Micromachines

Editorial

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154 KiB

Open AccessEditorial

Micro/Nano Devices for Chemical Analysis

by Manabu Tokeshi and Kiichi Sato

Micromachines 2016, 7(9), 164; https://doi.org/10.3390/mi7090164 - 9 Sep 2016

Cited by 7 | Viewed by 4145

Abstract

Since the concept of micro total analysis systems (µ-TAS) has been advocated, various kinds of micro/nano devices have been developed by researchers in many ﬁelds, such as in chemistry, chemical engineering, mechanical engineering, electric engineering, biology, and medicine, among others.[...] Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

Research

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2609 KiB

Open AccessArticle

High-Pressure Acceleration of Nanoliter Droplets in the Gas Phase in a Microchannel

by Yutaka Kazoe, Ippei Yamashiro, Kazuma Mawatari and Takehiko Kitamori

Micromachines 2016, 7(8), 142; https://doi.org/10.3390/mi7080142 - 15 Aug 2016

Cited by 4 | Viewed by 5040

Abstract

Microfluidics has been used to perform various chemical operations for pL–nL volumes of samples, such as mixing, reaction and separation, by exploiting diffusion, viscous forces, and surface tension, which are dominant in spaces with dimensions on the micrometer scale. To further develop this [...] Read more.

Microfluidics has been used to perform various chemical operations for pL–nL volumes of samples, such as mixing, reaction and separation, by exploiting diffusion, viscous forces, and surface tension, which are dominant in spaces with dimensions on the micrometer scale. To further develop this field, we previously developed a novel microfluidic device, termed a microdroplet collider, which exploits spatially and temporally localized kinetic energy. This device accelerates a microdroplet in the gas phase along a microchannel until it collides with a target. We demonstrated 6000-fold faster mixing compared to mixing by diffusion; however, the droplet acceleration was not optimized, because the experiments were conducted for only one droplet size and at pressures in the 10–100 kPa range. In this study, we investigated the acceleration of a microdroplet using a high-pressure (MPa) control system, in order to achieve higher acceleration and kinetic energy. The motion of the nL droplet was observed using a high-speed complementary metal oxide semiconductor (CMOS) camera. A maximum droplet velocity of ~5 m/s was achieved at a pressure of 1–2 MPa. Despite the higher fluid resistance, longer droplets yielded higher acceleration and kinetic energy, because droplet splitting was a determining factor in the acceleration and using a longer droplet helped prevent it. The results provide design guidelines for achieving higher kinetic energies in the microdroplet collider for various microfluidic applications. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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5891 KiB

Open AccessArticle

A Method of Three-Dimensional Micro-Rotational Flow Generation for Biological Applications

by Yaxiaer Yalikun, Yasunari Kanda and Keisuke Morishima

Micromachines 2016, 7(8), 140; https://doi.org/10.3390/mi7080140 - 10 Aug 2016

Cited by 15 | Viewed by 6597

Abstract

We report a convenient method to create a three-dimensional micro-rotational fluidic platform for biological applications in the direction of a vertical plane (out-of-plane) without contact in an open space. Unlike our previous complex fluidic manipulation system, this method uses a micro-rotational flow generated [...] Read more.

We report a convenient method to create a three-dimensional micro-rotational fluidic platform for biological applications in the direction of a vertical plane (out-of-plane) without contact in an open space. Unlike our previous complex fluidic manipulation system, this method uses a micro-rotational flow generated near a single orifice when the solution is pushed from the orifice by using a single pump. The three-dimensional fluidic platform shows good potential for fluidic biological applications such as culturing, stimulating, sorting, and manipulating cells. The pattern and velocity of the micro-rotational flow can be controlled by tuning the parameters such as the flow rate and the liquid-air interface height. We found that bio-objects captured by the micro-rotational flow showed self-rotational motion and orbital motion. Furthermore, the path length and position, velocity, and pattern of the orbital motion of the bio-object could be controlled. To demonstrate our method, we used embryoid body cells. As a result, the orbital motion had a maximum length of 2.4 mm, a maximum acceleration of 0.63 m/s², a frequency of approximately 0.45 Hz, a maximum velocity of 15.4 mm/s, and a maximum rotation speed of 600 rpm. The capability to have bio-objects rotate or move orbitally in three dimensions without contact opens up new research opportunities in three-dimensional microfluidic technology. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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2214 KiB

Open AccessCommunication

Microfluidic Autologous Serum Eye-Drops Preparation as a Potential Dry Eye Treatment

by Takao Yasui, Jumpei Morikawa, Noritada Kaji, Manabu Tokeshi, Kazuo Tsubota and Yoshinobu Baba

Micromachines 2016, 7(7), 113; https://doi.org/10.3390/mi7070113 - 4 Jul 2016

Cited by 1 | Viewed by 5540

Abstract

Dry eye is a problem in tearing quality and/or quantity and it afflicts millions of persons worldwide. An autologous serum eye-drop is a good candidate for dry eye treatment; however, the eye-drop preparation procedures take a long time and are relatively troublesome. Here [...] Read more.

Dry eye is a problem in tearing quality and/or quantity and it afflicts millions of persons worldwide. An autologous serum eye-drop is a good candidate for dry eye treatment; however, the eye-drop preparation procedures take a long time and are relatively troublesome. Here we use spiral microchannels to demonstrate a strategy for the preparation of autologous serum eye-drops, which provide benefits for all dry eye patients; 100% and 90% removal efficiencies are achieved for 10 μm microbeads and whole human blood cells, respectively. Since our strategy allows researchers to integrate other functional microchannels into one device, such a microfluidic device will be able to offer a new one-step preparation system for autologous serum eye-drops. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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1718 KiB

Open AccessArticle

Light-Addressable Potentiometric Sensor as a Sensing Element in Plug-Based Microfluidic Devices

by Ko-Ichiro Miyamoto, Takuya Sato, Minami Abe, Torsten Wagner, Michael J. Schöning and Tatsuo Yoshinobu

Micromachines 2016, 7(7), 111; https://doi.org/10.3390/mi7070111 - 1 Jul 2016

Cited by 18 | Viewed by 5633

Abstract

A plug-based microfluidic system based on the principle of the light-addressable potentiometric sensor (LAPS) is proposed. The LAPS is a semiconductor-based chemical sensor, which has a free addressability of the measurement point on the sensing surface. By combining a microfluidic device and LAPS, [...] Read more.

A plug-based microfluidic system based on the principle of the light-addressable potentiometric sensor (LAPS) is proposed. The LAPS is a semiconductor-based chemical sensor, which has a free addressability of the measurement point on the sensing surface. By combining a microfluidic device and LAPS, ion sensing can be performed anywhere inside the microfluidic channel. In this study, the sample solution to be measured was introduced into the channel in a form of a plug with a volume in the range of microliters. Taking advantage of the light-addressability, the position of the plug could be monitored and pneumatically controlled. With the developed system, the pH value of a plug with a volume down to 400 nL could be measured. As an example of plug-based operation, two plugs were merged in the channel, and the pH change was detected by differential measurement. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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5470 KiB

Open AccessArticle

Large-Scale Integration of All-Glass Valves on a Microfluidic Device

by Yaxiaer Yalikun and Yo Tanaka

Micromachines 2016, 7(5), 83; https://doi.org/10.3390/mi7050083 - 6 May 2016

Cited by 38 | Viewed by 6914

Abstract

In this study, we developed a method for fabricating a microfluidic device with integrated large-scale all-glass valves and constructed an actuator system to control each of the valves on the device. Such a microfluidic device has advantages that allow its use in various [...] Read more.

In this study, we developed a method for fabricating a microfluidic device with integrated large-scale all-glass valves and constructed an actuator system to control each of the valves on the device. Such a microfluidic device has advantages that allow its use in various fields, including physical, chemical, and biochemical analyses and syntheses. However, it is inefficient and difficult to integrate the large-scale all-glass valves in a microfluidic device using conventional glass fabrication methods, especially for the through-hole fabrication step. Therefore, we have developed a fabrication method for the large-scale integration of all-glass valves in a microfluidic device that contains 110 individually controllable diaphragm valve units on a 30 mm × 70 mm glass slide. This prototype device was fabricated by first sandwiching a 0.4-mm-thick glass slide that contained 110 1.5-mm-diameter shallow chambers, each with two 50-μm-diameter through-holes, between an ultra-thin glass sheet (4 μm thick) and another 0.7-mm-thick glass slide that contained etched channels. After the fusion bonding of these three layers, the large-scale microfluidic device was obtained with integrated all-glass valves consisting of 110 individual diaphragm valve units. We demonstrated its use as a pump capable of generating a flow rate of approximately 0.06–5.33 μL/min. The maximum frequency of flow switching was approximately 12 Hz. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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2322 KiB

Open AccessCommunication

High Throughput Studies of Cell Migration in 3D Microtissues Fabricated by a Droplet Microfluidic Chip

by Xiangchen Che, Jacob Nuhn, Ian Schneider and Long Que

Micromachines 2016, 7(5), 84; https://doi.org/10.3390/mi7050084 - 5 May 2016

Cited by 13 | Viewed by 5794

Abstract

Arrayed three-dimensional (3D) micro-sized tissues with encapsulated cells (microtissues) have been fabricated by a droplet microfluidic chip. The extracellular matrix (ECM) is a polymerized collagen network. One or multiple breast cancer cells were embedded within the microtissues, which were stored in arrayed microchambers [...] Read more.

Arrayed three-dimensional (3D) micro-sized tissues with encapsulated cells (microtissues) have been fabricated by a droplet microfluidic chip. The extracellular matrix (ECM) is a polymerized collagen network. One or multiple breast cancer cells were embedded within the microtissues, which were stored in arrayed microchambers on the same chip without ECM droplet shrinkage over 48 h. The migration trajectory of the cells was recorded by optical microscopy. The migration speed was calculated in the range of 3–6 µm/h. Interestingly, cells in devices filled with a continuous collagen network migrated faster than those where only droplets were arrayed in the chambers. This is likely due to differences in the length scales of the ECM network, as cells embedded in thin collagen slabs also migrate slower than those in thick collagen slabs. In addition to migration, this technical platform can be potentially used to study cancer cell-stromal cell interactions and ECM remodeling in 3D tumor-mimicking environments. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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2926 KiB

Open AccessArticle

Three-Dimensional Fabrication for Microfluidics by Conventional Techniques and Equipment Used in Mass Production

by Toyohiro Naito, Makoto Nakamura, Noritada Kaji, Takuya Kubo, Yoshinobu Baba and Koji Otsuka

Micromachines 2016, 7(5), 82; https://doi.org/10.3390/mi7050082 - 4 May 2016

Cited by 13 | Viewed by 6597

Abstract

This paper presents a simple three-dimensional (3D) fabrication method based on soft lithography techniques and laminated object manufacturing. The method can create 3D structures that have undercuts with general machines for mass production and laboratory scale prototyping. The minimum layer thickness of the [...] Read more.

This paper presents a simple three-dimensional (3D) fabrication method based on soft lithography techniques and laminated object manufacturing. The method can create 3D structures that have undercuts with general machines for mass production and laboratory scale prototyping. The minimum layer thickness of the method is at least 4 µm and bonding strength between layers is over 330 kPa. The performance reaches conventional fabrication techniques used for two-dimensionally (2D)-designed microfluidic devices. We fabricated some 3D structures, i.e., fractal structures, spiral structures, and a channel-in-channel structure, in microfluidic channels and demonstrated 3D microfluidics. The fabrication method can be achieved with a simple black light for bio-molecule detection; thus, it is useful for not only lab-scale rapid prototyping, but also for commercial manufacturing. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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6868 KiB

Open AccessFeature PaperArticle

High-Resolution Microfluidic Paper-Based Analytical Devices for Sub-Microliter Sample Analysis

by Keisuke Tenda, Riki Ota, Kentaro Yamada, Terence G. Henares, Koji Suzuki and Daniel Citterio

Micromachines 2016, 7(5), 80; https://doi.org/10.3390/mi7050080 - 2 May 2016

Cited by 63 | Viewed by 12009

Abstract

This work demonstrates the fabrication of microfluidic paper-based analytical devices (µPADs) suitable for the analysis of sub-microliter sample volumes. The wax-printing approach widely used for the patterning of paper substrates has been adapted to obtain high-resolution microfluidic structures patterned in filter paper. This [...] Read more.

This work demonstrates the fabrication of microfluidic paper-based analytical devices (µPADs) suitable for the analysis of sub-microliter sample volumes. The wax-printing approach widely used for the patterning of paper substrates has been adapted to obtain high-resolution microfluidic structures patterned in filter paper. This has been achieved by replacing the hot plate heating method conventionally used to melt printed wax features into paper by simple hot lamination. This patterning technique, in combination with the consideration of device geometry and the influence of cellulose fiber direction in filter paper, led to a model µPAD design with four microfluidic channels that can be filled with as low as 0.5 µL of liquid. Finally, the application to a colorimetric model assay targeting total protein concentrations is shown. Calibration curves for human serum albumin (HSA) were recorded from sub-microliter samples (0.8 µL), with tolerance against ±0.1 µL variations in the applied liquid volume. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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6946 KiB

Open AccessArticle

Magnetic Particle Plug-Based Assays for Biomarker Analysis

by Chayakom Phurimsak, Mark D. Tarn and Nicole Pamme

Micromachines 2016, 7(5), 77; https://doi.org/10.3390/mi7050077 - 26 Apr 2016

Cited by 9 | Viewed by 7863

Abstract

Conventional immunoassays offer selective and quantitative detection of a number of biomarkers, but are laborious and time-consuming. Magnetic particle-based assays allow easy and rapid selection of analytes, but still suffer from the requirement of tedious multiple reaction and washing steps. Here, we demonstrate [...] Read more.

Conventional immunoassays offer selective and quantitative detection of a number of biomarkers, but are laborious and time-consuming. Magnetic particle-based assays allow easy and rapid selection of analytes, but still suffer from the requirement of tedious multiple reaction and washing steps. Here, we demonstrate the trapping of functionalised magnetic particles within a microchannel for performing rapid immunoassays by flushing consecutive reagent and washing solutions over the trapped particle plug. Three main studies were performed to investigate the potential of the platform for quantitative analysis of biomarkers: (i) a streptavidin-biotin binding assay; (ii) a sandwich assay of the inflammation biomarker, C-reactive protein (CRP); and (iii) detection of the steroid hormone, progesterone (P4), towards a competitive assay. Quantitative analysis with low limits of detection was demonstrated with streptavidin-biotin, while the CRP and P4 assays exhibited the ability to detect clinically relevant analytes, and all assays were completed in only 15 min. These preliminary results show the great potential of the platform for performing rapid, low volume magnetic particle plug-based assays of a range of clinical biomarkers via an exceedingly simple technique. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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5887 KiB

Open AccessArticle

Quasi-Optical Terahertz Microfluidic Devices for Chemical Sensing and Imaging

by Lei Liu, Zhenguo Jiang, Syed Rahman, Md. Itrat Bin Shams, Benxin Jing, Akash Kannegulla and Li-Jing Cheng

Micromachines 2016, 7(5), 75; https://doi.org/10.3390/mi7050075 - 25 Apr 2016

Cited by 13 | Viewed by 7260

Abstract

We first review the development of a frequency domain quasi-optical terahertz (THz) chemical sensing and imaging platform consisting of a quartz-based microfluidic subsystem in our previous work. We then report the application of this platform to sensing and characterizing of several selected liquid [...] Read more.

We first review the development of a frequency domain quasi-optical terahertz (THz) chemical sensing and imaging platform consisting of a quartz-based microfluidic subsystem in our previous work. We then report the application of this platform to sensing and characterizing of several selected liquid chemical samples from 570–630 GHz. THz sensing of chemical mixtures including isopropylalcohol-water (IPA-H₂O) mixtures and acetonitrile-water (ACN-H₂O) mixtures have been successfully demonstrated and the results have shown completely different hydrogen bond dynamics detected in different mixture systems. In addition, the developed platform has been applied to study molecule diffusion at the interface between adjacent liquids in the multi-stream laminar flow inside the microfluidic subsystem. The reported THz microfluidic platform promises real-time and label-free chemical/biological sensing and imaging with extremely broad bandwidth, high spectral resolution, and high spatial resolution. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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2283 KiB

Open AccessArticle

Balloon Pump with Floating Valves for Portable Liquid Delivery

by Yuya Morimoto, Yumi Mukouyama, Shohei Habasaki and Shoji Takeuchi

Micromachines 2016, 7(3), 39; https://doi.org/10.3390/mi7030039 - 1 Mar 2016

Cited by 6 | Viewed by 8152

Abstract

In this paper, we propose a balloon pump with floating valves to control the discharge flow rates of sample solutions. Because the floating valves were made from a photoreactive resin, the shapes of the floating valves could be controlled by employing different exposure [...] Read more.

In this paper, we propose a balloon pump with floating valves to control the discharge flow rates of sample solutions. Because the floating valves were made from a photoreactive resin, the shapes of the floating valves could be controlled by employing different exposure patterns without any change in the pump configurations. Owing to the simple preparation process of the pump, we succeeded in changing the discharge flow rates in accordance with the number and length of the floating valves. Because our methods could be used to easily prepare balloon pumps with arbitrary discharge properties, we achieved several microfluidic operations by the integration of the balloon pumps with microfluidic devices. Therefore, we believe that the balloon pump with floating valves will be a useful driving component for portable microfluidic systems. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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1339 KiB

Open AccessArticle

A Microfluidic-Based Fabry-Pérot Gas Sensor

by Jin Tao, Qiankun Zhang, Yunfeng Xiao, Xiaoying Li, Pei Yao, Wei Pang, Hao Zhang, Xuexin Duan, Daihua Zhang and Jing Liu

Micromachines 2016, 7(3), 36; https://doi.org/10.3390/mi7030036 - 25 Feb 2016

Cited by 11 | Viewed by 6776

Abstract

We developed a micro-gas detector based on a Fabry-Pérot (FP) cavity embedded in a microfluidic channel. The detector was fabricated in two steps: a silicon substrate was bonded to a glass slide curved with a micro-groove, forming a microfluidic FP cavity; then an [...] Read more.

We developed a micro-gas detector based on a Fabry-Pérot (FP) cavity embedded in a microfluidic channel. The detector was fabricated in two steps: a silicon substrate was bonded to a glass slide curved with a micro-groove, forming a microfluidic FP cavity; then an optical fiber was inserted through a hole drilled at the center of the groove into the microfluidic FP cavity, forming an FP cavity. The light is partially reflected at the optical fiber endface and the silicon surface, respectively, generating an interference spectrum. The detection is implemented by monitoring the interference spectrum shift caused by the refractive index change of the FP cavity when a gas analyte passes through. This detection mechanism (1) enables detecting a wide range of analytes, including both organic and inorganic (inertia) gases, significantly enhancing its versatility; (2) does not disturb any gas flow so that it can collaborate with other detectors to improve sensing performances; and (3) ensures a fast sensing response for potential applications in gas chromatography systems. In the experiments, we used various gases to demonstrate the sensing capability of the detector and observed drastically different sensor responses. The estimated sensitivity of the detector is 812.5 nm/refractive index unit (RIU) with a detection limit of 1.2 × 10⁻⁶ RIU assuming a 1 pm minimum resolvable wavelength shift. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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4704 KiB

Open AccessArticle

Three-Dimensional Electro-Sonic Flow Focusing Ionization Microfluidic Chip for Mass Spectrometry

by Cilong Yu, Xiang Qian, Yan Chen, Quan Yu, Kai Ni and Xiaohao Wang

Micromachines 2015, 6(12), 1890-1902; https://doi.org/10.3390/mi6121463 - 4 Dec 2015

Cited by 15 | Viewed by 6987

Abstract

Increasing research efforts have been recently devoted to the coupling of microfluidic chip-integrated ionization sources to mass spectrometry (MS). Considering the limitations of microfluidic chips coupled with MS such as liquid spreading, dead volume, and manufacturing troubles, this paper proposed a new three-dimensional [...] Read more.

Increasing research efforts have been recently devoted to the coupling of microfluidic chip-integrated ionization sources to mass spectrometry (MS). Considering the limitations of microfluidic chips coupled with MS such as liquid spreading, dead volume, and manufacturing troubles, this paper proposed a new three-dimensional (3D) flow focusing (FF)-based microfluidic ionizing source. This source was fabricated by using the two-layer soft lithography method with the nozzle placed inside the chip. The proposed FF microfluidic chip can realize two-phase FF with liquid in air regardless of the viscosity ratio of the continuous and dispersed phases. MS results indicated that the proposed FF microfluidic chip can work as a typical electrical ionization source when supplied with high voltage and can serve as a sonic ionization source without high voltage. The electro-sonic FF ionization microfluidic chip is expected to have various applications, particularly in the integrated and portable applications of ionization sources coupling with portable MS in the future. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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4238 KiB

Open AccessArticle

All Silicon Micro-GC Column Temperature Programming Using Axial Heating

by Milad Navaei, Alireza Mahdavifar, Jean-Marie D. Dimandja, Gary McMurray and Peter J. Hesketh

Micromachines 2015, 6(7), 865-878; https://doi.org/10.3390/mi6070865 - 10 Jul 2015

Cited by 17 | Viewed by 6498

Abstract

In this work we present a high performance micro gas chromatograph column with a novel two dimensional axial heating technique for faster and more precise temperature programming, resulting in an improved separation performance. Three different axial resistive heater designs were simulated theoretically on [...] Read more.

In this work we present a high performance micro gas chromatograph column with a novel two dimensional axial heating technique for faster and more precise temperature programming, resulting in an improved separation performance. Three different axial resistive heater designs were simulated theoretically on a 3.0 m × 300 μm × 50 μm column for the highest temperature gradient on a 22 by 22 μm column. The best design was then micro-fabricated and evaluated experimentally. The simulation results showed that simultaneous temperature gradients in time and distance along the column are possible by geometric optimization of the heater when using forced convection. The gradients along the column continuously refocused eluting bands, offsetting part of the chromatographic band spreading. The utility of this method was further investigated for a test mixture of three hydrocarbons (hexane, octane, and decane). Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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Review

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8583 KiB

Open AccessReview

Microfluidic Approaches for Manipulating, Imaging, and Screening C. elegans

by Bhagwati P. Gupta and Pouya Rezai

Micromachines 2016, 7(7), 123; https://doi.org/10.3390/mi7070123 - 19 Jul 2016

Cited by 57 | Viewed by 10381

Abstract

The nematode C. elegans (worm) is a small invertebrate animal widely used in studies related to fundamental biological processes, disease modelling, and drug discovery. Due to their small size and transparent body, these worms are highly suitable for experimental manipulations. In recent years [...] Read more.

The nematode C. elegans (worm) is a small invertebrate animal widely used in studies related to fundamental biological processes, disease modelling, and drug discovery. Due to their small size and transparent body, these worms are highly suitable for experimental manipulations. In recent years several microfluidic devices and platforms have been developed to accelerate worm handling, phenotypic studies and screens. Here we review major tools and briefly discuss their usage in C. elegans research. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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2366 KiB

Open AccessReview

Advances in Microfluidic Paper-Based Analytical Devices for Food and Water Analysis

by Lori Shayne Alamo Busa, Saeed Mohammadi, Masatoshi Maeki, Akihiko Ishida, Hirofumi Tani and Manabu Tokeshi

Micromachines 2016, 7(5), 86; https://doi.org/10.3390/mi7050086 - 9 May 2016

Cited by 168 | Viewed by 17848

Abstract

Food and water contamination cause safety and health concerns to both animals and humans. Conventional methods for monitoring food and water contamination are often laborious and require highly skilled technicians to perform the measurements, making the quest for developing simpler and cost-effective techniques [...] Read more.

Food and water contamination cause safety and health concerns to both animals and humans. Conventional methods for monitoring food and water contamination are often laborious and require highly skilled technicians to perform the measurements, making the quest for developing simpler and cost-effective techniques for rapid monitoring incessant. Since the pioneering works of Whitesides’ group from 2007, interest has been strong in the development and application of microfluidic paper-based analytical devices (μPADs) for food and water analysis, which allow easy, rapid and cost-effective point-of-need screening of the targets. This paper reviews recently reported μPADs that incorporate different detection methods such as colorimetric, electrochemical, fluorescence, chemiluminescence, and electrochemiluminescence techniques for food and water analysis. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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979 KiB

Open AccessReview

Unconventional Electrochemistry in Micro-/Nanofluidic Systems

by Sahana Sarkar, Stanley C. S. Lai and Serge G. Lemay

Micromachines 2016, 7(5), 81; https://doi.org/10.3390/mi7050081 - 3 May 2016

Cited by 17 | Viewed by 16223

Abstract

Electrochemistry is ideally suited to serve as a detection mechanism in miniaturized analysis systems. A significant hurdle can, however, be the implementation of reliable micrometer-scale reference electrodes. In this tutorial review, we introduce the principal challenges and discuss the approaches that have been [...] Read more.

Electrochemistry is ideally suited to serve as a detection mechanism in miniaturized analysis systems. A significant hurdle can, however, be the implementation of reliable micrometer-scale reference electrodes. In this tutorial review, we introduce the principal challenges and discuss the approaches that have been employed to build suitable references. We then discuss several alternative strategies aimed at eliminating the reference electrode altogether, in particular two-electrode electrochemical cells, bipolar electrodes and chronopotentiometry. Full article

(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

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