2-D assembly of colloidal particles on a planar electrode

Prieve, Dennis C.; Sides, Paul J.; Wirth, Christopher L.

doi:10.1016/j.cocis.2010.01.005

Cited by 96 publications

(124 citation statements)

References 52 publications

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“…Attractive and repulsive interactions can be tuned by varying the geometry of the particles (and the walls), as well as the AC frequency and voltage. These remarkable phenomena may find applications in separation or self-assembly of colloids or in local flow generation in microfluidic devices [29,46].…”

Section: Discussionmentioning

confidence: 99%

“…The former effect of ICEP attraction to conducting walls has not yet been analyzed; it may play a role in colloidal self assembly on electrodes applying AC voltages [46][47][48][49][50][51]. This phenomenon is mainly understood in terms of electrohydrodynamic flows (what we would term "ICEO") induced on the electrodes, not the particles (typically latex spheres), but ICEP could be important for more polarizable particles.…”

Section: Introductionmentioning

confidence: 99%

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Induced‐charge electrophoresis near a wall

Kilic

Bazant

2011

Electrophoresis

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Induced-charge electrophoresis (ICEP) has mostly been analyzed for asymmetric particles in an infinite fluid, but channel walls in real systems further break symmetry and lead to dielectrophoresis (DEP) in local field gradients. Zhao and Bau (Langmuir, 23, 4053, 2007) predicted that a metal (ideally polarizable) cylinder is repelled from an insulating wall in a DC field. We revisit this problem with an AC field and show that attraction to the wall sets in at high frequency and leads to an equilibrium distance, where DEP balances ICEP, although, in three dimensions, a metal sphere is repelled from the wall at all frequencies. This conclusion, however, does not apply to asymmetric particles. Consistent with the experiments of Gangwal et al. (Phys. Rev. Lett., 100, 058302, 2008), we show that a metal/insulator Janus particle is always attracted to the wall in an AC field. The Janus particle tends to move toward its insulating end, perpendicular to the field, but ICEP torque rotates this end toward the wall. Under some conditions, the theory predicts steady translation along the wall, perpendicular to the field, at an equilibrium tilt angle around 45 degrees, consistent with the experiments, although improved models are needed for a complete understanding of this phenomenon.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Induced‐charge electrophoresis near a wall

Kilic

Bazant

2011

Electrophoresis

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“…Electrical-doublelayer forces thus plays a fundamental role in a wide range of physical scenarios including solution stability (DLVO theory in particular [3]), particle dynamics near electrodes [4], colloidal crystals [5,6], AFM measurements [7], coal flotation, swelling of clays [8], and in numerous biological applications [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Ray-theory approach to electrical-double-layer interactions

Schnitzer

2015

Phys. Rev. E

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A novel approach is presented for analyzing the double-layer interaction force between charged particles in electrolyte solution, in the limit where the Debye length is small compared with both inter-particle separation and particle size. The method, developed here for two planar convex particles of otherwise arbitrary geometry, yields a simple asymptotic approximation limited to neither small zeta potentials nor the "close-proximity" assumption underlying Derjaguin's approximation.Starting from the nonlinear Poisson-Boltzmann formulation, boundary-layer solutions describing the thin diffuse-charge layers are asymptotically matched to a WKBJ expansion valid in the bulk, where the potential is exponentially small. The latter expansion describes the bulk potential as superposed contributions conveyed by "rays" emanating normally from the boundary layers. On a special curve generated by the centres of all circles maximally inscribed between the two particles, the bulk stress -associated with the ray contributions interacting nonlinearly -decays exponentially with distance from the centre of the smallest of these circles. The force is then obtained by integrating the traction along this curve using Laplace's method. We illustrate the usefulness of our theory by comparing it, alongside Derjaguin's approximation, with numerical simulations in the case of two parallel cylinders at low potentials. By combining our result and Derjaguin's approximation, the interaction force is provided at arbitrary inter-particle separations. Our theory can be generalized to arbitrary three dimensional geometries, non-ideal electrolyte models, and other physical scenarios where exponentially decaying fields give rise to forces.

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“…The inset of Figure 1 illustrates the tangential, attractive EHD flow on an electrode surface near a covalently bound Au seed on PMMA. (3) As oligomers formed by EHD are transient, 47 e.g., when the voltage is removed, the assembled particles will dissolve back into the bulk solution without a strong attractive force with the surface. Here, carbodiimide cross-linking chemistry stabilizes oligomers after formation.…”

Section: Resultsmentioning

confidence: 99%

Driving Chemical Reactions in Plasmonic Nanogaps with Electrohydrodynamic Flow

Thrift

Nguyen

Darvishzadeh-Varcheie

et al. 2017

ACS Nano

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Nanoparticles from colloidal solutionwith controlled composition, size, and shapeserve as excellent building blocks for plasmonic devices and metasurfaces. However, understanding hierarchical driving forces affecting the geometry of oligomers and interparticle gap spacings is still needed to fabricate high-density architectures over large areas. Here, electrohydrodynamic (EHD) flow is used as a long-range driving force to enable carbodiimide cross-linking between nanospheres and produces oligomers exhibiting sub-nanometer gap spacing over mm 2 areas. Anhydride linkers between nanospheres are observed via surface-enhanced Raman scattering (SERS) spectroscopy. The anhydride linkers are cleavable via nucleophilic substitution and enable placement of nucleophilic molecules in electromagnetic hotspots. Atomistic simulations elucidate that the transient attractive force provided by EHD flow is needed to provide a sufficient residence time for anhydride cross-linking to overcome slow reaction kinetics. This synergistic analysis shows assembly involves an interplay between long-range driving forces increasing nanoparticle− nanoparticle interactions and probability that ligands are in proximity to overcome activation energy barriers associated with short-range chemical reactions. Absorption spectroscopy and electromagnetic full-wave simulations show that variations in nanogap spacing have a greater influence on optical response than variations in close-packed oligomer geometry. The EHD flow−anhydride cross-linking assembly method enables close-packed oligomers with uniform gap spacings that produce uniform SERS enhancement factors. These results demonstrate the efficacy of colloidal driving forces to selectively enable chemical reactions leading to future assembly platforms for large-area nanodevices.

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2-D assembly of colloidal particles on a planar electrode

Cited by 96 publications

References 52 publications

Induced‐charge electrophoresis near a wall

Induced‐charge electrophoresis near a wall

Ray-theory approach to electrical-double-layer interactions

Driving Chemical Reactions in Plasmonic Nanogaps with Electrohydrodynamic Flow

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