Recent theoretical studies have suggested a significant enhancement in electro-osmotic flows over hydrodynamically slipping surfaces, and experiments indeed measured O(1) enhancements. In this paper, we investigate whether an equivalent effect occurs the electrophoretic motion of colloidal particle whose surface exhibits hydrodynamic slip. To end, compute mobility uniformly charged spherical with slip length λ as function zeta (or surface) potential ζ diffuse-layer thickness κ−1. case thick...

The self-propulsion of a spherical squirmer – model swimming organism that achieves locomotion via steady tangential movement its surface is quantified across the transition from viscously to inertially dominated flow. Specifically, flow around computed for Reynolds numbers ( $Re$ ) between 0.01 and 1000 by numerical solution Navier–Stokes equations. A with fixed stroke direction considered. We find fluid inertia leads profound differences in pusher (propelled rear) versus puller front)...

The motion of a single Brownian probe particle subjected to constant external body force and immersed in dispersion colloidal particles is studied with view providing simple model for tracking microrheology experiments the active nonlinear regime. non-equilibrium configuration induced by calculated first order volume fraction over entire range Pe, accounting hydrodynamic excluded interactions between particles. Here, Pe dimensionless on probe, or Péclet number, characteristic measure degree...

The transient deformation of a weakly conducting (‘leaky dielectric’) drop under uniform DC electric field is computed via an axisymmetric boundary integral method, which accounts for surface charge convection and finite relaxation time scale over the interface charges. We focus on drops that attain ultimate oblate (major axis normal to applied field) steady-state configuration. computations predict as interfacial charging increases, shape transition from prolate parallel occurs at...

The locomotion of a spherical squirmer — model organism that achieves self-propulsion via steady tangential movement its surface is quantified at small Reynolds number R. Matched asymptotic expansions are employed to calculate the swimming velocity through O(R2). Approximations and vorticity fields around uniformly valid O(R) also constructed.

Advances over the past decade in nonlinear electrophoresis of charged, dielectric colloidal particles aqueous electrolytes are reviewed. Here, word refers to fact that ratio electrophoretic speed particle magnitude applied electric field—the mobility—is not independent field strength. This is stark contrast vast majority work on (linear) last century, where mobility assumed be a material property dependent only particle–electrolyte combination. The present discussion focused on: (i)...

Contemporary findings in the field of insulator-based electrokinetics have demonstrated that systems under influence direct current (DC) fields, dielectrophoresis (DEP) is not main electrokinetic mechanism responsible for particle manipulation but rather sum electroosmosis, linear and nonlinear electrophoresis. Recent microfluidic studies brought forth a methodology capable experimentally estimating electrophoretic mobility colloidal particles. This methodology, however, limited to particles...

We calculate the electrophoretic mobility M e of a spherical colloidal particle, using modified Poisson–Nernst–Planck (PNP) equations that account for steric repulsion between finite sized ions, through Bikerman's mean-field model (Bikerman, Phil. Mag ., vol. 33, 1942, p. 384). Ion effects are controlled by bulk volume fraction ions ν, and ν = 0 standard PNP recovered. An asymptotic analysis in thin-double-layer limit reveals at small zeta potentials (ζ < k B T / ≈ 25 mV) to increase...

The passage of ionic current across a charge-selective surface has been studied for over century and is relevant to well-established processes such as electrodialysis, electrodeposition, electrochromatography. Recent years have witnessed resurgence interest in this subject, motivated by experiments demonstrating transport ions solutes nanofluidic devices. In paper, we revisit build upon the prototypical problem one-dimensional ion flat ideally ion-selective surface, examining influence...

We quantify the transient deformation of a droplet immersed in weakly conductive (leaky dielectric) fluid upon exposure to uniform DC electric field. Capillary forces are assumed be sufficiently large that drop only slightly deviates from its equilibrium spherical shape. In particular, we account for (or linear) inertia via unsteady Stokes equations, and also finite electrical relaxation time over which interface charges. The temporal is governed by two dimensionless groups: (i) ratio...

Significance Contact between low- and high-salinity water occurs in many applications including enhanced oil recovery (EOR), desalination by reverse osmosis, or electric-power production (“blue energy”) pressure-retarded osmosis. The resulting salinity gradients can propel particles which cause fouling of osmosis membranes. In EOR the gradient transport functionalized nanoparticles into porous oil-bearing rock. Once transported, undertake situ sensing intervention activities At very high...

Low-profile and transient ingestible electronic capsules for diagnostics therapeutics can replace widely used yet invasive procedures such as endoscopies. Several gastrointestinal diseases reflux disease, Crohn's irritable bowel syndrome, eosinophilic esophagitis result in increased intercellular dilation epithelial barriers. Currently, the primary method of diagnosing monitoring barrier integrity is via endoscopic tissue biopsies followed by histological imaging. Here, a gelatin-based...

The gravitational settling of oil droplets solubilizing in an aqueous micellar solution contained a capillary channel is investigated. motion these active reflects competition between and Marangoni forces, the latter due to interfacial tension gradients generated by differences filled-micelle concentrations along oil-water interface. This studied varying surfactant concentration, density difference droplet continuous phase, viscosity phase. force enhances speed when compared...

Recent experiments have demonstrated that large-scale ion concentration gradients, or “concentration polarization,” can be generated from perm-selective transport through nanochannels nonuniform surface conduction around polarizable electrodes. The theoretical modeling of polarization phenomena is, however, a daunting task: for example, an analysis the above mentioned systems requires treatment set highly coupled, nonlinear partial differential equations concentrations, electric field, and...

The deformation of a weakly conducting, ‘leaky dielectric’, drop in density matched, immiscible conducting medium under uniform direct current (DC) electric field is quantified computationally. We exclusively consider prolate drops, for which the elongates direction applied field. Furthermore, majority this study, we assume and to have equal viscosities. Using axisymmetric boundary integral computations, delineate breakup regimes $Ca_{E}-Re_{E}$ parameter space, where $Ca_{E}$ capillary...

It is typically presumed that the phoretic motion of particles vanishes at large electrolyte concentration. A new study shows while this true for electrophoresis, diffusiophoretic mobility increases dramatically due to a gradient steric repulsion between finite-sized ions.

Abstract We present a continuum approach to predicting the electrophoretic mobility of charged dielectric colloidal particle in concentrated multivalent electrolyte. Our model takes into account steric (excluded volume) hindrance between ions via Bikerman’s ( Philos. Mag. , vol. 33, 1942, p. 384) and ion–ion electrostatic (Coulombic) correlations work Bazant et al. Phys. Rev. Lett. 106, 2011, 046102). The latter can result prediction an reversal, that is, migration velocity switches...

The adsorption of solid particles on the surface solubilizing oil droplets can significantly enhance droplets’ self-propulsion speeds.

A concentration gradient of surfactants in the presence polymers that non-covalently associate with will exhibit a continually varying distribution complexes different composition, charge, and size. Since diffusiophoresis colloids suspended solute depends on relaxation interactions between solutes particles, polymer/surfactant complexation alter rate driven by surfactant gradients relative to observed same absence polymers. microfluidic device was used measure solutions containing sodium...

Electrophoresis is the motion of a charged colloidal particle in an electrolyte under applied electric field. The electrophoretic velocity spherical depends on dimensionless field strength $\beta =a^*e^*E_\infty ^*/k_B^*T^*$ , defined as ratio product magnitude $E_\infty ^*$ and radius $a^*$ to thermal voltage $k_B^*T^*/e^*$ where $k_B^*$ Boltzmann's constant, $T^*$ absolute temperature, $e^*$ charge proton. In this paper, we develop spectral element algorithm compute spherical, rigid,...

A variety of microfluidic technologies utilise electrokinetic transport over rigid surfaces possessing rapid variations in charge. Here, as a paradigmatic model system for such situations, we consider electro-osmosis past flat plate discontinuous jump surface Although the problem is relatively simple to pose, our analysis highlights number interesting and somewhat surprising features. Notably, standard assumption that electric field outside diffuse screening layer equal uniform applied leads...

We present a theoretical scheme to calculate the electrophoretic motion of charged colloidal particles immersed in complex (non-Newtonian) fluids possessing shear-rate-dependent viscosities. demonstrate that this non-Newtonian rheology leads an explicit shape and size dependence velocity uniformly particle thin-Debye-layer regime, contrast electrophoresis Newtonian fluids. This is caused by stresses bulk (electroneutral) fluid outside Debye layer, whose magnitude naturally characterized...

We propose a microrheological technique to measure normal stress coefficients (NSCs) of complex fluids, which would represent the first quantitatively accurate measurement nonlinear rheological property by microrheology. Specifically, mechanical response almost all fluids ``weakly nonlinear'' deformations is described second-order fluid model. Two probes pulled with equal velocities through experience relative force that linear in and second NSCs fluid. compute coupling matrix between forces...