Quo vadis, plasmonic optical tweezers?

Kenneth B Crozier

doi:10.1038/s41377-019-0146-x

Abstract

Conventional optical tweezers based on traditional optical microscopes are subject to the diffraction limit, making the precise trapping and manipulation of very small particles challenging. Plasmonic optical tweezers can surpass this constraint, but many potential applications would benefit from further enhanced performance and/or expanded functionalities. In this Perspective, we discuss trends in plasmonic tweezers and describe important opportunities presented by its interdisciplinary combination with other techniques in nanoscience. We furthermore highlight several open questions concerning fundamentals that are likely to be important for many potential applications.

Highlights

One half of the Nobel Prize in Physics for 2018 was awarded to Arthur Ashkin, “for the optical tweezers and their application to biological systems.” This was truly well-deserved, as optical tweezers (Fig. 1a) have been an important scientific tool in many fields[1], especially for precise force measurements in biophysics
In other examples of early work, plasmonic tweezers were demonstrated that consisted of pairs of gold particles on glass substrates[3] and gold nanopillars protruding from a gold film[4]
The substrate acted as a heat sink, thereby reducing the temperature rise resulting from ohmic losses associated with plasmon excitation. We argue that these and other early works have laid the groundwork for several exciting opportunities in nanoscience for plasmonic tweezers

Summary

Introduction

One half of the Nobel Prize in Physics for 2018 was awarded to Arthur Ashkin, “for the optical tweezers and their application to biological systems.” This was truly well-deserved, as optical tweezers (Fig. 1a) have been an important scientific tool in many fields[1], especially for precise force measurements in biophysics. A small particle near the focused beam of traditional optical tweezers (Fig. 1a) will experience scattering forces (radiation pressure and spin curl force) and the gradient force The latter is proportional to the gradient of the intensity and is the source of the trapping potential that draws the particle to the laser beam focus. In other examples of early work, plasmonic tweezers were demonstrated that consisted of pairs of gold particles on glass substrates[3] and gold nanopillars protruding from a gold film[4] For the latter, the substrate (silicon) acted as a heat sink, thereby reducing the temperature rise resulting from ohmic losses associated with plasmon excitation. Recent work has expanded the repertoire of Crozier Light: Science & Applications (2019)8:35 a Radiation pressure