Parasitic trap cancellation using multiple frequency dielectrophoresis, demonstrated by loading cells into cages

Abstract

This paper presents a method of using multiple frequencies to counteract electric field distortions that interfere with the dielectrophoretic (DEP) manipulation of particles or cells. To demonstrate the technique, simulations were performed for a scenario in which cells were to be loaded into a cage whose walls created parasitic trapping sites that prevented cells from entering it. By employing negative DEP on one electrode in conjunction with positive DEP on another, these traps could be almost completely cancelled. The model predictions were validated experimentally: multiple frequency DEP was used to load many cells into a cage in a matter of seconds in fluid flows of up to 300 microm s(-1), which could not be done with single frequency DEP. Actively cancelling field distortions permits the presence of features that would otherwise be prohibited near regions of dielectrophoretic manipulation, significantly expanding the environments in which dielectrophoresis can be used.

Dielectrophoresis in microfluidics technology

“…This unique dielectric signature can be utilized to discriminate and identify cells from the other particles or to detect and isolate diseased or damaged cells by means of AC-DEP (DEP force spectra of different cell types can be found elsewhere [118,144]). AC-DEP has been implemented for the separation of cancer cells from blood stream [17,18], the separation of red blood cells and polystyrene particles [19], the separation of human leukocytes [20], the isolation of the malaria-infected cells from the blood [21,22], the separation of the electroporated and non-electroporated cells [23], the separation of the platelets from diluted whole blood [24], the separation of red blood cells and the white blood cells [25], the separation [26][27][28] and sorting [29] of viable and nonviable yeast cells, the separation of healthy and unhealthy oocyte cells [30], the characterization and the sorting stem cells and their differentiated progeny [31], the isolation of rare cells from biological fluids [32], the separation of three distinct bacterial clones of commonly used E. coli MC1061 strain [33], trapping of viable mammalian fibroplast cells [34], trapping of DNA molecules [35], trapping of single cancer and endothelial cells to investigate pairwise cell interactions [36], trapping of bacterial cells for the subsequent electrodisruption or electroporation [37], focusing of polystyrene particles [38], trapping of yeast cells [39], 3-D focusing of polystyrene particles and yeast cells [40], the separation of airborne bacterium, Micrococcus luteus, from a mixture with dust and polystyrene beads [41], trapping and isolation of human stem cell from heterogeneous solution [42], single-cell isolation [43], concentration and counting of polystyrene particles [44], the separation of polystyrene particles, Jurkat cells and HeLa cells …”

Dielectrophoretic monitoring of microorganisms in environmental applications

“…Urdaneta and Smela [36] employed a multiple frequency DEP (MFDEP) method, with positive and negative DEP forces to load nonviable yeast cells into a cage, where the microdevice walls acted as parasitic traps interfering with the cell loading. Employing negative DEP on an outer electrode (8 V RMS at 5 MHz), and positive DEP on an inner electrode (10 V RMS at 5 kHz), cell trapping onto walls was avoided with flow rates up to 2.5 mL/s.…”

“…Positive DEP is when particles are attracted to the regions with the higher electric field gradient, and negative DEP is when particles are repelled from those regions [30]. 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].…”

Continuous particle separation based on electrical properties using alternating current dielectrophoresis

“…However, in the case of direct current field, the non-conducting particles and cells experience only n-DEP [9]. DEP has been successfully implemented for cell sorting [10,11], sample preparation [12,13], cell detection [14,15,16], cell trapping [17], particle focusing [18,19], cell characterization [20] and cell patterning [21,22]. The dependence of the DEP force on the size and the electrical properties makes it possible for cell/ particle separation based on the size and electrical properties differences.…”