Optomechanically and Thermo-Optically Driven Interactions Between Gilded Vaterite Particles in Bubbles

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 challenging. Small physical and electromagnetic cross-sections of nanoparticles make long-range interactions, screened by a fluid environment, inefficient. To bypass the limitations, we demonstrated that forming micron-scale bubbles around gilded vaterite particles enables mediating long-range interactions via thermo-optical forces. Femtosecond laser illumination is used to induce the encapsulation of light-absorbing particles within long-lasting micron-scale bubbles. Distinct regimes of bubble growth are observed, facilitated by optical tweezers and fluid flow. In the femtosecond regime, long-lasting bubbles, stable for minutes or longer, are generated and remain intact even after the laser is turned off. Conversely, in the continuous-wave (CW) regime, the bubbles collapse immediately upon deactivation of the light source. Experiments show bubble-induced laser collimation over millimeter-scale distances owing to a negative lens action of the primary bubble. The refracted beams initiate the formation of secondary bubbles around nearby gilded vaterite particles. Consequently, the ability to control secondary bubble motion is demonstrated by pushing and pulling it with optical radiation pressure force and by thermocapillary (Marangoni) effect, respectively.