Hydrodynamic interactions hinder transport of flow-driven colloidal particles

Abstract

The flow-driven transport of interacting micron-sized particles occurs in many soft matter systems spanning from the translocation of proteins to moving emulsions in microfluidic devices. Here we combine experiments and...

Overcrowding induces fast colloidal solitons in a slowly rotating potential landscape

“…For low ω , it moves at a constant tangential speed ω R . By increasing ω , the mean speed decreases because the particle looses its synchronized phase with the moving potential due to the viscous drag 47 .…”

Overcrowding induces fast colloidal solitons in a slowly rotating potential landscape

“…In the experiments, the particles perform a Brownian motion in the time-dependent optical potential generated by the rotating laser beam. As previously shown 43 , these dynamics can be described by that of hard-spheres with diameter σ, where the center of mass position r i of each particle i moves according to the Langevin equation…”

“…Here U opt (r, t) is the time-dependent optical potential, µ = D/k B T is the particle mobility, and ζ i (t) are Gaussian white noise processes with ⟨ζ i (t)⟩ = 0 and ⟨ζ iα (t)ζ jβ (t ′ )⟩ = 2Dδ ij δ αβ δ(t − t ′ ). Because of the particle confinement in the radial direction is very strong and the radius of curvature is much greater than the mean distance between the colloidal particles, the motion can be restricted to a one-dimensional one along in a traveling-wave potential U (x, t) = (U 0 /2) cos(2πx/λ + M ωt) with x = Rϕ, where ϕ is the azimuthal angle 43,47,48 . Note that ω is the angular velocity of the rotation of the optical traps, which implies that the traveling wave has the frequency M ω for M traps.…”

“…The beam is characterized by a wavelength 1064 µm and power P = 3 W. The AODs have input frequency in the range [60, 90] MHz and it is produced via a two-channel radio frequency wave generator (DDSPA2X-D431b-34) which is addressed by a digital output card (National Instruments cDAQ NI-9403) with a refresh frequency of 150 kHz. More technical details on the experimental system can be found in a previous work 43 , which investigates the dynamics of a number of particles in the low filling regime, N < M . Numerical simulations.…”

“…For low ω, it moves at a constant tangential speed ωR. By increasing ω, the mean speed decreases because the particle looses its synchronized phase with the moving potential due to the viscous drag 43 . This situation changes when increasing N due to particle interactions such that, for N approaching M , the synchronization is restored due to jamming favored by hydrodynamic interactions 44 .…”