Electrodeless direct current dielectrophoresis using reconfigurable field‐shaping oil barriers

Abstract

We demonstrate dielectrophoretic (DEP) potential wells using pairs of insulating oil menisci to shape the DC electric field. These oil menisci are arranged in a configuration similar to the quadrupolar electrodes, typically used in DEP, and are shown to produce similar field gradients. While the one-pair well produces a focusing effect on particles in flow, the two-pair well results in creating spatial traps against crossflows. Uncharged polystyrene particles were used to map the DEP force fields and the experimental observations were compared against the field profiles obtained by numerically solving Maxwell's equations. We demonstrate trapping of a single particle due to negative DEP against a pressuredriven crossflow. This can be easily extended to trap and hold cells and other objects against flow for a longer time. We also show the results of particle trapping experiments performed to observe the effect of adjusting the oil menisci and the gap between two pairs of menisci in a four-menisci configuration on the nature of the DEP well formed at the center. A design parameter, Y, capturing the dimensions of the DEP energy well, is defined and simulations exploring the effects of different geometric features on Y are presented.

Dielectrophoretic focusing of particles in a microchannel constriction using DC‐biased AC flectric fields

“…We acknowledge that the DC dielectrophoretic focusing of particles has been suggested and studied in constrictions formed by an array or pairs of insulating micro-obstacles such as oil menisci [27,32,33]. In these works, however, it is necessary that either the particle size is comparable with the constriction width or the applied DC electric field is sufficiently large.…”

“…For example, particle focusing has been achieved by applying an external force field, such as optical [16], acoustic [17], electrophoretic [18], and AC dielectrophoretic [19][20][21][22], to manipulate particles directly to their equilibrium positions in the pressure-pumping particulate stream. In addition, particle focusing has also been achieved by using hydrodynamic filtration [23,24], hydrophoresis [25,26], DC dielectrophoresis [27], and inertia [28][29][30][31] etc.…”

Dielectrophoretic monitoring of microorganisms in environmental applications

“…Many different approaches have been employed to apply DEP forces on particles, the most traditional manner is to use arrays of microelectrodes of a variety of geometries [34] and locations within a microchannel, from lateral electrodes [35] to threedimensional (3-D) cages [36,37] and 3-D electrodes [38]. Other novel approaches include: insulator-based DEP (iDEP) with 3-D columns or posts [39][40][41][42], oil menisci [43], glass spheres [44], microchannel with a geometry gradient [45,46], insulating hurdles [1,47], nanopipettes [19,48], spiral microchannels [49,50], and conical-pore membranes [51].…”

Separation of mixtures of particles in a multipart microdevice employing insulator‐based dielectrophoresis

“…In 2007, Thwar et al [21] presented a dynamic system where dielectrophoretic traps were manipulated by the size of oil menisci. The channel had two different sets of menisci, which could be shaped in different sizes to act as two dielectrophoretic traps to separate samples.…”