Emergence of collective dynamical chirality for achiral active particles

Abstract

Emergence of collective dynamical chirality (CDC) at mesoscopic scales plays a key role in many formation processes of chiral structures in nature, which may also provide possible routines for people to fabricate complex chiral architectures. So far, most of reported CDCs are found in systems of active objects with individual structure chirality or/and dynamical chirality, and whether CDC can arise from simple and achiral units is still an attractive mystery. Here, we report a spontaneous formation of CDC in a system of both dynamically and structurally achiral particles motivated by active motion of cells adhered on a substrate. Active moving, confinement and hydrodynamic interaction are found to be the three key factors. Detailed analysis shows that the system can support abundant collective dynamical behaviors, including rotating droplet, rotating bubble, CDC oscillation, array of collective rotation, as well as interesting transitions such as chirality transition, structure transition and state reentrance.

Active colloids with collective mobility status and research opportunities

“…motion, spatial confinement, and hydrodynamic interaction. 124 A different conclusion arose when Bartolo and coworkers 82 considered vortices of motile particles with velocity-aligning interactions (Fig. 8B).…”

“…Hou and coworkers constructed a continuum theory to describe vortical motion of motile populations constrained by geometrical boundaries. 124 They concluded that collective dynamic chirality arises spontaneously in systems of both dynamically and structurally achiral particles, controlled physically by the active force and the resistance time over which particles maintain their motion. Intriguingly, chirality oscillation was found to be possible (Fig.…”

Nonequilibrium Dynamics of Chemically Active Particles

“…We considered ABPs moving in a two‐dimensional rectangular space with long‐range HI. [ 67 ] In simulations, we used the stochastic lattice Boltzmann method to address the long‐ range HI, [ 68 ] and rewrote the orientation equation as . [ 69‐71 ] Herein, denotes the angle of the total force vector, the resistance time τ measures the ability of ABPs resisting the external steering.…”

“…(Figure adapted with permissions from Ref. 67 and 73. Copyright 2017 and 2019 The Royal Society of Chemist.…”

Helical Flow States in Active Nematics

“…Activity can also induce self-organized flow states [13]. In confining channels, an extensile active stress induced instability to bend perturbations leads to selfsustained spontaneous flows [14][15][16][17][18] and spontaneous circulations [19][20][21][22][23][24][25][26][27] when the characteristic activity length scale act is comparable to the confinement size L. Vortex lattices arise when the characteristic length scale matches the confinement, which can be due to an array of obstacles or cavities [28][29][30][31][32][33][34], bound to spherical surfaces [35], or channel confinement [36][37][38][39]. Local circulations arise because act represents the characteristic vorticity length scale [40], associated with a peak in the enstrophy distribution [41][42][43][44], and a lattice of vortices represents stressfree solutions that lie at the interface of the stable and unstable modes in minimal continuum models of active fluids [45].…”