Electromagnetic Forces and Torques: From Dielectrophoresis to Optical Tweezers

Abstract

Electromagnetic forces and torques enable many key technologies, including optical tweezers or dielectrophoresis. Interestingly, both techniques rely on the same physical process: the interaction of an oscillating electric field with a particle of matter. This work provides a unified framework to understand this interaction both when considering fields oscillating at low frequencies�dielectrophoresis�and high frequencies�optical tweezers. We draw useful parallels between these two techniques, discuss the different and often unstated assumptions they are based upon, and illustrate key applications in the fields of physical and analytical chemistry, biosensing, and colloidal science.

Rotational Doppler Effect: A Review

“…This would be of particular interest in the rotation control of spherical micro particles and cells. [95,96] Actually such experiments have been already performed on micro-elements that are rotating within a trap, [97,98] or on the axis of a rotating fluid [57] using an OAM beam as a probe beam. The rotational Doppler effect would enable to probe the rotational diffusion of spherical colloidal particles.…”

Plasmonic Dipole and Quadrupole Scattering Modes Determine Optical Trapping, Optical Binding, and Swarming of Gold Nanoparticles

“…Since Ashkin and co-workers demonstrated the optical trapping of dielectric particles in 1986, this concept has become a widespread tool for manipulating micro- and nanoscale objects with high spatiotemporal resolution, endowed by the unique properties of light. − This technique has spurred numerous advancements across diverse fields, including fundamental research, material science, and biological studies. − Recently, the optical trapping of metallic nanoparticles (NPs) has garnered attention, particularly for their surface plasmon resonance (SPR) properties. , The collective oscillation of free electrons on the metal surface significantly amplifies the polarizability of metallic NPs, resulting in intensified induced optical forces. Consequently, the optical manipulation of metallic materials opens avenues for their application in various research fields, leveraging their inherent SPR-enhanced electric field and subsequent enhancement of their Raman and emissive properties. − …”

Colossal Optical Anisotropy from Atomic‐Scale Modulations

“…Birefringence is the dependence of the refractive index on the polarization of light travelling through a material and is of paramount importance for applications from classical to quantum optics. [1][2][3][4][5][6][7][8][9][10][11] The observation of birefringence in calcite as early as 1669 [12] -called Iceland spar at the time-eventually led to Fresnel's insight in 1821 that light is a transverse wave. [13,14] Calcite's record as the most birefringent material stood for over a century, with Δn = |n e − n o | = 0.17 in the visible, as analyzed and explained by Bragg; [15] here, n e and n o are respectively the extraordinary and ordinary refractive index.…”