Focusing and splitting streams of soft particles in microflows via viscosity gradients

Laumann, Matthias; Zimmermann, Walter

doi:10.1140/epje/i2019-11872-1

Cited by 8 publications

(17 citation statements)

References 47 publications

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“…Our results might be relevant for future studies on microswimmers in various complex environments involving hard walls or obstacle landscapes [65][66][67] , penetrable boundaries 68,69 , or external (viscosity) gradients [70][71][72] . For such scenarios, our results (or generalizations based on the same framework) can be used as reference calculations, e.g., to test machine-learning-based approaches to optimal microswimmer navigation 5,6 and perhaps also to help programming navigation systems for future microswimmer generations.…”

Section: Discussionmentioning

confidence: 87%

Hydrodynamics can determine the optimal route for microswimmer navigation

2021

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As compared to the well explored problem of how to steer a macroscopic agent, like an airplane or a moon lander, to optimally reach a target, optimal navigation strategies for microswimmers experiencing hydrodynamic interactions with walls and obstacles are far-less understood. Here, we systematically explore this problem and show that the characteristic microswimmer-flow-field crucially influences the navigation strategy required to reach a target in the fastest way. The resulting optimal trajectories can have remarkable and non-intuitive shapes, which qualitatively differ from those of dry active particles or motile macroagents. Our results provide insights into the role of hydrodynamics and fluctuations on optimal navigation at the microscale, and suggest that microorganisms might have survival advantages when strategically controlling their distance to remote walls.

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Section: Discussionmentioning

confidence: 87%

Hydrodynamics can determine the optimal route for microswimmer navigation

2021

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“…It can be shown that an infinite linear viscosity gradient, although associated with negative viscosity in parts of the fluid, yields mathematically the same result for the correction to the mobility matrix (§ D.1 of Appendix D) up to order as the odd symmetric gradient. This allows us to compare our results with previous works considering infinite gradients (Datt & Elfring 2019; Laumann & Zimmermann 2019).…”

Section: Particles In a Large Linear Viscosity Gradientmentioning

confidence: 59%

Hydrodynamic particle interactions in linear and radial viscosity gradients

Ziegler

Smith

2022

J. Fluid Mech.

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We present a versatile perturbative calculation scheme to determine the leading-order correction to the mobility matrix for particles in a low-Reynolds-number fluid with spatially variant viscosity. To this end, we exploit the Lorentz reciprocal theorem and the reflection method in the far field approximation. To demonstrate how to apply the framework to a particular choice of a viscosity field, we first study particles in a finite-size, interface-like, linear viscosity gradient. The extent of the latter should be significantly larger than the particle separation. Both situations of symmetrically and asymmetrically placed particles within such an odd symmetric viscosity gradient are considered. As a result, long-range flow fields are identified that decay by one order slower than their constant-viscosity counterparts. Self-mobilities for particle rotations and translations are affected, while for asymmetric placement, additional correction appears for the latter. The mobility terms associated with hydrodynamic interactions between the particles also need to be corrected, in a placement-specific manner. While the results are derived for the system of two particles, they apply also to many-particle systems. Furthermore, we treat the viscosity gradients induced by two particles with temperatures different from that of the surrounding fluid. Assuming a linear relation between fluid temperature and viscosity, we find that both the self-mobilities of the particles as well as the mobility terms for hydrodynamic interactions increase for hot particles and decrease for cold particles.

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“…nonactively-regulated) consequence of hydrodynamic interactions. Finally, our results might be relevant for future studies on microswimmers in various complex environments involving hard walls or obstacle landscapes [56][57][58], penetrable boundaries [59,60] or external (viscosity) gradients [61][62][63]. For such scenarios our results (or generalizations based on the same framework) can be used as reference calculations e.g.…”

Section: Discussionmentioning

confidence: 88%

Hydrodynamics can Determine the Optimal Route for Microswimmer Navigation

Daddi-Moussa-Ider,

Löwen,

Liebchen

2020

Preprint

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Contrasting the well explored problem on how to steer a macroscopic agent like an airplane or a moon lander to optimally reach a target, "optimal microswimming", i.e. the quest for the optimal navigation strategy for microswimmers, remains unsolved. Here, we systematically explore this problem and show that the characteristic flow field of microswimmers crucially influences the required navigation strategy to reach a target fastest. The resulting optimal trajectories can have remarkable and non-intuitive shapes, which qualitatively differ from those of dry active particles or motile macroagents. Our results provide generic insights into the role of hydrodynamics and fluctuations on optimal navigation at the microscale and suggest that microorganisms might have survival advantages when strategically controlling their distance to remote walls. In particular, when fluctuations are present, choosing the optimal strategy, which appropriately respects hydrdynamics, can halve the time to reach the target compared to cases microswimmers head straight towards it.

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Focusing and splitting streams of soft particles in microflows via viscosity gradients

Cited by 8 publications

References 47 publications

Hydrodynamics can determine the optimal route for microswimmer navigation

Hydrodynamics can determine the optimal route for microswimmer navigation

Hydrodynamic particle interactions in linear and radial viscosity gradients

Hydrodynamics can Determine the Optimal Route for Microswimmer Navigation

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