Influence of the filter grain morphology on separation efficiency in dielectrophoretic filtration

Recovery of noble materials from waste is essential for industries around the globe. Dielectrophoretic (DEP) filtration, an electrically switchable particle separation technique, can be applied to tackle this challenge. It is highly selective regarding particle size, material or shape. Expanding the scope of DEP towards high throughput and improving the trapping efficiency are vital to make DEP a viable robust alternative to conventional separation methods. DEP filtration works by selective immobilisation of particles in a porous medium by the action of an inhomogeneous electric field. The field inhomogeneity comes from scattering an electric field at the phase boundary between the particle suspension and the filter surface. In this article, we show how the filter structure affects the DEP separation. We study fixed bed filters of three different grain types and find that the morphology of the grains highly influences the DEP filter efficiency. Specifically, grains with irregular surface structure and high perceived angularity show high separation efficiency. We believe these insights into the design of DEP filtration will pave the way towards its application in, for example, the recovery of valuable materials from electronic waste dust.

A correlation of conductivity medium and bioparticle viability on dielectrophoresis-based biomedical applications

Dielectrophoresis (DEP) bioparticle research has progressed from micro to nano levels. It has proven to be a promising and powerful cell manipulation method with an accurate, quick, inexpensive, and label-free technique for therapeutic purposes. DEP, an electrokinetic phenomenon, induces particle movement as a result of polarization effects in a nonuniform electrical field. This review focuses on current research in the biomedical field that demonstrates a practical approach to DEP in terms of cell separation, trapping, discrimination, and enrichment under the influence of the conductive medium in correlation with bioparticle viability. The current review aims to provide readers with an in-depth knowledge of the fundamental theory and principles of the DEP technique, which is influenced by conductive medium and to identify and demonstrate the biomedical application areas. The high conductivity of physiological fluids presents obstacles and opportunities, followed by bioparticle viability in an electric field elaborated in detail. Finally, the drawbacks of DEP-based systems and the outlook for the future are addressed. This article will aid in advancing technology by bridging the gap between bioscience and engineering. We hope the insights presented in this review will improve cell suspension medium and promote DEP-viable bioparticle manipulation for health-care diagnostics and therapeutics.

Detection of Rare Objects by Flow Cytometry: Imaging, Cell Sorting, and Deep Learning Approaches

Flow cytometry nowadays is among the main working instruments in modern biology paving the way for clinics to provide early, quick, and reliable diagnostics of many blood-related diseases. The major problem for clinical applications is the detection of rare pathogenic objects in patient blood. These objects can be circulating tumor cells, very rare during the early stages of cancer development, various microorganisms and parasites in the blood during acute blood infections. All of these rare diagnostic objects can be detected and identified very rapidly to save a patient's life. This review outlines the main techniques of visualization of rare objects in the blood flow, methods for extraction of such objects from the blood flow for further investigations and new approaches to identify the objects automatically with the modern deep learning methods.

Thermal Shock Response of Yeast Cells Characterised by Dielectrophoresis Force Measurement

Dielectrophoresis is an electric force experienced by particles subjected to non-uniform electric fields. Recently, several technologies have been developed focused on the use of dielectrophoretic force (DEP) to manipulate and detect cells. On the other hand, there is no such great development in the field of DEP-based cell discrimination methods. Despite the demand for methods to differentiate biological cell states, most DEP developed methods have been focused on differentiation through geometric parameters. The novelty of the present work relies upon the point that a DEP force cell measurement is used as a discrimination method, capable of detecting heat killed yeast cells from the alive ones. Thermal treatment is used as an example of different biological state of cells. It comes from the fact that biological properties have their reflection in the electric properties of the particle, in this case a yeast cell. To demonstrate such capability of the method, 279 heat-killed cells were measured and compared with alive cells data from the literature. For each cell, six speeds were taken at different points in its trajectory inside a variable non-uniform electric field. The electric parameters in cell wall conductivity, cell membrane conductivity, cell membrane permittivity of the yeast cell from bibliography explains the DEP experimental force measured. Finally, alive and heat-treated cells were distinguished based on that measure. Our results can be explained through the well-known damage of cell structure characteristics of heat-killed cells.

Highlighting the uniqueness in dielectrophoretic enrichment of circulating tumor cells

Circulating tumor cells (CTCs) play an essential role in the metastasis of tumors, and thus can serve as a valuable prognostic factor for malignant diseases. As a result, the ability to isolate and characterize CTCs is essential. This review underlines the potential of dielectrophoresis for CTCs enrichment. It begins by summarizing the key performance parameters and challenges of CTCs isolation using microfluidics. The two main categories of CTCs enrichment-affinity-based and label-free methods-are analysed, emphasising the advantages and disadvantages of each as well as their clinical potential. While the main argument in favour of affinity-based methods is the strong specificity of CTCs isolation, the major advantage of the label-free technologies is in preserving the integrity of the cellular membrane, an essential requirement for downstream characterization. Moving forward, we try to answer the main question: "What makes dielectrophoresis a method of choice in CTCs isolation?" The uniqueness of dielectrophoretic CTCs enrichment resides in coupling the specificity of the isolation process with the conservation of the membrane surface. The specificity of the dielectrophoretic method stems from the differences in the dielectric properties between CTCs and other cells in the blood: the capacitances of the malignantly transformed cellular membranes of CTCs differ from those of other cells. Examples of dielectrophoretic devices are described and their performance evaluated. Critical requirements for using dielectrophoresis to isolate CTCs are highlighted. Finally, we consider that DEP has the potential of becoming a cytometric method for large-scale sorting and characterization of cells.

On the recent developments of insulator-based dielectrophoresis: A review

Insulator-based dielectrophoresis (iDEP), also known as electrodeless DEP, has become a well-known dielectrophoretic technique, no longer viewed as a new methodology. Significant advances on iDEP have been reported during the last 15 years. This review article aims to summarize some of the most important findings on iDEP organized by the type of dielectrophoretic mode: streaming and trapping iDEP. The former is primarily used for particle sorting, while the latter has great capability for particle enrichment. The characteristics of a wide array of devices are discussed for each type of dielectrophoretic mode in order to present an overview of the distinct designs and applications developed with iDEP. A short section on Joule heating effects and electrothermal flow is also included to highlight some of the challenges in the utilization of iDEP systems. The significant progress on iDEP illustrates its potential for a large number of applications, ranging from bioanalysis to clinical and biomedical assessments. The present article discusses the work on iDEP by numerous research groups around the world, with the aim of proving the reader with an overview of the state-of-the-art in iDEP microfluidic systems.