Active Particles in Viscosity Gradients

Datt, Charu; Elfring, Gwynn J.

doi:10.1103/physrevlett.123.158006

Cited by 74 publications

(94 citation statements)

References 31 publications

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“…Conservatively, for a typical cell radius [13], R ≈ 5 µm, flagellar length, ≈ 10 µm, and flagellar center of thrust, d ≈ 2, C. reinhardtii are generally expected to exhibit viscophobic behavior, d R ≈ 1 > 0.577. Furthermore, the prefactor in equation (S11) reduces to ≈ 1 2, which is similar in magnitude to recent squirmer models [25].…”

Section: Rotation Rate Of a Swimmer In A Viscosity Gradientsupporting

confidence: 82%

“…To focus on the effect of the viscosity gradient on the viscophobic turning behavior of the cells, we make the following simplifying assumptions in line with other recent simulations in viscosity gradients [25]…”

Section: Asymmetric Flagellar Propulsive Forcementioning

confidence: 99%

“…1e). Analysis of cell trajectories and complementary Langevin simulations reveals that the transition results from the competition between viscous accumulation due to reduced swimming speed 12,25 and a novel viscophobic reorientation mechanism. The latter is consistent with a physical, hydrodynamic phenomenon 10 , which results in an ensemble drift of swimming C. rein- hardtii down the viscosity gradient.…”

mentioning

confidence: 99%

“…For a directionally unbiased random walk, cell density is well known to scale inversely with local swimming speed 12,25,26 , ρ(x) ∝ 1 V (x). Accordingly, imposing a moderate viscosity gradient (∇η ≤ 3.4 × 10 −3 cP⋅µm −1 ) results in locally reduced swimming speed (Fig.…”

mentioning

confidence: 99%

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Viscophobic turning dictates microalgae transport in viscosity gradients

Stehnach

Waisbord

Walkama

et al. 2020

Preprint

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Gradients in fluid viscosity characterize microbiomes ranging from mucus layers on marine organisms and human viscera to biofilms. While such environments are widely recognized for their protective effects against pathogens and their ability to influence cell motility, the physical mechanisms controlling cell transport in viscosity gradients remain elusive, primarily due to a lack of quantitative observations. Through microfluidic experiments with a model biflagellated microalga (Chlamydomonas reinhardtii), we show that cells accumulate in high viscosity regions of weak gradients as expected, stemming from their locally reduced swimming speed. However, this expectation is subverted in strong viscosity gradients, where a novel viscophobic turning motility - consistent with a flagellar thrust imbalance - reorients the swimmers down the gradient and causes striking accumulation in low viscosity zones. Corroborated by Langevin simulations and a three-point force model of cell propulsion, our results illustrate how the competition between viscophobic turning and viscous slowdown ultimately dictates the fate of population scale microbial transport in viscosity gradients.

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Section: Rotation Rate Of a Swimmer In A Viscosity Gradientsupporting

confidence: 82%

Section: Asymmetric Flagellar Propulsive Forcementioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Viscophobic turning dictates microalgae transport in viscosity gradients

Stehnach

Waisbord

Walkama

et al. 2020

Preprint

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“…These results hence suggest the association of dynamic body shape changes of micro-organisms with their viscotactic behaviors. More recently, Datt and Elfring [138] considered a spherical squirmer model to show that viscotactic response can also occur with axisymmetric squirmers (Figure 9d), which generally turn toward regions of lower Figure 7. Phototaxis of artificial microswimmers.…”

Section: Viscotaxismentioning

confidence: 99%

Roads to Smart Artificial Microswimmers

Tsang

Demir

Ding

et al. 2020

Advanced Intelligent Systems

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Artificial microswimmers offer exciting opportunities for biomedical applications. The goal of these synthetics is to swim like natural micro‐organisms through biological environments and perform complex tasks such as drug delivery and microsurgery. Extensive efforts in the past several decades have focused on generating propulsion at the microscopic scale, which has engendered a variety of artificial microswimmers based on different physical and physicochemical mechanisms. Yet, these major advancements represent only the initial steps toward successful biomedical applications of microswimmers in realistic scenarios. A next step is to design “smart” microswimmers that can adapt their locomotion behaviors in response to environmental factors. Herein, recent progress in the development of microswimmers with intelligent behaviors is surveyed in three major areas: 1) adaptive locomotion across different media, 2) tactic behaviors in response to environment stimuli, and 3) multifunctional swimmers that can perform complex tasks. The emerging technologies and novel approaches used in developing these “smart” microswimmers, which enable them to display behaviors similar to biological cells, are discussed.

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Self‐Solidifying Active Droplets Showing Memory‐Induced Chirality

et al. 2023

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Most synthetic microswimmers do not reach the autonomy of their biological counterparts in terms of energy supply and diversity of motions. Here, this work reports the first all‐aqueous droplet swimmer powered by self‐generated polyelectrolyte gradients, which shows memory‐induced chirality while self‐solidifying. An aqueous solution of surface tension–lowering polyelectrolytes self‐solidifies on the surface of acidic water, during which polyelectrolytes are gradually emitted into the surrounding water and induce linear self‐propulsion via spontaneous symmetry breaking. The low diffusion coefficient of the polyelectrolytes leads to long‐lived chemical trails which cause memory effects that drive a transition from linear to chiral motion without requiring any imposed symmetry breaking. The droplet swimmer is capable of highly efficient removal (up to 85%) of uranium from aqueous solutions within 90 min, benefiting from self‐propulsion and flow‐induced mixing. These results provide a route to fueling self‐propelled agents which can autonomously perform chiral motion and collect toxins.

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Active Particles in Viscosity Gradients

Cited by 74 publications

References 31 publications

Viscophobic turning dictates microalgae transport in viscosity gradients

Viscophobic turning dictates microalgae transport in viscosity gradients

Roads to Smart Artificial Microswimmers

Self‐Solidifying Active Droplets Showing Memory‐Induced Chirality

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