Diffusion of self-propelled particles in complex media

Abstract

The diffusion of active microscopic organisms in complex environments plays an important role in a wide range of biological phenomena from cell colony growth to single organism transport. Here, we investigate theoretically and computationally the diffusion of a self-propelled particle (the organism) embedded in a complex medium composed of a collection of nonmotile solid particles that mimic soil or other cells. Under such conditions we find that the rotational relaxation time of the swimming direction depends on the swimming velocity and is drastically reduced compared to a pure Newtonian fluid. This leads to a dramatic increase (of several orders of magnitude) in the effective rotational diffusion coefficient of the self-propelled particles, which can lead to "self-trapping" of the active particles in such complex media. An analytical model is put forward that quantitatively captures the computational results. Our work sheds light on the role that the environment plays in the behavior of active systems and can be generalized in a straightforward fashion to understand other synthetic and biological active systems in heterogenous environments.

Behavioral response of insecticide-resistant mosquitoes against spatial repellent: A modified self-propelled particle model simulation

“…Mosquito flight behavior was simulated using the constrained SPP model [70,73,74]. We chose this approach based on the prior success of SPP in modeling insect social behaviors [69][70][71][72][73][74][75]. We modified the SPP model by adding attractant and repellent to influence the mosquito flight path.…”

“…To model mosquito reactions to spatial repellents, however, other parameters must be considered in the presence of repellents, because it is not clear how insecticide-resistant mosquitoes respond to these repellents. These additional parameters may be incorporated by modifying existing models, since SPP models allow for particle assemblies to be temporally and spatially reversible in complex media, e.g., media that includes barriers resembling a bed net or repellent situation faced by mosquitoes [69][70][71][72][73][74][75][76].…”

Non-Newtonian effects on the slip and mobility of a self-propelling active particle

“…Table 1 summarizes the theoretical studies which analysed self-propulsion in various regimes. The experimental and theoretical analysis of Gomez-Solano et al (2016) and Aragones, Yazdi & Alexander-Katz (2018) demonstrated that the translational swimming of a Janus particle is coupled to the rotational motion in a viscoelastic medium. Recently, Saad & Natale (2019) studied the effect of polymer entanglements on active motion and showed that the particle can escape the entangled confinements at time scales significantly shorter than the polymer relaxation time.…”

Active particles in geometrically confined viscoelastic fluids

“…Besides, an active particle (AP) in a viscoelastic fluid represents an example of a random walker in a nonequilibrium thermal bath, being of fundamental relevance for non-equilibrium statistical physics [21]. Despite holding such immense potential, theoretical studies involving the dynamics of self-propelled particles in complex fluids are rather scarce [22][23][24][25][26][27][28][29][30][31]. Experiments dealing with artificial microswimmers in viscoelastic fluids, demonstrate remarkable differences compared to entirely viscous environments [32,33].…”