Magnetic Actuation of Surface Walkers: The Effects of Confinement and Inertia

Fang, Wenzhen; Ham, Seokgyun; Qiao, Rui; Tao, Wen‐Quan

doi:10.1021/acs.langmuir.9b03487

Cited by 23 publications

(18 citation statements)

References 54 publications

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“…A counterclockwise rotating microroller at a fixed position always experiences forces in negative direction without hydrodynamic confinement effects (32,36). However, when the channel is confined beyond a certain threshold, magnitude of this force could decrease and eventually reverse in direction according to numerical simulations (36). We also observed the confinement effect in our simulations, in which a single microroller experienced positive total force, despite rotating counterclockwise in a 75 μm high microchannel.…”

Section: Engineeringsupporting

confidence: 56%

“…Other than microtopographies, flow fields generated by microrollers also interact with the narrow-channel boundaries, which could create additional resistive forces on the microrollers. A counterclockwise rotating microroller at a fixed position always experiences forces in negative direction without hydrodynamic confinement effects (32,36). However, when the channel is confined beyond a certain threshold, magnitude of this force could decrease and eventually reverse in direction according to numerical simulations (36).…”

Section: Engineeringmentioning

confidence: 99%

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Shape anisotropy-governed locomotion of surface microrollers on vessel-like microtopographies against physiological flows

Bozuyuk

Alapan

Aghakhani

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Surface microrollers are promising microrobotic systems for controlled navigation in the circulatory system thanks to their fast speeds and decreased flow velocities at the vessel walls. While surface propulsion on the vessel walls helps minimize the effect of strong fluidic forces, three-dimensional (3D) surface microtopography, comparable to the size scale of a microrobot, due to cellular morphology and organization emerges as a major challenge. Here, we show that microroller shape anisotropy determines the surface locomotion capability of microrollers on vessel-like 3D surface microtopographies against physiological flow conditions. The isotropic (single, 8.5 µm diameter spherical particle) and anisotropic (doublet, two 4 µm diameter spherical particle chain) magnetic microrollers generated similar translational velocities on flat surfaces, whereas the isotropic microrollers failed to translate on most of the 3D-printed vessel-like microtopographies. The computational fluid dynamics analyses revealed larger flow fields generated around isotropic microrollers causing larger resistive forces near the microtopographies, in comparison to anisotropic microrollers, and impairing their translation. The superior surface-rolling capability of the anisotropic doublet microrollers on microtopographical surfaces against the fluid flow was further validated in a vessel-on-a-chip system mimicking microvasculature. The findings reported here establish the design principles of surface microrollers for robust locomotion on vessel walls against physiological flows.

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Section: Engineeringsupporting

confidence: 56%

Section: Engineeringmentioning

confidence: 99%

Shape anisotropy-governed locomotion of surface microrollers on vessel-like microtopographies against physiological flows

Bozuyuk

Alapan

Aghakhani

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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“…The quick response characteristic of a ferrofluid upon the magnetic field makes it an attractive medium to manipulate droplets. Although many researchers have adopted the active magnetic field to manipulate the mobility and deformability of the ferrofluid droplet [9][10][11][12], few studies have reported on how the morphology evolution of ferrofluid droplets affects their subsequent freezing process. In this study, the morphology of ferrofluid droplets is manipulated by imposing an external magnetic field to control their freezing processes.…”

Section: Introductionmentioning

confidence: 99%

Freezing process of ferrofluid droplets: Numerical and scaling analyses

Fang

Zhang

et al. 2020

Phys. Rev. Fluids

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In this study we present numerical and scaling analyses of deformation and freezing processes of ferrofluid droplets under magnetic field effects. A multiphase flow model coupled with an enthalpy-based lattice Boltzmann model is developed to directly simulate the deformation and subsequent freezing processes of a ferrofluid droplet with considerations of both volume expansion and magnetization effects. Meanwhile, analytical models and scaling analyses are derived to reveal how the morphology of the ferrofluid droplet responds to the magnetic field and how the morphology evolution affects the freezing time. We find that the magnetic force induced by magnetic field gradient is much larger than that induced by the magnetization effect, leading to the flattening or elongation of a ferrofluid droplet under magnetic squeeze or lift conditions. The height of the ferrofluid droplet almost linearly decreases (increases) in the low magnetic strength regime for magnetic squeeze (lift) cases, while it follows a nonlinear scaling law under high magnetic squeeze conditions. Besides, the propagation of the freezing front well obeys the scaling law h ∼ t 0.5 for high magnetic squeeze cases, but deviates much from that at the final freezing stage for both magnetic absence and lift cases.

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“…2018 b ; Fang et al. 2020). Third, our results reveal an interesting feature that the induced translation occurs in the negative -direction (referred to as the backward mode in this work), opposite to what might be intuitively expected for an object rolling along a solid surface.…”

Section: Resultsmentioning

confidence: 99%

Wall-induced translation of a rotating particle in a shear-thinning fluid

et al. 2021

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Particle–wall interactions have broad biological and technological applications. In particular, some artificial microswimmers capitalize on their translation–rotation coupling near a wall to generate directed propulsion. Emerging biomedical applications of these microswimmers in complex biological fluids prompt questions on the impact of non-Newtonian rheology on their propulsion. In this work, we report some intriguing effects of shear-thinning rheology, a ubiquitous non-Newtonian behaviour of biological fluids, on the translation–rotation coupling of a particle near a wall. One particularly interesting feature revealed here is that the wall-induced translation by rotation can occur in a direction opposite to what might be intuitively expected for an object rolling on a solid substrate. We elucidate the underlying physical mechanism and discuss its implications on the design of micromachines and bacterial motion near walls in complex fluids.

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Magnetic Actuation of Surface Walkers: The Effects of Confinement and Inertia

Cited by 23 publications

References 54 publications

Shape anisotropy-governed locomotion of surface microrollers on vessel-like microtopographies against physiological flows

Shape anisotropy-governed locomotion of surface microrollers on vessel-like microtopographies against physiological flows

Freezing process of ferrofluid droplets: Numerical and scaling analyses

Wall-induced translation of a rotating particle in a shear-thinning fluid

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