Dynamics of a Self-Propelled Particle in a Harmonic Trap

Abstract

The dynamics of an active walker in a harmonic potential is studied experimentally, numerically and theoretically. At odds with usual models of self-propelled particles, we identify two dynamical states for which the particle condensates at finite distance from the trap center. In the first state, also found in other systems, the particle points radially outward the trap, while diffusing along the azimuthal direction. In the second state, the particle performs circular orbits around the center of the trap. We show that self-alignment, taking the form of a torque coupling the particle orientation and velocity, is responsible for the emergence of this second dynamical state. The transition between the two states is controlled by the persistence of the particle orientation. At low inertia, the transition is continuous. For large inertia the transition is discontinuous and a coexistence regime with intermittent dynamics develops. The two states survive in the over-damped limit or when the particle is confined by a curved hard wall. arXiv:1810.13303v1 [cond-mat.soft]

Robust boundary flow in chiral active fluid

“…Hexbug body is supported by twelve flexible legs that all bends slightly backwards. When turned on, the vibration motor sets Hexbug into forward hopping motion on a solid (PMMA) substrate [46,47]. As shown in Fig.…”

Inertial effects of self-propelled particles: From active Brownian to active Langevin motion

“…Typically these are hoppers with a Janus-like body or with tilted legs. In order to achieve self-propulsion, these macroscopic bodies are either placed on a vibrating table or are equipped with an internal vibration motor ("hexbugs") 23 . It has been shown that the dynamics of these hoppers is well described by active Brownian motion with inertia [24][25][26] .…”

“…These motions are only virtually damped. Another important realization are granulates made self-propelling on a vibrating plate [13][14][15][16][17][18][19][20][21][22] or equipped with an internal vibration motor 23 where it has been shown that the active Langevin model indeed describes their dynamics well [24][25][26] . Further examples for self-propelled particles with inertia range from mini-robots 27,28 to macroscopic swimmers like beetles flying at water interfaces 29 and whirling fruits self-propelling in air 30 .…”

Generalised ‘Arcsine’ laws for run-and-tumble particle in one dimension

“…For example E. Coli bacteria runs for some time along a straight line and then tumbles to randomly choose a new direction of run [35]. In the last few years there has been a lot of interests in studying RTPs at the individual level as they show interesting phenomena like, accumulation near boundaries [36][37][38], clustering [39][40][41], passive to active transition [42,43], climbing against the hill [44], Kramer's escape problem [45] etc.…”