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A special issue of Inventions (ISSN 2411-5134). This special issue belongs to the section "Inventions and Innovation in Energy and Thermal/Fluidic Science".

Deadline for manuscript submissions: closed (30 September 2018) | Viewed by 118934

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Special Issue Editor

Prof. Dr. Ruey-Jen Yang

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Guest Editor

Department of Engineering Science, National Cheng Kung University, Tainan 701, Taiwan
Interests: microfluidics; nanofluidics; electrokinetics; lab on a chip; energy conversion

Special Issue Information

Dear Colleagues,

Microfluidics and nanofluidics deal with fluid flows in geometries of micro/nano scales. New phenomena unique to these small scales bring exciting research interests in the past two decades. Practical applications can be found in the analysis of analytical chemistry, chemical engineering, biomedical devices, micro-thermal technologies, etc.

In this Special Issue, we invite contributions to report the state-of-the-art developments in the fields of microfluidics and nanofluidics including, but not limited to, micromixer, micropump, droplet, biomedical microfluidic devices, manipulation of micro-molecules and biofluids, lab-on-a-chip, micro total analysis, point-of-care devices, energy conversion, etc. Practical devices that demonstrate capabilities to solve real-world problems are of particular interest.

Prof. Ruey-Jen Yang
Guest Editor

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Keywords

microfluidics
nanofluidics
electrokinetics
lab-on-a-chip
energy Conversion

Published Papers (13 papers)

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Editorial

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2 pages, 150 KiB

Open AccessEditorial

Microfluidics and Nanofluidics

by Ruey-Jen Yang

Inventions 2019, 4(1), 12; https://doi.org/10.3390/inventions4010012 - 11 Feb 2019

Cited by 1 | Viewed by 5715

Abstract

Microfluidics and nanofluidics deal with fluid flows in geometries of micro/nano scales [...] Full article

(This article belongs to the Special Issue Microfluidics and Nanofluidics)

Research

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14 pages, 2096 KiB

Open AccessArticle

Wax-Printed Fluidic Time Delays for Automating Multi-Step Assays in Paper-Based Microfluidic Devices (MicroPADs)

by E. Brandon Strong, Carsten Knutsen, Jay T. Wells, Aditya R. Jangid, Megan L. Mitchell, Nathaniel W. Martinez and Andres W. Martinez

Inventions 2019, 4(1), 20; https://doi.org/10.3390/inventions4010020 - 19 Mar 2019

Cited by 19 | Viewed by 7929

Abstract

Microfluidic paper-based analytical devices (microPADs) have emerged as a promising platform for point-of-care diagnostic devices. While the inherent wicking properties of microPADs allow for fluid flow without supporting equipment, this also presents a major challenge in achieving robust fluid control, which becomes especially important when performing complex multi-step assays. Herein, we describe an ideal method of fluid control mediated by wax-printed fluidic time delays. This method relies on a simple fabrication technique, does not utilize chemicals/reagents that could affect downstream assays, is readily scalable, and has a wide temporal range of tunable fluid control. The delays are wax printed on both the top and bottom of pre-fabricated microPAD channels, without subsequent heating, to create hemi-/fully-enclosed channels. With these wax printed delays, we were able to tune the time it took aqueous solutions to wick across a 25 mm-long channel between 3.6 min and 13.4 min. We then employed these fluid delays in the sequential delivery of four dyes to a test zone. Additionally, we demonstrated the automation of two simple enzymatic assays with this fluid control modality. This method of fluid control may allow future researchers to automate more complex assays, thereby further advancing microPADs toward real-world applications. Full article

(This article belongs to the Special Issue Microfluidics and Nanofluidics)

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11 pages, 1085 KiB

Open AccessArticle

A Microfluidic Cell Stretch Device to Investigate the Effects of Stretching Stress on Artery Smooth Muscle Cell Proliferation in Pulmonary Arterial Hypertension

by Kae Sato, Manami Nitta and Aiko Ogawa

Inventions 2019, 4(1), 1; https://doi.org/10.3390/inventions4010001 - 26 Dec 2018

Cited by 17 | Viewed by 8825

Abstract

A microfluidic cell stretch device was developed to investigate the effects of stretching stress on pulmonary artery smooth muscle cell (PASMC) proliferation in pulmonary arterial hypertension (PAH). The microfluidic device harbors upper cell culture and lower control channels, separated by a stretchable poly(dimethylsiloxane) membrane that acts as a cell culture substrate. The lower channel inlet was connected to a vacuum pump via a digital switch-controlled solenoid valve. For cyclic stretch at heartbeat frequency (80 bpm), the open or close time for each valve was set to 0.38 s. Proliferation of normal PASMCs and those obtained from patients was enhanced by the circumferential stretching stimulation. This is the first report showing patient cells increased in number by stretching stress. These results are consistent with the abnormal proliferation observed in PAH. Circumferential stretch stress was applied to the cells without increasing the pressure inside the microchannel. Our data may suggest that the stretch stress itself promotes cell proliferation in PAH. Full article

(This article belongs to the Special Issue Microfluidics and Nanofluidics)

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11 pages, 2592 KiB

Open AccessArticle

Chemical-Free Extraction of Functional Mitochondria Using a Microfluidic Device

by Yu-Han Hsiao, Ching-Wen Li, Jui-Chih Chang, Sung-Tzu Chen, Chin-San Liu and Gou-Jen Wang

Inventions 2018, 3(4), 68; https://doi.org/10.3390/inventions3040068 - 27 Sep 2018

Cited by 3 | Viewed by 6205

Abstract

This paper proposes the use of a chip-based microfluidic device to extract functional and chemical free mitochondria. A simple microfluidic device was designed and fabricated. An osteosarcoma cybrid cell line was employed to demonstrate the efficiency of the proposed microfluidic device. The membrane proteins (mitochondrial complex I-V and Tom20) and morphology of the extracted mitochondria were examined by Western blot and transmission electron microscopy (TEM), respectively. The purity and mitochondrial membrane potential of the extracted mitochondria were individually measured by 10-N-alkyl acridine orange and tetramethylrhodamine ethyl ester staining via flow cytometry. Experimental results revealed that expressed pattern of complex I–V in device-extracted mitochondria was close to that of mitochondria in total cell lysis and device extraction significantly prevented chemical modification of complex IV protein via a conventional kit, although device extract similar amounts of mitochondria to the conventional kit revealed by Tom20 expression. Furthermore, purity of device-extracted mitochondria was above 93.7% and mitochondria still retained normal activity after device extraction proven by expression of mitochondrial membrane potential as well as the entire mitochondrial morphology. These results confirmed that the proposed microfluidic device could obtain functional mitochondria without structural damage. Full article

(This article belongs to the Special Issue Microfluidics and Nanofluidics)

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11 pages, 4437 KiB

Open AccessArticle

Gene Delivery System Using Droplet Injector and Temperature-Controlled Planarian Holder

by Michael Lee, Jing-Jie Syu, Chia-Ying Chu and Yen-Wen Lu

Inventions 2018, 3(3), 57; https://doi.org/10.3390/inventions3030057 - 21 Aug 2018

Cited by 1 | Viewed by 5684

Abstract

A microinjection system for gene delivery to a planarian was presented with materials widely used by manufacturers. The system consists of a nanoliter droplet generator/injector and a planarian holder. Glass capillary needles were used to consistently generate droplets and to inject droplets into a planarian. The holder provides a low-temperature environment that immobilizes the planarian for injection. Our system was tested and showed successful injections of microbeads and droplets with double-stranded RNA into the planarian. The results demonstrated the capability of our system as an alternative for gene delivery for studying gene functions in planarians or other living objects for regenerative medicine studies. Full article

(This article belongs to the Special Issue Microfluidics and Nanofluidics)

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17 pages, 4575 KiB

Open AccessArticle

Examining the Effect of Flow Rate Ratio on Droplet Generation and Regime Transition in a Microfluidic T-Junction at Constant Capillary Numbers

by Katerina Loizou, Voon-Loong Wong and Buddhika Hewakandamby

Inventions 2018, 3(3), 54; https://doi.org/10.3390/inventions3030054 - 10 Aug 2018

Cited by 28 | Viewed by 7697

Abstract

The focus of this work is to examine the effect of flow rate ratio (quotient of the dispersed phase flow rate over the continuous phase flow rate) on a regime transition from squeezing to dripping at constant capillary numbers. The effect of the flow rate ratio on the volume of droplets generated in a microfluidic T-junction is discussed, and a new scaling law to estimate their volume is proposed. Existing work on a regime transition reported by several researchers focuses on the effect of the capillary number on regime transition, and the results that are presented in this paper advance the current understanding by indicating that the flow rate ratio is another parameter that dictates regime transition. In this paper, the transition between squeezing and dripping regimes is reported at constant capillary numbers, with a transition region identified between squeezing and dripping regimes. Dripping is observed at lower flow rate ratios and squeezing at higher flow rate ratios, with a transition region between the two regimes at flow rate ratios between 1 and 2. This is presented in a flow regime map that is constructed based on the observed mechanism. A scaling model is proposed to characterise droplet volume in terms of flow rate ratio and capillary number. The effect of flow rate ratio on the non-dimensional droplet volume is presented, and lastly, the droplet volume is expressed in terms of a range of parameters, such as the viscosity ratio between the dispersed and the continuous phase, capillary number, and the geometrical characteristics of the channels. Full article

(This article belongs to the Special Issue Microfluidics and Nanofluidics)

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13 pages, 5432 KiB

Open AccessArticle

Cyclic Block Copolymer Microchannel Fabrication and Sealing for Microfluidics Applications

by Chia-Yi Yen, Moh-Ching O. Chang, Zong-Fu Shih, Yi-Hsing Lien and Chia-Wen Tsao

Inventions 2018, 3(3), 49; https://doi.org/10.3390/inventions3030049 - 16 Jul 2018

Cited by 8 | Viewed by 6979

Abstract

High mechanical rigidity, chemical resistance, and ultraviolet-visible light transmissivity of thermoplastics are attractive characteristics in microfluidics because various biomedical microfluidic devices require solvent, acid, or base manipulation, and optical observation or detection. The cyclic block copolymer (CBC) is a new class of thermoplastics with excellent optical properties, low water absorption, favorable chemical resistance, and low density, which make it ideal for use in polymer microfluidic applications. In the polymer microfabrication process, front-end microchannel fabrication and post-end bonding are critical steps that determine the success of polymer microfluidic devices. In this study, for the first time, we verified the performance of CBC created through front-end microchannel fabrication by applying hot embossing and post-end sealing and bonding, and using thermal fusion and ultraviolet (UV)/ozone surface-assist bonding methods. Two grades of CBC were evaluated and compared with two commonly used cyclic olefin polymers, cyclic olefin copolymers (COC), and cyclic olefin polymers (COP). The results indicated that CBCs provided favorable pattern transfer (>99%) efficiency and high bonding strength in microchannel fabrication and bonding procedures, which is ideal for use in microfluidics. Full article

(This article belongs to the Special Issue Microfluidics and Nanofluidics)

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9 pages, 1628 KiB

Open AccessArticle

Adjustment and Measurement of Contact Angle with Electrowetting on a Quartz-Crystal Microbalance

by Jing-Wei Lin, Da-Shin Wang and Shih-Kang Fan

Inventions 2018, 3(3), 46; https://doi.org/10.3390/inventions3030046 - 10 Jul 2018

Cited by 3 | Viewed by 5791

Abstract

Electrowetting-on-dielectric (EWOD) has been widely exploited as an actuating force to manipulate liquids by surface tension and modulation of the contact angle on a microscale. To evaluate EWOD, an optical measurement of the droplet contact angle is conventional, but is constrained by the optical properties of the liquid, especially when two liquid phases (e.g., water in oil) are involved. We developed a non-optical method to study EWOD using a quartz-crystal microbalance (QCM). A QCM provides a promising technique for mass sensing, and has been developed for the study of liquid viscosity, density and contact angle. In this research, a QCM was employed to generate EWOD and concurrently to measure the variation of the contact angle. The contact angle of droplets of water in air and in oil was evaluated. The voltage-dependent oil film between a water droplet and the QCM surface was sensed. A modified QCM model considering a voltage-dependent oil film was derived for the analysis of the contact angle. Full article

(This article belongs to the Special Issue Microfluidics and Nanofluidics)

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14 pages, 1851 KiB

Open AccessArticle

The Separation of Microalgae Using Dean Flow in a Spiral Microfluidic Device

by Ming-Lung Lee and Da-Jeng Yao

Inventions 2018, 3(3), 40; https://doi.org/10.3390/inventions3030040 - 21 Jun 2018

Cited by 14 | Viewed by 7340

Abstract

A cell-in-droplet encapsulation using Dean flow in a spiral microfluidic device was applied to separate microalgae. In recent years, researchers have been interested in separating micro particles using microfluidic chips because of its great advantages in relation to various applications such as in biotechnology, medical examination, and cell studies. The main disadvantage of these microfluidic chips is particle clogging that decreases the separation yield, which then creates difficulties during the investigation of the particles. The microfluidic chip that is introduced in this work is a combination of two distinct designs—a spiral microchannel design to separate microalgae of various sizes, and a microdroplet generation design for cell encapsulation. The yield of the separation is enhanced through the concept of dominant forces (Dean drag force and lift force) in a spiral microchannel design, together with a design of the microdroplet generation that narrows the volume to facilitate cell observation. We report the development of cells, particle separation, and microdroplet generation. Using the spiral microchannel design can solve the clogging problem by distributing the microalgae evenly for the microdroplet generation section. A spiral microfluidics design was used as a separator for the different sized particles and a microdroplets generation design was used to encapsulate the separated particles. As for the design for the microdroplets generation section, a 3-way microchannel was designed. In this research, two kinds of microalgae have been used: the smaller one is chlorella vulgaris and the bigger one is cosmarium. Because of all of these benefits, this device might be an alternative for cell applications using droplet-based platforms. With a different channel height design, the separation efficiency for Chlorella vulgaris is about 75–80% and for Cosmarium is about 60–72%. Full article

(This article belongs to the Special Issue Microfluidics and Nanofluidics)

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18 pages, 6384 KiB

Open AccessArticle

Numerical Study on Single Flowing Liquid and Supercritical CO₂ Drop in Microchannel: Thin Film, Flow Fields, and Interfacial Profile

by Ning Qin, Yu Feng, John Z. Wen and Carolyn L. Ren

Inventions 2018, 3(2), 35; https://doi.org/10.3390/inventions3020035 - 01 Jun 2018

Cited by 4 | Viewed by 6289

Abstract

Taylor segments, as a common feature in two- or multi-phase microflows, are a strong flow pattern candidate for applications when enhanced heat or mass transfer is particularly considered. A thin film that separates these segments from touching the solid channel and the flow fields near and inside the segment are two key factors that influence (either restricting or improving) the performance of heat and mass transfer. In this numerical study, a computational fluid dynamics (CFD) method and dense carbon dioxide (CO₂) and water are applied and used as a fluid pair, respectively. One single flowing liquid or supercritical CO₂ drop enclosed by water is traced in fixed frames of a long straight microchannel. The thin film, flow fields near and within single CO₂ drop, and interfacial distributions of CO₂ subjected to diffusion and local convections are focused on and discussed. The computed thin film is generally characterized by a thickness of 1.3~2.2% of the channel width (150 µm). Flow vortexes are formed within the hydrodynamic capsular drop. The interfacial distribution profile of CO₂ drop is controlled by local convections near the interface and the interphase diffusion, the extent of which is subject to the drop size and drop speed as well. Full article

(This article belongs to the Special Issue Microfluidics and Nanofluidics)

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9 pages, 2520 KiB

Open AccessArticle

Rapid Paper-Based System for Human Serum Creatinine Detection

by Lung-Ming Fu, Chin-Chung Tseng, Wei-Jhong Ju and Ruey-Jen Yang

Inventions 2018, 3(2), 34; https://doi.org/10.3390/inventions3020034 - 28 May 2018

Cited by 21 | Viewed by 11226

Abstract

An integrated system consisting of a paper-based chip and a smart detection device is proposed for determining the human serum creatinine concentration based on Jaffé reaction theory. In the proposed approach, the reaction zone of the paper-based chip is implanted with picric acid and NaOH reagent and dried at 35 °C for 20 min. Human serum creatinine is dripped onto the reaction zone of the chip. A Jaffé reaction is induced by heating the chip at 37 °C for 5 min and the creatinine concentration is then derived by analyzing the RGB (red, green and blue) intensity of the resulting Janovsky complex using self-written analysis software installed on a smartphone. The validity of the proposed method is demonstrated using control samples with creatinine concentrations ranging from 0.2~8 mg/dL. The detection results obtained for 32 real-world creatinine samples are shown to be in excellent agreement with those obtained using a standard macroscale method (R² = 0.9994). Overall, the results show that the proposed system provides a compact, low-cost and reliable approach for human serum creatinine concentration detection. Full article

(This article belongs to the Special Issue Microfluidics and Nanofluidics)

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Review

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14 pages, 797 KiB

Open AccessReview

PDMS-Based Microfluidic Devices for Cell Culture

by Stefania Torino, Brunella Corrado, Mario Iodice and Giuseppe Coppola

Inventions 2018, 3(3), 65; https://doi.org/10.3390/inventions3030065 - 06 Sep 2018

Cited by 82 | Viewed by 13355

Abstract

Microfluidic technology has affirmed itself as a powerful tool in medical and biological research by offering the possibility of managing biological samples in tiny channels and chambers. Among the different applications, the use of microfluidics for cell cultures has attracted much interest from scientists worldwide. Traditional cell culture methods need high quantities of samples and reagents that are strongly reduced in miniaturized systems. In addition, the microenvironment is better controlled by scaling down. In this paper, we provide an overview of the aspects related to the design of a novel microfluidic culture chamber, the fabrication approach based on polydimethylsiloxane (PDMS) soft-lithography, and the most critical issues in shrinking the size of the system. Full article

(This article belongs to the Special Issue Microfluidics and Nanofluidics)

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25 pages, 7067 KiB

Open AccessReview

A Review of Current Methods in Microfluidic Device Fabrication and Future Commercialization Prospects

by Bruce K. Gale, Alexander R. Jafek, Christopher J. Lambert, Brady L. Goenner, Hossein Moghimifam, Ugochukwu C. Nze and Suraj Kumar Kamarapu

Inventions 2018, 3(3), 60; https://doi.org/10.3390/inventions3030060 - 28 Aug 2018

Cited by 308 | Viewed by 23823

Abstract

Microfluidic devices currently play an important role in many biological, chemical, and engineering applications, and there are many ways to fabricate the necessary channel and feature dimensions. In this review, we provide an overview of microfabrication techniques that are relevant to both research and commercial use. A special emphasis on both the most practical and the recently developed methods for microfluidic device fabrication is applied, and it leads us to specifically address laminate, molding, 3D printing, and high resolution nanofabrication techniques. The methods are compared for their relative costs and benefits, with special attention paid to the commercialization prospects of the various technologies. Full article

(This article belongs to the Special Issue Microfluidics and Nanofluidics)

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