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Micromachines
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Micro/Nanoscale Electrokinetics
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Micro/Nanoscale Electrokinetics

A topical collection in Micromachines (ISSN 2072-666X). This collection belongs to the section "C1: Micro/Nanoscale Electrokinetics".

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Editors

Prof. Dr. Xiangchun Xuan

E-Mail Website
Collection Editor
Department of Mechanical Engineering, Clemson University, Clemson, SC 29634, USA
Interests: microfluidics; electrokinetics; magnetofluidics; viscoelasticity
Special Issues, Collections and Topics in MDPI journals
Dr. Rodrigo Martinez-Duarte

E-Mail Website
Collection Editor
Department of Mechanical Engineering, Clemson University, Clemson, SC 29634, USA
Interests: micromanufacturing; biomanufacturing; carbonaceous materials; electrokinetics; microfluidics; bacteria; composites; healthcare diagnostics; multicultural collaboration
Special Issues, Collections and Topics in MDPI journals

Topical Collection Information

Dear Colleagues,

Micro/nanofluidic chips have found increasing applications in the analysis of chemical and biological samples over the past two decades. Electrokinetics has become the method of choice in these micro/nanochips for transporting, manipulating and sensing ions, (bio)molecules, fluids and (bio)particles, etc., due to the high maneuverability, scalability, sensitivity, and integrability. The involved phenomena, which cover electro-osmosis, electrophoresis, dielectrophoresis, electrohydrodynamics, electrothermal flow, diffusioosmosis, diffusiophoresis, streaming potential, current, etc., arise from either the inherent or the induced surface charge of the solid–liquid interface under DC and/or AC electric fields. To review the state-of-the-art of micro/nanochip electrokinetics, this Topical Collection of Micromachines welcomes all original research or review articles on the fundamentals and applications of any electrokinetic phenomena in both microfluidic and nanofluidic devices.

Prof. Dr. Xiangchun Xuan
Dr. Rodrigo Martinez-Duarte
Collection Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the collection website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • electrokinetics
  • micro/nanofluidics
  • electroosmosis
  • electrophoresis
  • diffusioosmosis
  • diffusiophoresis
  • streaming potential/current
  • dielectrophoresis
  • induced charge electrokinetics
  • electrical sensing

Published Papers (5 papers)

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2025

Jump to: 2024

35 pages, 3239 KiB  
Review
A Review on AC-Dielectrophoresis of Nanoparticles
by Tonoy K. Mondal, Aaditya V. B. Bangaru and Stuart J. Williams
Micromachines 2025, 16(4), 453; https://doi.org/10.3390/mi16040453 - 11 Apr 2025
Viewed by 437
Abstract
Dielectrophoresis at the nanoscale has gained significant attention in recent years as a low-cost, rapid, efficient, and label-free technique. This method holds great promise for various interdisciplinary applications related to micro- and nanoscience, including biosensors, microfluidics, and nanomachines. The innovation and development of [...] Read more.
Dielectrophoresis at the nanoscale has gained significant attention in recent years as a low-cost, rapid, efficient, and label-free technique. This method holds great promise for various interdisciplinary applications related to micro- and nanoscience, including biosensors, microfluidics, and nanomachines. The innovation and development of such devices and platforms could promote wider applications in the field of nanotechnology. This review aims to provide an overview of recent developments and applications of nanoparticle dielectrophoresis, where at least one dimension of the geometry or the particles being manipulated is equal to or less than 100 nm. By offering a theoretical foundation to understand the processes and challenges that occur at the nanoscale—such as the need for high field gradients—this article presents a comprehensive overview of the advancements and applications of nanoparticle dielectrophoresis platforms over the past 15 years. This period has been characterized by significant progress, as well as persistent challenges in the manipulation and separation of nanoscale objects. As a foundation for future research, this review will help researchers explore new avenues and potential applications across various fields. Full article
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19 pages, 2387 KiB  
Review
Electro-Elastic Instability and Turbulence in Electro-osmotic Flows of Viscoelastic Fluids: Current Status and Future Directions
by Chandi Sasmal
Micromachines 2025, 16(2), 187; https://doi.org/10.3390/mi16020187 - 4 Feb 2025
Viewed by 778
Abstract
The addition of even minute amounts of solid polymers, measured in parts per million (ppm), into a simple Newtonian fluid like water significantly alters the flow behavior of the resulting polymer solutions due to the introduction of fluid viscoelasticity. This viscoelastic behavior, which [...] Read more.
The addition of even minute amounts of solid polymers, measured in parts per million (ppm), into a simple Newtonian fluid like water significantly alters the flow behavior of the resulting polymer solutions due to the introduction of fluid viscoelasticity. This viscoelastic behavior, which arises due to the stretching and relaxation phenomena of polymer molecules, leads to complex flow dynamics that are starkly different from those seen in simple Newtonian fluids under the same conditions. In addition to polymer solutions, many other fluids, routinely used in various industries and our daily lives, exhibit viscoelastic properties, including emulsions; foams; suspensions; biological fluids such as blood, saliva, and cerebrospinal fluid; and suspensions of biomolecules like DNA and proteins. In various microfluidic platforms, these viscoelastic fluids are often transported using electro-osmotic flows (EOFs), where an electric field is applied to control fluid movement. This method provides more precise and accurate flow control compared to pressure-driven techniques. However, several experimental and numerical studies have shown that when either the applied electric field strength or the fluid elasticity exceeds a critical threshold, the flow in these viscoelastic fluids becomes unstable and asymmetric due to the development of electro-elastic instability (EEI). These instabilities are driven by the normal elastic stresses in viscoelastic fluids and are not observed in Newtonian fluids under the same conditions, where the flow remains steady and symmetric. As the electric field strength or fluid elasticity is further increased, these instabilities can transition into a more chaotic and turbulent-like flow state, referred to as electro-elastic turbulence (EET). This article comprehensively reviews the existing literature on these EEI and EET phenomena, summarizing key findings from both experimental and numerical studies. Additionally, this article presents a detailed discussion of future research directions, emphasizing the need for further investigations to fully understand and harness the potential of EEI and EET in various practical applications, particularly in microscale flow systems where better flow control and increased transport rates are essential. Full article
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10 pages, 3639 KiB  
Article
On-Chip DNA Assembly via Dielectrophoresis
by Xichuan Rui, Lin-Sheng Wu and Xin Zhao
Micromachines 2025, 16(1), 76; https://doi.org/10.3390/mi16010076 - 11 Jan 2025
Viewed by 794
Abstract
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 [...] Read more.
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
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2024

Jump to: 2025

35 pages, 15586 KiB  
Review
Constrained Volume Micro- and Nanoparticle Collection Methods in Microfluidic Systems
by Tanner N. Wells, Holger Schmidt and Aaron R. Hawkins
Micromachines 2024, 15(6), 699; https://doi.org/10.3390/mi15060699 - 25 May 2024
Cited by 1 | Viewed by 1391
Abstract
Particle trapping and enrichment into confined volumes can be useful in particle processing and analysis. This review is an evaluation of the methods used to trap and enrich particles into constrained volumes in microfluidic and nanofluidic systems. These methods include physical, optical, electrical, [...] Read more.
Particle trapping and enrichment into confined volumes can be useful in particle processing and analysis. This review is an evaluation of the methods used to trap and enrich particles into constrained volumes in microfluidic and nanofluidic systems. These methods include physical, optical, electrical, magnetic, acoustic, and some hybrid techniques, all capable of locally enhancing nano- and microparticle concentrations on a microscale. Some key qualitative and quantitative comparison points are also explored, illustrating the specific applicability and challenges of each method. A few applications of these types of particle trapping are also discussed, including enhancing biological and chemical sensors, particle washing techniques, and fluid medium exchange systems. Full article
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16 pages, 2767 KiB  
Article
Optimizing Optical Dielectrophoretic (ODEP) Performance: Position- and Size-Dependent Droplet Manipulation in an Open-Chamber Oil Medium
by Md Aminul Islam and Sung-Yong Park
Micromachines 2024, 15(1), 119; https://doi.org/10.3390/mi15010119 - 11 Jan 2024
Cited by 1 | Viewed by 2221
Abstract
An optimization study is presented to enhance optical dielectrophoretic (ODEP) performance for effective manipulation of an oil-immersed droplet in the floating electrode optoelectronic tweezers (FEOET) device. This study focuses on understanding how the droplet’s position and size, relative to light illumination, affect the [...] Read more.
An optimization study is presented to enhance optical dielectrophoretic (ODEP) performance for effective manipulation of an oil-immersed droplet in the floating electrode optoelectronic tweezers (FEOET) device. This study focuses on understanding how the droplet’s position and size, relative to light illumination, affect the maximum ODEP force. Numerical simulations identified the characteristic length (Lc) of the electric field as a pivotal factor, representing the location of peak field strength. Utilizing 3D finite element simulations, the ODEP force is calculated through the Maxwell stress tensor by integrating the electric field strength over the droplet’s surface and then analyzed as a function of the droplet’s position and size normalized to Lc. Our findings reveal that the optimal position is xopt= Lc+ r, (with r being the droplet radius), while the optimal droplet size is ropt = 5Lc, maximizing light-induced field perturbation around the droplet. Experimental validations involving the tracking of droplet dynamics corroborated these findings. Especially, a droplet sized at r = 5Lc demonstrated the greatest optical actuation by performing the longest travel distance of 13.5 mm with its highest moving speed of 6.15 mm/s, when it was initially positioned at x0= Lc+ r = 6Lc from the light’s center. These results align well with our simulations, confirming the criticality of both the position (xopt) and size (ropt) for maximizing ODEP force. This study not only provides a deeper understanding of the position- and size-dependent parameters for effective droplet manipulation in FEOET systems, but also advances the development of low-cost, disposable, lab-on-a-chip (LOC) devices for multiplexed biological and biochemical analyses. Full article
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