Microfabrication technologies in dielectrophoresis applications—A review

Abstract

DEP is an established technique for particle manipulation. Although first demonstrated in the 1950s, it was not until the development of miniaturization techniques in the 1990s that DEP became a popular research field. The 1990s saw an explosion of DEP publications using microfabricated metal electrode arrays to sort a wide variety of cells. The concurrent development of microfluidics enabled devices for flow management and better understanding of the interaction between hydrodynamic and electrokinetic forces. Starting in the 2000s, alternative techniques have arisen to overcome common problems in metal-electrode DEP, such as electrode fouling, and to increase the throughput of the system. Insulator-based DEP and light-induced DEP are the most significant examples. Most recently, new 3D techniques such as carbon-electrode DEP, contactless DEP, and the use of doped PDMS have further simplified the fabrication process. The constant desire of the community to develop practical solutions has led to devices which are more user friendly, less expensive, and are capable of higher throughput. The state-of-the-art of fabricating DEP devices is critically reviewed in this work. The focus is on how different fabrication techniques can boost the development of practical DEP devices to be used in different settings such as clinical cell sorting and infection diagnosis, industrial food safety, and enrichment of particle populations for drug development.

Enhanced contactless dielectrophoresis enrichment and isolation platform via cell-scale microstructures

“…Several different designs of DEP separation devices have been developed, [17][18][19][20] with the inhomogeneity of the electric field generating the DEP force achieved either by the shapes of the electrodes, referred to as classical DEP, 21,22 or by inclusion of insulating structures into the otherwise largely uniform field, referred to as insulator DEP (iDEP) 23,24 and contactless DEP (cDEP). 25,26 Dielectrophoretic separation is based on bioelectrical cell properties and is independent of the cells' genotype.…”

“…Viability of mammalian cells in negative DEP devices, where the DEP force is pushing the cells away from electrodes, can be as high as 97%; 27 however, to the authors' knowledge, no viability study has been published on trapping-based high-throughput DEP systems. Development of 3D electrodes has allowed for extended range of the DEP force and higher throughput 20,28 at the cost of more complex fabrication. Alternatively, the DEP force can be generated by placing insulating structures to distort an otherwise uniform electric field.…”

Enrichment of diluted cell populations from large sample volumes using 3D carbon-electrode dielectrophoresis

“…Hence, of particular interest here is the use of 3D electrodes, spanning the height of the microfluidic channel, to improve throughput when compared to more traditional planar devices. 3D electrodes have been implemented using different fabrication techniques 29 such as electroplating, 30,31 metallization of 3D structures, [32][33][34] and casting of conductive resins. 35 Here, we use 3D carbon electrodes to implement dielectrophoresis (carbonDEP) and enrich a yeast population originally diluted in a large sample volume.…”

“…40 The advantages and disadvantages of using carbonDEP over other DEP techniques have been detailed several times before. 22,29,41,42 Briefly, the fabrication of 3D electrodes is relatively low cost and straightforward; carbon has a wider electrochemical stability window than noble metals which reduces the chance of sample electrolysis for a given applied voltage; and carbon offers excellent chemical inertness and biocompatibility. Although the electrical conductivity of glassy carbon is less than that of metals, it is in the same order of indium tin oxide, [43][44][45] and an effective DEP force can be generated by polarizing the carbon electrodes with tens of volts.…”

Dielectrophoretic capture of low abundance cell population using thick electrodes

“…DEP is defined as the movement of a polarizable particle in a non-uniform electric field. 6 In the case of biological cells, the DEP force applied on the cell is function of its polarizability, which depends on its membrane and cytoplasmic electrical properties, as well as its size, on the electrical properties of the medium and on the applied electric field (amplitude, gradient and frequency). The cell response to the electric field is very specific and can allow differentiation of cells even with similar shape or size without requiring biochemical or magnetic labeling.…”