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

Abstract

In this work we show that two absorbing microbeads can briefly share the same optical trap while creating microscopic explosions. Optical forces pull the particles towards the waist of the trapping beam, 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. Hence effectively coupling all the trajectories to each cavitation event. We find that when two microbeads reach the waist simultaneously within a distance of 2.9 µm from the beam center in the transverse plane, a larger explosion might result in ejection from the trap. The measured maximum radial displacements ∆ρc due to cavitation are ∆ρc = 3.9 ± 2.2 µm when the particles reach simultaneously with maximum bubble sizes Rmax = 6.2 ± 3.1 µm, while for individual cases when one of the particles is outside 2.9 µm prior to cavitation ∆ρc is 2.7 ± 1.2 µm and Rmax = 4.2 ± 1.6 µm. We also measure the characteristic timescale of two particle coalescence which is a measure of the expected time that the particles can stay trapped near the waist. The measurements are fitted by a Poisson decaying exponential probability distribution.A simple one dimensional model shows that the characteristic timescales for transient trapping of multiple absorbing particles decrease as more objects are added.

Microparticle transport networks with holographic optical tweezers and cavitation bubbles

“…The particles that travel in the array of traps interact with each other via the vapor explosions, resulting in particles chasing each other (Video 7). However, if the particles converge in a trap it is likely that at least one es ejected due to larger vapor explosions [25]. We observe a much larger enhancement, compared with the case of a single particle (light blue symbols) in the network, specially in the case of the square lattice when n ≤ 16.…”

“…The particles that travel in the array of traps interact with each other via the vapor explosions, resulting in particles chasing each other (Video 7). However, if the particles converge in a trap it is likely that at least one es ejected due to larger vapor explosions [25]. (L 2 = 6.3 µm) and the large circle (R 2 = 13.2 µm).…”

Optical Manipulation of Fibroblasts with Femtosecond Pulse and CW Laser

“…In addition, the shrinkage of the bubbles caused the particles to be pushed away from their original positions with extremely fast speed, as shown in Figure 6e,f. The direction and velocity of the push caused by bubbles was related to the size and position of the bubble, and the directed manipulation of the target object was expected by studying the bubble dynamics [42]. The white virtual coils indicate the particles at the laser focus.…”

“…and velocity of the push caused by bubbles was related to the size and position of the bubble, and the directed manipulation of the target object was expected by studying the bubble dynamics [42]. The white virtual coils indicate the particles at the laser focus.…”

Juggling with Light

“…Unable to further pursue this research with the technology of his time, Ashkin urged researchers to resolve the puzzle of the colliding droplets with high-speed photography. Recently, there has been renewed interest in this attempt [7][8][9]. Notably, Moore et al [8] have observed oscillations of two silica particles for up to a few minutes.…”