Fluidic vortices generated from optical vortices in a microdroplet cavity

TL;DR

This paper demonstrates how optical vortices in a microdroplet cavity can generate and control micro-flows within the droplet, revealing circular flow patterns that depend on optical power and symmetry.

Contribution

It introduces an experimental method to generate and map optically induced micro-flows in microdroplets using fluorescent nanoparticles, highlighting the control via optical power and symmetry breaking.

Findings

Flow speed increases with optical power

Flow patterns are circular unless symmetry is broken

Optical control can direct analytes within microcavities

Abstract

We harness the momentum of light resonating inside a micro-droplet cavity, to experimentally generate micro-flows within the envelope of the drop. We 3D map these optically induced flows by using fluorescent nanoparticles; which reveals circular micro-streams. The flows are parametrically studied and, as expected, exhibit an increase of rotation speed with optical power. The flow is non-circular only when we intentionally break the axial symmetry of the droplet. Besides the fundamental interest in light-flow interactions including in opto-fluidic cavities, the optically controlled flows can serve in bringing analytes into the maximum-power region of the microcavity.