Orientational order and morphology of clusters of self-assembled Janus swimmers

Abstract

Due to the combined effect of anisotropic interactions and activity, Janus swimmers are capable to self-assemble in a wide variety of structures, many more than their equilibrium counterpart. This might lead to the development of novel active materials capable of performing tasks without any central control. Their potential application in designing such materials endows trying to understand the fundamental mechanism in which these swimmers self-assemble. In the present work, we study a quasi-two dimensional semi-dilute suspensions of two classes of amphiphilic spherical swimmers whose direction of motion can be tuned: either swimmers propelling in the direction of the hydrophobic patch (WP), or swimmers propelling in the opposite direction (towards the hydrophilic side) (AP). In both systems we have systematically tuned swimmers' hydrophobic strength and signature, and observed that the anisotropic interactions, characterized by the angular attractive potential and its interaction range, in competition with the active stress, pointing towards or against the attractive patch gives rise to a rich aggregation phenomenology. arXiv:1905.08541v1 [cond-mat.soft]

Induced correlations and rupture of molecular chaos by anisotropic dissipative Janus hard disks

“…After such a transient period, an anisotropy vector s i , whose direction is distributed uniformly in the interval [0, 2π[, is assigned to each disk. Once this has been done, the disks start to collide following the collision rules (10). Of course, the coefficients of restitution α BB , α W W , α BW and α W B , where the subindices state the sides at contact during the collision, may be freely chosen.…”

“…It is interesting to point out that, with the proper adjustment of the parameters, a system of Janus particles embodies analogies with the so-called 'microswimmers', which are the prototype systems of active matter [9,10]. These swimmers, which constitute presently a 'hot' and highly attractive research topic within statistical physics, are capable of self-propelling without any external energy input.…”

Minimal numerical ingredients describe chemical microswimmers’ 3-D motion

“…the Lattice Boltzmann (LB) method. 32,[37][38][39][40][41][42][43][44][45][46] Nevertheless, we note particularly relevant studies where LB approaches were utilised to study the behaviour of raspberry-type and other shape anisotropic microswimmers. 47,48 Like MPCD, dissipative particle dynamics (DPD) 49 coarse-grains the solvent as point-like fluid particles ( packets of fluid molecules), and thus inherently includes the effects of thermal noise while solving the Navier-Stokes equations.…”