Sound-mediated stable configurations for polystyrene particles

Abstract

Here we report an experimental observation of the self-organization effect of polystyrene particles formed by acoustically induced interaction forces. Two types of stable configurations are observed experimentally: one is mechanically equilibrium and featured by nonzero interparticle separations, and the other corresponds to a closely packed assembly, which is created by strong attractions among the aggregated particles. For the former case involving two or three particles, the most probable interparticle separations (counted for numerous independent initial arrangements) agree well with the theoretical predictions. For the latter case, the number of the final stable configurations grows with the particle number, and the occurrence probability of each configuration is interpreted by a simple geometric model.

Cluster formation by acoustic forces and active fluctuations in levitated granular matter

“…2a. The corresponding cluster statistics retain memory of the formation process [12]: the ground-state configuration is determined by the spatial angle of approach that the sixth particle takes towards the 5-particle cluster (see Supplementary Movie 3). Assuming that docking onto the 5-cluster is equally likely for any angle of approach (see Fig.…”

“…While depletion interactions drive clustering and assembly in colloids [7][8][9][10], no equivalent short-range attractions exist between macroscopic grains. To overcome this limitation, we introduce an experimental approach based on acoustic levitation and trapping of granular matter [2,12,13]. Scattered sound establishes short-range attractions between small particles [14], while detuning the acoustic trap generates active fluctuations [15].…”

Acoustic micro‐beam vortex generator for flow actuation inside droplets

“…However, in this case, as the floating aggregate is already showing a self‐assembling structure, the cause might be attributed to the high frequency used here. As the wavelength $$\lambda \approx 3{d}_{{\rm{p}}}$$, the interparticle force due to secondary scattering can become dominant 57–59 . Thus, the increase of the concentration of particles due to the formation of the toroidal particle structure can play a major role in reducing the distance between particles, thus leading to the self‐assembling process.…”

“…As the wavelength λ d ≈ 3 p , the interparticle force due to secondary scattering can become dominant. [57][58][59] Thus, the increase of the concentration of particles due to the formation of the toroidal particle structure can play a major role in reducing the distance between particles, thus leading to the self-assembling process. As particles formed a larger apparent particle, the process can continue attracting more particles that approach the aggregate, as can be observed during the process.…”

Three-dimensional trapping and assembly of small particles with synchronized spherical acoustical vortices

“…Such vortices can indeed be synthesized with miniaturized, flat holographic transducers [15,24]. In such studies, the secondary radiation forces [50][51][52] should be considered since it could strongly affect the particle dynamics (while this effect is less important for small-sized particles [51]).…”