport of individual nano-objects by a hybrid electrothermoplasmonic nanotweezer

Abstract

Plasmon-enhanced optical trapping is being actively studied to provide efficient manipulation of nanometre-sized objects. However, a long-standing issue with previously proposed solutions is how to controllably load the trap on-demand without relying on Brownian diffusion. Here, we show that the photo-induced heating of a nanoantenna in conjunction with an applied a.c. electric field can initiate rapid microscale fluid motion and particle transport with a velocity exceeding 10 μm s(-1), which is over two orders of magnitude faster than previously predicted. Our electrothermoplasmonic device enables on-demand long-range and rapid delivery of single nano-objects to specific plasmonic nanoantennas, where they can be trapped and even locked in place. We also present a physical model that elucidates the role of both heat-induced fluidic motion and plasmonic field enhancement in the plasmon-assisted optical trapping process. Finally, by applying a d.c. field or low-frequency a.c. field (below 10 Hz) while the particle is held in the trap by the gradient force, the trapped nano-objects can be immobilized into plasmonic hotspots, thereby providing the potential for effective low-power nanomanufacturing on-chip.

Opto-thermoelectric nanotweezers

“…The optical intensity we used was 0.05-0.4 mW μm -2 , which is 2-3 orders lower than the typical optical intensity in optical tweezers (10-100 mW μm -2 ). Different from the plasmon-enhanced optical force on plasmonic nanoantennas, which is limited by the decay length of LSPs 15,26 , the temperature gradient field has a much larger working range (Figs. 1g and h).…”

“…But the Joule loss can also be turned into an advantage. It has been demonstrated that the heat generated can benefit optical trapping by creating an electrothermoplasmonic flow that delivers nanoparticles to the trapping site 15 . Optical confinement of single nanoparticles or macromolecules has been achieved via a dynamic temperature field 16,17 .…”

Hybrid optofluidics and three-dimensional manipulation based on hybrid photothermal waveguides

“…Control of microscale solid or liquid inclusions is generally a momentous feat in integrated physical detection 43 and chemical reaction 16 . In contrast to other optofluidic systems that demand plasmonic structures 19 or specific surface patterns 44 , hybrid optofluidic flow can aggregate particles without limitations on the particles material or the requirement of a substrate, giving a circular arrangement under buoyancy convection and a mixture of square lattices under thermocapillary convection.…”

“…To achieve light-driven manipulation with extensive scale, the synergistic integration of optical systems and microfluidic flow has been utilized to control particle movement in a process called optofluidic manipulation 15,16 . Previous works have demonstrated optofluidic flows, including buoyancy convection stimulated by plasmonic heating [17][18][19][20][21] and thermocapillary flows stimulated by laser-induced microbubbles [22][23][24][25] . Despite fast fluid velocity and extensive scaling, photothermally induced fluidic trapping has been simply applied in massive aggregation and long-range transport [17][18][19][20][21][22][23][24][25] .…”

Dark spots along slowly scaling chains of plasmonic nanoparticles

“…Near-and far-field responses supported by the dielectric geometry of the system are determined by the hybridized localized surface plasmon-polariton (LSP) modes [3]. Engineering of such optical responses has provided a formidable variety of nanophotonic tools that include nanoantenna devices [4,5], surface-enhanced Raman scattering (SERS) substrates [6][7][8][9][10], integrated optical devices [11], metasurfaces [12], plasmon-induced loss devices [13], etc. In general, when the symmetry of a plasmonic configuration of nanoparticles is broken, a larger variety of coupling mechanisms between NP plasmons are possible [5], which exponentially broadens the capability of light interaction and manipulation.…”