Detention Times of Microswimmers Close to Surfaces: Influence of Hydrodynamic Interactions and Noise

Abstract

After colliding with a surface, microswimmers reside there during the detention time. They accumulate and may form complex structures such as biofilms. We introduce a general framework to calculate the distribution of detention times using the method of first-passage times and study how rotational noise and hydrodynamic interactions influence the escape from a surface. We compare generic swimmer models to the simple active Brownian particle. While the respective detention times of source dipoles are smaller, the ones of pullers are larger by up to several orders of magnitude, and pushers show both trends. We apply our results to the more realistic squirmer model, for which we use lubrication theory, and validate them by simulations with multiparticle collision dynamics.

Microalgae Scatter off Solid Surfaces by Hydrodynamic and Contact Forces

“…Our observations, then, differ from theoretical estimates of microorganismal capture by curved obstacles, based either on hydrodynamic [23,28] or steric [26] interactions, where escape results purely from noise (although Ref. [28] discusses using a constant torque to mimic flagellar activity). The scattering discussed so far proceeds according to a largely predictable dynamics and could be described as deterministic.…”

“…The outcome of such intrinsically complex dynamics is simple: θ out is uniformly distributed across the available range of values, independently of θ in [ Fig. 4(a)], a behavior in sharp contrast to that of minimal models of puller microorganisms [23,28]. At the same time, the probability P rs of performing random rather than deterministic scattering depends strongly on θ in .…”

“…The experiments reveal that the scattering is not simply steric, as previously suggested [5], but follows qualitatively different rules depending on the angle of incidence, with direct evidence of purely hydrodynamic interaction at large angles, and a multistage steric or hydrodynamic process at small angles. The latter is terminated by direct flagellar contact with the surface preventing the extended trapping around the convex structure predicted by minimal models [23,26,28] avoid long-term trapping independently of obstacle size and shape might in fact represent a significant advantage for a soil alga such as Chlamydomonas, which in nature needs to navigate a heterogeneous porous material. Together with these deterministic interactions, we report the existence of random scatterings, and propose a mechanism to explain their likelihood.…”

Hotspots of boundary accumulation: dynamics and statistics of micro-swimmers in flowing films

“…Pullers are bound more strongly, because their equilibrium orientation is perpendicular to the surface (blue peaks at +p=2). Indeed, Schaar et al [71] have shown that the detention times of pullers in the absence of external flow can be several orders of magnitudes larger than those of pusher or source doublet swimmers.…”

Species-dependent hydrodynamics of flagellum-tethered bacteria in early biofilm development

“…In the spirit of previous hydrodynamic models of microorganisms that successfully elucidate physical mechanisms behind a variety of complex behaviours [17][18][19], we develop a hydrodynamic model for spinning motility where part of the flagellum is attached to the surface. General models of free swimmers near a surface have shown how hydrodynamic interactions can trap swimmers at surfaces [9,20,21] and cause other changes in behaviour including circular swimming [22][23][24][25], suppressed tumbling [26] and self-organization [27]. Our model shows a wide range of behaviours which vary with the degree of constraint on the flagellum, the torque exerted by the flagellar motor and the flexibility of the flagellar hook.…”