Perspective on light-induced transport of particles: from optical forces to phoretic motion

Abstract

Propulsive effects of light, which often remain unnoticed in our daily-life experience, manifest themselves on spatial scales ranging from subatomic to astronomical. Light-mediated forces can indeed confine individual atoms, cooling their effective temperature very close to absolute zero, as well as contribute to cosmological phenomena such as the formation of stellar planetary systems. In this review, we focus on the transport processes that light can initiate on small spatial scales. In particular, we discuss in depth various light-induced mechanisms for the controlled transport of microscopic particles; these mechanisms rely on the direct transfer of momentum between the particles and the incident light waves, on the combination of optical forces with external forces of other nature, and on light-triggered phoretic motion. After a concise theoretical overview of the physical origins of optical forces, we describe how these forces can be harnessed to guide particles either in continuous bulk media or in the proximity of a constraining interface under various configurations of the illuminating light beams (radiative, evanescent, or plasmonics fields). Subsequently, we introduce particle transport techniques that complement optical forces with counteracting forces of non-optical nature. We finally discuss particle actuation schemes where light acts as a fine knob to trigger and/or modulate phoretic motion in spatial gradients of non-optical (e.g., electric, chemical, or temperature) fields. We conclude by outlining possible future fundamental and applied directions for research in light-induced particle transport. We believe that this comprehensive review can inspire diverse, interdisciplinary scientific communities to devise novel, unorthodox ways of assembling and manipulating materials with light.

Coherent oscillations of a levitated birefringent microsphere in vacuum driven by nonconservative rotation-translation coupling

“…Among the numerous artificial analogs, colloidal heat engines are, perhaps, the simplest (1). Directed motion is extracted either by imposing temperature gradients or isothermally, through a ratcheting mechanism (1,4). In the latter case, time-varying potentials can give the required effect (5).…”

Microscale Marangoni Surfers

“…In self-phoresis, a particle propels with a velocity that is proportional to a selfgenerated gradient via a phoretic mobility coefficient [10]. Self-thermophoresis, whereby motion is induced by the asymmetric heating of light-absorbing Janus particles [11], is particularly interesting due to the unique properties of light as a source of self-propulsion [12]. Here, the propulsion velocity is V ¼ −D T ∇T, where both the thermophoretic mobility D T [13] and the self-generated thermal gradient are independent of particle size [14].…”

Noise Sensitivities for an Atom Shuttled by a Moving Optical Lattice via Shortcuts to Adiabaticity

“…The standing wave phase can be changed in time, moving the interference pattern, in different ways, e.g., [ 9 , 52 ]: One of the laser beams can be moved by mechanically moving a mirror [ 7 ]; the phase of one of the laser beams can be controlled with an electro-optical modulator; or a frequency mismatch between the counterpropagating beams controlled by acousto-optical modulators produces a phase . Of course all these methods are amenable to an imperfect control and fluctuations.…”