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Micromachines, Volume 6, Issue 11 (November 2015)

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Open AccessArticle Modeling of Hysteresis in Piezoelectric Actuator Based on Segment Similarity
Micromachines 2015, 6(11), 1805-1824; https://doi.org/10.3390/mi6111456
Received: 18 September 2015 / Revised: 2 November 2015 / Accepted: 3 November 2015 / Published: 17 November 2015
Cited by 1 | Viewed by 1873 | PDF Full-text (6202 KB) | HTML Full-text | XML Full-text
Abstract
To successfully exploit the full potential of piezoelectric actuators in micro/nano positioning systems, it is essential to model their hysteresis behavior accurately. A novel hysteresis model for piezoelectric actuator is proposed in this paper. Firstly, segment-similarity, which describes the similarity relationship between hysteresis [...] Read more.
To successfully exploit the full potential of piezoelectric actuators in micro/nano positioning systems, it is essential to model their hysteresis behavior accurately. A novel hysteresis model for piezoelectric actuator is proposed in this paper. Firstly, segment-similarity, which describes the similarity relationship between hysteresis curve segments with different turning points, is proposed. Time-scale similarity, which describes the similarity relationship between hysteresis curves with different rates, is used to solve the problem of dynamic effect. The proposed model is formulated using these similarities. Finally, the experiments are performed with respect to a micro/nano-meter movement platform system. The effectiveness of the proposed model is verified as compared with the Preisach model. The experimental results show that the proposed model is able to precisely predict the hysteresis trajectories of piezoelectric actuators and performs better than the Preisach model. Full article
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Open AccessReview Constriction Channel Based Single-Cell Mechanical Property Characterization
Micromachines 2015, 6(11), 1794-1804; https://doi.org/10.3390/mi6111457
Received: 2 September 2015 / Revised: 2 November 2015 / Accepted: 10 November 2015 / Published: 16 November 2015
Cited by 13 | Viewed by 2397 | PDF Full-text (3110 KB) | HTML Full-text | XML Full-text
Abstract
This mini-review presents recent progresses in the development of microfluidic constriction channels enabling high-throughput mechanical property characterization of single cells. We first summarized the applications of the constriction channel design in quantifying mechanical properties of various types of cells including red blood cells, [...] Read more.
This mini-review presents recent progresses in the development of microfluidic constriction channels enabling high-throughput mechanical property characterization of single cells. We first summarized the applications of the constriction channel design in quantifying mechanical properties of various types of cells including red blood cells, white blood cells, and tumor cells. Then we highlighted the efforts in modeling the cellular entry process into the constriction channel, enabling the translation of raw mechanical data (e.g., cellular entry time into the constriction channel) into intrinsic cellular mechanical properties such as cortical tension or Young’s modulus. In the end, current limitations and future research opportunities of the microfluidic constriction channels were discussed. Full article
(This article belongs to the Special Issue Optofluidics 2015) Printed Edition available
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Open AccessReview Droplet Manipulations in Two Phase Flow Microfluidics
Micromachines 2015, 6(11), 1768-1793; https://doi.org/10.3390/mi6111455
Received: 25 September 2015 / Revised: 3 November 2015 / Accepted: 6 November 2015 / Published: 13 November 2015
Cited by 25 | Viewed by 5638 | PDF Full-text (9077 KB) | HTML Full-text | XML Full-text
Abstract
Even though droplet microfluidics has been developed since the early 1980s, the number of applications that have resulted in commercial products is still relatively small. This is partly due to an ongoing maturation and integration of existing methods, but possibly also because of [...] Read more.
Even though droplet microfluidics has been developed since the early 1980s, the number of applications that have resulted in commercial products is still relatively small. This is partly due to an ongoing maturation and integration of existing methods, but possibly also because of the emergence of new techniques, whose potential has not been fully realized. This review summarizes the currently existing techniques for manipulating droplets in two-phase flow microfluidics. Specifically, very recent developments like the use of acoustic waves, magnetic fields, surface energy wells, and electrostatic traps and rails are discussed. The physical principles are explained, and (potential) advantages and drawbacks of different methods in the sense of versatility, flexibility, tunability and durability are discussed, where possible, per technique and per droplet operation: generation, transport, sorting, coalescence and splitting. Full article
(This article belongs to the Special Issue Droplet Microfluidics: Techniques and Technologies)
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Open AccessArticle Using a Microfluidic Gradient Generator to Characterize BG-11 Medium for the Growth of Cyanobacteria Synechococcus elongatus PCC7942
Micromachines 2015, 6(11), 1755-1767; https://doi.org/10.3390/mi6111454
Received: 2 September 2015 / Revised: 31 October 2015 / Accepted: 5 November 2015 / Published: 13 November 2015
Cited by 3 | Viewed by 2690 | PDF Full-text (1377 KB) | HTML Full-text | XML Full-text
Abstract
The photosynthetic cyanobacterium Synechococcus elongatus PCC7942 has recently gained great attention for its ability to directly convert CO2 into renewable chemicals upon genetic engineering. Thus, it is of great interest to increase the growth speed and lower the medium requirement for cultivating this [...] Read more.
The photosynthetic cyanobacterium Synechococcus elongatus PCC7942 has recently gained great attention for its ability to directly convert CO2 into renewable chemicals upon genetic engineering. Thus, it is of great interest to increase the growth speed and lower the medium requirement for cultivating this cyanobacterium. The cultivation medium of Synechococcus elongatus PCC7942 has been developed, which consists of many inorganic and metal ingredients with a specific composition, known as the BG-11 medium. In this work, we analyzed the concentration effect of each ingredient and identified the absolutely essential components in BG-11 medium for cyanobacteria growth using the concentration gradient generator chip (CGGC) fabricated by MEMS technology. As shown by our results, removal of the individual component sodium nitrate, potassium phosphate, or magnesium sulfate from the BG-11 medium led to severe growth inhibition of Synechococcus elongatus PCC7942. Contrary to our expectation, increasing concentration of the crucial ingredients showed either insignificant or negative impact on cell growth. Overall, standard growth could be achieved without supplementation of ethylenediaminetetraacetic acid (EDTA) disodium, sodium carbonate, or sodium citrate to the culture medium. Further improvement of the CGGC-based microfluidic system based on this preliminary study may broaden its application range to analyze more complicated correlations. Full article
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Open AccessArticle The Structure of Wheel Check Valve Influence on Air Block Phenomenon of Piezoelectric Micro-Pump
Micromachines 2015, 6(11), 1745-1754; https://doi.org/10.3390/mi6111452
Received: 3 August 2015 / Revised: 29 October 2015 / Accepted: 4 November 2015 / Published: 13 November 2015
Cited by 5 | Viewed by 2491 | PDF Full-text (3295 KB) | HTML Full-text | XML Full-text
Abstract
To improve the stability and reliability of the piezoelectric micro-pump, the cause of air block phenomenon is analyzed on the structure of wheel check valve. During the movement of the bubble in the micro-channel, pressure drop occurs, the main factor which influences the [...] Read more.
To improve the stability and reliability of the piezoelectric micro-pump, the cause of air block phenomenon is analyzed on the structure of wheel check valve. During the movement of the bubble in the micro-channel, pressure drop occurs, the main factor which influences the bubble going through is opening height of the wheel check valve. Five groups of wheel check valves with different structures are used to test the wheel check valve opening height and air block probability. The experiment results show that reducing the wheel check valve thickness or diameter ratio can both increase the wheel check valve opening height, and decrease the air block probability. Through experiment, the optimum combination of the wheel check valve structure is obtained within the samples: as the thickness is 0.02 mm, the diameter ratio is 1.2, the wheel check valve opening height gets 252 µm, and within the given bubble volume, the air block probability is less than 2%. Full article
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Open AccessArticle Development of a Flexible Lead-Free Piezoelectric Transducer for Health Monitoring in the Space Environment
Micromachines 2015, 6(11), 1729-1744; https://doi.org/10.3390/mi6111453
Received: 15 September 2015 / Revised: 29 October 2015 / Accepted: 3 November 2015 / Published: 13 November 2015
Cited by 19 | Viewed by 2295 | PDF Full-text (3238 KB) | HTML Full-text | XML Full-text
Abstract
In this work we report on the fabrication process for the development of a flexible piezopolymeric transducer for health monitoring applications, based on lead-free, piezoelectric zinc oxide (ZnO) thin films. All the selected materials are compatible with the space environment and were deposited [...] Read more.
In this work we report on the fabrication process for the development of a flexible piezopolymeric transducer for health monitoring applications, based on lead-free, piezoelectric zinc oxide (ZnO) thin films. All the selected materials are compatible with the space environment and were deposited by the RF magnetron sputtering technique at room temperature, in view of preserving the total flexibility of the structures, which is an important requirement to guarantee coupling with cylindrical fuel tanks whose integrity we want to monitor. The overall transducer architecture was made of a c-axis-oriented ZnO thin film coupled to a pair of flexible Polyimide foils coated with gold (Au) electrodes. The fabrication process started with the deposition of the bottom electrode on Polyimide foils. The ZnO thin film and the top electrode were then deposited onto the Au/Polyimide substrates. Both the electrodes and ZnO layer were properly patterned by wet-chemical etching and optical lithography. The assembly of the final structure was then obtained by gluing the upper and lower Polyimide foils with an epoxy resin capable of guaranteeing low outgassing levels, as well as adequate thermal and electrical insulation of the transducers. The piezoelectric behavior of the prototypes was confirmed and evaluated by measuring the mechanical displacement induced from the application of an external voltage. Full article
(This article belongs to the Special Issue Piezoelectric MEMS)
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Open AccessArticle Development of Micro-Grippers for Tissue and Cell Manipulation with Direct Morphological Comparison
Micromachines 2015, 6(11), 1710-1728; https://doi.org/10.3390/mi6111451
Received: 2 September 2015 / Revised: 20 October 2015 / Accepted: 2 November 2015 / Published: 6 November 2015
Cited by 23 | Viewed by 2895 | PDF Full-text (11643 KB) | HTML Full-text | XML Full-text
Abstract
Although tissue and cell manipulation nowadays is a common task in biomedical analysis, there are still many different ways to accomplish it, most of which are still not sufficiently general, inexpensive, accurate, efficient or effective. Several problems arise both for in vivo or [...] Read more.
Although tissue and cell manipulation nowadays is a common task in biomedical analysis, there are still many different ways to accomplish it, most of which are still not sufficiently general, inexpensive, accurate, efficient or effective. Several problems arise both for in vivo or in vitro analysis, such as the maximum overall size of the device and the gripper jaws (like in minimally-invasive open biopsy) or very limited manipulating capability, degrees of freedom or dexterity (like in tissues or cell-handling operations). This paper presents a new approach to tissue and cell manipulation, which employs a conceptually new conjugate surfaces flexure hinge (CSFH) silicon MEMS-based technology micro-gripper that solves most of the above-mentioned problems. The article describes all of the phases of the development, including topology conception, structural design, simulation, construction, actuation testing and in vitro observation. The latter phase deals with the assessment of the function capability, which consists of taking a series of in vitro images by optical microscopy. They offer a direct morphological comparison between the gripper and a variety of tissues. Full article
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Open AccessArticle Eye Vision Testing System and Eyewear Using Micromachines
Micromachines 2015, 6(11), 1690-1709; https://doi.org/10.3390/mi6111449
Received: 7 September 2015 / Revised: 28 October 2015 / Accepted: 29 October 2015 / Published: 6 November 2015
Cited by 3 | Viewed by 3029 | PDF Full-text (7556 KB) | HTML Full-text | XML Full-text
Abstract
Proposed is a novel eye vision testing system based on micromachines that uses micro-optic, micromechanic, and microelectronic technologies. The micromachines include a programmable micro-optic lens and aperture control devices, pico-projectors, Radio Frequency (RF), optical wireless communication and control links, and energy harvesting and [...] Read more.
Proposed is a novel eye vision testing system based on micromachines that uses micro-optic, micromechanic, and microelectronic technologies. The micromachines include a programmable micro-optic lens and aperture control devices, pico-projectors, Radio Frequency (RF), optical wireless communication and control links, and energy harvesting and storage devices with remote wireless energy transfer capabilities. The portable lightweight system can measure eye refractive powers, optimize light conditions for the eye under testing, conduct color-blindness tests, and implement eye strain relief and eye muscle exercises via time sequenced imaging. A basic eye vision test system is built in the laboratory for near-sighted (myopic) vision spherical lens refractive error correction. Refractive error corrections from zero up to −5.0 Diopters and −2.0 Diopters are experimentally demonstrated using the Electronic-Lens (E-Lens) and aperture control methods, respectively. The proposed portable eye vision test system is suited for children’s eye tests and developing world eye centers where technical expertise may be limited. Design of a novel low-cost human vision corrective eyewear is also presented based on the proposed aperture control concept. Given its simplistic and economical design, significant impact can be created for humans with vision problems in the under-developed world. Full article
(This article belongs to the Special Issue Micro/Nano Photonic Devices and Systems)
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Open AccessReview Progress of MEMS Scanning Micromirrors for Optical Bio-Imaging
Micromachines 2015, 6(11), 1675-1689; https://doi.org/10.3390/mi6111450
Received: 16 September 2015 / Revised: 17 October 2015 / Accepted: 28 October 2015 / Published: 5 November 2015
Cited by 10 | Viewed by 3175 | PDF Full-text (5896 KB) | HTML Full-text | XML Full-text
Abstract
Microelectromechanical systems (MEMS) have an unmatched ability to incorporate numerous functionalities into ultra-compact devices, and due to their versatility and miniaturization, MEMS have become an important cornerstone in biomedical and endoscopic imaging research. To incorporate MEMS into such applications, it is critical to [...] Read more.
Microelectromechanical systems (MEMS) have an unmatched ability to incorporate numerous functionalities into ultra-compact devices, and due to their versatility and miniaturization, MEMS have become an important cornerstone in biomedical and endoscopic imaging research. To incorporate MEMS into such applications, it is critical to understand underlying architectures involving choices in actuation mechanism, including the more common electrothermal, electrostatic, electromagnetic, and piezoelectric approaches, reviewed in this paper. Each has benefits and tradeoffs and is better suited for particular applications or imaging schemes due to achievable scan ranges, power requirements, speed, and size. Many of these characteristics are fabrication-process dependent, and this paper discusses various fabrication flows developed to integrate additional optical functionality beyond simple lateral scanning, enabling dynamic control of the focus or mirror surface. Out of this provided MEMS flexibility arises some challenges when obtaining high resolution images: due to scanning non-linearities, calibration of MEMS scanners may become critical, and inherent image artifacts or distortions during scanning can degrade image quality. Several reviewed methods and algorithms have been proposed to address these complications from MEMS scanning. Given their impact and promise, great effort and progress have been made toward integrating MEMS and biomedical imaging. Full article
(This article belongs to the Special Issue Optical Microsystems)
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Open AccessArticle Digital Microfluidic System with Vertical Functionality
Micromachines 2015, 6(11), 1655-1674; https://doi.org/10.3390/mi6111448
Received: 1 September 2015 / Revised: 19 October 2015 / Accepted: 27 October 2015 / Published: 4 November 2015
Cited by 4 | Viewed by 2240 | PDF Full-text (2137 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Digital (droplet) microfluidics (DµF) is a powerful platform for automated lab-on-a-chip procedures, ranging from quantitative bioassays such as RT-qPCR to complete mammalian cell culturing. The simple MEMS processing protocols typically employed to fabricate DµF devices limit their functionality to two dimensions, and hence [...] Read more.
Digital (droplet) microfluidics (DµF) is a powerful platform for automated lab-on-a-chip procedures, ranging from quantitative bioassays such as RT-qPCR to complete mammalian cell culturing. The simple MEMS processing protocols typically employed to fabricate DµF devices limit their functionality to two dimensions, and hence constrain the applications for which these devices can be used. This paper describes the integration of vertical functionality into a DµF platform by stacking two planar digital microfluidic devices, altering the electrode fabrication process, and incorporating channels for reversibly translating droplets between layers. Vertical droplet movement was modeled to advance the device design, and three applications that were previously unachievable using a conventional format are demonstrated: (1) solutions of calcium dichloride and sodium alginate were vertically mixed to produce a hydrogel with a radially symmetric gradient in crosslink density; (2) a calcium alginate hydrogel was formed within the through-well to create a particle sieve for filtering suspensions passed from one layer to the next; and (3) a cell spheroid formed using an on-chip hanging-drop was retrieved for use in downstream processing. The general capability of vertically delivering droplets between multiple stacked levels represents a processing innovation that increases DµF functionality and has many potential applications. Full article
(This article belongs to the Special Issue Droplet Microfluidics: Techniques and Technologies)
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Open AccessArticle Fabrication of a Micromachined Capacitive Switch Using the CMOS-MEMS Technology
Micromachines 2015, 6(11), 1645-1654; https://doi.org/10.3390/mi6111447
Received: 29 August 2015 / Revised: 21 October 2015 / Accepted: 26 October 2015 / Published: 2 November 2015
Cited by 6 | Viewed by 2114 | PDF Full-text (10702 KB) | HTML Full-text | XML Full-text
Abstract
The study investigates the design and fabrication of a micromachined radio frequency (RF) capacitive switch using the complementary metal oxide semiconductor-microelectromechanical system (CMOS-MEMS) technology. The structure of the micromachined switch is composed of a membrane, eight springs, four inductors, and coplanar waveguide (CPW) [...] Read more.
The study investigates the design and fabrication of a micromachined radio frequency (RF) capacitive switch using the complementary metal oxide semiconductor-microelectromechanical system (CMOS-MEMS) technology. The structure of the micromachined switch is composed of a membrane, eight springs, four inductors, and coplanar waveguide (CPW) lines. In order to reduce the actuation voltage of the switch, the springs are designed as low stiffness. The finite element method (FEM) software CoventorWare is used to simulate the actuation voltage and displacement of the switch. The micromachined switch needs a post-CMOS process to release the springs and membrane. A wet etching is employed to etch the sacrificial silicon dioxide layer, and to release the membrane and springs of the switch. Experiments show that the pull-in voltage of the switch is 12 V. The switch has an insertion loss of 0.8 dB at 36 GHz and an isolation of 19 dB at 36 GHz. Full article
(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)
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Open AccessArticle A Double Emulsion-Based, Plastic-Glass Hybrid Microfluidic Platform for Protein Crystallization
Micromachines 2015, 6(11), 1629-1644; https://doi.org/10.3390/mi6111446
Received: 17 August 2015 / Revised: 21 October 2015 / Accepted: 22 October 2015 / Published: 28 October 2015
Cited by 3 | Viewed by 2873 | PDF Full-text (4182 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This paper reports the design and construction of a plastic-glass hybrid microfluidic platform for performing protein crystallization trials in nanoliter double emulsions. The double emulsion-based protein crystallization trials were implemented with both the vapor-diffusion method and microbatch method by controlling the diffusion of [...] Read more.
This paper reports the design and construction of a plastic-glass hybrid microfluidic platform for performing protein crystallization trials in nanoliter double emulsions. The double emulsion-based protein crystallization trials were implemented with both the vapor-diffusion method and microbatch method by controlling the diffusion of water between the inner and outer phases and by eliminating water evaporation. Double emulsions, whose inner and outer environments can be easily adjusted, can provide ideal conditions to explore protein crystallization with the advantages of a convection-free environment and a homogeneous interface. The property of the water-oil interface was demonstrated to be a critical factor for nucleation, and appropriate surfactants should be chosen to prevent protein adsorption at the interface. The results from the volume effect study showed a trend of fewer crystals and longer incubation time when the protein solution volume became smaller, suggesting that the nucleation in protein crystallization process can be controlled by changing the volume of protein solutions. Finally, sparse matrix screening was achieved using the double emulsion-based microbatch method. The double emulsion-based approach for protein crystallization is a promising tool for enhancing the crystal quality by controlling the nucleation process. Full article
(This article belongs to the Special Issue Droplet Microfluidics: Techniques and Technologies)
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Open AccessArticle The Fringe-Capacitance of Etching Holes for CMOS-MEMS
Micromachines 2015, 6(11), 1617-1628; https://doi.org/10.3390/mi6111445
Received: 7 July 2015 / Revised: 21 October 2015 / Accepted: 21 October 2015 / Published: 28 October 2015
Cited by 2 | Viewed by 1995 | PDF Full-text (4465 KB) | HTML Full-text | XML Full-text
Abstract
Movable suspended microstructures are the common feature of sensors or devices in the fields of Complementary-Metal-Oxide-Semiconductors and Micro-Electro-Mechanical Systems which are usually abbreviated as CMOS-MEMS. To suspend the microstructures, it is commonly to etch the sacrificial layer under the microstructure layer. For large-area [...] Read more.
Movable suspended microstructures are the common feature of sensors or devices in the fields of Complementary-Metal-Oxide-Semiconductors and Micro-Electro-Mechanical Systems which are usually abbreviated as CMOS-MEMS. To suspend the microstructures, it is commonly to etch the sacrificial layer under the microstructure layer. For large-area microstructures, it is necessary to design a large number of etching holes on the microstructure to enhance the etchant uniformly and rapidly permeate into the sacrificial layer. This paper aims at evaluating the fringe capacitance caused by etching holes on microstructures and developing empirical formulas. The formula of capacitance compensation term is derived by curve-fitting on the simulation results by the commercial software ANSYS. Compared with the ANSYS simulation, the deviation of the present formula is within ±5%. The application to determine the capacitance of an electrostatic micro-beam with etching holes is demonstrated in a microstructure experiment, which agrees very well with the experimental data, and the maximum deviation is within ±8%. The present formula is with simple form, wide application range, high accuracy, and easy to use. It is expected to provide the micro-device designers to estimate the capacitance of microstructures with etching holes and predominate in the device characteristics. Full article
(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)
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Open AccessArticle Reduction of Friction of Metals Using Laser-Induced Periodic Surface Nanostructures
Micromachines 2015, 6(11), 1606-1616; https://doi.org/10.3390/mi6111444
Received: 21 August 2015 / Revised: 27 September 2015 / Accepted: 20 October 2015 / Published: 28 October 2015
Cited by 13 | Viewed by 2732 | PDF Full-text (4370 KB) | HTML Full-text | XML Full-text
Abstract
We report on the effect of femtosecond-laser-induced periodic surface structures (LIPSS) on the tribological properties of stainless steel. Uniform periodic nanostructures were produced on AISI 304L (American Iron and Steel Institute steel grade) steel surfaces using an 800-nm femtosecond laser. The spatial periods [...] Read more.
We report on the effect of femtosecond-laser-induced periodic surface structures (LIPSS) on the tribological properties of stainless steel. Uniform periodic nanostructures were produced on AISI 304L (American Iron and Steel Institute steel grade) steel surfaces using an 800-nm femtosecond laser. The spatial periods of LIPSS measured by field emission scanning electron microscopy ranged from 530 to 570 nm. The tribological properties of smooth and textured surfaces with periodic nanostructures were investigated using reciprocating ball-on-flat tests against AISI 440C balls under both dry and starved oil lubricated conditions. The friction coefficient of LIPSS covered surfaces has shown a lower value than that of the smooth surface. The induced periodic nanostructures demonstrated marked potential for reducing the friction coefficient compared with the smooth surface. Full article
(This article belongs to the collection Laser Micromachining and Microfabrication)
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Open AccessArticle Multifunctional Platform with CMOS-Compatible Tungsten Microhotplate for Pirani, Temperature, and Gas Sensor
Micromachines 2015, 6(11), 1597-1605; https://doi.org/10.3390/mi6111443
Received: 26 July 2015 / Revised: 16 October 2015 / Accepted: 20 October 2015 / Published: 28 October 2015
Cited by 3 | Viewed by 1841 | PDF Full-text (3594 KB) | HTML Full-text | XML Full-text
Abstract
A multifunctional platform based on the microhotplate was developed for applications including a Pirani vacuum gauge, temperature, and gas sensor. It consisted of a tungsten microhotplate and an on-chip operational amplifier. The platform was fabricated in a standard complementary metal oxide semiconductor (CMOS) [...] Read more.
A multifunctional platform based on the microhotplate was developed for applications including a Pirani vacuum gauge, temperature, and gas sensor. It consisted of a tungsten microhotplate and an on-chip operational amplifier. The platform was fabricated in a standard complementary metal oxide semiconductor (CMOS) process. A tungsten plug in standard CMOS process was specially designed as the serpentine resistor for the microhotplate, acting as both heater and thermister. With the sacrificial layer technology, the microhotplate was suspended over the silicon substrate with a 340 nm gap. The on-chip operational amplifier provided a bias current for the microhotplate. This platform has been used to develop different kinds of sensors. The first one was a Pirani vacuum gauge ranging from 1-1 to 105 Pa. The second one was a temperature sensor ranging from -20 to 70 °C. The third one was a thermal-conductivity gas sensor, which could distinguish gases with different thermal conductivities in constant gas pressure and environment temperature. In the fourth application, with extra fabrication processes including the deposition of gas-sensitive film, the platform was used as a metal-oxide gas sensor for the detection of gas concentration. Full article
(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)
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Open AccessArticle Rounding of Negative Dry Film Resist by Diffusive Backside Exposure Creating Rounded Channels for Pneumatic Membrane Valves
Micromachines 2015, 6(11), 1588-1596; https://doi.org/10.3390/mi6111442
Received: 7 September 2015 / Revised: 29 September 2015 / Accepted: 16 October 2015 / Published: 28 October 2015
Cited by 2 | Viewed by 2291 | PDF Full-text (2077 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Processing of dry film resist is an easy, low-cost, and fast way to fabricate microfluidic structures. Currently, common processes are limited to creating solely rectangular channels. However, it has shown that rounded channels are necessary to ensure proper closing of pneumatic membrane valves [...] Read more.
Processing of dry film resist is an easy, low-cost, and fast way to fabricate microfluidic structures. Currently, common processes are limited to creating solely rectangular channels. However, it has shown that rounded channels are necessary to ensure proper closing of pneumatic membrane valves for microfluidic devices. Here, we introduce a modification to the standard lithography process, in order to create rounded channels for microfluidic structures. Therefore, a diffuser element was inserted into in the optical path between the light source and glass substrate, which is then exposed through the backside, hence altering the exposure to the dry resist spatially. Characterization of the process was carried out with different exposure times, features sizes, and substrate thickness. The process modification is almost effortless and can be integrated in any lithography process. Full article
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