Self-sustaining charging of identical colliding particles

Siu, Theo; Cotton, Jake; Mattson, Gregory; Shinbrot, Troy

doi:10.1103/physreve.89.052208

Cited by 30 publications

(25 citation statements)

References 12 publications

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“…20 for more details about the apparatus. Note that the absence of an external electric field will also ensure that induction-based charging mechanisms 10,27,28 are not likely to be significant (see Supplementary Information). Particles in the raw videos were identified and tracked with the algorithm developed by Crocker and Grier 29 .…”

Section: Methodsmentioning

confidence: 99%

Direct observation of particle interactions and clustering in charged granular streams

et al. 2015

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Clustering of fine particles is of crucial importance in settings ranging from the early stages of planet formation [1][2][3] to the coagulation of industrial powders and airborne pollutants [4][5][6][7] . Models of such clustering typically focus on inelastic deformation and cohesion 1,4,6,8 . However, even in charge-neutral particle systems comprising grains of the same dielectric material, tribocharging can generate large amounts of net positive or negative charge on individual particles, resulting in long-range electrostatic forces [9][10][11] . The e ects of such forces on cluster formation are not well understood and have so far not been studied in situ. Here we report the first observations of individual collide-and-capture events between charged submillimetre particles, including Kepler-like orbits. Charged particles can become trapped in their mutual electrostatic energy well and aggregate via multiple bounces. This enables the initiation of clustering at relative velocities much larger than the upper limit for sticking after a head-on collision, a long-standing issue known from pre-planetary dust aggregation 1,12 . Moreover, Coulomb interactions together with dielectric polarization are found to stabilize characteristic molecule-like configurations, providing new insights for the modelling of clustering dynamics in a wide range of microscopic dielectric systems, such as charged polarizable ions, biomolecules and colloids [13][14][15][16] . One of the key difficulties in studying the interplay between repulsive contact forces, short-range cohesion and long-range electrostatic forces during cluster formation has been to obtain sufficiently detailed experimental data. Seeing how this process unfolds demands in situ observation of the collision trajectories among charged grains to extract quantitative information about their interactions. This requires the grains to be freed from gravity and tracked with high spatial and temporal resolution to capture individual collision events 17,18 . We overcome these obstacles with the set-up shown in Fig. 1a (refs 19,20). The granular material, in our experiments fused zirconium dioxide-silicate grains a few hundred micrometres in diameter, is contained in a vessel mounted inside a 3.0-m-tall cylindrical chamber. We evacuate this chamber to mitigate air drag. When a shutter covering a small orifice at the bottom of the vessel is opened, particles fall out freely, forming a dilute stream. Outside the chamber, a high-speed video camera falls alongside the grains, guided by low-friction rails. In the co-moving frame seen by the camera, the effect of gravity is eliminated, making it possible to track particle interactions in detail for about 0.2 s until the camera is decelerated by a foam pad. The same apparatus also allows determination of the net charge on individual grains: during free fall a horizontal electric field can be applied and the resulting horizontal acceleration observed by the camera gives the charge to mass ratio, q/m.Using particles with a narrow size d...

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Section: Methodsmentioning

confidence: 99%

Direct observation of particle interactions and clustering in charged granular streams

et al. 2015

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“…[2]). This differs from earlier simulations 7,8,9,10 of collisional grains in which contact times are short, and so for completeness we follow this first simulation with additional simulations in which we investigate the effect of varying .…”

Section: High Neutralization Resultsmentioning

confidence: 83%

“…Modeling approaches have been presented previously 7,8,9,10 ; in the present work, each particle has the same radius, R, and is fixed in a close-packed hexagonal lattice as depicted in Fig. 2(a).…”

Section: (D)mentioning

confidence: 99%

“…In previous work 7,8,9,10 , it was demonstrated that the mechanism of repetitive polarization and neutralization defined by Eq's [1] and [2] leads to exponential growth in charging. This occurs because the electric field defined by Eq.…”

Section: (D)mentioning

confidence: 99%

“…In these panels, we reproduce voltage and charge plots showing that the quantitative charging behaviors in the three experiments appear to behave similarly. In this paper, we analyze this problem and show that this charging behavior is reproduced using a recently described first-principles model 7,8,9,10 . We show fits of this model to the three experiments in each panel of Fig.…”

Section: Introductionmentioning

confidence: 99%

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