Emergent collective colloidal currents generated via exchange dynamics in a broken dimer state

Abstract

Controlling the flow of matter down to micrometer-scale confinement is of central importance in materials and environmental sciences, with direct applications in nano-microfluidics, drug delivery and biothechnology. Currents of microparticles are usually generated with external field gradients of different nature [e.g., electric, magnetic, optical, thermal or chemical ones] which are difficult to control over spatially extended regions and samples. Here we demonstrate a general strategy to assemble and transport polarizable microparticles in fluid media through combination of confinement and magnetic dipolar interactions. We use a homogeneous magnetic modulation to assemble dispersed particles into rotating dimeric state and frustrated binary lattices, and generate collective edge currents which arise from a novel, field-1 arXiv:1911.01698v2 [cond-mat.soft]

Impact of dipole–dipole interactions on motility-induced phase separation

“…The usage of a three-dimensional dipole-dipole interaction, eqn (5), in our 2D system, can be considered as a minimal description of a monolayer of (spherical) colloidal particles sedimented in a plane and interacting via three-dimensional dipole-dipole interactions. Experimental examples of this situation could be paramagnetic colloids, 68,69 ferromagnetic rollers, 19,65 as well as metallodielectric Janus particles. 12,15,63 3.…”

Spontaneous Chiral Symmetry Breaking and Lane Formation in Ferromagnetic Ferrofluids

“…[7][8][9][10] Depending on the scale, chirality can enter the system either via molecular asymmetry, [2,11] chiral geometry, [10,[12][13][14] surface-induced symmetry breaking [15][16][17] or by rotation of particles driven by an external magnetic field. [5,[18][19][20][21] The intriguing diversity of chiral active matter manifests itself in the rich variety of newly discovered phenomena, most notably long-range synchronization and flocking, [22][23][24][25] active turbulence, [26] emergence of spontaneous flow and edge currents, [19,27,28] odd viscosity, which causes flow perpendicular to applied stress, [18,29,30] and the related odd elasticity. [31,32] Possibly the most extensively studied approach in the quest for understanding these intricate phenomena is the use of an alternating magnetic field as the external source of energy.…”