Editorial

3 pages, 166 KiB

Open AccessEditorial

Editorial for the Special Issue on Micromachines for Dielectrophoresis

by Rodrigo Martinez-Duarte

Micromachines 2022, 13(3), 417; https://doi.org/10.3390/mi13030417 - 08 Mar 2022

Viewed by 1619

Dielectrophoresis (DEP) remains an effective technique for the label-free identification and manipulation of targeted particles ranging from inert particles to biomolecules and cells [...] Full article

(This article belongs to the Special Issue Micromachines for Dielectrophoresis)

Research

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20 pages, 2799 KiB

Open AccessArticle

Analytical Guidelines for Designing Curvature-Induced Dielectrophoretic Particle Manipulation Systems

by Akshay Kale, Amirreza Malekanfard and Xiangchun Xuan

Micromachines 2020, 11(7), 707; https://doi.org/10.3390/mi11070707 - 21 Jul 2020

Cited by 9 | Viewed by 3349

Abstract

Curvature-induced dielectrophoresis (C-iDEP) is an established method of applying electrical energy gradients across curved microchannels to obtain a label-free manipulation of particles and cells. This method offers several advantages over the other DEP-based methods, such as increased chip area utilisation, simple fabrication, reduced [...] Read more.

Curvature-induced dielectrophoresis (C-iDEP) is an established method of applying electrical energy gradients across curved microchannels to obtain a label-free manipulation of particles and cells. This method offers several advantages over the other DEP-based methods, such as increased chip area utilisation, simple fabrication, reduced susceptibility to Joule heating and reduced risk of electrolysis in the active region. Although C-iDEP systems have been extensively demonstrated to achieve focusing and separation of particles, a detailed mathematical analysis of the particle dynamics has not been reported yet. This work computationally confirms a fully analytical dimensionless study of the electric field-induced particle motion inside a circular arc microchannel, the simplest design of a C-iDEP system. Specifically, the analysis reveals that the design of a circular arc microchannel geometry for manipulating particles using an applied voltage is fully determined by three dimensionless parameters. Simple equations are established and numerically confirmed to predict the mutual relationships of the parameters for a comprehensive range of their practically relevant values, while ensuring design for safety. This work aims to serve as a starting point for microfluidics engineers and researchers to have a simple calculator-based guideline to develop C-iDEP particle manipulation systems specific to their applications. Full article

(This article belongs to the Special Issue Micromachines for Dielectrophoresis)

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12 pages, 2141 KiB

Open AccessArticle

Highly Localized Enrichment of Trypanosoma brucei Parasites Using Dielectrophoresis

by Devin Keck, Callie Stuart, Josie Duncan, Emily Gullette and Rodrigo Martinez-Duarte

Micromachines 2020, 11(6), 625; https://doi.org/10.3390/mi11060625 - 26 Jun 2020

Cited by 6 | Viewed by 3150

Abstract

Human African trypanosomiasis (HAT), also known as sleeping sickness, is a vector-borne neglected tropical disease endemic to rural sub-Saharan Africa. Current methods of early detection in the affected rural communities generally begin with general screening using the card agglutination test for trypanosomiasis (CATT), [...] Read more.

Human African trypanosomiasis (HAT), also known as sleeping sickness, is a vector-borne neglected tropical disease endemic to rural sub-Saharan Africa. Current methods of early detection in the affected rural communities generally begin with general screening using the card agglutination test for trypanosomiasis (CATT), a serological test. However, the gold standard for confirmation of trypanosomiasis remains the direct observation of the causative parasite, Trypanosoma brucei. Here, we present the use of dielectrophoresis (DEP) to enrich T. brucei parasites in specific locations to facilitate their identification in a future diagnostic assay. DEP refers to physical movement that can be selectively induced on the parasites when exposing them to electric field gradients of specific magnitude, phase and frequency. The long-term goal of our work is to use DEP to selectively trap and enrich T. brucei in specific locations while eluting all other cells in a sample. This would allow for a diagnostic test that enables the user to characterize the presence of parasites in specific locations determined a priori instead of relying on scanning a sample. In the work presented here, we report the characterization of the conditions that lead to high enrichment, 780% in 50 s, of the parasite in specific locations using an array of titanium microelectrodes. Full article

(This article belongs to the Special Issue Micromachines for Dielectrophoresis)

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22 pages, 7914 KiB

Open AccessArticle

Protein Dielectrophoresis: I. Status of Experiments and an Empirical Theory

by Ralph Hölzel and Ronald Pethig

Micromachines 2020, 11(5), 533; https://doi.org/10.3390/mi11050533 - 22 May 2020

Cited by 37 | Viewed by 3615

Abstract

The dielectrophoresis (DEP) data reported in the literature since 1994 for 22 different globular proteins is examined in detail. Apart from three cases, all of the reported protein DEP experiments employed a gradient field factor

\nabla E_{m}^{2}

that is much smaller [...] Read more.

The dielectrophoresis (DEP) data reported in the literature since 1994 for 22 different globular proteins is examined in detail. Apart from three cases, all of the reported protein DEP experiments employed a gradient field factor

\nabla E_{m}^{2}

that is much smaller (in some instances by many orders of magnitude) than the ~4 × 10²¹ V²/m³ required, according to current DEP theory, to overcome the dispersive forces associated with Brownian motion. This failing results from the macroscopic Clausius–Mossotti (CM) factor being restricted to the range 1.0 > CM > −0.5. Current DEP theory precludes the protein’s permanent dipole moment (rather than the induced moment) from contributing to the DEP force. Based on the magnitude of the β-dispersion exhibited by globular proteins in the frequency range 1 kHz–50 MHz, an empirically derived molecular version of CM is obtained. This factor varies greatly in magnitude from protein to protein (e.g., ~37,000 for carboxypeptidase; ~190 for phospholipase) and when incorporated into the basic expression for the DEP force brings most of the reported protein DEP above the minimum required to overcome dispersive Brownian thermal effects. We believe this empirically-derived finding validates the theories currently being advanced by Matyushov and co-workers. Full article

(This article belongs to the Special Issue Micromachines for Dielectrophoresis)

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17 pages, 25542 KiB

Open AccessArticle

Dielectrophoretic Immobilization of Yeast Cells Using CMOS Integrated Microfluidics

by Honeyeh Matbaechi Ettehad, Pouya Soltani Zarrin, Ralph Hölzel and Christian Wenger

Micromachines 2020, 11(5), 501; https://doi.org/10.3390/mi11050501 - 15 May 2020

Cited by 17 | Viewed by 3235

Abstract

This paper presents a dielectrophoretic system for the immobilization and separation of live and dead cells. Dielectrophoresis (DEP) is a promising and efficient investigation technique for the development of novel lab-on-a-chip devices, which characterizes cells or particles based on their intrinsic and physical [...] Read more.

This paper presents a dielectrophoretic system for the immobilization and separation of live and dead cells. Dielectrophoresis (DEP) is a promising and efficient investigation technique for the development of novel lab-on-a-chip devices, which characterizes cells or particles based on their intrinsic and physical properties. Using this method, specific cells can be isolated from their medium carrier or the mixture of cell suspensions (e.g., separation of viable cells from non-viable cells). Main advantages of this method, which makes it favorable for disease (blood) analysis and diagnostic applications are, the preservation of the cell properties during measurements, label-free cell identification, and low set up cost. In this study, we validated the capability of complementary metal-oxide-semiconductor (CMOS) integrated microfluidic devices for the manipulation and characterization of live and dead yeast cells using dielectrophoretic forces. This approach successfully trapped live yeast cells and purified them from dead cells. Numerical simulations based on a two-layer model for yeast cells flowing in the channel were used to predict the trajectories of the cells with respect to their dielectric properties, varying excitation voltage, and frequency. Full article

(This article belongs to the Special Issue Micromachines for Dielectrophoresis)

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15 pages, 9466 KiB

Open AccessArticle

Driving Waveform Design of Electrophoretic Display Based on Optimized Particle Activation for a Rapid Response Speed

by Wenyao He, Zichuan Yi, Shitao Shen, Zhenyu Huang, Linwei Liu, Taiyuan Zhang, Wei Li, Li Wang, Lingling Shui, Chongfu Zhang and Guofu Zhou

Micromachines 2020, 11(5), 498; https://doi.org/10.3390/mi11050498 - 14 May 2020

Cited by 22 | Viewed by 4032

Abstract

Electrophoretic displays (EPDs) have excellent paper-like display features, but their response speed is as long as hundreds of milliseconds. This is particularly important when optimizing the driving waveform for improving the response speed. Hence, a driving waveform design based on the optimization of [...] Read more.

Electrophoretic displays (EPDs) have excellent paper-like display features, but their response speed is as long as hundreds of milliseconds. This is particularly important when optimizing the driving waveform for improving the response speed. Hence, a driving waveform design based on the optimization of particle activation was proposed by analyzing the electrophoresis performance of particles in EPD pixels. The particle activation in the driving waveform was divided into two phases: the improving particle activity phase and the uniform reference grayscale phase. First, according to the motion characteristics of particles in improving the particle activity phase, the real-time EPD brightness value can be obtained by an optical testing device. Secondly, the derivative of the EPD brightness curve was used to obtain the inflection point, and the inflection point was used as the duration of improving particle activity phase. Thirdly, the brightness curve of the uniform reference grayscale phase was studied to set the driving duration for obtaining a white reference grayscale. Finally, a set of four-level grayscale driving waveform was designed and validated in a commercial E-ink EPD. The experimental results showed that the proposed driving waveform can cause a reduction by 180 ms in improving particle activity phase and 120 ms in uniform reference grayscale phase effectively, and a unified reference grayscale can be achieved in uniform reference grayscale phase at the same time. Full article

(This article belongs to the Special Issue Micromachines for Dielectrophoresis)

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13 pages, 3873 KiB

Open AccessArticle

Passive Dielectrophoretic Focusing of Particles and Cells in Ratchet Microchannels

by Song-Yu Lu, Amirreza Malekanfard, Shayesteh Beladi-Behbahani, Wuzhou Zu, Akshay Kale, Tzuen-Rong Tzeng, Yao-Nan Wang and Xiangchun Xuan

Micromachines 2020, 11(5), 451; https://doi.org/10.3390/mi11050451 - 25 Apr 2020

Cited by 16 | Viewed by 4303

Abstract

Focusing particles into a tight stream is critical for many microfluidic particle-handling devices such as flow cytometers and particle sorters. This work presents a fundamental study of the passive focusing of polystyrene particles in ratchet microchannels via direct current dielectrophoresis (DC DEP). We [...] Read more.

Focusing particles into a tight stream is critical for many microfluidic particle-handling devices such as flow cytometers and particle sorters. This work presents a fundamental study of the passive focusing of polystyrene particles in ratchet microchannels via direct current dielectrophoresis (DC DEP). We demonstrate using both experiments and simulation that particles achieve better focusing in a symmetric ratchet microchannel than in an asymmetric one, regardless of the particle movement direction in the latter. The particle focusing ratio, which is defined as the microchannel width over the particle stream width, is found to increase with an increase in particle size or electric field in the symmetric ratchet microchannel. Moreover, it exhibits an almost linear correlation with the number of ratchets, which can be explained by a theoretical formula that is obtained from a scaling analysis. In addition, we have demonstrated a DC dielectrophoretic focusing of yeast cells in the symmetric ratchet microchannel with minimal impact on the cell viability. Full article

(This article belongs to the Special Issue Micromachines for Dielectrophoresis)

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14 pages, 2920 KiB

Open AccessArticle

Frequency Response of Induced-Charge Electrophoretic Metallic Janus Particles

by Chong Shen, Zhiyu Jiang, Lanfang Li, James F. Gilchrist and H. Daniel Ou-Yang

Micromachines 2020, 11(3), 334; https://doi.org/10.3390/mi11030334 - 24 Mar 2020

Cited by 14 | Viewed by 4645

Abstract

The ability to manipulate and control active microparticles is essential for designing microrobots for applications. This paper describes the use of electric and magnetic fields to control the direction and speed of induced-charge electrophoresis (ICEP) driven metallic Janus microrobots. A direct current (DC) [...] Read more.

The ability to manipulate and control active microparticles is essential for designing microrobots for applications. This paper describes the use of electric and magnetic fields to control the direction and speed of induced-charge electrophoresis (ICEP) driven metallic Janus microrobots. A direct current (DC) magnetic field applied in the direction perpendicular to the electric field maintains the linear movement of particles in a 2D plane. Phoretic force spectroscopy (PFS), a phase-sensitive detection method to detect the motions of phoretic particles, is used to characterize the frequency-dependent phoretic mobility and drag coefficient of the phoretic force. When the electric field is scanned over a frequency range of 1 kHz–1 MHz, the Janus particles exhibit an ICEP direction reversal at a crossover frequency at ~30 kH., Below this crossover frequency, the particle moves in a direction towards the dielectric side of the particle, and above this frequency, the particle moves towards the metallic side. The ICEP phoretic drag coefficient measured by PFS is found to be similar to that of the Stokes drag. Further investigation is required to study microscopic interpretations of the frequency at which ICEP mobility switched signs and the reason why the magnitudes of the forward and reversed modes of ICEP are so different. Full article

(This article belongs to the Special Issue Micromachines for Dielectrophoresis)

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14 pages, 1787 KiB

Open AccessArticle

Selective Retrieval of Individual Cells from Microfluidic Arrays Combining Dielectrophoretic Force and Directed Hydrodynamic Flow

by Pierre-Emmanuel Thiriet, Joern Pezoldt, Gabriele Gambardella, Kevin Keim, Bart Deplancke and Carlotta Guiducci

Micromachines 2020, 11(3), 322; https://doi.org/10.3390/mi11030322 - 20 Mar 2020

Cited by 11 | Viewed by 4539

Abstract

Hydrodynamic-based microfluidic platforms enable single-cell arraying and analysis over time. Despite the advantages of established microfluidic systems, long-term analysis and proliferation of cells selected in such devices require off-chip recovery of cells as well as an investigation of on-chip analysis on cell phenotype, [...] Read more.

Hydrodynamic-based microfluidic platforms enable single-cell arraying and analysis over time. Despite the advantages of established microfluidic systems, long-term analysis and proliferation of cells selected in such devices require off-chip recovery of cells as well as an investigation of on-chip analysis on cell phenotype, requirements still largely unmet. Here, we introduce a device for single-cell isolation, selective retrieval and off-chip recovery. To this end, singularly addressable three-dimensional electrodes are embedded within a microfluidic channel, allowing the selective release of single cells from their trapping site through application of a negative dielectrophoretic (DEP) force. Selective capture and release are carried out in standard culture medium and cells can be subsequently mitigated towards a recovery well using micro-engineered hybrid SU-8/PDMS pneumatic valves. Importantly, transcriptional analysis of recovered cells revealed only marginal alteration of their molecular profile upon DEP application, underscored by minor transcriptional changes induced upon injection into the microfluidic device. Therefore, the established microfluidic system combining targeted DEP manipulation with downstream hydrodynamic coordination of single cells provides a powerful means to handle and manipulate individual cells within one device. Full article

(This article belongs to the Special Issue Micromachines for Dielectrophoresis)

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12 pages, 4393 KiB

Open AccessArticle

Driving Waveform Design of Electrowetting Displays Based on an Exponential Function for a Stable Grayscale and a Short Driving Time

by Zichuan Yi, Zhenyu Huang, Shufa Lai, Wenyao He, Li Wang, Feng Chi, Chongfu Zhang, Lingling Shui and Guofu Zhou

Micromachines 2020, 11(3), 313; https://doi.org/10.3390/mi11030313 - 16 Mar 2020

Cited by 32 | Viewed by 2829

Abstract

The traditional driving waveform of the electrowetting display (EWD) has many disadvantages, such as the large oscillation of the target grayscale aperture ratio and a long time for achieving grayscale. Therefore, a driving waveform based on the exponential function was proposed in this [...] Read more.

The traditional driving waveform of the electrowetting display (EWD) has many disadvantages, such as the large oscillation of the target grayscale aperture ratio and a long time for achieving grayscale. Therefore, a driving waveform based on the exponential function was proposed in this study. First, the maximum driving voltage value of 30 V was obtained by testing the hysteresis curve of the EWD pixel unit. Secondly, the influence of the time constant on the driving waveform was analyzed, and the optimal time constant of the exponential function was designed by testing the performance of the aperture ratio. Lastly, an EWD panel was used to test the driving effect of the exponential-function-driving waveform. The experimental results showed that a stable grayscale and a short driving time could be realized when the appropriate time constant value was designed for driving EWDs. The aperture ratio oscillation range of the gray scale could be reduced within 0.95%, and the driving time of a stable grayscale was reduced by 30% compared with the traditional driving waveform. Full article

(This article belongs to the Special Issue Micromachines for Dielectrophoresis)

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14 pages, 4213 KiB

Open AccessArticle

Polarizability-Dependent Sorting of Microparticles Using Continuous-Flow Dielectrophoretic Chromatography with a Frequency Modulation Method

by Jasper Giesler, Georg R. Pesch, Laura Weirauch, Marc-Peter Schmidt, Jorg Thöming and Michael Baune

Micromachines 2020, 11(1), 38; https://doi.org/10.3390/mi11010038 - 28 Dec 2019

Cited by 8 | Viewed by 3314

Abstract

The separation of microparticles with respect to different properties such as size and material is a research field of great interest. Dielectrophoresis, a phenomenon that is capable of addressing multiple particle properties at once, can be used to perform a chromatographic separation. However, [...] Read more.

The separation of microparticles with respect to different properties such as size and material is a research field of great interest. Dielectrophoresis, a phenomenon that is capable of addressing multiple particle properties at once, can be used to perform a chromatographic separation. However, the selectivity of current dielectrophoretic particle chromatography (DPC) techniques is limited. Here, we show a new approach for DPC based on differences in the dielectrophoretic mobilities and the crossover frequencies of polystyrene particles. Both differences are addressed by modulating the frequency of the electric field to generate positive and negative dielectrophoretic movement to achieve multiple trap-and-release cycles of the particles. A chromatographic separation of different particle sizes revealed the voltage dependency of this method. Additionally, we showed the frequency bandwidth influence on separation using one example. The DPC method developed was tested with model particles, but offers possibilities to separate a broad range of plastic and metal microparticles or cells and to overcome currently existing limitations in selectivity. Full article

(This article belongs to the Special Issue Micromachines for Dielectrophoresis)

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14 pages, 407 KiB

Open AccessReview

High-Sensitivity in Dielectrophoresis Separations

by Benjamin G. Hawkins, Nelson Lai and David S. Clague

Micromachines 2020, 11(4), 391; https://doi.org/10.3390/mi11040391 - 09 Apr 2020

Cited by 11 | Viewed by 2595

Abstract

The applications of dielectrophoretic (DEP) techniques for the manipulation of cells in a label-free fashion within microfluidic systems continue to grow. However, a limited number of methods exist for making highly sensitive separations that can isolate subtle phenotypic differences within a population of [...] Read more.

The applications of dielectrophoretic (DEP) techniques for the manipulation of cells in a label-free fashion within microfluidic systems continue to grow. However, a limited number of methods exist for making highly sensitive separations that can isolate subtle phenotypic differences within a population of cells. This paper explores efforts to leverage that most compelling aspect of DEP—an actuation force that depends on particle electrical properties—in the background of phenotypic variations in cell size. Several promising approaches, centering around the application of multiple electric fields with spatially mapped magnitude and/or frequencies, are expanding the capability of DEP cell separation. Full article

(This article belongs to the Special Issue Micromachines for Dielectrophoresis)

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