Optomechanically and Themo-optically driven Interactions between Gilded Vaterite Nanoparticles in Bubbles

TL;DR

This paper demonstrates long-range interactions between gilded vaterite nanoparticles in bubbles mediated by thermo-optical forces, enabling control over particle dynamics at millimeter scales using laser-induced bubble formation and refractive effects.

Contribution

It introduces a novel method of mediating long-range nanoparticle interactions through bubble-induced thermo-optical effects, surpassing previous limitations of short-range forces.

Findings

Long-lasting micron-scale bubbles can be formed around nanoparticles using femtosecond laser illumination.

Bubbles act as negative lenses, collimating laser beams over millimeter distances.

Secondary bubble formation and manipulation are achieved via optical radiation pressure and thermocapillary effects.

Abstract

The capability to tailor mutual interactions between colloidal nanoparticles strongly depends on the length scales involved. While electrostatic and optomechanically driven interactions can cover nano and micron-scale landscapes, controlling inter-particle dynamics at larger distances remains a challenge. Small physical and electromagnetic cross-sections of nanoparticles make long-range interactions, screened by a fluid environment, inefficient. To bypass the limitations, we demonstrate that forming micron-scale bubbles around gilded vaterite nanoparticles enables mediating long-range interactions via thermo-optical forces. Femtosecond laser illumination leads to the encapsulation of light-absorbing particles inside long-lasting micron-scale bubbles, which in turn behave as negative lenses refracting incident light. Our experiments reveal the bubble-induced collimation of laser beams, traversing over mm-scale distances. The collimated beams are visualized with the aid of phase-contrast Schlieren imaging, which reveals refractive index variations, caused by temperature gradients within the fluid. We demonstrate that the refracted beams initiate the formation of secondary bubbles around nearby gilded vaterite particles. As the consequence, we demonstrate the ability to control secondary bubble motion by pushing and pulling it with optical radiation pressure force and by thermocapillary Marangoni effect, respectively. The latter facilitates interactions over millimeter-scale distances, which are otherwise unachievable. Apart from exploring new physical effects, mediating long-range interactions can find a use in a range of applications including drug design and screening, photochemistry, design of colloidal suspensions, and many others.