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Micromachines
Volume 7
Issue 3
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Micromachines, Volume 7, Issue 3 (March 2016) – 18 articles

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7367 KiB  
Article
An Investigation of Processes for Glass Micromachining
by Nguyen Van Toan, Masaya Toda and Takahito Ono
Micromachines 2016, 7(3), 51; https://doi.org/10.3390/mi7030051 - 22 Mar 2016
Cited by 33 | Viewed by 8692
Abstract
This paper presents processes for glass micromachining, including sandblast, wet etching, reactive ion etching (RIE), and glass reflow techniques. The advantages as well as disadvantages of each method are presented and discussed in light of the experiments. Sandblast and wet etching techniques are [...] Read more.
This paper presents processes for glass micromachining, including sandblast, wet etching, reactive ion etching (RIE), and glass reflow techniques. The advantages as well as disadvantages of each method are presented and discussed in light of the experiments. Sandblast and wet etching techniques are simple processes but face difficulties in small and high-aspect-ratio structures. A sandblasted 2 cm × 2 cm Tempax glass wafer with an etching depth of approximately 150 µm is demonstrated. The Tempax glass structure with an etching depth and sides of approximately 20 μm was observed via the wet etching process. The most important aspect of this work was to develop RIE and glass reflow techniques. The current challenges of these methods are addressed here. Deep Tempax glass pillars having a smooth surface, vertical shapes, and a high aspect ratio of 10 with 1-μm-diameter glass pillars, a 2-μm pitch, and a 10-μm etched depth were achieved via the RIE technique. Through-silicon wafer interconnects, embedded inside the Tempax glass, are successfully demonstrated via the glass reflow technique. Glass reflow into large cavities (larger than 100 μm), a micro-trench (0.8-μm wide trench), and a micro-capillary (1-μm diameter) are investigated. An additional optimization of process flow was performed for glass penetration into micro-scale patterns. Full article
(This article belongs to the Special Issue Glass Micromachining)
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5897 KiB  
Article
Microfluidic Device to Measure the Speed of C. elegans Using the Resistance Change of the Flexible Electrode
by Jaehoon Jung, Masahiro Nakajima, Masaru Takeuchi, Zoran Najdovski, Qiang Huang and Toshio Fukuda
Micromachines 2016, 7(3), 50; https://doi.org/10.3390/mi7030050 - 19 Mar 2016
Cited by 11 | Viewed by 6251
Abstract
This work presents a novel method to assess the condition of Caenorhabditis elegans (C. elegans) through a resistance measurement of its undulatory locomotion speed inside a micro channel. As the worm moves over the electrode inside the micro channel, the length [...] Read more.
This work presents a novel method to assess the condition of Caenorhabditis elegans (C. elegans) through a resistance measurement of its undulatory locomotion speed inside a micro channel. As the worm moves over the electrode inside the micro channel, the length of the electrode changes, consequently behaving like a strain gauge. In this paper, the electrotaxis was applied for controlling the direction of motion of C. elegans as an external stimulus, resulting in the worm moving towards the cathode of the circuit. To confirm the proposed measurement method, a microfluidic device was developed that employs a sinusoidal channel and a thin polydimethylsiloxane (PDMS) layer with an electrode. The PDMS layer maintains a porous structure to enable the flexibility of the electrode. In this study, 6 measurements were performed to obtain the speed of an early adult stage C. elegans, where the measured average speed was 0.35 (±0.05) mm/s. The results of this work demonstrate the application of our method to measure the speed of C. elegans undulatory locomotion. This novel approach can be applied to make such measurements without an imaging system, and more importantly, allows directly to detect the locomotion of C. elegans using an electrical signal (i.e., the change in resistance). Full article
(This article belongs to the Special Issue Micro/Nano Robotics)
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2220 KiB  
Article
Nonlinear Dynamic Behavior of a Bi-Axial Torsional MEMS Mirror with Sidewall Electrodes
by Mehmet Ozdogan and Shahrzad Towfighian
Micromachines 2016, 7(3), 42; https://doi.org/10.3390/mi7030042 - 18 Mar 2016
Cited by 12 | Viewed by 5784
Abstract
Nonlinear dynamic responses of a Micro-Electro-Mechanical Systems (MEMS) mirror with sidewall electrodes are presented that are in close agreement with previously-reported experimental data. An analysis of frequency responses reveals softening behavior, and secondary resonances originated from the dominant quadratic nonlinearity. The quadratic nonlinearity [...] Read more.
Nonlinear dynamic responses of a Micro-Electro-Mechanical Systems (MEMS) mirror with sidewall electrodes are presented that are in close agreement with previously-reported experimental data. An analysis of frequency responses reveals softening behavior, and secondary resonances originated from the dominant quadratic nonlinearity. The quadratic nonlinearity is an electromechanical coupling effect caused by the electrostatic force. This effect is reflected in our mathematical model used to simulate the dynamic response of the micro-mirror. The effects of increased forcing and decreased damping on the frequency response are investigated as the mirrors are mostly used in vacuum packages. The results can predict MEMS mirror behaviors in optical devices better than previously-reported models. Full article
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5630 KiB  
Article
Digital Micromirror Device (DMD)-Based High-Cycle Torsional Fatigue Testing Micromachine for 1D Nanomaterials
by Chenchen Jiang, Dayong Hu and Yang Lu
Micromachines 2016, 7(3), 49; https://doi.org/10.3390/mi7030049 - 14 Mar 2016
Cited by 17 | Viewed by 7957
Abstract
Fatigue behavior of nanomaterials could ultimately limit their applications in variable nano-devices and flexible nanoelectronics. However, very few existing nanoscale mechanical testing instruments were designed for dedicated fatigue experiments, especially for the challenging torsional cyclic loading. In this work, a novel high-cycle torsion [...] Read more.
Fatigue behavior of nanomaterials could ultimately limit their applications in variable nano-devices and flexible nanoelectronics. However, very few existing nanoscale mechanical testing instruments were designed for dedicated fatigue experiments, especially for the challenging torsional cyclic loading. In this work, a novel high-cycle torsion straining micromachine, based on the digital micromirror device (DMD), has been developed for the torsional fatigue study on various one-dimensional (1D) nanostructures, such as metallic and semiconductor nanowires. Due to the small footprint of the DMD chip itself and its cable-remote controlling mechanisms, it can be further used for the desired in situ testing under high-resolution optical or electron microscopes (e.g., scanning electron microscope (SEM)), which allows real-time monitoring of the fatigue testing status and construction of useful structure-property relationships for the nanomaterials. We have then demonstrated its applications for testing nanowire samples with diameters about 100 nm and 500 nm, up to 1000 nm, and some of them experienced over hundreds of thousands of loading cycles before fatigue failure. Due to the commercial availability of the DMD and millions of micromirrors available on a single chip, this platform could offer a low-cost and high-throughput nanomechanical solution for the uncovered torsional fatigue behavior of various 1D nanostructures. Full article
(This article belongs to the Special Issue Micro/Nano Robotics)
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3418 KiB  
Article
Experimental Analysis of Porosity and Permeability in Pressed Paper
by Juhwan Park, Joong Ho Shin and Je-Kyun Park
Micromachines 2016, 7(3), 48; https://doi.org/10.3390/mi7030048 - 14 Mar 2016
Cited by 26 | Viewed by 8873
Abstract
In this paper, we report an analysis of pressed paper in terms of porosity and permeability. Previously, we reported a pressed paper that exhibits decreased porosity and permeability. Additionally, its applications into programmed sample delivery as well as flow rate control were reported. [...] Read more.
In this paper, we report an analysis of pressed paper in terms of porosity and permeability. Previously, we reported a pressed paper that exhibits decreased porosity and permeability. Additionally, its applications into programmed sample delivery as well as flow rate control were reported. However, there is a need for a theoretical analysis of pressed paper in terms of porosity and permeability for a more precise design principle and its applications because porosity and permeability are important factors in determining fluidic behavior. Here, we propose a theoretical model for analyzing decreased porosity and permeability in pressed paper. Porosity and permeability of pressed paper were quantitatively calculated using experimental results with a theoretical model. Furthermore, based on the analyzed results of porosity and permeability in pressed paper, a porosity–permeability relationship was investigated. Full article
(This article belongs to the Special Issue Paper-Based Microfluidic Devices for Point-of-Care Diagnostics)
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4384 KiB  
Review
Liquid Core ARROW Waveguides: A Promising Photonic Structure for Integrated Optofluidic Microsensors
by Genni Testa, Gianluca Persichetti and Romeo Bernini
Micromachines 2016, 7(3), 47; https://doi.org/10.3390/mi7030047 - 11 Mar 2016
Cited by 32 | Viewed by 8270
Abstract
In this paper, we introduce a liquid core antiresonant reflecting optical waveguide (ARROW) as a novel optofluidic device that can be used to create innovative and highly functional microsensors. Liquid core ARROWs, with their dual ability to guide the light and the fluids [...] Read more.
In this paper, we introduce a liquid core antiresonant reflecting optical waveguide (ARROW) as a novel optofluidic device that can be used to create innovative and highly functional microsensors. Liquid core ARROWs, with their dual ability to guide the light and the fluids in the same microchannel, have shown great potential as an optofluidic tool for quantitative spectroscopic analysis. ARROWs feature a planar architecture and, hence, are particularly attractive for chip scale integrated system. Step by step, several improvements have been made in recent years towards the implementation of these waveguides in a complete on-chip system for highly-sensitive detection down to the single molecule level. We review applications of liquid ARROWs for fluids sensing and discuss recent results and trends in the developments and applications of liquid ARROW in biomedical and biochemical research. The results outlined show that the strong light matter interaction occurring in the optofluidic channel of an ARROW and the versatility offered by the fabrication methods makes these waveguides a very promising building block for optofluidic sensor development. Full article
(This article belongs to the Special Issue Optofluidics 2015)
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3893 KiB  
Article
Microstructure-Enhanced Liquid–Liquid Extraction in a Real-Time Fluorescence Detection Microfluidic Chip
by Penghui Xiong, Xiangyu Chen, Ying Xiong, Gang Liu and Yangchao Tian
Micromachines 2016, 7(3), 46; https://doi.org/10.3390/mi7030046 - 10 Mar 2016
Cited by 9 | Viewed by 6783
Abstract
Microfluidic system is widely employed in the detection of environmental contaminants and biological specimens. One of the critical issues which limits the applications of microfluidic chips is the limit of detection of trace specimens. Liquid–liquid extraction is of great importance in the preprocessing [...] Read more.
Microfluidic system is widely employed in the detection of environmental contaminants and biological specimens. One of the critical issues which limits the applications of microfluidic chips is the limit of detection of trace specimens. Liquid–liquid extraction is of great importance in the preprocessing in microfluidic devices. In this paper, we developed a real-time fluorescence detection microfluidic chip combined with a microstructure-enhanced liquid–liquid laminar extraction technique, which concentrated the trace compound and realized real-time monitoring. Auxiliary microstructures integrated in the microfluidic chip were applied to increase the extraction efficiency, which was proved by the FEM (finite element method) simulation as well. A common fluorescence probe, Rhodamine 6G (Rh6g), was used in the experiment to demonstrate the performance of the microfluidic system. It revealed that the liquid–liquid laminar extraction combined with auxiliary microstructures of a cross shape was an effective method for enrichment. The efficiency of microstructure-enhanced liquid–liquid extraction was increased by 350% compared to the traditional laminar flow extraction. Full article
(This article belongs to the Collection Lab-on-a-Chip)
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7035 KiB  
Article
Photochemical Synthesis and Versatile Functionalization Method of a Robust Porous Poly(ethylene glycol methacrylate-co-allyl methacrylate) Monolith Dedicated to Radiochemical Separation in a Centrifugal Microfluidic Platform
by Marion Losno, Ivan Ferrante, René Brennetot, Jérôme Varlet, Cécile Blanc, Bernard Grenut, Etienne Amblard, Stéphanie Descroix and Clarisse Mariet
Micromachines 2016, 7(3), 45; https://doi.org/10.3390/mi7030045 - 10 Mar 2016
Cited by 9 | Viewed by 6352
Abstract
The use of a centrifugal microfluidic platform is an alternative to classical chromatographic procedures for radiochemistry. An ion-exchange support with respect to the in situ light-addressable process of elaboration is specifically designed to be incorporated as a radiochemical sample preparation module in centrifugal [...] Read more.
The use of a centrifugal microfluidic platform is an alternative to classical chromatographic procedures for radiochemistry. An ion-exchange support with respect to the in situ light-addressable process of elaboration is specifically designed to be incorporated as a radiochemical sample preparation module in centrifugal microsystem devices. This paper presents a systematic study of the synthesis of the polymeric porous monolith poly(ethylene glycol methacrylate-co-allyl methacrylate) used as a solid-phase support and the versatile and robust photografting process of the monolith based on thiol-ene click chemistry. The polymerization reaction is investigated, varying the formulation of the polymerisable mixture. The robustness of the stationary phase was tested in concentrated nitric acid. Thanks to their unique “easy-to-use” features, centrifugal microfluidic platforms are potential successful candidates for the downscaling of chromatographic separation of radioactive samples (automation, multiplexing, easy integration in glove-boxes environment, and low cost of maintenance). Full article
(This article belongs to the Special Issue Centrifugal (Compact-Disc) Microfluidics for Extreme POC)
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140 KiB  
Editorial
Micromachines Beyond Silicon-Based Technologies: A Letter from the New Editor-in-Chief
by Nam-Trung Nguyen
Micromachines 2016, 7(3), 44; https://doi.org/10.3390/mi7030044 - 9 Mar 2016
Cited by 1 | Viewed by 3610
Abstract
It is my pleasure to assume the role of the Editor-in-Chief of Micromachines from March 2016.[...] Full article
2831 KiB  
Article
Dealing with Magnetic Disturbances in Human Motion Capture: A Survey of Techniques
by Gabriele Ligorio and Angelo Maria Sabatini
Micromachines 2016, 7(3), 43; https://doi.org/10.3390/mi7030043 - 9 Mar 2016
Cited by 56 | Viewed by 6418
Abstract
Magnetic-Inertial Measurement Units (MIMUs) based on microelectromechanical (MEMS) technologies are widespread in contexts such as human motion tracking. Although they present several advantages (lightweight, size, cost), their orientation estimation accuracy might be poor. Indoor magnetic disturbances represent one of the limiting factors for [...] Read more.
Magnetic-Inertial Measurement Units (MIMUs) based on microelectromechanical (MEMS) technologies are widespread in contexts such as human motion tracking. Although they present several advantages (lightweight, size, cost), their orientation estimation accuracy might be poor. Indoor magnetic disturbances represent one of the limiting factors for their accuracy, and, therefore, a variety of work was done to characterize and compensate them. In this paper, the main compensation strategies included within Kalman-based orientation estimators are surveyed and classified according to which degrees of freedom are affected by the magnetic data and to the magnetic disturbance rejection methods implemented. By selecting a representative method from each category, four algorithms were obtained and compared in two different magnetic environments: (1) small workspace with an active magnetic source; (2) large workspace without active magnetic sources. A wrist-worn MIMU was used to acquire data from a healthy subject, whereas a stereophotogrammetric system was adopted to obtain ground-truth data. The results suggested that the model-based approaches represent the best compromise between the two testbeds. This is particularly true when the magnetic data are prevented to affect the estimation of the angles with respect to the vertical direction. Full article
(This article belongs to the Special Issue Magnetic MEMS)
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3064 KiB  
Communication
Capillary Self-Alignment of Microchips on Soft Substrates
by Bo Chang, Quan Zhou, Zhigang Wu, Zhenhua Liu, Robin H. A. Ras and Klas Hjort
Micromachines 2016, 7(3), 41; https://doi.org/10.3390/mi7030041 - 4 Mar 2016
Cited by 19 | Viewed by 9261
Abstract
Soft micro devices and stretchable electronics have attracted great interest for their potential applications in sensory skins and wearable bio-integrated devices. One of the most important steps in building printed circuits is the alignment of assembled micro objects. Previously, the capillary self-alignment of [...] Read more.
Soft micro devices and stretchable electronics have attracted great interest for their potential applications in sensory skins and wearable bio-integrated devices. One of the most important steps in building printed circuits is the alignment of assembled micro objects. Previously, the capillary self-alignment of microchips driven by surface tension effects has been shown to be able to achieve high-throughput and high-precision in the integration of micro parts on rigid hydrophilic/superhydrophobic patterned surfaces. In this paper, the self-alignment of microchips on a patterned soft and stretchable substrate, which consists of hydrophilic pads surrounded by a superhydrophobic polydimethylsiloxane (PDMS) background, is demonstrated for the first time. A simple process has been developed for making superhydrophobic soft surface by replicating nanostructures of black silicon onto a PDMS surface. Different kinds of PDMS have been investigated, and the parameters for fabricating superhydrophobic PDMS have been optimized. A self-alignment strategy has been proposed that can result in reliable self-alignment on a soft PDMS substrate. Our results show that capillary self-alignment has great potential for building soft printed circuits. Full article
(This article belongs to the Special Issue Building by Self-Assembly)
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5258 KiB  
Article
Fabrication and Measurement of a Suspended Nanochannel Microbridge Resonator Monolithically Integrated with CMOS Readout Circuitry
by Gabriel Vidal-Álvarez, Eloi Marigó, Francesc Torres and Núria Barniol
Micromachines 2016, 7(3), 40; https://doi.org/10.3390/mi7030040 - 2 Mar 2016
Cited by 6 | Viewed by 5609
Abstract
We present the fabrication and characterization of a suspended microbridge resonator with an embedded nanochannel. The suspended microbridge resonator is electrostatically actuated, capacitively sensed, and monolithically integrated with complementary metal-oxide-semiconductor (CMOS) readout circuitry. The device is fabricated using the back end of line [...] Read more.
We present the fabrication and characterization of a suspended microbridge resonator with an embedded nanochannel. The suspended microbridge resonator is electrostatically actuated, capacitively sensed, and monolithically integrated with complementary metal-oxide-semiconductor (CMOS) readout circuitry. The device is fabricated using the back end of line (BEOL) layers of the AMS 0.35 μm commercial CMOS technology, interconnecting two metal layers with a contact layer. The fabricated device has a 6 fL capacity and has one of the smallest embedded channels so far. It is able to attain a mass sensitivity of 25 ag/Hz using a fully integrable electrical transduction. Full article
(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)
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2283 KiB  
Article
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 8138
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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4570 KiB  
Article
Allergy Testing and Drug Screening on an ITO-Coated Lab-on-a-Disc
by Ho Chin Kwok, Pui Man Lau, Shu Yuen Wu, Ho Pui HO, Minghui Gao, Yiu Wa Kwan, Chun Kwok Wong and Siu Kai Kong
Micromachines 2016, 7(3), 38; https://doi.org/10.3390/mi7030038 - 27 Feb 2016
Cited by 7 | Viewed by 9141
Abstract
A lab-on-a-disc (LOAD) is a centrifugal microfluidic set-up based on centrifugal force without using micro-pumps to drive reagents and cells to various chambers through channels and valves for reactions. A LOAD coated with conductive transparent indium tin oxide (ITO) for thermal control was [...] Read more.
A lab-on-a-disc (LOAD) is a centrifugal microfluidic set-up based on centrifugal force without using micro-pumps to drive reagents and cells to various chambers through channels and valves for reactions. A LOAD coated with conductive transparent indium tin oxide (ITO) for thermal control was developed to screen allergy-blocking agents. When the acridine orange (AO)-loaded KU-812 human basophilic cells were activated in the LOAD by stimuli, AO trapped in the cytoplasmic granules was released externally as an allergic mediator mimetic to report degranulation. This response was monitored by fluorescence when the released AO in supernatant had been transferred, with a higher spinning speed, from the reaction chamber to detection chamber in the LOAD where AO reacted with exogenous DNA. We report here the principles of the system and an improved LOAD set-up with the ITO-coated glass resistive microheater to run assays at 37 °C. By using this platform, we demonstrate here for the first time that triptolide, an active ingredient from the Chinese medicine herb Tripterygium wilfordii Hook f., was able to suppress the fMLP-mediated degranulation in basophils. This serves as an example how LOADs can be used to screen agents to alleviate symptoms of allergy. Full article
(This article belongs to the Special Issue Centrifugal (Compact-Disc) Microfluidics for Extreme POC)
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2115 KiB  
Article
Mathematical Modelling and Simulation Research of Thermal Engraving Technology Based on PMMA Material
by Xiaowei Han, Xiaowei Liu and Li Tian
Micromachines 2016, 7(3), 37; https://doi.org/10.3390/mi7030037 - 26 Feb 2016
Cited by 2 | Viewed by 5303
Abstract
We proposed a thermal engraving technology based on heat transfer theory and polymer rheology in microfluidic field. Then, we established a 3D model of the thermal engraving process based on polymethyl methacrylate (PMMA) material. We could employ the model to analyze the influence [...] Read more.
We proposed a thermal engraving technology based on heat transfer theory and polymer rheology in microfluidic field. Then, we established a 3D model of the thermal engraving process based on polymethyl methacrylate (PMMA) material. We could employ the model to analyze the influence of temperature and speed on microchannel processing through the finite element simulation. Thus, we gained the optimal processing parameters. The orthogonal experiments were carried out within the parameter ranges obtained by the simulation results. Finally, we fabricated the smooth microchannel, the average roughness of which was 0.3 μm, by using the optimal parameters. Furthermore, we examined the surface morphology and wettability. Our work provides a convenient technological support for a fast, low-cost, and large-scale manufacturing method of microfluidic chips. Full article
(This article belongs to the Collection Lab-on-a-Chip)
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1339 KiB  
Article
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 6767
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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3672 KiB  
Article
Sandwiched Long-Period Fiber Grating Fabricated by MEMS Process for CO2 Gas Detection
by Chao-Wei Wu and Chia-Chin Chiang
Micromachines 2016, 7(3), 35; https://doi.org/10.3390/mi7030035 - 25 Feb 2016
Cited by 15 | Viewed by 5423
Abstract
This paper presents an optical fiber gas sensor based on sandwiched long-period fiber grating (SLPFG) that is fabricated via the microelectromechanical systems (MEMS) process and coated with amino silica adsorbent for carbon dioxide (CO2) gas sensing. The amine-modified nanoporous silica foams [...] Read more.
This paper presents an optical fiber gas sensor based on sandwiched long-period fiber grating (SLPFG) that is fabricated via the microelectromechanical systems (MEMS) process and coated with amino silica adsorbent for carbon dioxide (CO2) gas sensing. The amine-modified nanoporous silica foams were coated onto the SLPFG for CO2 adsorption. To characterize the CO2 adsorption of the SLPFG sensor, a gas sensing test was conducted with a mixed gas consisting of 15% CO2 and 85% nitrogen at a flow rate of 0.2 L/min. The results showed that the spectra of the SLPFG were varied with the gas flow within 21 min. After that, the transmission spectra of the SLPFG held steady and exhibited no further change. This phenomenon was caused by the adsorption saturation of the amine-modified nanoporous silica foams which were coated onto the SLPFG. During the absorption process, the transmission was increasing by about 11.27 dB (from −23.11 to −11.84 dB), and the increasing rate of transmission was 0.4598 dB/min. Repeatable adsorption and desorption experiment results showed that the SLPFG CO2 gas sensor exhibited good repeatability and a short response time. The recovery rate for each cycle was about 85%, and the required recovery time was short. Therefore, elaborated SLPFG gas sensor could potentially be used as a gas sensor for monitoring CO2 adsorption in the context of various industrial, agricultural, and household applications. Full article
(This article belongs to the Special Issue Recent Advances in Smart System)
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1774 KiB  
Article
Surface Free Energy Determination of APEX Photosensitive Glass
by William R. Gaillard, Emanuel Waddell and John D. Williams
Micromachines 2016, 7(3), 34; https://doi.org/10.3390/mi7030034 - 23 Feb 2016
Cited by 5 | Viewed by 5185
Abstract
Surface free energy (SFE) plays an important role in microfluidic device operation. Photosensitive glasses such as APEX offer numerous advantages over traditional glasses for microfluidics, yet the SFE for APEX has not been previously reported. We calculate SFE with the Owens/Wendt geometric method [...] Read more.
Surface free energy (SFE) plays an important role in microfluidic device operation. Photosensitive glasses such as APEX offer numerous advantages over traditional glasses for microfluidics, yet the SFE for APEX has not been previously reported. We calculate SFE with the Owens/Wendt geometric method by using contact angles measured with the Sessile drop technique. While the total SFE for APEX is found to be similar to traditional microstructurable glasses, the polar component is lower, which is likely attributable to composition. The SFE was modified at each stage of device fabrication, but the SFE of the stock and fully processed glass was found to be approximately the same at a value of 51 mJ·m−2. APEX exhibited inconsistent wetting behavior attributable to an inhomogeneous surface chemical composition. Means to produce more consistent wetting of photosensitive glass for microfluidic applications are discussed. Full article
(This article belongs to the Special Issue Glass Micromachining)
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