Microfluidic rheology of active particle suspensions: Kinetic theory

Alonso-Matilla, Roberto; Ezhilan, Barath; Saintillan, David

doi:10.1063/1.4954193

Cited by 21 publications

(47 citation statements)

References 58 publications

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“…Also, the authors [23] numerically verified the experimental observations of [20], where a super-fluid state is reached by using pusher swimming particles.…”

Section: Introductionsupporting

confidence: 52%

“…Self-propelled nanofluid is reducing the viscosity of the host fluid because the particles create a stretching pathway in the extensional shearing direction [23]. This stretching pathway makes the fluid moving easier and faster, and thus reducing the overall viscosity.…”

Section: Viscosity Model and Heat Transfer Efficiency Of Self-propellmentioning

confidence: 99%

“…The constitutive law that governs the relationship between the ratio of the viscosity of the suspension of rod active particles and that of the solvent is derived in [23] and is given by the following relation:…”

Section: Viscosity Model and Heat Transfer Efficiency Of Self-propellmentioning

confidence: 99%

“…However, what is missing is a simple relation that shows the main physical ingredients involved in the rheology of the active matter. Recently Matilla et al [23] investigated numerically and analytically the rheology of active rod-shaped particles at a microfluidic length scale. They developed a simple theory that describes the anomalous rheological behaviour of the self-propelled particles.…”

Section: Introductionmentioning

confidence: 99%

“…In the coming sections, the proposed formula by [23] will be introduced and discussed. Also, the authors [23] numerically verified the experimental observations of [20], where a super-fluid state is reached by using pusher swimming particles.…”

Section: Introductionmentioning

confidence: 99%

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Self-propelled nanofluids a path to a highly effective coolant

Hasadi

Crapper

2017

Applied Thermal Engineering

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We propose a new self-propelled nanofluid having advantageous thermal and rheological properties at the same time. The nanofluid consists of a low volume fraction of self-propelled particles known as Artificial Bacterial Flagella (ABF), which will swim as pushers in a manner similar to the swimming of E-coil microorganisms with flagella. A theoretical model is introduced, describing the mechanisms responsible for the reduction of viscosity. The model shows that the swimming velocity of the particle and its geometry play an essential role in the reduction of the suspension viscosity. The results obtained from the theoretical model compare qualitatively with experiments in the literature. The model shows a significant decrease in viscosity at very low volume fractions, and that the viscosity of the suspension is reduced as the volume fraction of the particles increases. Using an in-house finite volume code, we numerically simulate natural convection effects in our ABF self-propelled nanofuid inside a square cavity heated from its vertical sides. Simulations are conducted at volume fractions of 0.7%, 0.8% and 0.83%, comparing the performance of a self-propelled nanofluid with conventional non-active nanofluids (i.e. carbon nanotubes in water). The results show that the heat transfer rate measured by the Nusselt number is three times higher than for the case of classical nanofluids and pure water at the same operating conditions and 0.83% volume fraction of particles. Also, due to the very dilute volume fractions of particles in the proposed nanofluid, their stability can endure for long operating times. There is also a significant decrease in the viscosity (around 25 times lower than water) which will result in a significant reduction in the pumping power.2

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“…Also, the authors [23] numerically verified the experimental observations of [20], where a super-fluid state is reached by using pusher swimming particles.…”

Section: Introductionsupporting

confidence: 52%

Section: Viscosity Model and Heat Transfer Efficiency Of Self-propellmentioning

confidence: 99%

Section: Viscosity Model and Heat Transfer Efficiency Of Self-propellmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Self-propelled nanofluids a path to a highly effective coolant

Hasadi

Crapper

2017

Applied Thermal Engineering

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Rheology of bacterial suspensions under confinement

2019

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As a paradigmatic model of active fluids, bacterial suspensions show intriguing rheological responses drastically different from their counterpart colloidal suspensions. Although the flow of bulk bacterial suspensions has been extensively studied, the rheology of bacterial suspensions under confinement has not been experimentally explored. Here, using a microfluidic viscometer, we systematically measure the rheology of dilute E. coli suspensions under different degrees of confinement. Our study reveals a strong confinement effect: the viscosity of bacterial suspensions decreases substantially when the confinement scale is comparable or smaller than the run length of bacteria. Moreover, we also investigate the microscopic dynamics of bacterial suspensions including velocity profiles, bacterial density distributions and single bacterial dynamics in shear flows. These measurements allow us to construct a simple heuristic model based on the boundary layer of upstream swimming bacteria near confining walls, which qualitatively explains our experimental observations. Our study sheds light on the influence of the boundary layer of collective bacterial motions on the flow of confined bacterial suspensions. Our results provide a benchmark for testing different rheological models of active fluids and are useful for understanding the transport of microorganisms in confined geometries.

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