Opto-thermoelectric nanotweezers

Abstract

Optical manipulation of plasmonic nanoparticles provides opportunities for fundamental and technical innovation in nanophotonics. Optical heating arising from the photon-to-phonon conversion is considered as an intrinsic loss in metal nanoparticles, which limits their applications. We show here that this drawback can be turned into an advantage, by developing an extremely low-power optical tweezing technique, termed opto-thermoelectric nanotweezers (OTENT). Through optically heating a thermoplasmonic substrate, alight-directed thermoelectric field can be generated due to spatial separation of dissolved ions within the heating laser spot, which allows us to manipulate metal nanoparticles of a wide range of materials, sizes and shapes with single-particle resolution. In combination with dark-field optical imaging, nanoparticles can be selectively trapped and their spectroscopic response can be resolved in-situ. With its simple optics, versatile low-power operation, applicability to diverse nanoparticles, and tuneable working wavelength, OTENT will become a powerful tool in colloid science and nanotechnology.

“Hot” in Plasmonics: Temperature‐Related Concepts and Applications of Metal Nanostructures

“…It is important to note that by contrast to standard nanotweezing schemes, all examples in Figure use much lower laser powers (a few mW or less) to manipulate and assemble nanostructures. In this context, recently Lin et al showed that thermophoresis can also be used to sculpt structures into versatile shapes by selectively manipulating individual particles of different material compositions, sizes and shapes …”

Thermal Optofluidics: Principles and Applications

“…Moreover, the fiber‐based trapping scheme is readily integrated with other optical systems to extend the manipulation from 2D to 3D. Recently, thermophoresis‐induced optical manipulation and assembling techniques have been extensively studied by Zheng and co‐workers via particle surface modification and surface entropy tuning …”

“…Using a customized particle‐surface modification process, Lin et al recently developed optothermoelectric nanotweezers, which exploit the electrolyte Seebeck effect to manipulate metallic particles . A cationic surfactant, cetyltrimethylammonium chloride (CTAC), was used to modify the particle surfaces.…”

“…Under a temperature gradient, ion thermophoresis induces the displacement of negative Cl − ions and positive micellar ions; a thermoelectric field is thus formed in the direction of the hot side, which pushes the positively charged particles to the hot center and traps them there. Reproduced with permission . Copyright 2018, Springer Nature.…”

Digital Assembly of Colloidal Particles for Nanoscale Manufacturing

“…Finally, the use of high NA lens, high laser power, and complex optical setup in optical tweezers makes them difficult to use for large‐scale and widespread applications in digital manufacturing. To overcome these challenges, opto‐thermophoretic tweezers have been developed to trap and manipulate particles of a wider range of sizes, shapes, and compositions using low optical power . Opto‐thermophoretic tweezers provide an opportunity for nanoparticle assembly and printing, thus enhancing the field of nanoscale manufacturing.…”