Search Results (86)

Cancers are diseases described by the irregular spread of cells that have developed invasive features, enabling them to invade adjacent tissues. The specific diagnosis and effective management of oncological treatments depend on the timely detection of circulating tumor cells (CTCs) in a patient’s bloodstream. One of the most promising approaches to CTC separation from blood fractions involves the dielectrophoresis (DEP) technique. This research presents a new DEP-based bionic system designed for MDA-MB-231 breast cancer cell isolation from white blood cell (WBC) subtypes with a viable approach to cell viability. This work leverages the principle that every cell type possesses a unique dielectric fingerprint. This dielectrophoresis microfluidic device is designed to act as a scanner, reading these fingerprints to achieve a continuous, label-free separation of cancer cells from blood components with a high efficiency. In the proposed system that consists of three different stages, the first stage allows for separating B-lymphocytes and Monocytes from Granulocytes and MDA-MB-231 cells. The separation of B-lymphocytes from Monocytes occurs in the second step, while the last step concerns the separation of Granulocytes and MDA-MB-231 cells. In the analysis, x-y graphs of the electric potentials, velocity fields, pressure distributions, and cellular DEP forces applied to the cells, as well as the resulting particle paths, are provided. The model predicts that the system operates with a separation efficiency of nearly 92%. This work focuses on an investigation of the impact of electrode potentials, the velocity of cells, the number of electrodes, the width of the channel, and the output angles on enhancing the separation efficiency of particles. Full article

Dielectrophoresis (DEP) has been used for decades to estimate the passive electrical properties of cells. However, the body of work on cell electrophysiology derived from Clausius–Mossotti analysis of DEP-derived data pales to insignificance against the wider backdrop of cell electrophysiology based on the Goldman–Hodgkin–Katz equation measured by patch clamp, which focuses on membrane potential V_m—a parameter which does not appear in the Clausius–Mossotti model—and values of patch clamp-derived membrane conductance which, shorn of double-layer conductivity, are often orders of magnitude lower than those derived from DEP. Conversely, the body of work on DEP analysis is more substantial than that reporting the electrical properties of the extracellular (ζ) potential. To address this, several studies have recently been published into the interconnections between the electrical properties determined by the Clausius–Mossotti model, V_m, and ζ-potential, which analyzed the effect of varying the suspending medium conductivity over a wide range, from below 50 mSm⁻¹ to above 1.5 Sm⁻¹. The results of these studies identified relationships between the cytoplasm conductivity, V_m, membrane conductance and capacitance, surface conductance, whole-cell resistance, and ζ-potential. Significantly, many of these relationships only become apparent when analyzed as a function of the conductivity of the suspending medium. This paper assembles these interconnections, using several separate studies approaching different parameter connections, to draw together a set of equations which collectively form a “cellular electrome”. This demonstrates that analysis of the Clausius–Mossotti factor across multiple conductivities allows determination of not only passive electrical properties, but also the membrane and ζ-potential, and accurately predicts DEP behavior at higher conductivity for the first time. Full article

Driven by the growing demand for sustainable resource utilization, the recovery of valuable constituents from spent lithium-ion batteries (LIBs) has attracted considerable attention, whereas conventional recycling processes remain energy-intensive, inefficient, and environmentally detrimental. Herein, an efficient and environmentally benign separation strategy integrating dielectrophoresis (DEP) and magnetophoresis (MAP) is proposed for isolating the primary components of “black mass” from spent LIBs, i.e., lithium iron phosphate (LFP) and graphite microparticles. A coupled electric–magnetic–fluid dynamic model is established to predict particle motion behavior, and a custom-designed microparticle separator is developed for continuous LFP–graphite separation. Numerical simulations are performed to analyze microparticle trajectories under mutual effects of DEP and MAP and to evaluate the feasibility of binary separation. Structural optimization revealed that the optimal separator configuration comprised an electrode spacing of 2 mm and a ferromagnetic body length of 5 mm with 3 mm spacing. Additionally, a numerical study also found that an auxiliary flow velocity ratio of 3 resulted in the best particle focusing effect. Furthermore, the effects of key operational parameters, including electric and magnetic field strengths and flow velocity, on particle migration were systematically investigated. The findings revealed that these factors significantly enhanced the lateral migration disparity between LFP and graphite within the separation channel, thereby enabling complete separation of LFP particles with high purity and recovery under optimized conditions. Overall, this study provides a theoretical foundation for the development of high-performance and environmentally sustainable LIBs recovery technologies. Full article

Electric fields (EFs) have emerged as effective, non-chemical tools for modulating microbial populations in complex matrices such as wastewater. This review consolidates current advances on EF-induced alterations in microbial structures and functions, focusing on both vegetative cells and spores. Key parameters affected include membrane thickness, transmembrane potential, electrical conductivity, and dielectric permittivity, with downstream impacts on ion homeostasis, metabolic activity, and viability. Such bioelectrical modifications underpin EF-based detection methods—particularly impedance spectroscopy and dielectrophoresis—which enable rapid, label-free, in situ microbial monitoring. Beyond detection, EFs can induce sublethal or lethal effects, enabling selective inactivation without chemical input. This review addresses the influence of field type (DC, AC, pulsed), intensity, and exposure duration, alongside limitations such as species-specific variability, heterogeneous environmental conditions, and challenges in achieving uniform field distribution. Emerging research highlights the integration of EF-based platforms with biosensors, machine learning, and real-time analytics for enhanced environmental surveillance. By linking microbiological mechanisms with engineering solutions, EF technologies present significant potential for sustainable water quality management. Their multidisciplinary applicability positions them as promising components of next-generation wastewater monitoring and treatment systems, supporting global efforts toward efficient, adaptive, and environmentally benign microbial control strategies. Full article

In practical dielectrophoretic cell interaction experiments, cells do not always exhibit circular or rod-like shapes, making the study of dielectrophoretic interactions among irregularly shaped particles of significant importance. We established a mathematical model for curved particles to analyze their mutual dielectrophoretic interactions, incorporating particle deformability by varying their shear modulus, and employed the arbitrary Lagrangian–Eulerian method to describe particle motion and deformation. The results demonstrate that under the influence of a direct current electric field, curved particles undergo rotation, deformation, and mutual attraction due to dielectrophoresis, eventually forming a stable alignment parallel to the applied electric field. Adjusting the electric field strength effectively modulates the interaction intensity and movement velocity between particles. This study elucidates the fundamental principles governing dielectrophoretic interactions among deformable curved particles in DC electric fields, providing theoretical guidance for dielectrophoretic manipulation experiments involving biological cells, metallic particles, and other entities under DC electric fields. Full article

Dielectrophoresis (DEP) has been widely employed in microfluidic platforms for particle or cell manipulation in biomedical science applications due to its accurate, fast, label-free, and low-cost diagnostic technique. However, the application of the DEP technique towards protein manipulation has yet to be extensively explored due to the challenges of the complexity of protein itself, such as its complex morphologies, extremely minuscule particle size, inherent electrical properties, and temperature sensitivity, which make it relatively more challenging. Furthermore, given that protein DEP investigation requires entering the micro- to nano-scale level of DEP configuration, various challenging factors such as electrohydrodynamic effects, electrolysis, joule heating, and electrothermal force that emerge will make it more difficult in realizing protein DEP investigation. This review study has discussed the fundamental theory of DEP and considerations toward protein DEP manipulation. In particular, it focused on the DEP theoretical principle towards protein, protein DEP application challenges, microfluidic platform considerations, medium considerations, and a critically reviewed list of protein bioparticles that have been investigated were all highlighted. Full article

The precise preparation and application of nanomicrospheres is currently an emerging research hotspot in the cutting-edge cross-disciplines. As an important functional material, nanosized microspheres show a broad application prospect in biomedicine, chemical engineering, materials science, and other fields. However, microspheres with good monodispersity are still facing technical bottlenecks, such as complicated preparation process and high cost. In this study, a multistage cyclic dielectrophoresis (MC-DEP) technique is innovatively proposed to successfully realize the high-resolution sorting of submicron microspheres. A dielectrophoresis chip adopts a unique electrode design, in which the electrodes are arranged at the top and bottom of the microchannel at the same time. This symmetric electrode structure effectively eliminates the difference in the distribution of dielectrophoretic force in the perpendicular direction and ensures the homogeneity of the initial state of particle sorting. Three pairs of focusing electrodes are in the front section of the microchannel for preaggregation of the microspheres, and the deflection electrodes in the back section are to realize particle size sorting. After this, the upper and lower limits of particle size are limited by multiple cycles of sorting. The multistage cyclic sorting increases the stability of particle deflection under dielectrophoretic forces and reduces the error perturbation caused by the fluid environment. The experimental results show that the multistage cycling sorting scheme significantly improves the monodispersity of the microspheres, and the coefficient of variation of the particle size is significantly reduced from the initial 12.3% to 5.4% after three cycles of sorting, which fully verifies the superior performance of this technology. Full article

This paper presents a novel microfluidic device that integrates dielectrophoresis (DEP) forces with a membrane filter to concentrate and trap microparticles in a narrow region for enhanced optical analysis. The device combines the broad particle capture capability of a membrane filter with the precision of DEP to focus particles in regions optimized for optical measurements. The device features transparent indium tin oxide (ITO) top electrodes on a glass substrate and gold (Au) bottom electrodes patterned on a small area of the membrane filter, with spacers to control the gaps between the electrodes. This configuration enables precise particle concentration at a specific location and facilitates real-time optical detection. Experiments using 0.8 μm fluorescent polystyrene (PS) beads and Escherichia coli (E. coli) bacteria demonstrated effective particle trapping and concentration, with fluorescence intensity increasing proportionally to particle concentration. The application of DEP forces in a small region of the membrane filter resulted in a significant enhancement of fluorescence intensity, showcasing the effectiveness of the DEP-enhanced design for improving particle concentration and optical measurement sensitivity. The device also showed promising potential for bacterial detection, particularly with E. coli, by achieving a linear increase in fluorescence intensity with increasing bacterial concentration. These results highlight the device’s potential for precise and efficient microparticle concentration and detection. Full article

On-chip gene synthesis has the potential to improve the synthesis throughput and reduce the cost exponentially. While there exist several microarray-based oligo synthesis technologies, on-chip gene assembly has yet to be demonstrated. This work introduces a novel on-chip DNA assembly method via dielectrophoresis (DEP) that can potentially be integrated with microarray-based oligo synthesis on the same chip. Our DEP chip can selectively manipulate oligos and guide their movement without perturbing the surrounding fluid medium, thus aiding in DNA assembly. Helical forked electrode design has been optimized for compatibility with DEP, ensuring efficient control over target oligos. By applying an alternating current signal set at 2 MHz, we successfully achieve the desired directed movement of oligonucleotides. Additionally, chemical treatments combined with photoirradiation enabled the connection of complementary gene sequences and the subsequent release of single-stranded DNA products. Sequencing results validate the effective assembly of DNA fragments, approximately 500 base pairs in length, using our DEP device. Full article

Dielectrophoresis (DEP) cell separation technology is an effective means of separating target cells which are only marginally present in a wide variety of cells. To develop highly efficient cell separation devices, detailed analysis of the nonuniform electric field’s intensity distribution within the device is needed, as it affects separation performance. Here we analytically expressed the distributions of the electric field and DEP force in a parallel-plate cell separation DEP device by employing electrostatic analysis through the Fourier series method. The solution was approximated by extrapolating a novel approximate equation as a boundary condition for the potential between adjacent fingers of interdigitated electrodes and changing the underlying differential equation into a solvable form. The distributions of the potential and electric fields obtained by the analytical solution were compared with those from numerical simulations using finite element method software to verify their accuracy. As a result, it was found that the two agreed well, and the analytical solution was obtained with good accuracy. Three-dimensional fluorescence imaging analysis was performed using live non-tumorigenic human mammary (MCF10A) cells. The distribution of cell clusters adsorbed on the interdigitated electrodes was compared with the analytically obtained distribution of the DEP force, and the mechanism underlying cell adsorption on the electrode surface was discussed. Furthermore, parametric analysis using the width and spacing of these electrodes as variables revealed that spacing is crucial for determining DEP force. The results suggested that for cell separation devices using interdigitated electrodes, optimization by adjusting electrode spacing could significantly enhance device performance. Full article

Prostate cancer (PCa) remains a significant health threat, with chemoresistance and recurrence posing major challenges despite advances in treatment. The epithelial to mesenchymal transition (EMT), a biochemical process where cells lose epithelial features and gain mesenchymal traits, is linked to chemoresistance and metastasis. Electrical impedance spectroscopy (EIS), a novel label-free electrokinetic technique, offers promise in detecting cell phenotype changes. In this study, we employed EIS to detect EMT in prostate cancer cells (PCCs). PC3, DU145, and LNCaP cells were treated with EMT induction media for five days. EIS characterization revealed unique impedance spectra correlating with metastatic potential, distinguishing DU145 EMT+ and EMT− cells, and LNCaP EMT+ and EMT− cells (in combination with dielectrophoresis), with comparisons made to epithelial and mesenchymal controls. These changes were supported by shifts in electrical signatures, morphologies, and protein expression, including the downregulation of E-cadherin and upregulation of vimentin. No phenotype change was observed in PC3 cells, which maintained a mesenchymal phenotype. EMT+ cells were also distinguishable from mixtures of EMT+ and EMT− cells. This study demonstrates key advancements: the application of EIS and dielectrophoresis for label-free EMT detection in PCCs, characterization of cell electrical signatures after EMT, and EIS sensitivity to EMT transitions. Detecting EMT in PCa is important to the development of more effective treatments and overcoming the challenges of chemoresistance. Full article

Surface plasmon resonance (SPR) has been extensively employed in biological sensing, environmental detection, as well as chemical industry. Nevertheless, the performance possessed by conventional surface plasmon resonance (SPR) biosensors can be further limited by the transport of analyte molecules to the sensing surface, noteworthily when small molecules or low levels of substances are being detected. In this study, a rapid and highly sensitive SPR biosensor is introduced to enhance the ability of the target analytes’ collection by integrating AC electroosmosis (ACEO) and dielectrophoresis (DEP). Both the above-mentioned phenomena principally arise from the generation of the AC electric fields. This generation can be tailored by shaping the interdigitated electrodes (IDEs) that also serve as the SPR biomarker sensing area. The effects exerted by different parameters (e.g., the frequency and voltage of the AC electric field as well as microelectrode structures) are considered in the iSPR (interdigitated SPR) biosensor operation, and the iSPR biosensors are optimized with the sensitivity. The results of this study confirm that the iSPR can efficiently concentrate small molecules into the SPR sensing area, such that SPR reactions achieve an order of magnitude increase, and the detection time is shortened. The rapid and sensitive sensor takes on critical significance in the development of on-site diagnostics in a wide variety of human and animal health applications. Full article

The manipulation of single particles remains a topic of interest with many applications. Here we characterize the impact of selected parameters on the motion of single particles thanks to dielectrophoresis (DEP) induced by visible light, in a technique called Light-induced Dielectrophoresis, or LiDEP, also known as optoelectronic tweezers, optically induced DEP, and image-based DEP. Baker’s yeast and Candida cells are exposed to an electric field gradient enabled by shining a photoconductive material with a specific pattern of visible light, and their response is measured in terms of the average cell velocity towards the gradient. The impact on cell velocity when varying the shape and color of the light pattern, as well as the distance from the cell to the pattern, is presented. The experimental setup featured a commercial light projector featuring digital light processing (DLP) technology but mechanically modified to accommodate a 40× microscope objective lens. The minimal resolution achieved on the light pattern was 8 µm. Experimental results show the capability for single cell manipulation and the possibility of using different shapes, colors, and distances to determine the average cell velocity. Full article

This paper presents a novel microfluidic dielectrophoresis (DEP) system to focus and separate cells of similar size based on their structural differences, which is more challenging than separation by size. Because, in this case, the DEP force is only proportional to the polarizabilities of cells, we used live and dead yeast cells as bio-particles to investigate the chip efficiency. Our designed chip consists of three sections. First, we focused on cells at the center of the microchannel by employing a negative DEP phenomenon. After that, cells were separated due to the different deflection from high-electric-field areas. Finally, a novel outlet design was utilized to facilitate separation by increasing the gap between the two groups of cells. The proposed sheath-free design has one inlet for target cell injection requiring only one pump to control the flow rate, which reduces costs and complexity. Successful discrimination of the particles was achieved by using DEP force as a label-free and highly efficient technique. As an accessible and cost-effective method, soft lithography with a 3D-printed resin mold was used to fabricate the microfluidic parts. The microchannel was made of polydimethylsiloxane (PDMS) material that is biocompatible. The electrodes were made of gold due to its biocompatibility and non-oxidation, and a titanium layer was sputtered as the buffer layer for the adhesion of the sputtered gold layer to the glass. A standard microfabrication process was employed to create the electrode pattern. O₂ plasma treatment yielded leakage-free bonding between the patterned glass and PDMS structure containing the microfluidic channel. The maximum voltage applied to the electrodes (26 V) was lower than the threshold value for cell electroporation. The simulations and experimental results both confirm the effectiveness of the proposed microfluidic chip. Full article

Dielectrophoresis (DEP), a precision nonlinear electrokinetic tool utilized within microfluidic devices, can induce bioparticle polarization that manifests as motion in the electric field; this phenomenon has been leveraged for phenotypic cellular and biomolecular detection, making DEP invaluable for diagnostic applications. As device operation times lengthen, reproducibility and precision decrease, which has been postulated to be caused by ion gradients within the supporting electrolyte medium. This research focuses on characterizing pH gradients above, at, and below the electrode charging frequency (0.2–1.4 times charging frequency) in an aqueous electrolyte solution in order to extend the parameter space for which microdevice-imposed artifacts on cells in clinical diagnostic devices have been characterized. The nonlinear alternating current (AC) electric fields (0.07 V_pp/μm) required for DEP were generated via planar T-shaped and star-shaped microelectrodes overlaid by a 70 μm high microfluidic chamber. The experiments were designed to quantify pH changes temporally and spatially in the two microelectrode geometries. In parallel, a 50 nm hafnium oxide (HfO₂) thin film on the microelectrodes was tested to provide insights into the role of Faradaic surface reactions on the pH. Electric field simulations were conducted to provide insights into the gradient shape within the microelectrode geometries. Frequency dependence was also examined to ascertain ion electromigration effects above, at, and below the electrode charging frequency. The results revealed Faradaic reactions above, at, and below the electrode charging frequency. Comparison experiments further demonstrated that pH changes caused by Faradaic reactions increased inversely with frequency and were more pronounced in the star-shaped geometry. Finally, HfO₂ films demonstrated frequency-dependent properties, impeding Faradaic reactions. Full article