Special Issue "Microfluidic Machines"

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

Deadline for manuscript submissions: 30 September 2020.

Special Issue Editors

Prof. Dr. Ion Stiharu
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Guest Editor
Department of Mechanical and Industrial Engineering, Concordia University, Sir George William Campus, 1455 De Maisonneuve Blvd. W., Montreal, Quebec, Canada
Interests: microsystems; sensing (inertial, flow, load, strain); design of MEMS; data processing; modeling of coupled micro and macro systems; packaging of microsensors; MEMS for turbulence control; microfabrication; non-conventional microfabrication; rapid prototyping; migration from auto to aero; reliability of MEMS; failure models; test methodologies
Special Issues and Collections in MDPI journals
Dr. Anas Alazzam
Website
Guest Editor
Department of Mechanical Engineering, Khalifa University, Abu Dhabi, UAE
Interests: bio-applications of MEMS and micro-fluidic devices; micro-fabrication; separation and manipulation of living cells; micro-sensors

Special Issue Information

Dear Colleagues,

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Over the past decade, microfluidics has been witnessing a major progress in terms of fabrication techniques, materials used, and applications. The scope of this Special Issue is to gather a collection of substantial contributions to the fundamentals and applications of fluid dynamics in microscale machines. This includes microfluidics for applications in life sciences, manufacturing, pharmaceutical, biomedical tests, biomedical dispensing systems, defense, public health, agriculture, and many other such areas. The scope includes also other types of applications that represent subsets of the above topics such as drug delivery systems, µTAS, point-of-care devices, LoC microsystems, mixing devices, particles and droplets manipulation systems, single cell analysis, phase separators, nanoparticle sources, integration of microelectronics, and integration of photonics. Integration of MEMS, digital microfluidics, microfluidic platforms for automatic test of liquid or two-phase specimens, components for classic and nonclassic actuation within microfluidics, micropumps, optical tweezers, and other alternate solutions to actuation within microfluidics are strongly encouraged. Papers on any other topic related to microfluidics are welcomed.

The papers that will be considered for publication will cover topics related to the configuration of such circuits, the fabrication processes, technologies and techniques of fabrication, materials compatibility and selection, design, modeling, analysis, simulation, performance evaluation, environmental aspects, etc. Papers based on microfluidics or other such materials will also be considered for publication, and their submission is highly encouraged.

This call for papers by Micromachines for this Special Issue is motivated by the great interest and progress that microfluidics has made over past two decades.

The Special Issue also calls for a competition for the most relevant picture taken of a microfluidic device, platform, or part of that. The scope of the picture competition is to attract and motivate new research into this field of investigation.

Prof. Dr. Ion Stiharu
Dr. Anas Alazzam
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 1600 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.

Published Papers (6 papers)

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Research

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Open AccessArticle
Dielectrophoretic Microfluidic Device for Separating Microparticles Based on Size with Sub-Micron Resolution
Micromachines 2020, 11(7), 653; https://doi.org/10.3390/mi11070653 - 30 Jun 2020
Abstract
This article details the mathematical model of a microfluidic device aimed at separating any binary heterogeneous sample of microparticles into two homogeneous samples based on size with sub-micron resolution. The device consists of two sections, where the upstream section is dedicated to focusing [...] Read more.
This article details the mathematical model of a microfluidic device aimed at separating any binary heterogeneous sample of microparticles into two homogeneous samples based on size with sub-micron resolution. The device consists of two sections, where the upstream section is dedicated to focusing of microparticles, while the downstream section is dedicated to separation of the focused stream of microparticles into two samples based on size. Each section has multiple planar electrodes of finite size protruding into the microchannel from the top and bottom of each sidewall; each top electrode aligns with a bottom electrode and they form a pair leading to multiple pairs of electrodes on each side. The focusing section subjects all microparticles to repulsive dielectrophoretic force, from each set of the electrodes, to focus them next to one of the sidewalls. This separation section pushes the big microparticles toward the interior, away from the wall, of the microchannel using repulsive dielectrophoretic force, while the small microparticles move unaffected to achieve the desired degree of separation. The operating frequency of the set of electrodes in the separation section is maintained equal to the cross-over frequency of the small microparticles. The working of the device is demonstrated by separating a heterogeneous mixture consisting of polystyrene microparticles of different size (radii of 2 and 2.25 μm) into two homogeneous samples. The mathematical model is used for parametric study, and the performance is quantified in terms of separation efficiency and separation purity; the parameters considered include applied electric voltages, electrode dimensions, outlet widths, number of electrodes, and volumetric flowrate. The separation efficiencies and separation purities for both microparticles are 100% for low volumetric flow rates, a large number of electrode pairs, large electrode dimensions, and high differences between voltages in both sections. Full article
(This article belongs to the Special Issue Microfluidic Machines)
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Open AccessFeature PaperArticle
Micro-Pattern of Graphene Oxide Films Using Metal Bonding
Micromachines 2020, 11(4), 399; https://doi.org/10.3390/mi11040399 - 10 Apr 2020
Abstract
Recently, graphene has been explored in several research areas according to its outstanding combination of mechanical and electrical features. The ability to fabricate micro-patterns of graphene facilitates its integration in emerging technologies such as flexible electronics. This work reports a novel micro-pattern approach [...] Read more.
Recently, graphene has been explored in several research areas according to its outstanding combination of mechanical and electrical features. The ability to fabricate micro-patterns of graphene facilitates its integration in emerging technologies such as flexible electronics. This work reports a novel micro-pattern approach of graphene oxide (GO) film on a polymer substrate using metal bonding. It is shown that adding ethanol to the GO aqueous dispersion enhances substantially the uniformity of GO thin film deposition, which is a great asset for mass production. On the other hand, the presence of ethanol in the GO solution hinders the fabrication of patterned GO films using the standard lift-off process. To overcome this, the fabrication process provided in this work takes advantage of the chemical adhesion between the GO or reduced GO (rGO) and metal films. It is proved that the adhesion between the metal layer and GO or rGO is stronger than the adhesion between the latter and the polymer substrate (i.e., cyclic olefin copolymer used in this work). This causes the removal of the GO layer underneath the metal film during the lift-off process, leaving behind the desired GO or rGO micro-patterns. The feasibility and suitability of the proposed pattern technique is confirmed by fabricating the patterned electrodes inside a microfluidic device to manipulate living cells using dielectrophoresis. This work adds great value to micro-pattern GO and rGO thin films and has immense potential to achieve high yield production in emerging applications. Full article
(This article belongs to the Special Issue Microfluidic Machines)
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Open AccessArticle
A Microfluidic Concentration Gradient Maker with Tunable Concentration Profiles by Changing Feed Flow Rate Ratios
Micromachines 2020, 11(3), 284; https://doi.org/10.3390/mi11030284 - 10 Mar 2020
Cited by 1
Abstract
Microfluidic chips—in which chemical or biological fluid samples are mixed into linear or nonlinear concentration distribution profiles—have generated enormous enthusiasm of their ability to develop patterns for drug release and their potential toxicology applications. These microfluidic devices have untapped potential for varying concentration [...] Read more.
Microfluidic chips—in which chemical or biological fluid samples are mixed into linear or nonlinear concentration distribution profiles—have generated enormous enthusiasm of their ability to develop patterns for drug release and their potential toxicology applications. These microfluidic devices have untapped potential for varying concentration patterns by the use of one single device or by easy-to-operate procedures. To address this challenge, we developed a soft-lithography-fabricated microfluidic platform that enabled one single device to be used as a concentration maker, which could generate linear, bell-type, or even S-type concentration profiles by tuning the feed flow rate ratios of each independent inlet. Here, we present an FFRR (feed flow rate ratio) adjustment approach to generate tens of types of concentration gradient profiles with one single device. To demonstrate the advantages of this approach, we used a Christmas-tree-like microfluidic chip as the demo. Its performance was analyzed using numerical simulation models and experimental investigations, and it showed an excellent time response (~10 s). With on-demand flow rate ratios, the FFRR microfluidic device could be used for many lab-on-a-chip applications where flexible concentration profiles are required for analysis. Full article
(This article belongs to the Special Issue Microfluidic Machines)
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Open AccessArticle
Surface Response Based Modeling of Liposome Characteristics in a Periodic Disturbance Mixer
Micromachines 2020, 11(3), 235; https://doi.org/10.3390/mi11030235 - 25 Feb 2020
Cited by 1
Abstract
Liposomes nanoparticles (LNPs) are vesicles that encapsulate drugs, genes, and imaging labels for advanced delivery applications. Control and tuning liposome physicochemical characteristics such as size, size distribution, and zeta potential are crucial for their functionality. Liposome production using micromixers has shown better control [...] Read more.
Liposomes nanoparticles (LNPs) are vesicles that encapsulate drugs, genes, and imaging labels for advanced delivery applications. Control and tuning liposome physicochemical characteristics such as size, size distribution, and zeta potential are crucial for their functionality. Liposome production using micromixers has shown better control over liposome characteristics compared with classical approaches. In this work, we used our own designed and fabricated Periodic Disturbance Micromixer (PDM). We used Design of Experiments (DoE) and Response Surface Methodology (RSM) to statistically model the relationship between the Total Flow Rate (TFR) and Flow Rate Ratio (FRR) and the resulting liposomes physicochemical characteristics. TFR and FRR effectively control liposome size in the range from 52 nm to 200 nm. In contrast, no significant effect was observed for the TFR on the liposomes Polydispersity Index (PDI); conversely, FRR around 2.6 was found to be a threshold between highly monodisperse and low polydispersed populations. Moreover, it was shown that the zeta potential is independent of TFR and FRR. The developed model presented on the paper enables to pre-establish the experimental conditions under which LNPs would likely be produced within a specified size range. Hence, the model utility was demonstrated by showing that LNPs were produced under such conditions. Full article
(This article belongs to the Special Issue Microfluidic Machines)
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Open AccessArticle
A Microfluidic Rotational Motor Driven by Circular Vibrations
Micromachines 2019, 10(12), 809; https://doi.org/10.3390/mi10120809 - 23 Nov 2019
Cited by 1
Abstract
Constructing micro-sized machines always involves the problem of how to bring the energy (electric, magnetic, light, electro wetting, vibrational, etc.) source to the device to produce mechanical movements. The paper presents a rotational micro-sized motor (the diameter of the rotor is 350 µm) [...] Read more.
Constructing micro-sized machines always involves the problem of how to bring the energy (electric, magnetic, light, electro wetting, vibrational, etc.) source to the device to produce mechanical movements. The paper presents a rotational micro-sized motor (the diameter of the rotor is 350 µm) driven by low frequency (200–700 Hz) circular vibrations, made by two piezoelectric actuators, through the medium of a water droplet with diameter of 1 mm (volume 3.6 µL). The theoretical model presents how to produce the circular streaming (rotation) of the liquid around an infinitely long pillar with micro-sized diameter. The practical application has been focused to make a time-stable circular stream of the medium around the finite long vibrated pillar with diameter of 80 µm in the presence of disturbances produced by the vibrated plate where the pillar is placed. Only the time-stable circular stream in the water droplet around the pillar produces enough energy to rotate the micro-sized rotor. The rotational speed of the rotor is controlled in both directions from −20 rad/s to +26 rad/s. 3D printed mechanical amplifiers of vibrations, driven by piezoelectric actuators, amplify the amplitude of the piezoelectric actuator up to 20 µm in the frequency region of 200 to 700 Hz. Full article
(This article belongs to the Special Issue Microfluidic Machines)
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Review

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Open AccessReview
Desktop Fabrication of Lab-On-Chip Devices on Flexible Substrates: A Brief Review
Micromachines 2020, 11(2), 126; https://doi.org/10.3390/mi11020126 - 23 Jan 2020
Cited by 1
Abstract
Flexible microfluidic devices are currently in demand because they can be mass-produced in resource-limited settings using simple and inexpensive fabrication tools. Finding new ways to fabricate microfluidic platforms on flexible substrates has been a hot area. Integration of customized detection tools for different [...] Read more.
Flexible microfluidic devices are currently in demand because they can be mass-produced in resource-limited settings using simple and inexpensive fabrication tools. Finding new ways to fabricate microfluidic platforms on flexible substrates has been a hot area. Integration of customized detection tools for different lab-on-chip applications has made this area challenging. Significant advancements have occurred in the area over the last decade; therefore, there is a need to review such interesting fabrication tools employed on flexible substrates, such as paper and plastics. In this short review, we review individual fabrication tools and their combinations that have been used to develop such platforms in the past five years. These tools are not only simple and low-cost but also require minimal skills for their operation. Moreover, key examples of plastic-based flexible substrates are also presented, because a diverse range of plastic materials have prevailed recently for a variety of lab-on-chip applications. This review should attract audience of various levels, i.e., from hobbyists to scientists, and from high school students to postdoctoral researchers, to produce their own flexible devices in their own settings. Full article
(This article belongs to the Special Issue Microfluidic Machines)
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