Dielectrophoresis (DEP) is a label-free, accurate, fast, low-cost diagnostic technique that uses the principles of polarization and the motion of bioparticles in applied electric fields. This technique has been proven to be beneficial in various fields, including environmental research, polymer research, biosensors, microfluidics, medicine and diagnostics. Biomedical science research is one of the major research areas that could potentially benefit from DEP technology for diverse applications. Nevertheless, many medical science research investigations have yet to benefit from the possibilities offered by DEP. This paper critically reviews the fundamentals, recent progress, current challenges, future directions and potential applications of research investigations in the medical sciences utilizing DEP technique. This review will also act as a guide and reference for medical researchers and scientists to explore and utilize the DEP technique in their research fields.

This paper introduces a dielectrophoretic system for the manipulation and separation of microparticles. The system is composed of five layers and utilizes microarray dot electrodes. We validated our system by conducting size-dependent manipulation and separation experiments on 1, 5 and 15 μm polystyrene particles. Our findings confirm the capability of the proposed device to rapidly and efficiently manipulate and separate microparticles of various dimensions, utilizing positive and negative dielectrophoresis (DEP) effects. Larger size particles were repelled and concentrated in the center of the dot by negative DEP, while the smaller sizes were attracted and collected by the edge of the dot by positive DEP.

Dielectrophoresis (DEP), the induced movement of dielectric particles placed in a nonuniform electric field, has been used as a potential technique for manipulation and separation of many biological samples without destructive consequences to the cell. Cells of the same genotype in different physiological and pathological states have unique morphological and structural features, therefore, it is possible to differentiate between them using their DEP responses. This paper reports the experimental discrimination of normal and dengue-infected human hepatic fetal epithelial cells (WRL-68 cells) based on their DEP crossover frequency, at which no resultant movement occurs in the cells in response to the DEP force. A microarray dot electrode was used to conduct the DEP experiments. The DEP forces applied to the cells were quantified by analyzing the light intensity shift within the electrode's dot region based on the Cumulative Modal Intensity Shift image analysis technique. The differences in dielectric properties between infected and uninfected cells were exploited by plotting a unique DEP spectrum for each set of cells. We observed that the crossover frequency decreased from 220 kHz for the normal WRL-68 cells to 140 kHz after infection with the dengue virus in a medium conductivity of 100 μS/cm. We conclude that the change in the DEP crossover frequency between dengue-infected cells and their healthy counterparts should allow direct characterization of these cell types by exploiting their electrophysiological properties.

During the last three decades; dielectrophoresis (DEP) has become a vital tool for cell manipulation and characterization due to its non-invasiveness. It is very useful in the trend towards point-of-care systems. Currently, most efforts are focused on using DEP in biomedical applications, such as the spatial manipulation of cells, the selective separation or enrichment of target cells, high-throughput molecular screening, biosensors and immunoassays. A significant amount of research on DEP has produced a wide range of microelectrode configurations. In this paper; we describe the microarray dot electrode, a promising electrode geometry to characterize and manipulate cells via DEP. The advantages offered by this type of microelectrode are also reviewed. The protocol for fabricating planar microelectrodes using photolithography is documented to demonstrate the fast and cost-effective fabrication process. Additionally; different state-of-the-art Lab-on-a-Chip (LOC) devices that have been proposed for DEP applications in the literature are reviewed. We also present our recently designed LOC device, which uses an improved microarray dot electrode configuration to address the challenges facing other devices. This type of LOC system has the capability to boost the implementation of DEP technology in practical settings such as clinical cell sorting, infection diagnosis, and enrichment of particle populations for drug development.

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In this paper, three-dimensional (3D) porous carbon interdigitated electrode arrays (IDEAs) are developed utilizing standard photolithography of electrospun mats of SU-8 photoresist nanofibers. Porous IDEAs have the potential to produce higher aspect ratio than non-porous electrode due to the reduced stress at the interface between the substrate and the carbon structure [1]. In a first step, a layer of polymeric nanofibers is deposited on a silicon substrate by optimizing the conditions for far-field electrospinning of SU-8 photoresist. Subsequently, the SU-8 mat is patterned using conventional photolithography to generate the polymer precursor for the carbon electrode structure. Finally, the polymer precursor is pyrolysed at 900°C in an inert atmosphere to produce a porous carbon IDEA [2]. The porous carbon IDEAs were optimized as a function of the nanofibers diameter, thickness of the electrospun SU-8 mat and width/gap ratio of the IDEAs. To characterize the porous carbon IDEAs, electrochemistry studies (cyclic voltammetry and electrical impedance spectroscopy) were conducted and the results were compared with traditional flat carbon IDEAs (the latter was fabricated by spin coating a non-porous SU-8 film on a silicon substrate).  The redox amplification factor of both porous and flat carbon IDEAs was studied to gain an understanding of the effect of electrode porosity on the redox amplification. This factor was optimized for width and gap of the IDEAs and the nanofibers diameter.   Acknowledgments This research is supported by Flagship grant project number FL001A-14AET, Transdisiplinary Research Grant Scheme (TRGS TR002A-2014B) from University of Malaya and Ministry of Science Technology and Innovation (MOSTI) Science Fund (SF-020-2014).   References 1.         Sharma, C.S., A. Sharma, and M. Madou, Multiscale carbon structures fabricated by direct micropatterning of electrospun mats of SU-8 photoresist nanofibers. Langmuir, 2010. 26(4): p. 2218-2222. 2.         Kamath, R.R. and M.J. Madou, Three-Dimensional Carbon Interdigitated Electrode Arrays for Redox-Amplification. Analytical chemistry, 2014. 86(6): p. 2963-2971.