Electrohydrodynamics of particle-covered drops

Ouriemi, Malika; Vlahovska, Petia M.

doi:10.1017/jfm.2014.289

Cited by 40 publications

(36 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The characteristics of the particles are summarized in Table I. The experimental set-up has the same design as the one used in [24]. A uniform DC electric field is created in a parallel-plate chamber made of two 7.6cm by 10.5 cm brass electrodes separated by a gap of 4.5cm.…”

Section: A Materialsmentioning

confidence: 99%

“…Fluid interfaces provide additional functionality opening new routes for the bottom-up fabrication of novel structurally complex materials [19][20][21][22]. Recent works [23][24][25][26] find that microparticles constrained on a drop surface can form various structures in the presence of applied uniform electric field. The underlying mechanisms are still under investigation but a major driving force in this system is the flow created by the electric shear stresses due to accumulation of charges at the interface.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Electrohydrodynamic Deformation and Rotation of a Particle-Coated Drop

Ouriemi

Vlahovska

2015

Langmuir

View full text Add to dashboard Cite

A dielectric drop suspended in conducting liquid and subjected to an uniform electric field deforms into an ellipsoid whose major axis is either perpendicular or tilted (due to Quincke rotation effect) relative to the applied field. We experimentally study the effect of surface-adsorbed colloidal particles on these classic electrohydrodynamic phenomena. We observe that at high surface coverage (> 90%), the electrohydrodynamic flow is suppressed, oblate drop deformation is enhanced, and the threshold for tilt is decreased compared to the particle-free drop. The deformation data are well explained by a capsule model, which assumes that the particle monolayer acts as an elastic interface. The reduction of the threshold field for rotation is likely related to drop asphericity.

show abstract

Section: A Materialsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electrohydrodynamic Deformation and Rotation of a Particle-Coated Drop

Ouriemi

Vlahovska

2015

Langmuir

View full text Add to dashboard Cite

show abstract

“…The deformation of drops can be induced and investigated using various experimental tools, including atomic force microscopes, 21,22 microfluidic devices, [23][24][25] and by utilizing mechanical shearing 26,27 or electric fields. [28][29][30][31][32] For manipulating particles at drop surfaces or in the bulk of a drop, there are many physical or chemical approaches, such as pH-controlled particle assembly, 33 acoustic wave-induced bulk and surface particle convection, 34 magnetic field-directed particle assembly, 35 and electric field-assisted particle arrangements. 36 In this work, we explore the possibilities of employing electric fields as a contactless method for both drop deformation and the manipulation of particles at drop interfaces.…”

Section: Introductionmentioning

confidence: 99%

Particle-covered drops in electric fields: drop deformation and surface particle organization

et al. 2018

View full text Add to dashboard Cite

Drops covered by adsorbed particles are a prominent research topic because they hold promise for a variety of practical applications. Unlocking the enormous potential of particle-laden drops in new material fabrication, for instance, requires understanding how surface particles affect the electrical and deformation properties of drops, as well as developing new routes for particle manipulation at the interface of drops. In this study, we utilized electric fields to experimentally investigate the mechanics of particle-covered silicone oil drops suspended in castor oil, as well as particle assembly at drop surfaces. We used particles with electrical conductivities ranging from insulating polystyrene to highly conductive silver. When subjected to electric fields, drops can change shape, rotate, or break apart. In the first part of this work, we demonstrate how the deformation magnitude and shape of drops, as well as their electrical properties, are affected by electric field strength, particle size, conductivity, and coverage. We also discuss the role of electrohydrodynamic flows on drop deformation. In the second part, we present the electric field-directed assembly and organization of particles at drop surfaces. In this regard, we studied various parameters in detail, including electric field strength, particle size, coverage, and electrical conductivity. Finally, we present a novel method for controlling the local particle coverage and packing of particles on drop surfaces by simply tuning the frequency of the applied electric field. This approach is expected to find uses in optical materials and applications.

show abstract

“…All of these suggest that multibody hydrodynamic interactions play a significant role in the collective dynamics and phase behavior of suspensions of active rotors and these effects should not be neglected in studies of similar active systems. For example, hydrodynamic interactions could influence or drive the formation of the peculiar dynamical structures experimentally observed at the interface of drops covered with colloidal particles [49,50].In this Letter we considered only torques that are perpendicular to the particle monolayer. Due to the symmetry of the generated flows, the particles remain confined to the monolayer and do not move transversely.…”

mentioning

confidence: 99%

Collective Dynamics in a Binary Mixture of Hydrodynamically Coupled Microrotors

2015

View full text Add to dashboard Cite

We study numerically the collective dynamics of self-rotating non-aligning particles by considering a monolayer of spheres driven by constant clockwise or counterclockwise torques. We show that hydrodynamic interactions alter the emergence of large-scale dynamical patterns compared to those observed in dry systems. In dilute suspensions, the flow stirred by the rotors induces clustering of opposite-spin rotors, while at higher densities same-spin rotors phase separate. Above a critical rotor density, dynamic hexagonal crystals form. Our findings underscore the importance of inclusion of the many-body, long-range hydrodynamic interactions in predicting the phase behavior of active particles.PACS numbers: 47.57. 47.63.mf, 83.10.Tv, 64.75.Xc Systems of motile and interacting units can exhibit non-equilibrium phenomena such as self-organization and directed motion at large scales [1]. Theoretical studies of active matter report clustering [2], phase separations [3][4][5] and rotating structures [6]. Some of these phenomena have been observed in experiments of bacterial suspensions [7] or chemically-activated motile colloids [8].The collective motion of translating units such as bacteria has received much interest [1]. On the other hand, little is known about spinning units, partly because such systems were realized experimentally only recently. Active rotation of particles can be achieved using external forcing such as rotating magnetic fields [9,10], uniform electric fields (the Quincke rotation effect) [11] or chemical reactions [12]. Self-assembly from polymers by motile bacteria can create micro-rotors [13]. In biological systems, the dancing volvox [14], uniflagellar algae C. reinhardtii [15] and bacteria T. majus [16] exhibit rotorlike behaviors. Rising interest in rotor systems generated theoretical studies exploring rotor pair dynamics [17,18], non-equilibrium structure formation [19], dynamics at interfaces [20,21], rheology of suspensions [22,23], and phase separation driven by active rotation [24,25].Models of the collective behavior of active matter often neglect particle motion due to the flow stirred by the other particles [4,5,24,26], tacitly assuming that the observed phase behavior of the "dry" system would persist in a system with fluid motion. However in the viscosity-dominated world of colloidal-size particles, hydrodynamic interaction generates a long-range correlation, which can play an important role in the self-organization in many-body systems [27][28][29]. For example, in the studies of micro-swimmers, it was found that the hydrodynamic interactions determine the collective motion of squirmers (self-propelled spheres with no aligning interaction) [30] and the recently observed self-organization of bacteria into a macro-scale bidirectional vortex when confined inside a drop [31] can only be explained by accounting for the fluid-mediated interactions [32]. It is the hydrodynamic interactions that cause two point rotors spinning in the opposite direction to translate [18] or undergo complex...

show abstract

Electrohydrodynamics of particle-covered drops

Cited by 40 publications

References 21 publications

Electrohydrodynamic Deformation and Rotation of a Particle-Coated Drop

Electrohydrodynamic Deformation and Rotation of a Particle-Coated Drop

Particle-covered drops in electric fields: drop deformation and surface particle organization

Collective Dynamics in a Binary Mixture of Hydrodynamically Coupled Microrotors

Contact Info

Product

Resources

About