Near-wall hydrodynamic slip triggers swimming state transition of micro-organisms

Poddar, Antarip; Bandopadhyay, Aditya; Chakraborty, Suman

doi:10.1017/jfm.2020.243

Cited by 26 publications

(34 citation statements)

References 106 publications

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“…This is markedly different from the near-wall motion of other swimmers with a priori prescribed surface slip (e.g. spherical squirmers), for which the strongest slip might not be localized around the most efficient region, thus leading to increase or decrease of their swimming velocities due to confinement [60]. It is also consistent with experiments wherein active drops have been observed to perform quasi-two-dimensional motion near a wall, while being pinned to it by gravity [61].…”

Section: Discussionmentioning

confidence: 62%

Instability and self-propulsion of active droplets along a wall

Desai¹,

Michelin²

2021

Preprint

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Active droplets can swim spontaneously in viscous flows as a result of the non-linear convective transport of a chemical solute produced at their surface by the Marangoni and/or phoretic flows generated by this solute's inhomogeneous distribution, provided the ratio of convective-to-diffusive solute transport, or Péclet number Pe is large enough. As the result of their net buoyancy, active drops typically evolve at a small finite distance d from rigid boundaries. Yet, existing models systematically focus on unbounded flows, ignoring the effect of the wall proximity on the intrisicallynonlinear nature of their propulsion mechanism. In contrast, we obtain here a critical insight on the propulsion of active drops near walls by analysing their stability to non-axisymmetric perturbations and the resulting emergence of self-propulsion along the wall with no limiting assumption on the walldistance d. Dipolar or quadrupolar axisymmetric (levitating) base states are identified depending on d and Pe. Perhaps counter-intuitively, a reduction in the drop-wall separation d is observed to destabilize these modes and to promote self-propulsion, as a result from the confinement-induced localisation of the chemical gradients driving the motion. In addition, quadrupolar states are more unstable than their dipolar counterparts due to the redistribution of the chemical perturbation by the base flow, favouring the emergence of stronger slip forcing on the drop surface.

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Section: Discussionmentioning

confidence: 62%

Instability and self-propulsion of active droplets along a wall

Desai¹,

Michelin²

2021

Preprint

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“…The problem of steric collision has been circumvented by employing an electrostatic-type, short-ranged repulsive force at the plane wall (Spagnolie & Lauga 2012): The parameters have typical values 200, 100, respectively, so that the swimmer does not approach closer than 0.01 times the swimmer radius. Such a scenario was previously encountered by others in relation to ‘squirmers’ (Spagnolie & Lauga 2012; Li & Ardekani 2014; Poddar, Bandopadhyay & Chakraborty 2020), as well as self-diffusiophoretic microswimmers (Ibrahim & Liverpool 2016), and different forms of repulsive potentials were employed. It is noteworthy that the squirmer models only deal with the hydrodynamics of the microswimmer, and the wall-induced distortion of the scalar field (e.g.…”

Section: Resultsmentioning

confidence: 99%

Steering a thermally activated micromotor with a nearby isothermal wall

2021

Self Cite

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“…2016; Poddar et al. 2020, 2021), simulations were performed for a wide range of initial configurations, and the swimming trajectories were categorized based on their observed long-term behaviours. This procedure would take a significant computational time, amplified by the fine resolution of different parameters required to uncover any non-trivial motion characteristics.…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, the velocity components are given in an associated cylindrical coordinate system . In view of using those general solutions, we define a bispherical coordinate system and relate it to the cylindrical coordinates by (Happel & Brenner 1983) A corresponding diagrammatic depiction can be found in Poddar, Bandopadhyay & Chakraborty (2020). In this bispherical system, and denote the plane wall and the particle surface, respectively.…”

Section: Problem Formulationmentioning

confidence: 99%

Thermotactic navigation of an artificial microswimmer near a plane wall

Poddar

2023

J. Fluid Mech.

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Despite significant advances in the field of man-made micro- and nanomotors, it remains a challenge to precisely control their motion in bounded environments. Here, we present a theoretical analysis of a thermally activated micromotor near a plane wall under the action of a background linear temperature field. The coupling between the autonomous and field-directed motions has been resolved using a combined analytical–numerical framework comprising general solutions in bispherical coordinates and the reciprocal theorem for creeping flows. Results reveal giant augmentation in swimming speeds, the controlling parameter zones for positive and negative thermotaxes and the flexibility of steering perpendicular to the field gradient for an isolated micromotor. Boundary-instigated thermo-fluidic modulations at different levels of confinements and preferential orientations cause directional switching of both the vertical translation and rotation parallel to the wall, thereby drastically altering the phase portraits of the swimmer dynamics. Contrasting trajectory characteristics, e.g. escape, attraction, are partitioned by unstable separatrices in the phase portraits, while competitive repulsion (attraction) after attraction (repulsion) characteristics emerge for different relative field strengths $\mathcal {S}$ and gradient orientations $\theta _T$ . Below $\mathcal {S}=0.25$ , highly counter-intuitive trajectories result when the micromotor is initially launched from an overlapping escape zone. Moreover, external-field-assisted microswimming can uniquely tune the directionality of wall-parallel translation, broadening the scope of dynamic regulation of self-propulsion. Thus, providing insights into a precisely controlled fuel-free actuation of micromotors near a physical obstacle, the present study stands as a step toward addressing the increasing demand for successful implementation of micromotors in futuristic clinical and environmental applications.

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Near-wall hydrodynamic slip triggers swimming state transition of micro-organisms

Cited by 26 publications

References 106 publications

Instability and self-propulsion of active droplets along a wall

Instability and self-propulsion of active droplets along a wall

Steering a thermally activated micromotor with a nearby isothermal wall

Thermotactic navigation of an artificial microswimmer near a plane wall

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