Special Issue "Insights and Advancements in Microfluidics"

A special issue of Micromachines (ISSN 2072-666X).

Deadline for manuscript submissions: closed (15 January 2017)

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Guest Editor
Prof. Dr. Weihua Li

School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522, Australia
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Phone: +61-2-4221-3490
Fax: +61-2-4221-4577
Interests: microfluidics and nanofluidics; lab on a chip; smart materials and structures; rheology; intelligent mechatronics
Guest Editor
Prof. Dr. Hengdong Xi

School of Aeronautics, Northwestern Polytechnical University, Shaanxi, China
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Interests: turbulence; microfluidics; convection; polymeric drag reduction and polymer additives
Guest Editor
Dr. Say Hwa Tan

Queensland Micro- and Nanotechnology Centre, Griffith University, Brisbane, QLD 4111, Australia
Website | E-Mail
Interests: microfluidics and nanofluidics; lab-on-a-chip; droplets; emulsions; bubbles; electrohydrodynamic; intelligent systems; smart microdevices; liquid metals

Special Issue Information

Dear Colleagues,

Microfluidics has developed rapidly over the past three decades. Relentless diagnostic, medical and chemical applications have been demonstrated in various applications, plateforms and tools. Have microfluidics realized its full potential? Or is it only a leveraging academic tool? In this Special Issue, we focus on both insights and advancements in microfluidics. We invite emerging investigators and pioneers to contribute commentaries, perspectives and insightful reviews on related topics. The various insights from esteemed colleagues will be collated. We will also discuss technological breakthrough of original works in both short communications and full papers. The main idea is to stimulate the community and to provide an unique collection of insightful papers. We will also cover various topics ranging from 3D printing, paper-based microfludics to conventional polymer-based microfluidics which contributes to the technological advancements.

Prof. Dr. Weihua Li
Prof. Dr. Hengdong Xi
Dr. Say Hwa Tan
Guest 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 papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue 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 1200 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

  • Insights
  • Advancement
  • Perspective
  • Microfluidics
  • Lab on a chip
  • Development

Published Papers (20 papers)

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Editorial

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Open AccessEditorial Editorial for the Special Issue on the Insights and Advancements in Microfluidics
Micromachines 2017, 8(8), 254; https://doi.org/10.3390/mi8080254
Received: 15 August 2017 / Revised: 15 August 2017 / Accepted: 15 August 2017 / Published: 17 August 2017
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Abstract
We present a total of 19 articles in this special issue of Micromachines entitled, ”Insights and Advancements in Microfluidics.”[...] Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available

Research

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Open AccessArticle Large-Area and High-Throughput PDMS Microfluidic Chip Fabrication Assisted by Vacuum Airbag Laminator
Micromachines 2017, 8(7), 218; https://doi.org/10.3390/mi8070218
Received: 15 May 2017 / Revised: 23 June 2017 / Accepted: 29 June 2017 / Published: 12 July 2017
Cited by 1 | PDF Full-text (2296 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
One of the key fabrication steps of large-area microfluidic devices is the flexible-to-hard sheet alignment and pre-bonding. In this work, the vacuum airbag laminator (VAL) which is commonly used for liquid crystal display (LCD) production has been applied for large-area microfluidic device fabrication.
[...] Read more.
One of the key fabrication steps of large-area microfluidic devices is the flexible-to-hard sheet alignment and pre-bonding. In this work, the vacuum airbag laminator (VAL) which is commonly used for liquid crystal display (LCD) production has been applied for large-area microfluidic device fabrication. A straightforward, efficient, and low-cost method has been achieved for 400 × 500 mm2 microfluidic device fabrication. VAL provides the advantages of precise alignment and lamination without bubbles. Thermal treatment has been applied to achieve strong PDMS–glass and PDMS–PDMS bonding with maximum breakup pressure of 739 kPa, which is comparable to interference-assisted thermal bonding method. The fabricated 152 × 152 mm2 microfluidic chip has been successfully applied for droplet generation and splitting. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessArticle Fabrication of All Glass Bifurcation Microfluidic Chip for Blood Plasma Separation
Micromachines 2017, 8(3), 67; https://doi.org/10.3390/mi8030067
Received: 12 December 2016 / Revised: 9 February 2017 / Accepted: 20 February 2017 / Published: 24 February 2017
Cited by 3 | PDF Full-text (5400 KB) | HTML Full-text | XML Full-text
Abstract
An all-glass bifurcation microfluidic chip for blood plasma separation was fabricated by a cost-effective glass molding process using an amorphous carbon (AC) mold, which in turn was fabricated by the carbonization of a replicated furan precursor. To compensate for the shrinkage during AC
[...] Read more.
An all-glass bifurcation microfluidic chip for blood plasma separation was fabricated by a cost-effective glass molding process using an amorphous carbon (AC) mold, which in turn was fabricated by the carbonization of a replicated furan precursor. To compensate for the shrinkage during AC mold fabrication, an enlarged photoresist pattern master was designed, and an AC mold with a dimensional error of 2.9% was achieved; the dimensional error of the master pattern was 1.6%. In the glass molding process, a glass microchannel plate with negligible shape errors (~1.5%) compared to AC mold was replicated. Finally, an all-glass bifurcation microfluidic chip was realized by micro drilling and thermal fusion bonding processes. A separation efficiency of 74% was obtained using the fabricated all-glass bifurcation microfluidic chip. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessArticle Analysis of Liquid–Liquid Droplets Fission and Encapsulation in Single/Two Layer Microfluidic Devices Fabricated by Xurographic Method
Micromachines 2017, 8(2), 49; https://doi.org/10.3390/mi8020049
Received: 16 December 2016 / Revised: 26 January 2017 / Accepted: 4 February 2017 / Published: 10 February 2017
Cited by 3 | PDF Full-text (5844 KB) | HTML Full-text | XML Full-text
Abstract
This paper demonstrates a low cost fabrication approach for microscale droplet fission and encapsulation. Using a modified xurography method, rapid yet reliable microfluidic devices with flexible designs (single layer and double layer) are developed to enable spatial control of droplet manipulation. In this
[...] Read more.
This paper demonstrates a low cost fabrication approach for microscale droplet fission and encapsulation. Using a modified xurography method, rapid yet reliable microfluidic devices with flexible designs (single layer and double layer) are developed to enable spatial control of droplet manipulation. In this paper, two different designs are demonstrated, i.e., droplet fission (single layer) and droplet encapsulation (double layer). In addition, the current fabrication approach reduces the overall production interval with the introduction of a custom-made polydimethylsiloxane (PDMS) aligner. Apart from that, the fabricated device is able to generate daughter droplets with the coefficient of variance (CV) below 5% and double emulsions with CV maintained within 10% without involvement of complex surface wettability modification. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessArticle Thermoplastic Micromodel Investigation of Two-Phase Flows in a Fractured Porous Medium
Micromachines 2017, 8(2), 38; https://doi.org/10.3390/mi8020038
Received: 16 September 2016 / Revised: 30 December 2016 / Accepted: 19 January 2017 / Published: 26 January 2017
Cited by 1 | PDF Full-text (7319 KB) | HTML Full-text | XML Full-text
Abstract
In the past few years, micromodels have become a useful tool for visualizing flow phenomena in porous media with pore structures, e.g., the multifluid dynamics in soils or rocks with fractures in natural geomaterials. Micromodels fabricated using glass or silicon substrates incur high
[...] Read more.
In the past few years, micromodels have become a useful tool for visualizing flow phenomena in porous media with pore structures, e.g., the multifluid dynamics in soils or rocks with fractures in natural geomaterials. Micromodels fabricated using glass or silicon substrates incur high material cost; in particular, the microfabrication-facility cost for making a glass or silicon-based micromold is usually high. This may be an obstacle for researchers investigating the two-phase-flow behavior of porous media. A rigid thermoplastic material is a preferable polymer material for microfluidic models because of its high resistance to infiltration and deformation. In this study, cyclic olefin copolymer (COC) was selected as the substrate for the micromodel because of its excellent chemical, optical, and mechanical properties. A delicate micromodel with a complex pore geometry that represents a two-dimensional (2D) cross-section profile of a fractured rock in a natural oil or groundwater reservoir was developed for two-phase-flow experiments. Using an optical visualization system, we visualized the flow behavior in the micromodel during the processes of imbibition and drainage. The results show that the flow resistance in the main channel (fracture) with a large radius was higher than that in the surrounding area with small pore channels when the injection or extraction rates were low. When we increased the flow rates, the extraction efficiency of the water and oil in the mainstream channel (fracture) did not increase monotonically because of the complex two-phase-flow dynamics. These findings provide a new mechanism of residual trapping in porous media. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessArticle Dynamic Electroosmotic Flows of Power-Law Fluids in Rectangular Microchannels
Micromachines 2017, 8(2), 34; https://doi.org/10.3390/mi8020034
Received: 12 December 2016 / Revised: 16 January 2017 / Accepted: 18 January 2017 / Published: 24 January 2017
Cited by 7 | PDF Full-text (2174 KB) | HTML Full-text | XML Full-text
Abstract
Dynamic characteristics of electroosmosis of a typical non-Newtonian liquid in a rectangular microchannel are investigated by using numerical simulations. The non-Newtonian behavior of liquids is assumed to obey the famous power-law model and then the mathematical model is solved numerically by using the
[...] Read more.
Dynamic characteristics of electroosmosis of a typical non-Newtonian liquid in a rectangular microchannel are investigated by using numerical simulations. The non-Newtonian behavior of liquids is assumed to obey the famous power-law model and then the mathematical model is solved numerically by using the finite element method. The results indicate that the non-Newtonian effect produces some noticeable dynamic responses in electroosmotic flow. Under a direct current (DC) driving electric field, it is found that the fluid responds more inertly to an external electric field and the steady-state velocity profile becomes more plug-like as the flow behavior index decreases. Under an alternating current (AC) driving electric field, the fluid is observed to experience more significant acceleration and the amplitude of oscillating velocity becomes larger as the fluid behavior index decreases. Furthermore, our investigation also shows that electroosmotic flow of power-law fluids under an AC/DC combined driving field is enhanced as compared with that under a pure DC electric field. These dynamic predictions are of practical use for the design of electroosmotically-driven microfluidic devices that analyze and process non-Newtonian fluids such as biofluids and polymeric solutions. Full article
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Open AccessArticle A Y-Shaped Microfluidic Device to Study the Combined Effect of Wall Shear Stress and ATP Signals on Intracellular Calcium Dynamics in Vascular Endothelial Cells
Micromachines 2016, 7(11), 213; https://doi.org/10.3390/mi7110213
Received: 13 October 2016 / Revised: 17 November 2016 / Accepted: 18 November 2016 / Published: 23 November 2016
Cited by 5 | PDF Full-text (3633 KB) | HTML Full-text | XML Full-text
Abstract
The intracellular calcium dynamics in vascular endothelial cells (VECs) in response to wall shear stress (WSS) and/or adenosine triphosphate (ATP) have been commonly regarded as an important factor in regulating VEC function and behavior including proliferation, migration and apoptosis. However, the effects of
[...] Read more.
The intracellular calcium dynamics in vascular endothelial cells (VECs) in response to wall shear stress (WSS) and/or adenosine triphosphate (ATP) have been commonly regarded as an important factor in regulating VEC function and behavior including proliferation, migration and apoptosis. However, the effects of time-varying ATP signals have been usually neglected in the past investigations in the field of VEC mechanobiology. In order to investigate the combined effects of WSS and dynamic ATP signals on the intracellular calcium dynamic in VECs, a Y-shaped microfluidic device, which can provide the cultured cells on the bottom of its mixing micro-channel with stimuli of WSS signal alone and different combinations of WSS and ATP signals in one single micro-channel, is proposed. Both numerical simulation and experimental studies verify the feasibility of its application. Cellular experimental results also suggest that a combination of WSS and ATP signals rather than a WSS signal alone might play a more significant role in VEC Ca2+ signal transduction induced by blood flow. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessArticle An Interference-Assisted Thermal Bonding Method for the Fabrication of Thermoplastic Microfluidic Devices
Micromachines 2016, 7(11), 211; https://doi.org/10.3390/mi7110211
Received: 20 September 2016 / Revised: 8 November 2016 / Accepted: 17 November 2016 / Published: 22 November 2016
Cited by 3 | PDF Full-text (5270 KB) | HTML Full-text | XML Full-text
Abstract
Solutions for the bonding and sealing of micro-channels in the manufacturing process of microfluidic devices are limited; therefore, further technical developments are required to determine these solutions. In this study, a new bonding method for thermoplastic microfluidic devices was developed by combining an
[...] Read more.
Solutions for the bonding and sealing of micro-channels in the manufacturing process of microfluidic devices are limited; therefore, further technical developments are required to determine these solutions. In this study, a new bonding method for thermoplastic microfluidic devices was developed by combining an interference fit with a thermal treatment at low pressure. This involved a process of first injection molding thermoplastic substrates with a microchannel structure, and then performing bonding experiments at different bonding conditions. The results indicated the successful bonding of microchannels over a wide range of bonding pressures with the help of the interference fit. The study also determined additional advantages of the proposed bonding method by comparing the method with the conventional thermal bonding method. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessArticle Rapid Capture and Analysis of Airborne Staphylococcus aureus in the Hospital Using a Microfluidic Chip
Micromachines 2016, 7(9), 169; https://doi.org/10.3390/mi7090169
Received: 3 August 2016 / Revised: 1 September 2016 / Accepted: 12 September 2016 / Published: 15 September 2016
Cited by 6 | PDF Full-text (1276 KB) | HTML Full-text | XML Full-text
Abstract
In this study we developed a microfluidic chip for the rapid capture, enrichment and detection of airborne Staphylococcus (S.) aureus. The whole analysis took about 4 h and 40 min from airborne sample collection to loop-mediated isothermal amplification (LAMP), with
[...] Read more.
In this study we developed a microfluidic chip for the rapid capture, enrichment and detection of airborne Staphylococcus (S.) aureus. The whole analysis took about 4 h and 40 min from airborne sample collection to loop-mediated isothermal amplification (LAMP), with a detection limit down to about 27 cells. The process did not require DNA purification. The chip was validated using standard bacteria bioaerosol and was directly used for clinical airborne pathogen sampling in hospital settings. This is the first report on the capture and analysis of airborne S. aureus using a novel microfluidic technique, a process that could have a very promising platform for hospital airborne infection prevention (HAIP). Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessArticle A Reconfigurable Microfluidics Platform for Microparticle Separation and Fluid Mixing
Micromachines 2016, 7(8), 139; https://doi.org/10.3390/mi7080139
Received: 1 July 2016 / Revised: 1 August 2016 / Accepted: 3 August 2016 / Published: 8 August 2016
Cited by 2 | PDF Full-text (4412 KB) | HTML Full-text | XML Full-text
Abstract
Microfluidics is an engineering tool used to control and manipulate fluid flows, with practical applications for lab-on-a-chip, point-of-care testing, and biological/medical research. However, microfluidic platforms typically lack the ability to create a fluidic duct, having an arbitrary flow path, and to change the
[...] Read more.
Microfluidics is an engineering tool used to control and manipulate fluid flows, with practical applications for lab-on-a-chip, point-of-care testing, and biological/medical research. However, microfluidic platforms typically lack the ability to create a fluidic duct, having an arbitrary flow path, and to change the path as needed without additional design and fabrication processes. To address this challenge, we present a simple yet effective approach for facile, on-demand reconfiguration of microfluidic channels using flexible polymer tubing. The tubing provides both a well-defined, cross-sectional geometry to allow reliable fluidic operation and excellent flexibility to achieve a high degree of freedom for reconfiguration of flow pathways. We demonstrate that microparticle separation and fluid mixing can be successfully implemented by reconfiguring the shape of the tubing. The tubing is coiled around a 3D-printed barrel to make a spiral microchannel with a constant curvature for inertial separation of microparticles. Multiple knots are also made in the tubing to create a highly tortuous flow path, which induces transverse secondary flows, Dean flows, and, thus, enhances the mixing of fluids. The reconfigurable microfluidics approach, with advantages including low-cost, simplicity, and ease of use, can serve as a promising complement to conventional microfabrication methods, which require complex fabrication processes with expensive equipment and lack a degree of freedom for reconfiguration. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Review

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Open AccessReview Microfluidic and Nanofluidic Resistive Pulse Sensing: A Review
Micromachines 2017, 8(7), 204; https://doi.org/10.3390/mi8070204
Received: 17 April 2017 / Revised: 11 June 2017 / Accepted: 21 June 2017 / Published: 25 June 2017
Cited by 3 | PDF Full-text (3787 KB) | HTML Full-text | XML Full-text
Abstract
The resistive pulse sensing (RPS) method based on the Coulter principle is a powerful method for particle counting and sizing in electrolyte solutions. With the advancement of micro- and nano-fabrication technologies, microfluidic and nanofluidic resistive pulse sensing technologies and devices have been developed.
[...] Read more.
The resistive pulse sensing (RPS) method based on the Coulter principle is a powerful method for particle counting and sizing in electrolyte solutions. With the advancement of micro- and nano-fabrication technologies, microfluidic and nanofluidic resistive pulse sensing technologies and devices have been developed. Due to the unique advantages of microfluidics and nanofluidics, RPS sensors are enabled with more functions with greatly improved sensitivity and throughput and thus have wide applications in fields of biomedical research, clinical diagnosis, and so on. Firstly, this paper reviews some basic theories of particle sizing and counting. Emphasis is then given to the latest development of microfuidic and nanofluidic RPS technologies within the last 6 years, ranging from some new phenomena, methods of improving the sensitivity and throughput, and their applications, to some popular nanopore or nanochannel fabrication techniques. The future research directions and challenges on microfluidic and nanofluidic RPS are also outlined. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessReview Recent Advances and Future Perspectives on Microfluidic Liquid Handling
Micromachines 2017, 8(6), 186; https://doi.org/10.3390/mi8060186
Received: 23 May 2017 / Revised: 3 June 2017 / Accepted: 8 June 2017 / Published: 12 June 2017
Cited by 24 | PDF Full-text (3564 KB) | HTML Full-text | XML Full-text
Abstract
The interdisciplinary research field of microfluidics has the potential to revolutionize current technologies that require the handling of a small amount of fluid, a fast response, low costs and automation. Microfluidic platforms that handle small amounts of liquid have been categorised as continuous-flow
[...] Read more.
The interdisciplinary research field of microfluidics has the potential to revolutionize current technologies that require the handling of a small amount of fluid, a fast response, low costs and automation. Microfluidic platforms that handle small amounts of liquid have been categorised as continuous-flow microfluidics and digital microfluidics. The first part of this paper discusses the recent advances of the two main and opposing applications of liquid handling in continuous-flow microfluidics: mixing and separation. Mixing and separation are essential steps in most lab-on-a-chip platforms, as sample preparation and detection are required for a variety of biological and chemical assays. The second part discusses the various digital microfluidic strategies, based on droplets and liquid marbles, for the manipulation of discrete microdroplets. More advanced digital microfluidic devices combining electrowetting with other techniques are also introduced. The applications of the emerging field of liquid-marble-based digital microfluidics are also highlighted. Finally, future perspectives on microfluidic liquid handling are discussed. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessReview A Perspective on the Rise of Optofluidics and the Future
Micromachines 2017, 8(5), 152; https://doi.org/10.3390/mi8050152
Received: 13 February 2017 / Revised: 29 April 2017 / Accepted: 2 May 2017 / Published: 8 May 2017
Cited by 6 | PDF Full-text (1759 KB) | HTML Full-text | XML Full-text
Abstract
In the recent past, the field of optofluidics has thrived from the immense efforts of researchers from diverse communities. The concept of optofluidics combines optics and microfluidics to exploit novel properties and functionalities. In the very beginning, the unique properties of liquid, such
[...] Read more.
In the recent past, the field of optofluidics has thrived from the immense efforts of researchers from diverse communities. The concept of optofluidics combines optics and microfluidics to exploit novel properties and functionalities. In the very beginning, the unique properties of liquid, such as mobility, fungibility and deformability, initiated the motivation to develop optical elements or functions using fluid interfaces. Later on, the advancements of microelectromechanical system (MEMS) and microfluidic technologies enabled the realization of optofluidic components through the precise manipulation of fluids at microscale thus making it possible to streamline complex fabrication processes. The optofluidic system aims to fully integrate optical functions on a single chip instead of using external bulky optics, which can consequently lower the cost of system, downsize the system and make it promising for point-of-care diagnosis. This perspective gives an overview of the recent developments in the field of optofluidics. Firstly, the fundamental optofluidic components will be discussed and are categorized according to their basic working mechanisms, followed by the discussions on the functional instrumentations of the optofluidic components, as well as the current commercialization aspects of optofluidics. The paper concludes with the critical challenges that might hamper the transformation of optofluidic technologies from lab-based procedures to practical usages and commercialization. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessFeature PaperReview The Use of Microfluidics in Cytotoxicity and Nanotoxicity Experiments
Micromachines 2017, 8(4), 124; https://doi.org/10.3390/mi8040124
Received: 28 February 2017 / Revised: 6 April 2017 / Accepted: 7 April 2017 / Published: 12 April 2017
Cited by 2 | PDF Full-text (3123 KB) | HTML Full-text | XML Full-text
Abstract
Many unique chemical compounds and nanomaterials are being developed, and each one requires a considerable range of in vitro and/or in vivo toxicity screening in order to evaluate their safety. The current methodology of in vitro toxicological screening on cells is based on
[...] Read more.
Many unique chemical compounds and nanomaterials are being developed, and each one requires a considerable range of in vitro and/or in vivo toxicity screening in order to evaluate their safety. The current methodology of in vitro toxicological screening on cells is based on well-plate assays that require time-consuming manual handling or expensive automation to gather enough meaningful toxicology data. Cost reduction; access to faster, more comprehensive toxicity data; and a robust platform capable of quantitative testing, will be essential in evaluating the safety of new chemicals and nanomaterials, and, at the same time, in securing the confidence of regulators and end-users. Microfluidic chips offer an alternative platform for toxicity screening that has the potential to transform both the rates and efficiency of nanomaterial testing, as reviewed here. The inherent advantages of microfluidic technologies offer high-throughput screening with small volumes of analytes, parallel analyses, and low-cost fabrication. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessReview The Self-Propulsion of the Spherical Pt–SiO2 Janus Micro-Motor
Micromachines 2017, 8(4), 123; https://doi.org/10.3390/mi8040123
Received: 22 February 2017 / Revised: 5 April 2017 / Accepted: 5 April 2017 / Published: 12 April 2017
Cited by 6 | PDF Full-text (4337 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The double-faced Janus micro-motor, which utilizes the heterogeneity between its two hemispheres to generate self-propulsion, has shown great potential in water cleaning, drug delivery in micro/nanofluidics, and provision of power for a novel micro-robot. In this paper, we focus on the self-propulsion of
[...] Read more.
The double-faced Janus micro-motor, which utilizes the heterogeneity between its two hemispheres to generate self-propulsion, has shown great potential in water cleaning, drug delivery in micro/nanofluidics, and provision of power for a novel micro-robot. In this paper, we focus on the self-propulsion of a platinum–silica (Pt–SiO2) spherical Janus micro-motor (JM), which is one of the simplest micro-motors, suspended in a hydrogen peroxide solution (H2O2). Due to the catalytic decomposition of H2O2 on the Pt side, the JM is propelled by the established concentration gradient known as diffusoiphoretic motion. Furthermore, as the JM size increases to O (10 μm), oxygen molecules nucleate on the Pt surface, forming microbubbles. In this case, a fast bubble propulsion is realized by the microbubble cavitation-induced jet flow. We systematically review the results of the above two distinct mechanisms: self-diffusiophoresis and microbubble propulsion. Their typical behaviors are demonstrated, based mainly on experimental observations. The theoretical description and the numerical approach are also introduced. We show that this tiny motor, though it has a very simple structure, relies on sophisticated physical principles and can be used to fulfill many novel functions. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessReview Advances in Single Cell Impedance Cytometry for Biomedical Applications
Micromachines 2017, 8(3), 87; https://doi.org/10.3390/mi8030087
Received: 31 January 2017 / Revised: 27 February 2017 / Accepted: 7 March 2017 / Published: 12 March 2017
Cited by 9 | PDF Full-text (8768 KB) | HTML Full-text | XML Full-text
Abstract
Microfluidics impedance cytometry is an emerging research tool for high throughput analysis of dielectric properties of cells and internal cellular components. This label-free method can be used in different biological assays including particle sizing and enumeration, cell phenotyping and disease diagnostics. Herein, we
[...] Read more.
Microfluidics impedance cytometry is an emerging research tool for high throughput analysis of dielectric properties of cells and internal cellular components. This label-free method can be used in different biological assays including particle sizing and enumeration, cell phenotyping and disease diagnostics. Herein, we review recent developments in single cell impedance cytometer platforms, their biomedical and clinical applications, and discuss the future directions and challenges in this field. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessReview Droplet Microfluidics for the Production of Microparticles and Nanoparticles
Micromachines 2017, 8(1), 22; https://doi.org/10.3390/mi8010022
Received: 17 October 2016 / Revised: 6 January 2017 / Accepted: 6 January 2017 / Published: 14 January 2017
Cited by 16 | PDF Full-text (5895 KB) | HTML Full-text | XML Full-text
Abstract
Droplet microfluidics technology is recently a highly interesting platform in material fabrication. Droplets can precisely monitor and control entire material fabrication processes and are superior to conventional bulk techniques. Droplet production is controlled by regulating the channel geometry and flow rates of each
[...] Read more.
Droplet microfluidics technology is recently a highly interesting platform in material fabrication. Droplets can precisely monitor and control entire material fabrication processes and are superior to conventional bulk techniques. Droplet production is controlled by regulating the channel geometry and flow rates of each fluid. The micro-scale size of droplets results in rapid heat and mass-transfer rates. When used as templates, droplets can be used to develop reproducible and scalable microparticles with tailored sizes, shapes and morphologies, which are difficult to obtain using traditional bulk methods. This technology can revolutionize material processing and application platforms. Generally, microparticle preparation methods involve three steps: (1) the formation of micro-droplets using a microfluidics generator; (2) shaping the droplets in micro-channels; and (3) solidifying the droplets to form microparticles. This review discusses the production of microparticles produced by droplet microfluidics according to their morphological categories, which generally determine their physicochemical properties and applications. Full article
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Open AccessReview Polymer Microfluidics: Simple, Low-Cost Fabrication Process Bridging Academic Lab Research to Commercialized Production
Micromachines 2016, 7(12), 225; https://doi.org/10.3390/mi7120225
Received: 26 September 2016 / Revised: 26 November 2016 / Accepted: 7 December 2016 / Published: 10 December 2016
Cited by 20 | PDF Full-text (1275 KB) | HTML Full-text | XML Full-text
Abstract
Using polymer materials to fabricate microfluidic devices provides simple, cost effective, and disposal advantages for both lab-on-a-chip (LOC) devices and micro total analysis systems (μTAS). Polydimethylsiloxane (PDMS) elastomer and thermoplastics are the two major polymer materials used in microfluidics. The fabrication of PDMS
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Using polymer materials to fabricate microfluidic devices provides simple, cost effective, and disposal advantages for both lab-on-a-chip (LOC) devices and micro total analysis systems (μTAS). Polydimethylsiloxane (PDMS) elastomer and thermoplastics are the two major polymer materials used in microfluidics. The fabrication of PDMS and thermoplastic microfluidic device can be categorized as front-end polymer microchannel fabrication and post-end microfluidic bonding procedures, respectively. PDMS and thermoplastic materials each have unique advantages and their use is indispensable in polymer microfluidics. Therefore, the proper selection of polymer microfabrication is necessary for the successful application of microfluidics. In this paper, we give a short overview of polymer microfabrication methods for microfluidics and discuss current challenges and future opportunities for research in polymer microfluidics fabrication. We summarize standard approaches, as well as state-of-art polymer microfluidic fabrication methods. Currently, the polymer microfluidic device is at the stage of technology transition from research labs to commercial production. Thus, critical consideration is also required with respect to the commercialization aspects of fabricating polymer microfluidics. This article provides easy-to-understand illustrations and targets to assist the research community in selecting proper polymer microfabrication strategies in microfluidics. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessFeature PaperPerspective Digital PCR: Endless Frontier of ‘Divide and Conquer’
Micromachines 2017, 8(8), 231; https://doi.org/10.3390/mi8080231
Received: 28 June 2017 / Revised: 18 July 2017 / Accepted: 18 July 2017 / Published: 25 July 2017
Cited by 1 | PDF Full-text (941 KB) | HTML Full-text | XML Full-text
Abstract
Digital polymerase chain reaction (PCR) is becoming ever more recognized amid the overwhelming revolution in DNA quantification, genomics, genetics, and diagnostics led by technologies such as next generation sequencing and studies at the single-cell level. The demand to quantify the amount of DNA
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Digital polymerase chain reaction (PCR) is becoming ever more recognized amid the overwhelming revolution in DNA quantification, genomics, genetics, and diagnostics led by technologies such as next generation sequencing and studies at the single-cell level. The demand to quantify the amount of DNA and RNA has been driven to the molecular level and digital PCR, with its unprecedented quantification capability, is sure to shine in the coming era. Two decades ago, it emerged as a concept; yet one decade ago, integration with microfluidics invigorated this field. Today, many methods have come to public knowledge and applications surrounding digital PCR is mounting. However, to reach wider accessibility and better practicality, efforts are needed to tackle the remaining problems. This perspective looks back at several inspiring and influential digital PCR approaches in the past and tries to provide a futuristic picture of the trends of digital PCR technologies to come. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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Open AccessPerspective High-Throughput Particle Manipulation Based on Hydrodynamic Effects in Microchannels
Micromachines 2017, 8(3), 73; https://doi.org/10.3390/mi8030073
Received: 14 January 2017 / Accepted: 23 February 2017 / Published: 1 March 2017
Cited by 10 | PDF Full-text (7127 KB) | HTML Full-text | XML Full-text
Abstract
Microfluidic techniques are effective tools for precise manipulation of particles and cells, whose enrichment and separation is crucial for a wide range of applications in biology, medicine, and chemistry. Recently, lateral particle migration induced by the intrinsic hydrodynamic effects in microchannels, such as
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Microfluidic techniques are effective tools for precise manipulation of particles and cells, whose enrichment and separation is crucial for a wide range of applications in biology, medicine, and chemistry. Recently, lateral particle migration induced by the intrinsic hydrodynamic effects in microchannels, such as inertia and elasticity, has shown its promise for high-throughput and label-free particle manipulation. The particle migration can be engineered to realize the controllable focusing and separation of particles based on a difference in size. The widespread use of inertial and viscoelastic microfluidics depends on the understanding of hydrodynamic effects on particle motion. This review will summarize the progress in the fundamental mechanisms and key applications of inertial and viscoelastic particle manipulation. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics) Printed Edition available
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