Shear-induced laning transition in a confined colloidal film

Abstract

Using Brownian dynamics (BD) simulations we investigate a dense system of charged colloids exposed to shear flow in a confined (slit-pore) geometry. The equilibrium system at zero flow consists of three, well-pronounced layers with square-like crystalline in-plane structure. We demonstrate that, for sufficiently large shear rates, the middle layer separates into two sublayers where the particles organize into moving lanes with opposite velocities. The formation of this micro-laned state results in a destruction of the applied shear profile. It has a strong impact not only on the structure of the system, but also on its rheology as measured by the stress tensor. At higher shear rates we observe a disordered state and finally a recrystallization reminiscent of the behavior of bilayer films. We expect the shear-induced laning to be a generic feature of thin films with three or more layers.

Superadiabatic demixing in nonequilibrium colloids

“…Lane formation constitutes a genuine nonequilibrium self-organization process that has attracted much interest in the literature since it occurs in strikingly different areas, ranging from colloidal systems [13][14][15][16][17][18] , plasmas 19,20 , and lattice models 21 , to different kinds of living systems, such as bacteria in channels 22 , ant trails 23 , and groups of pedestrians 24 . Laning has also been studied when the external driving directions of the two species are non-parallel to each other 25 , have high shear rates 26 , or other characteristics such as rotating magnetic field in channels, and periodic driving with different friction coefficients [27][28][29] . Studies were devoted to the influence of noise and of hydrodynamic interactions 30,31 , as well as the characteristics of the transition toward laning in two-dimensional systems 32 .…”

“…We summarize by inserting the adiabatic-superadiabatic splitting, Eqs. (26) and (27), into the velocity equation of motion, Eq. (16), and into the differential current, Eq.…”

Dynamical modes of sheared confined microscale matter

“…Further, the material response to shear is intimately connected to the nonequilibrium dynamics of the constituent elements, that have been the subject of recent research with non-Brownian particles, 13,14 polymer-, 15 active bacteria-, 16 and colloidal suspensions in amorphous, [17][18][19] fluid-, 20,21 as well as crystalline states. [22][23][24][25] Colloidal suspensions under external fields have proven to be a powerful test bed system, that is used to study the role of channel geometry 9,17,26 hydrodynamic interactions, 24,27 frictional interparticle contact and lubrication, 28,29 as well as plastic events, [30][31][32] to cite a few. Key advantages of using colloidal particles are the possibilities to directly visualize the particle dynamics via video microscopy, and to tune the pair interactions using external fields.…”

Dynamical modes of sheared confined microscale matter

“…Placing such materials inside strong spatial confinement has severe impact on their response to external deformations, which is crucial for a multitude of applications such as thin-film lubrication [4][5][6][7], microfluidic devices [8,9] and colloidal machines at the microscale [10][11][12], to name a few. Further, the material response to shear is intimately connected to the non-equilibrium dynamics of the constituent elements, that have been the subject of recent research with non-Brownian particles [13,14], polymer- [15], active bacteria- [16], and colloidal suspensions in amorphous [17][18][19], fluid- [20,21], as well as crystalline states [22][23][24][25].…”