arXiv subjects

Viridiana Carmona-Sosa

Publications and source records attributed to Viridiana Carmona-Sosa.

2 recordsLinked to original sources

arXiv2016

Transient trapping of two microparticles interacting with optical tweezers and cavitation bubbles

In this work we show that two absorbing microbeads can briefly share the same optical trap. Optical forces pull the particles towards the waist of the trapping beam. However, once a particle reaches the vicinity of the waist, the surrounding liquid is superheated creating an explosion or cavitation bubble that pushes the particle away while lengthening or shortening the trajectories of the surrounding particles. In this way each particle briefly interacts with the beam waist at different times. We find that when two microbeads reach the waist simultaneously, a larger explosion might result in ejection from the trap. We measure the characteristic timescale of two particle coalescence near the waist and find a Poisson decaying exponential probability distribution. The results are consistent with a simple simulation and show why the characteristic timescales for transient trapping of multiple absorbing particles decrease as more objects are added.

physics.optics↗

arXiv2016

Characterization of periodic cavitation in an optical tweezer

Microscopic vapor explosions or cavitation bubbles can be generated periodically in an optical tweezer with a microparticle that partially absorbs at the trapping laser wavelength. In this work we measure the size distribution and the production rate of cavitation bubbles for microparticles with a diameter of 3 $μ$m using high speed video recording and a fast photodiode. We find that there is a lower bound for the maximum bubble radius $R_{max}\sim 2~μ$m which can be explained in terms of the microparticle size. More than $94 \%$ of the measured $R_{max}$ are in the range between 2 and 6 $μ$m, while the same percentage of the measured individual frequencies $f_i$ or production rates are between 10 and 200 Hz. The photodiode signal yields an upper bound for the lifetime of the bubbles, which is at most twice the value predicted by the Rayleigh equation. We also report empirical relations between $R_{max}$, $f_i$ and the bubble lifetimes.

physics.flu-dyn↗