Trapping and manipulation of microparticles using laser-induced convection currents and photophoresis

Abstract

Abstract:In this work we demonstrate optical trapping and manipulation of microparticles suspended in water due to laser-induced convection currents. Convection currents are generated due to laser light absorption in an hydrogenated amorphous silicon (a:Si-H) thin film. The particles are dragged towards the beam's center by the convection currents (Stokes drag force) allowing trapping with powers as low as 0.8 mW. However, for powers >3 mW trapped particles form a ring around the beam due to two competing forces: Stokes drag and thermo-photophoretic forces. Additionally, we show that dynamic beam shaping can be used to trap and manipulate multiple particles by photophotophoresis without the need of lithographically created resistive heaters.

Controllable generation and manipulation of micro-bubbles in water with absorptive colloid particles by CW laser radiation

“…In our situation, the whole depth of the liquid is heated, and their influence is not so strong as in the system of E. Flores-Flores et al [34]. However, the heating is not perfectly symmetric, and horizontal convection is distinctly seen in Visualization 1 and Visualization 2.…”

“…It should be noted that as in any case of inhomogeneous heating of a liquid-filled cell, the convection currents appear that also can contribute to the bubbles accumulation and ordering [34]. In our situation, the whole depth of the liquid is heated, and their influence is not so strong as in the system of E. Flores-Flores et al [34].…”

Theory and Practice of Computational Modeling and Simulation of Optical Tweezers

“…Heating introduces a wide range of effects, from changes in the viscosity of the surrounding fluid due to increased temperature, convection currents, and effects such as thermophoresis (Flores-Flores et al, 2015). If there are liquid-liquid or liquid-gas interfaces present, the dependence of surface tension on temperature can produce strong flows due to Marangoni convection (Miniewicz et al, 2016).…”

Spin and momentum of the light fields in inhomogeneous dispersive media with application to surface plasmon-polariton waves

“…Such fields are necessary elements of various modern applications aimed at optical trapping, sorting, delivering, selective treatment, positioning and some other precise manipulations with extremely small quantities of matter [4][5][6][7]. In these areas, the dynamical characteristics of optical fields, first of all the spatial distribution of their energy, as well as their momentum and angular momentum (AM), play a crucial role.…”