Numerical simulation of dielectrophoretic ratchet structures

Hughes, Michael

doi:10.1088/0022-3727/37/8/017

Cited by 10 publications

(9 citation statements)

References 20 publications

(41 reference statements)

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“…We calculated the electric field distribution and the energy of the system for different particle configurations in order to understand why individual Janus particles orient in the direction of the electric field in such a manner and to model the formation of staggered chains. The total electric energy W e of the system can be obtained by integrating the local energy density, w es (defined in the Appendix), over the subdomain volume ( V ) W e = ∫ V w es d V Particles responding to dielectrophoretic force are attracted (if they are more polarizable than the media) to the high field intensity area in an electric field gradient so that the minimum potential energy is reached when the particles are closest to the point of highest electric field strength. , …”

Section: Modeling Of Janus Particle Orientation and Staggered Chain F...mentioning

confidence: 99%

Dielectrophoretic Assembly of Metallodielectric Janus Particles in AC Electric Fields

2008

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"Janus" particles with two hemispheres of different polarizability or charge demonstrate a multitude of interesting effects in external electric fields. We reported earlier how particles with one metallic hemisphere and one dielectric hemisphere self-propel in low-frequency alternating current (AC) electric fields. Here, we demonstrate the assembly of such Janus particles driven by AC electric fields at frequencies above 10 kHz. We investigated the relation between field-induced dielectrophoretic force, field distribution, and structure of the assemblies. The phase space for electric field intensity and frequency was explored for particle concentrations large enough to form a monolayer on a glass surface between two gold electrodes. A rich variety of metallodielectric particle structures and dynamics were uncovered, which are very different from those obtained from directed assembly of plain dielectric or plain conductive particles under the action of fields of similar frequency and intensity. The metallodielectric particles assemble into new types of chain structures, where the metallized halves of neighboring particles align into lanes along the direction of the electric field, while the dielectric halves face in alternating direction. The staggered chains may assemble in various orientations to form different types of two-dimensional metallodielectric crystals. The experimental results on the formation of staggered chains are interpreted by means of numerical simulations of the electric energy of the system. The assembly of Janus metallodielectric particles may find applications in liquid-borne microcircuits and materials with directional electric and heat transfer.

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Section: Modeling Of Janus Particle Orientation and Staggered Chain F...mentioning

confidence: 99%

Dielectrophoretic Assembly of Metallodielectric Janus Particles in AC Electric Fields

2008

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“…Ratchets have been used for quantum tunneling ratchets (Linke et al 1999(Linke et al , 2002, dielectrophoretic rectification of Brownian motion (Hughes 2004) and action of molecular motors (Kulic et al 2005;Julicher et al 1997). Topological ratchet structures were also used as a rectifier that forces the otherwise random mechanical motion of droplets into a specific direction by means of localized asymmetric potential (Linke et al 2006;Buguin et al 2002;Ding et al 2007Ding et al , 2009.…”

Section: List Of Symbolsmentioning

confidence: 99%

Propulsion of droplets on micro- and sub-micron ratchet surfaces in the Leidenfrost temperature regime

Lopez-Oña

Nikitopoulos

et al. 2010

Microfluid Nanofluid

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Spatially periodic systems with localized asymmetric surface structures (ratchets) can induce directed transport of matter (liquid/particles) in the absence of net force. Here, we show that propulsion for the directed motion of water droplets levitating on heated ratchet surfaces in the Leidenfrost (film boiling) regime is significantly enhanced as the ratchet period decreases down to micro-and sub-micrometers. At the temperature range slightly above the threshold temperature of droplet motion, sub-micron ratchets yield water droplet velocities reaching *40 cm/s, a speed that has never been achieved with any chemical and topological gradient surfaces. This dramatic increase in the droplet velocity is attributed to an enhanced heat transfer through the local contacts between ratchet peaks and bottom of the droplet. A hydrophobic coating on the ratchet surfaces is found to further increase the droplet velocity and decrease the threshold temperature of the droplet motion. The results suggest that miniaturized ratchet surfaces can potentially be used in diverse applications requiring control over fluid transport and heat transfer such as two phase cooling systems for microprocessors and fuel injection for combustion technology and that for those applications the design of ratchet dimensions and surface chemistry are critically important.

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“…44 For particles that experience positive DEP the minimum potential energy is reached when the particles are closest to the point of highest electric field strength. 45,46 At low AC field frequencies, the counterions in the double layer have enough time to follow each change in sign of the field direction and migrate in and out of the double layer to the bulk solution. The particles are attracted to each other (indicated by the high energy density red color) due to positive DEP (Fig.…”

Section: Ac Dielectrophoresismentioning

confidence: 99%