One-, two-, and three-dimensional organization of colloidal particles using nonuniform alternating current electric fields

Abstract

We demonstrate here the use of nonuniform alternating current (AC) electric fields, generated by planar electrodes, for the organization of num-sized particles into one-, two-, and three-dimensional assemblies. The electrodes, with separations that vary from 35 to 300 num, are made of gold deposited on glass substrata. Latex, silica and graphite particles have been examined inside organic or aqueous media in order to illustrate the general applicability of the technique. Theoretical predictions of the particle response under the electric fields are experimentally confirmed for all the above particle/media combinations and can thus be used as a valuable design tool. The size and shape of the final structures are mainly dependent on the electrode shape and dimensions, but are also subject to the particle type and operating conditions. Particle organization in one dimension (strings) is achieved under conditions of positive or negative dielectrophoresis in the space between two energized electrodes. Two-dimensional particle organization (ordered, planar particles assemblies) was observed under conditions of negative dielectrophoresis, when quadrupole electrodes were employed. Moreover, when negative dielectrophoresis and stronger electric fields are applied (of the order of 50 kV(rms) m(-1)), three-dimensional, pyramid-like structures with a vertical dimension 1000-fold higher than that of the corresponding (planar) electrodes can be assembled. These 3-D structures can grow as free-standing assemblies, or inside templates etched in the substratum. The dielectrophoresis (DEP)-organized particle assemblies can subsequently be rendered permanent via the in situ fixing (cross-linking) of the individual particles.

Particle patterning using fluidics and electric fields

“…At these frequencies DEP will be dominant because electrophoretic movement is highly attenuated: however other dipole-dipole interactions or else fluid flows may also be involved. Although 3-D assemblies of colloids can be produced most easily by 3-D electrode arrays [43], planar arrays can also give rise to some 3-D structures [44,45].…”

“…If pattern assembly is carried out in a matrix that can be solidified by temperature change [46], solvent removal, polymerisation [47,48] or cross-linking [44,49,50], then micro-or nano-composites can be prepared. Surface…”

Calculation of the electric polarizability of a charged spherical dielectric particle by the theory of colloidal electrokinetics

“…In recent years, dielectrophoretic particle manipulation using microelectrodes has been widely investigated [4][5][6]. The accurate computation of DEP forces is essential in terms of the interpretation of experimentally observed phenomena.…”

Enhanced discrimination of normal oocytes using optically induced pulling-up dielectrophoretic force

“…The CM factor, which can determine the dielectrophoretic mobility of the cells, can be affected by the composition of the cytoplasm and nucleus 22 and the conductivity and permittivity of the cytoplasm. 23,24 Therefore, different cytoplasmic contents between normal and abnormal oocytes would induce the differences in their mobility due to the optically induced DEP force. We calculated the CM factor of oocyte by decreasing the conductivity of the cytoplasm from 5 mS/cm, which is a normal value, to 0.2 mS/cm of ͓Fig.…”