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Micromachines, Volume 9, Issue 10 (October 2018)

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Open AccessArticle Fabrication and Optimization of High Aspect Ratio Through-Silicon-Vias Electroplating for 3D Inductor
Micromachines 2018, 9(10), 528; https://doi.org/10.3390/mi9100528 (registering DOI)
Received: 9 September 2018 / Revised: 12 October 2018 / Accepted: 12 October 2018 / Published: 18 October 2018
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Abstract
In this study, the filling process of high aspect ratio through-silicon-vias (TSVs) under dense conditions using the electroplating method was efficiently achieved and optimized. Pulsed power was used as the experimental power source and the electroplating solution was prepared with various additive concentrations.
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In this study, the filling process of high aspect ratio through-silicon-vias (TSVs) under dense conditions using the electroplating method was efficiently achieved and optimized. Pulsed power was used as the experimental power source and the electroplating solution was prepared with various additive concentrations. Designed control variable experiments were conducted to determine the optimized method. In the control variable experiments, the relationship of multiple experimental variables, including current density (0.25–2 A/dm2), additive concentration (0.5–2 mL/L), and different shapes of TSVs (circle, oral, and square), were systematically analyzed. Considering the electroplating speed and quality, the influence of different factors on experimental results and the optimized parameters were determined. The results showed that increasing current density improved the electroplating speed but decreased the quality. Additives worked well, whereas their concentrations were controlled within a suitable range. The TSV shape also influenced the electroplating result. When the current density was 1.5 A/dm2 and the additive concentration was 1 mL/L, the TSV filling was relatively better. With the optimized parameters, 500-μm-deep TSVs with a high aspect ratio of 10:1 were fully filled in 20 h, and the via density reached 70/mm2. Finally, optimized parameters were adopted, and the electroplating of 1000-μm-deep TSVs with a diameter of 100 μm was completed in 45 h, which is the deepest and smallest through which a three-dimensional inductor has ever been successfully fabricated. Full article
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Open AccessEditorial Editorial for the Special Issue on Interface Circuits for Microsensor Integrated Systems
Micromachines 2018, 9(10), 527; https://doi.org/10.3390/mi9100527
Received: 15 October 2018 / Accepted: 15 October 2018 / Published: 17 October 2018
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Abstract
Recent advances in sensing technologies, especially those for Microsensor Integrated Systems, have led to several new commercial applications. [...] Full article
(This article belongs to the Special Issue Interface Circuits for Microsensor Integrated Systems)
Open AccessArticle Remote Microwave and Field-Effect Sensing Techniques for Monitoring Hydrogel Sensor Response
Micromachines 2018, 9(10), 526; https://doi.org/10.3390/mi9100526
Received: 29 August 2018 / Revised: 5 October 2018 / Accepted: 11 October 2018 / Published: 17 October 2018
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Abstract
This paper presents two novel techniques for monitoring the response of smart hydrogels composed of synthetic organic materials that can be engineered to respond (swell or shrink, change conductivity and optical properties) to specific chemicals, biomolecules or external stimuli. The first technique uses
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This paper presents two novel techniques for monitoring the response of smart hydrogels composed of synthetic organic materials that can be engineered to respond (swell or shrink, change conductivity and optical properties) to specific chemicals, biomolecules or external stimuli. The first technique uses microwaves both in contact and remote monitoring of the hydrogel as it responds to chemicals. This method is of great interest because it can be used to non-invasively monitor the response of subcutaneously implanted hydrogels to blood chemicals such as oxygen and glucose. The second technique uses a metal-oxide-hydrogel field-effect transistor (MOHFET) and its associated current-voltage characteristics to monitor the hydrogel’s response to different chemicals. MOHFET can be easily integrated with on-board telemetry electronics for applications in implantable biosensors or it can be used as a transistor in an oscillator circuit where the oscillation frequency of the circuit depends on the analyte concentration. Full article
(This article belongs to the Special Issue MEMS Technology for Biomedical Imaging Applications)
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Open AccessArticle Controlling Normal Stiffness in Droplet-Based Linear Bearings
Micromachines 2018, 9(10), 525; https://doi.org/10.3390/mi9100525
Received: 25 September 2018 / Revised: 12 October 2018 / Accepted: 15 October 2018 / Published: 17 October 2018
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Abstract
While capillary forces are negligible relative to gravity at the macroscale, they provide adequate force to effectively manipulate millimeter to micro meter objects. The fluidic actuation can be accomplished using droplets that also act as bearings. While rotary droplet bearings have been previously
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While capillary forces are negligible relative to gravity at the macroscale, they provide adequate force to effectively manipulate millimeter to micro meter objects. The fluidic actuation can be accomplished using droplets that also act as bearings. While rotary droplet bearings have been previously demonstrated, this paper addresses the positioning accuracy of a droplet-based bearing consisting of a droplet between a moving plate and a stationary substrate with constrained wetting region under a normal load. Key wetting cases are analyzed using both closed form analytical approximations and numerical simulations. The vertical force and stiffness characteristics are analyzed in relation to the wetting boundaries of the supporting surface. Case studies of different wetting boundaries are presented and summarized. Design strategies are presented for maximizing load carrying capability and stiffness. These results show that controlled wetting and opposing droplet configurations can create much higher stiffness fluidic bearings than simple droplets. Full article
(This article belongs to the Special Issue Microscale Surface Tension and Its Applications)
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Open AccessArticle Automatic Manipulation of Magnetically Actuated Helical Microswimmers in Static Environments
Micromachines 2018, 9(10), 524; https://doi.org/10.3390/mi9100524
Received: 18 September 2018 / Revised: 9 October 2018 / Accepted: 12 October 2018 / Published: 16 October 2018
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Abstract
Electromagnetically actuated microswimmers have been widely used in various biomedical applications due to their minor invasive traits and their easy access to confined environments. In order to guide the microswimmers autonomously towards a target, an obstacle-free path must be computed using path planning
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Electromagnetically actuated microswimmers have been widely used in various biomedical applications due to their minor invasive traits and their easy access to confined environments. In order to guide the microswimmers autonomously towards a target, an obstacle-free path must be computed using path planning algorithms, meanwhile a motion controller must be formulated. However, automatic manipulations of magnetically actuated microswimmers are underdeveloped and still are challenging topics. In this paper, we develop an automatic manipulation system for magnetically actuated helical microswimmers in static environments, which mainly consists of a mapper, a path planner, and a motion controller. First, the mapper processes the captured image by morphological transformations and then labels the free space and the obstacle space. Second, the path planner explores the obstacle-free space to find a feasible path from the start to the goal by a global planning algorithm. Last, the motion controller guides the helical microswimmers along the desired path by a closed-loop algorithm. Experiments are conducted to verify the effectiveness of the proposed automatic manipulation. Furthermore, our proposed approach presents the first step towards applications of microswimmers for targeted medical treatments, such as micromanipulation, targeted therapy, and targeted drug delivery. Full article
(This article belongs to the Special Issue Microswimmer)
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Open AccessArticle Dual Sacrificial Molding: Fabricating 3D Microchannels with Overhang and Helical Features
Micromachines 2018, 9(10), 523; https://doi.org/10.3390/mi9100523
Received: 30 August 2018 / Revised: 26 September 2018 / Accepted: 11 October 2018 / Published: 16 October 2018
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Abstract
Fused deposition modeling (FDM) has become an indispensable tool for 3D printing of molds used for sacrificial molding to fabricate microfluidic devices. The freedom of design of a mold is, however, restricted to the capabilities of the 3D printer and associated materials. Although
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Fused deposition modeling (FDM) has become an indispensable tool for 3D printing of molds used for sacrificial molding to fabricate microfluidic devices. The freedom of design of a mold is, however, restricted to the capabilities of the 3D printer and associated materials. Although FDM has been used to create a sacrificial mold made with polyvinyl alcohol (PVA) to produce 3D microchannels, microchannels with free-hanging geometries are still difficult to achieve. Herein, dual sacrificial molding was devised to fabricate microchannels with overhang or helical features in PDMS using two complementary materials. The method uses an FDM 3D printer equipped with two extruders and filaments made of high- impact polystyrene (HIPS) and PVA. HIPS was initially removed in limonene to reveal the PVA mold harboring the design of microchannels. The PVA mold was embedded in PDMS and subsequently removed in water to create microchannels with 3D geometries such as dual helices and multilayer pyramidal networks. The complementary pairing of the HIPS and PVA filaments during printing facilitated the support of suspended features of the PVA mold. The PVA mold was robust and retained the original design after the exposure to limonene. The resilience of the technique demonstrated here allows us to create microchannels with geometries not attainable with sacrificial molding with a mold printed with a single material. Full article
(This article belongs to the Special Issue Optofluidics: From Fundamental Research to Applications)
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Open AccessArticle Experimental Study of the Influence of Ink Properties and Process Parameters on Ejection Volume in Electrohydrodynamic Jet Printing
Micromachines 2018, 9(10), 522; https://doi.org/10.3390/mi9100522
Received: 19 August 2018 / Revised: 29 September 2018 / Accepted: 1 October 2018 / Published: 16 October 2018
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Abstract
Electrohydrodynamic jet (e-jet) printing has very promising applications due to its high printing resolution and material compatibility. It is necessary to know how to choose the printing parameters to get the right ejection volume. The previous scaling law of the ejection volume in
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Electrohydrodynamic jet (e-jet) printing has very promising applications due to its high printing resolution and material compatibility. It is necessary to know how to choose the printing parameters to get the right ejection volume. The previous scaling law of the ejection volume in e-jet printing borrows the scaling law of the ejection volume of an unstable isolated droplet charged to the Rayleigh limit. The influence of viscosity, applied voltage amplitude, and nozzle-to-substrate distance on the ejection volume in e-jet printing was not taken into account in the scaling law. This study investigated the influence of viscosity, conductivity, applied voltage, and nozzle-to-substrate distance on the ejection volume. The ejection volume increases with viscosity and decreases with applied voltage and nozzle-to-substrate distance. The average electric field was kept unchanged while changing the nozzle-to-substrate distance by changing the applied voltage according to the electric field model of a semi-infinite wire perpendicular to an infinite large planar counter electrode. The ejection volume decreases with conductivity as V ~ K 0.6 , which is different from the previous scaling law, which concludes that V ~ K 1 . Finally, a model about the relation between the ejection volume and four parameters was established by regression analysis using a third-order polynomial. Two more experiments were done, and the predicted results of the fitted model accorded well with the experiments. The model can be used to choose the ink properties and process parameters to get the right ejection volume. Full article
(This article belongs to the Special Issue Printed Flexible and Stretchable Electronics)
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Open AccessCommunication Multiple Light Coupling and Routing via a Microspherical Resonator Integrated in a T-Shaped Optical Fiber Configuration System
Micromachines 2018, 9(10), 521; https://doi.org/10.3390/mi9100521
Received: 18 September 2018 / Revised: 7 October 2018 / Accepted: 9 October 2018 / Published: 15 October 2018
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Abstract
We demonstrate a three-port, light guiding and routing T-shaped configuration based on the combination of whispering gallery modes (WGMs) and micro-structured optical fibers (MOFs). This system includes a single mode optical fiber taper (SOFT), a slightly tapered MOF and a BaTiO3 microsphere
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We demonstrate a three-port, light guiding and routing T-shaped configuration based on the combination of whispering gallery modes (WGMs) and micro-structured optical fibers (MOFs). This system includes a single mode optical fiber taper (SOFT), a slightly tapered MOF and a BaTiO3 microsphere for efficient light coupling and routing between these two optical fibers. The BaTiO3 glass microsphere is semi-immersed into one of the hollow capillaries of the MOF taper, while the single mode optical fiber taper is placed perpendicularly to the latter and in contact with the equatorial region of the microsphere. Experimental results are presented for different excitation and reading conditions through the WGM microspherical resonator, namely, through single mode optical fiber taper or the MOF. The experimental results indicate that light coupling between the MOF and the single mode optical fiber taper is facilitated at specific wavelengths, supported by the light localization characteristics of the BaTiO3 glass microsphere, with spectral Q-factors varying between 4.5 × 103 and 6.1 × 103, depending on the port and parity excitation. Full article
(This article belongs to the Special Issue Glassy Materials Based Microdevices)
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Open AccessArticle Assessing the Reusability of 3D-Printed Photopolymer Microfluidic Chips for Urine Processing
Micromachines 2018, 9(10), 520; https://doi.org/10.3390/mi9100520
Received: 26 September 2018 / Revised: 11 October 2018 / Accepted: 14 October 2018 / Published: 15 October 2018
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Abstract
Three-dimensional (3D) printing is emerging as a method for microfluidic device fabrication boasting facile and low-cost fabrication, as compared to conventional fabrication approaches, such as photolithography, for poly(dimethylsiloxane) (PDMS) counterparts. Additionally, there is an increasing trend in the development and implementation of miniaturized
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Three-dimensional (3D) printing is emerging as a method for microfluidic device fabrication boasting facile and low-cost fabrication, as compared to conventional fabrication approaches, such as photolithography, for poly(dimethylsiloxane) (PDMS) counterparts. Additionally, there is an increasing trend in the development and implementation of miniaturized and automatized devices for health monitoring. While nonspecific protein adsorption by PDMS has been studied as a limitation for reusability, the protein adsorption characteristics of 3D-printed materials have not been well-studied or characterized. With these rationales in mind, we study the reusability of 3D-printed microfluidics chips. Herein, a 3D-printed cleaning chip, consisting of inlets for the sample, cleaning solution, and air, and a universal outlet, is presented to assess the reusability of a 3D-printed microfluidic device. Bovine serum albumin (BSA) was used a representative urinary protein and phosphate-buffered solution (PBS) was chosen as the cleaning agent. Using the 3-(4-carboxybenzoyl)quinoline-2-carboxaldehyde (CBQCA) fluorescence detection method, the protein cross-contamination between samples and the protein uptake of the cleaning chip were assessed, demonstrating a feasible 3D-printed chip design and cleaning procedure to enable reusable microfluidic devices. The performance of the 3D-printed cleaning chip for real urine sample handling was then validated using a commercial dipstick assay. Full article
(This article belongs to the Special Issue 3D Printed Microfluidic Devices)
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Open AccessArticle Tunnel Encapsulation Technology for Durability Improvement in Stretchable Electronics Fabrication
Micromachines 2018, 9(10), 519; https://doi.org/10.3390/mi9100519
Received: 18 September 2018 / Revised: 10 October 2018 / Accepted: 12 October 2018 / Published: 14 October 2018
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Abstract
Great diversity of process technologies and materials have been developed around stretchable electronics. A subset of them, which are made up of zigzag metal foil and soft silicon polymers, show advantages of being easy to manufacture and low cost. However, most of the
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Great diversity of process technologies and materials have been developed around stretchable electronics. A subset of them, which are made up of zigzag metal foil and soft silicon polymers, show advantages of being easy to manufacture and low cost. However, most of the circuits lack durability due to stress concentration of interconnects entirely embedded in elastic polymer silicone such as polydimethylsiloxane (PDMS). In our demonstration, tunnel encapsulation technology was introduced to relieve stress of these conductors when they were stretched to deform in and out of plane. It was realized by dissolving the medium of Polyvinyl Alcohol (PVA), previous cured together with circuits in polymer, to form the micro-tunnel which not only guarantee the stretchability of interconnect, but also help to improve the durability. With the protection of tunnel, the serpentine could stably maintain the designed shape and electrical performance after 50% strain cycling over 20,000 times. Finally, different materials for encapsulation were employed to provide promising options for applications in portable biomedical devices which demand duplicate distortion. Full article
(This article belongs to the Special Issue Flexible Electronics: Fabrication and Ubiquitous Integration)
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Open AccessArticle Nanoindentation of Bi2Se3 Thin Films
Micromachines 2018, 9(10), 518; https://doi.org/10.3390/mi9100518
Received: 21 August 2018 / Revised: 6 October 2018 / Accepted: 12 October 2018 / Published: 14 October 2018
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Abstract
The nanomechanical properties and nanoindentation responses of bismuth selenide (Bi2Se3) thin films are investigated in this study. The Bi2Se3 thin films are deposited on c-plane sapphire substrates using pulsed laser deposition. The microstructural properties of
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The nanomechanical properties and nanoindentation responses of bismuth selenide (Bi2Se3) thin films are investigated in this study. The Bi2Se3 thin films are deposited on c-plane sapphire substrates using pulsed laser deposition. The microstructural properties of Bi2Se3 thin films are analyzed by means of X-ray diffraction (XRD). The XRD results indicated that Bi2Se3 thin films are exhibited the hexagonal crystal structure with a c-axis preferred growth orientation. Nanoindentation results showed the multiple “pop-ins” displayed in the loading segments of the load-displacement curves, suggesting that the deformation mechanisms in the hexagonal-structured Bi2Se3 films might have been governed by the nucleation and propagation of dislocations. Further, an energetic estimation of nanoindentation-induced dislocation associated with the observed pop-in effects was made using the classical dislocation theory. Full article
(This article belongs to the Special Issue Small Scale Deformation using Advanced Nanoindentation Techniques)
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Open AccessArticle Pseudo-Continuous Flow FTIR System for Glucose, Fructose and Sucrose Identification in Mid-IR Range
Micromachines 2018, 9(10), 517; https://doi.org/10.3390/mi9100517
Received: 24 August 2018 / Revised: 29 September 2018 / Accepted: 9 October 2018 / Published: 13 October 2018
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Abstract
In this paper, we present a new FTIR-based microfluidic system for Glucose, Fructose and Sucrose detection. The proposed microfluidic system is based on a pseudo-continuous flow coupled to a microscope-FTIR instrument. The detection and characterization of sugar samples were performed by recording their
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In this paper, we present a new FTIR-based microfluidic system for Glucose, Fructose and Sucrose detection. The proposed microfluidic system is based on a pseudo-continuous flow coupled to a microscope-FTIR instrument. The detection and characterization of sugar samples were performed by recording their absorption spectrum in the wavelength range 700–1000 cm 1 of the Mid-IR region. The proposed pseudo-continuous flow system is designed to improve the uniformity of the sample distribution in the analyzed area versus conventional systems. The obtained results for different sugars concentrations, show a very low measurement error of 4.35% in the absorption peak intensity, which is ten times lower than the error obtained using the conventional measurements. Full article
(This article belongs to the Special Issue Microfluidic Sensors)
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Open AccessArticle Rapid Prototyping of Polymer-Based Rolled-Up Microfluidic Devices
Micromachines 2018, 9(10), 516; https://doi.org/10.3390/mi9100516
Received: 18 September 2018 / Revised: 3 October 2018 / Accepted: 10 October 2018 / Published: 13 October 2018
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Abstract
This work presents the simple and rapid fabrication of a polymer-based microfluidic prototype manufactured by rolling up thin films of polymer. The thin films were fabricated via a casting method and rolled up around a center core with the aid of plasma activation
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This work presents the simple and rapid fabrication of a polymer-based microfluidic prototype manufactured by rolling up thin films of polymer. The thin films were fabricated via a casting method and rolled up around a center core with the aid of plasma activation to create a three-dimensional (3D) spiral microchannel, hence reducing the time and cost of manufacture. In this work, rolled-up devices with single or dual fluidic networks fabricated from a single or two films were demonstrated for heat sink or heat exchanger applications, respectively. The experimental results show good heat transfer in the rolled-up system at various flow rates for both heat sink and heat exchanger devices, without any leakages. The rolled-up microfluidic system creates multiple curved channels, allowing for the generation of Dean vortices, which in turn lead to an enhancement of heat and mass transfer and prevention of fouling formation. These benefits enable the devices to be employed for many diverse applications, such as heat-transfer devices, micromixers, and sorters. To our knowledge, this work would be the first report on a microfluidic prototype of 3D spiral microchannel made from rolled-up polymeric thin film. This novel fabrication approach may represent the first step towards the development of a pioneering prototype for roll-to-roll processing, permitting the mass production of polymer-based microchannels from single or multiple thin films. Full article
(This article belongs to the Section Micro/Nanofluidics and Lab on a Chip)
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Open AccessArticle Ultrahigh Frequency Ultrasonic Transducers Design with Low Noise Amplifier Integrated Circuit
Micromachines 2018, 9(10), 515; https://doi.org/10.3390/mi9100515
Received: 30 August 2018 / Revised: 8 October 2018 / Accepted: 8 October 2018 / Published: 12 October 2018
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Abstract
This paper describes the design of an ultrahigh frequency ultrasound system combined with tightly focused 500 MHz ultrasonic transducers and high frequency wideband low noise amplifier (LNA) integrated circuit (IC) model design. The ultrasonic transducers are designed using Aluminum nitride (AlN) piezoelectric thin
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This paper describes the design of an ultrahigh frequency ultrasound system combined with tightly focused 500 MHz ultrasonic transducers and high frequency wideband low noise amplifier (LNA) integrated circuit (IC) model design. The ultrasonic transducers are designed using Aluminum nitride (AlN) piezoelectric thin film as the piezoelectric element and using silicon lens for focusing. The fabrication and characterization of silicon lens was presented in detail. Finite element simulation was used for transducer design and evaluation. A custom designed LNA circuit is presented for amplifying the ultrasound echo signal with low noise. A Common-source and Common-gate (CS-CG) combination structure with active feedback is adopted for the LNA design so that high gain and wideband performances can be achieved simultaneously. Noise and distortion cancelation mechanisms are also employed in this work to improve the noise figure (NF) and linearity. Designed by using a 0.35 μm complementary metal oxide semiconductor (CMOS) technology, the simulated power gain of the echo signal wideband amplifier is 22.5 dB at 500 MHz with a capacitance load of 1.0 pF. The simulated NF at 500 MHz is 3.62 dB. Full article
(This article belongs to the Special Issue MEMS Technology for Biomedical Imaging Applications)
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Open AccessArticle Thermal Performance of Micro Hotplates with Novel Shapes Based on Single-Layer SiO2 Suspended Film
Micromachines 2018, 9(10), 514; https://doi.org/10.3390/mi9100514
Received: 15 September 2018 / Revised: 30 September 2018 / Accepted: 1 October 2018 / Published: 11 October 2018
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Abstract
In this paper, two kinds of suspended micro hotplate with novel shapes of multibeam structure and reticular structure are designed. These designs have a reliable mechanical strength, so they can be designed and fabricated on single-layer SiO2 suspended film through a simplified
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In this paper, two kinds of suspended micro hotplate with novel shapes of multibeam structure and reticular structure are designed. These designs have a reliable mechanical strength, so they can be designed and fabricated on single-layer SiO2 suspended film through a simplified process. Single-layer suspended film helps to reduce power consumption. Based on the new film shapes, different resistance heaters with various widths and thicknesses are designed. Then, the temperature uniformity and power consumption of different micro hotplates are compared to study the effect of these variables and obtain the one with the optimal thermal performance. We report the simulations of temperature uniformity and give the corresponding infrared images in measurement. The experimental temperature differences are larger than those of the simulation. Experimental results show that the lowest power consumption and the minimum temperature difference are 43 mW and 50 °C, respectively, when the highest temperature on the suspended platform (240 × 240 μm2) is 450 °C. Compared to the traditional four-beam micro hotplate, temperature non-uniformity is reduced by about 30–50%. Full article
(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)
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Open AccessArticle Size-Dependent and Property-Independent Passive Microdroplet Sorting by Droplet Transfer on Dot Rails
Micromachines 2018, 9(10), 513; https://doi.org/10.3390/mi9100513
Received: 15 September 2018 / Revised: 9 October 2018 / Accepted: 9 October 2018 / Published: 11 October 2018
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Abstract
A fully passive microdroplet sorting method is presented in this paper. On the rails with dot patterns, the droplets were sorted in different ways depending on their size. However, the effect of droplet properties on the threshold size of the sorting was eliminated.
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A fully passive microdroplet sorting method is presented in this paper. On the rails with dot patterns, the droplets were sorted in different ways depending on their size. However, the effect of droplet properties on the threshold size of the sorting was eliminated. The droplet positions on two railways and the Laplace pressure of the droplets on the dot patterns allowed selective droplet transfer according to size. Different gaps between the rails altered the threshold size of the transfer. However, the threshold size was independent of the droplet’s surface tension and viscosity because the droplet transfer utilized only the droplet position and Laplace pressure without lateral flow to sort targets. This feature has a high potential for bio/chemical applications requiring categorization of droplet targets consisting of various mixtures as pre- or post-elements. Full article
(This article belongs to the Section Micro-/Nano-system and Technology)
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Open AccessArticle Investigating Tungsten Carbide Micro-Hole Drilling Characteristics by Desktop Micro-ECM with NaOH Solution
Micromachines 2018, 9(10), 512; https://doi.org/10.3390/mi9100512
Received: 20 August 2018 / Revised: 4 October 2018 / Accepted: 8 October 2018 / Published: 11 October 2018
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Abstract
Due to their hardness and low tool wear, tungsten carbides are widely used in industrial applications, such as spray nozzles, wire drawing dies and spinning nozzles. However, there is no conventional machining process that is capable of fabricating micro-holes, slots and complicated shapes
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Due to their hardness and low tool wear, tungsten carbides are widely used in industrial applications, such as spray nozzles, wire drawing dies and spinning nozzles. However, there is no conventional machining process that is capable of fabricating micro-holes, slots and complicated shapes in tungsten carbide. In this study, a low-cost desktop micro electro-chemical machining (ECM) was developed to investigate the characteristics of tungsten carbide micro-hole drilling. The performance parameters of the machining conditions by desktop micro-ECM, such as the machining time, material removal rate, relative tool wear rate, surface quality and dimensional accuracy, were also investigated in this study. The experimental results demonstrate that the low-cost desktop micro-ECM could fabricate micro-holes in the tungsten cemented carbide (WC-Co) workpiece. Full article
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Open AccessArticle Automatic Frequency Tuning Technology for Dual-Mass MEMS Gyroscope Based on a Quadrature Modulation Signal
Micromachines 2018, 9(10), 511; https://doi.org/10.3390/mi9100511
Received: 17 September 2018 / Revised: 5 October 2018 / Accepted: 8 October 2018 / Published: 10 October 2018
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Abstract
In order to eliminate the frequency mismatch of MEMS (Microelectromechanical Systems) gyroscopes, this paper proposes a frequency tuning technology based on a quadrature modulation signal. A sinusoidal signal having a frequency greater the gyroscope operating bandwidth is applied to the quadrature stiffness correction
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In order to eliminate the frequency mismatch of MEMS (Microelectromechanical Systems) gyroscopes, this paper proposes a frequency tuning technology based on a quadrature modulation signal. A sinusoidal signal having a frequency greater the gyroscope operating bandwidth is applied to the quadrature stiffness correction combs, and the modulation signal containing the frequency split information is then excited at the gyroscope output. The effects of quadrature correction combs and frequency tuning combs on the resonant frequency of gyroscope are analyzed. The tuning principle based on low frequency input excitation is analyzed, and the tuning system adopting this principle is designed and simulated. The experiments are arranged to verify the theoretical analysis. The wide temperature range test (-20 C –60 C ) demonstrates the reliability of the tuning system with a maximum mismatch frequency of less than 0.3 Hz. The scale factor test and static test were carried out at three temperature conditions (−20 C, room temperature, 60 C), and the scale factor, zero-bias instability, and angle random walk are improved. Moreover, the closed-loop detection method is adopted, which improves the scale factor nonlinearity and bandwidth under the premise of maintaining the same static performances compared with the open-loop detection by tuning. Full article
(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)
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Open AccessArticle Integrity Assessment of a Hybrid DBS Probe that Enables Neurotransmitter Detection Simultaneously to Electrical Stimulation and Recording
Micromachines 2018, 9(10), 510; https://doi.org/10.3390/mi9100510
Received: 15 September 2018 / Revised: 5 October 2018 / Accepted: 5 October 2018 / Published: 10 October 2018
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Abstract
Deep brain stimulation (DBS) is a successful medical therapy for many treatment resistant neuropsychiatric disorders such as movement disorders; e.g., Parkinson’s disease, Tremor, and dystonia. Moreover, DBS is becoming more and more appealing for a rapidly growing number of patients with other neuropsychiatric
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Deep brain stimulation (DBS) is a successful medical therapy for many treatment resistant neuropsychiatric disorders such as movement disorders; e.g., Parkinson’s disease, Tremor, and dystonia. Moreover, DBS is becoming more and more appealing for a rapidly growing number of patients with other neuropsychiatric diseases such as depression and obsessive compulsive disorder. In spite of the promising outcomes, the current clinical hardware used in DBS does not match the technological standards of other medical applications and as a result could possibly lead to side effects such as high energy consumption and others. By implementing more advanced DBS devices, in fact, many of these limitations could be overcome. For example, a higher channels count and smaller electrode sites could allow more focal and tailored stimulation. In addition, new materials, like carbon for example, could be incorporated into the probes to enable adaptive stimulation protocols by biosensing neurotransmitters in the brain. Updating the current clinical DBS technology adequately requires combining the most recent technological advances in the field of neural engineering. Here, a novel hybrid multimodal DBS probe with glassy carbon microelectrodes on a polyimide thin-film device assembled on a silicon rubber tubing is introduced. The glassy carbon interface enables neurotransmitter detection using fast scan cyclic voltammetry and electrophysiological recordings while simultaneously performing electrical stimulation. Additionally, the presented DBS technology shows no imaging artefacts in magnetic resonance imaging. Thus, we present a promising new tool that might lead to a better fundamental understanding of the underlying mechanism of DBS while simultaneously paving our way towards better treatments. Full article
(This article belongs to the Special Issue Neural Microelectrodes: Design and Applications)
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Open AccessArticle Photolithographic Patterning of Cytop with Limited Contact Angle Degradation
Micromachines 2018, 9(10), 509; https://doi.org/10.3390/mi9100509
Received: 2 September 2018 / Revised: 28 September 2018 / Accepted: 3 October 2018 / Published: 9 October 2018
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Abstract
Cytop is a commercially available amorphous fluoropolymer with excellent characteristics including electric insulation, water and oil repellency, chemical resistance, and moisture-proof property, making it an attractive material as hydrophobic layers in electrowetting-on-dielectric (EWOD) devices. However, its highly hydrophobic surface makes it difficult for
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Cytop is a commercially available amorphous fluoropolymer with excellent characteristics including electric insulation, water and oil repellency, chemical resistance, and moisture-proof property, making it an attractive material as hydrophobic layers in electrowetting-on-dielectric (EWOD) devices. However, its highly hydrophobic surface makes it difficult for photoresists to be directly coated on the surface. To pattern Cytop, plasma treatment prior to applying photoresists is required to promote the adhesion between the photoresist and the Cytop coating. This approach inevitably causes hydrophobicity loss in the final EWOD devices. Thus, a damage-reduced recipe for Cytop patterning is urgently needed. In this paper, we first characterized the damage caused by two categories of surface treatment methods: plasma treatment and metal treatment. Parameters such as plasma gas source (Ar/O2), plasma treatment time (0–600 s), metal target (Al/Cu/Cr/Au), metal deposition process (magnetron sputtering or e-beam evaporation) were varied. Film thickness, wettability, and roughness were quantified by ellipsometry measurements, contact angle measurements, and atom force microscope (AFM), respectively. We then evaluated the effectiveness of annealing in damage reduction. Experimental results show that: (1) annealing is necessary in restoring hydrophobicity as well as smoothing surfaces; (2) specified film thickness can be obtained by controlling plasma treatment time; (3) “Ar/O2 plasma treatment + an AZ5214 soft mask + annealing” is a feasible recipe; (4) “an Al/Cu/Cr/Au hard mask + annealing” is feasible as well. Full article
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Open AccessArticle Generation of Color Images by Utilizing a Single Composite Diffractive Optical Element
Micromachines 2018, 9(10), 508; https://doi.org/10.3390/mi9100508
Received: 30 August 2018 / Revised: 4 October 2018 / Accepted: 4 October 2018 / Published: 9 October 2018
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Abstract
This paper presents an approach that is capable of producing a color image using a single composite diffractive optical element (CDOE). In this approach, the imaging function of a DOE and the spectral deflection characteristics of a grating were combined together to obtain
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This paper presents an approach that is capable of producing a color image using a single composite diffractive optical element (CDOE). In this approach, the imaging function of a DOE and the spectral deflection characteristics of a grating were combined together to obtain a color image at a certain position. The DOE was designed specially to image the red, green, and blue lights at the same distance along an optical axis, and the grating was designed to overlay the images to an off-axis position. We report the details of the design process of the DOE and the grating, and the relationship between the various parameters of the CDOE. Following the design and numerical simulations, a CDOE was fabricated, and imaging experiments were carried out. Both the numerical simulations and the experimental verifications demonstrated a successful operation of this new approach. As a platform based on coaxial illumination and off-axis imaging, this system is featured with simple structures and no cross-talk of the light fields, which has huge potentials in applications such as holographic imaging. Full article
(This article belongs to the Special Issue Product/Process Fingerprint in Micro Manufacturing)
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Open AccessArticle A Novel Electronic Interface for Micromachined Si-Based Photomultipliers
Micromachines 2018, 9(10), 507; https://doi.org/10.3390/mi9100507
Received: 18 September 2018 / Accepted: 1 October 2018 / Published: 8 October 2018
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Abstract
In this manuscript, the authors propose a novel interface for silicon photomultipliers based on a second-generation voltage conveyor as an active element, performing as a transimpedance amplifier. Due to the absence of internal feedback, this solution offers a static bandwidth regardless of the
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In this manuscript, the authors propose a novel interface for silicon photomultipliers based on a second-generation voltage conveyor as an active element, performing as a transimpedance amplifier. Due to the absence of internal feedback, this solution offers a static bandwidth regardless of the tunable gain level. The simulation results have shown good performances, confirming the possibility of the proposed interface being effectively used in different scenarios. A preliminary hybrid solution has also been developed using second-generation current conveyors and measurements conducted on an equivalent discrete-elements board, which is promising. Full article
(This article belongs to the Special Issue Interface Circuits for Microsensor Integrated Systems)
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Open AccessArticle A Plasmonic Fiber Based Glucometer and Its Temperature Dependence
Micromachines 2018, 9(10), 506; https://doi.org/10.3390/mi9100506
Received: 20 August 2018 / Revised: 28 September 2018 / Accepted: 1 October 2018 / Published: 5 October 2018
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Abstract
We present the plasmonic fiber based optical glucometer. A thin gold layer is coated on clad-free core of multimode optical fiber along 3 cm length to excite surface plasmons at 632.8 nm wavelength. Glucose oxidase is immobilized on the metal surface for glucose
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We present the plasmonic fiber based optical glucometer. A thin gold layer is coated on clad-free core of multimode optical fiber along 3 cm length to excite surface plasmons at 632.8 nm wavelength. Glucose oxidase is immobilized on the metal surface for glucose sensing. The effective surface refractive index increases by gluconic acid and hydrogen peroxide that are generated upon glucose injection, leading to plasmonic condition change with a consequence of optical power change at the fiber output. We obtain limit of detection of glucose concentration of 6.75 mg/dL, indicating higher sensitivity than the wavelength interrogating SPR glucometer that uses a spectrometer of 1nm spectral resolution. The coefficient of variation is 8.6% at a glucose concentration of 80 mg/dL at room temperature. We also examine the effects of ambient temperature variations from −10 °C to 40 °C on the performance of the presented sensor and compared them with those on commercially available glucometers that are based on enzyme electrodes. We find that the presented fiber sensor produced standard deviation of 12.1 mg/dL at a glucose concentration of 80 mg/dL under such varying temperature, which is, even without additional temperature correction function, comparable to the commercialized ones. Full article
(This article belongs to the Special Issue NANO KOREA 2018)
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Open AccessArticle Unexpected Phase Behavior of Pluronic Polymer-Organic Derivative Mixtures Depending on Temperature in Aqueous Solution
Micromachines 2018, 9(10), 505; https://doi.org/10.3390/mi9100505
Received: 15 September 2018 / Revised: 28 September 2018 / Accepted: 1 October 2018 / Published: 5 October 2018
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Abstract
The phase behavior of amphiphilic Pluronic block copolymers in aqueous solution is of importance for a broad spectrum of practical applications but has not been fully exploited yet. Here, the phase behavior of the mixture of the Pluronic P65 and P105 triblock copolymer,
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The phase behavior of amphiphilic Pluronic block copolymers in aqueous solution is of importance for a broad spectrum of practical applications but has not been fully exploited yet. Here, the phase behavior of the mixture of the Pluronic P65 and P105 triblock copolymer, (which have the same composition of PEO and PPO but the different molecular weight) and organic derivative, 5-methyl salicylic acid (5mS), in aqueous solution has been investigated by using small angle neutron scattering (SANS). According to the temperature and the 5mS concentration, SANS measurements showed that the P65-5mS mixtures sequentially transform into a random coil, sphere, vesicle, cylinder, and vesicle again, while the P105-5mS mixtures form spherical particles with two different sizes without any topological phase transition. Upon heating, the formation of two different kinds of the vesicle structure of amphiphilic block copolymer in aqueous solution is very unusual. This phase behavior was explained as the coupled effect of the simultaneous increase of the hydrophobicity of the polymer and the solubility of 5mS molecules upon heating. This result gives fundamental information for the practical use of Pluronic polymers in nano- and bio-science and it provides a simple route for the fabrication of the nanostructure without a complicated procedure. Full article
(This article belongs to the Special Issue NANO KOREA 2018)
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Open AccessArticle An Exact Solution for Power-Law Fluids in a Slit Microchannel with Different Zeta Potentials under Electroosmotic Forces
Micromachines 2018, 9(10), 504; https://doi.org/10.3390/mi9100504
Received: 18 September 2018 / Revised: 3 October 2018 / Accepted: 3 October 2018 / Published: 5 October 2018
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Abstract
Electroosmotic flow (EOF) is one of the most important techniques in a microfluidic system. Many microfluidic devices are made from a combination of different materials, and thus asymmetric electrochemical boundary conditions should be applied for the reasonable analysis of the EOF. In this
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Electroosmotic flow (EOF) is one of the most important techniques in a microfluidic system. Many microfluidic devices are made from a combination of different materials, and thus asymmetric electrochemical boundary conditions should be applied for the reasonable analysis of the EOF. In this study, the EOF of power-law fluids in a slit microchannel with different zeta potentials at the top and bottom walls are studied analytically. The flow is assumed to be steady, fully developed, and unidirectional with no applied pressure. The continuity equation, the Cauchy momentum equation, and the linearized Poisson-Boltzmann equation are solved for the velocity field. The exact solutions of the velocity distribution are obtained in terms of the Appell’s first hypergeometric functions. The velocity distributions are investigated and discussed as a function of the fluid behavior index, Debye length, and the difference in the zeta potential between the top and bottom. Full article
(This article belongs to the Special Issue Micro/Nano-Chip Electrokinetics, Volume III)
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Open AccessCommunication Mechanical Fatigue Resistance of Piezoelectric PVDF Polymers
Micromachines 2018, 9(10), 503; https://doi.org/10.3390/mi9100503
Received: 18 September 2018 / Revised: 28 September 2018 / Accepted: 3 October 2018 / Published: 4 October 2018
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Abstract
The fatigue resistance of piezoelectric PVDF has been under question in recent years. While some report that a significant degradation occurs after 106 cycles of repeated voltage input, others report that the reported degradation originates from the degraded metal electrodes instead of
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The fatigue resistance of piezoelectric PVDF has been under question in recent years. While some report that a significant degradation occurs after 106 cycles of repeated voltage input, others report that the reported degradation originates from the degraded metal electrodes instead of the piezoelectric PVDF itself. Here, we report the piezoelectric response and remnant polarization of PVDF during 107 cycles of repeated compression and tension, with silver paste-based electrodes to eliminate any electrode effect. After applying repeated tension and compression of 1.8% for 107 times, we do not observe any notable decrease in the output voltage generated by PVDF layers. The results from tension experiments show stable remnant polarization of 5.5 μC/cm2, however, the remnant polarization measured after repeated compression exhibits a 7% decrease as opposed to the tensed PVDF. These results suggest a possible anisotropic response to stress direction. The phase analyses by Raman spectroscopy reveals no significant change in the phase content, demonstrating the fatigue resistance of PVDF. Full article
(This article belongs to the Special Issue Nanogenerators in Korea)
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Open AccessArticle Fabrication of a Malaria-Ab ELISA Bioassay Platform with Utilization of Syringe-Based and 3D Printed Assay Automation
Micromachines 2018, 9(10), 502; https://doi.org/10.3390/mi9100502
Received: 30 August 2018 / Revised: 26 September 2018 / Accepted: 30 September 2018 / Published: 2 October 2018
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Abstract
We report on the fabrication of a syringe-based platform for automation of a colorimetric malaria-Ab assay. We assembled this platform from inexpensive disposable plastic syringes, plastic tubing, easily-obtainable servomotors, and an Arduino microcontroller chip, which allowed for system automation. The automated system can
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We report on the fabrication of a syringe-based platform for automation of a colorimetric malaria-Ab assay. We assembled this platform from inexpensive disposable plastic syringes, plastic tubing, easily-obtainable servomotors, and an Arduino microcontroller chip, which allowed for system automation. The automated system can also be fabricated using stereolithography (SLA) to print elastomeric reservoirs (used instead of syringes), while platform framework, including rack and gears, can be printed with fused deposition modeling (FDM). We report on the optimization of FDM and SLA print parameters, as well as post-production processes. A malaria-Ab colorimetric test was successfully run on the automated platform, with most of the assay reagents dispensed from syringes. Wash solution was dispensed from an SLA-printed elastomeric reservoir to demonstrate the feasibility of both syringe and elastomeric reservoir-based approaches. We tested the platform using a commercially available malaria-Ab colorimetric assay originally designed for spectroscopic plate readers. Unaided visual inspection of the assay solution color change was sufficient for qualitative detection of positive and negative samples. A smart phone application can also be used for quantitative measurement of the assay color change. Full article
(This article belongs to the Special Issue 3D Printed Microfluidic Devices)
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Open AccessArticle Shear Mode Bulk Acoustic Resonator Based on Inclined c-Axis AlN Film for Monitoring of Human Hemostatic Parameters
Micromachines 2018, 9(10), 501; https://doi.org/10.3390/mi9100501
Received: 25 July 2018 / Revised: 27 September 2018 / Accepted: 29 September 2018 / Published: 30 September 2018
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Abstract
Measurement of hemostatic parameters is essential for patients receiving long-term oral anticoagulant agents. In this paper, we present a shear mode bulk acoustic resonator based on an inclined c-axis aluminum nitride (AlN) film for monitoring the human hemostatic parameters. During the blood
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Measurement of hemostatic parameters is essential for patients receiving long-term oral anticoagulant agents. In this paper, we present a shear mode bulk acoustic resonator based on an inclined c-axis aluminum nitride (AlN) film for monitoring the human hemostatic parameters. During the blood coagulation process, the resonant frequency of the device decreases along with a step-ladder profile due to the viscosity change during the formation of fibers in blood, revealing the sequential coagulation stages. Two hemostatic parameters with clinical significance, prothrombin time (PT) along with its derived measure of international normalized ratio (INR), are determined from time-frequency curves of the device. Furthermore, the resonator is compared with a commercial coagulometer by monitoring the hemostatic parameters for one month in a patient taking the oral anticoagulant. The results are consistent. In addition, thanks to the excellent potential for integration, miniaturization and the availability of direct digital signals, the proposed device has promising application for point of care coagulation monitoring. Full article
(This article belongs to the Section Micro-/Nano-system and Technology)
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Open AccessArticle Chronic Intracortical Recording and Electrochemical Stability of Thiol-ene/Acrylate Shape Memory Polymer Electrode Arrays
Micromachines 2018, 9(10), 500; https://doi.org/10.3390/mi9100500
Received: 18 August 2018 / Revised: 24 September 2018 / Accepted: 27 September 2018 / Published: 29 September 2018
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Abstract
Current intracortical probe technology is limited in clinical implementation due to the short functional lifetime of implanted devices. Devices often fail several months to years post-implantation, likely due to the chronic immune response characterized by glial scarring and neuronal dieback. It has been
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Current intracortical probe technology is limited in clinical implementation due to the short functional lifetime of implanted devices. Devices often fail several months to years post-implantation, likely due to the chronic immune response characterized by glial scarring and neuronal dieback. It has been demonstrated that this neuroinflammatory response is influenced by the mechanical mismatch between stiff devices and the soft brain tissue, spurring interest in the use of softer polymer materials for probe encapsulation. Here, we demonstrate stable recordings and electrochemical properties obtained from fully encapsulated shape memory polymer (SMP) intracortical electrodes implanted in the rat motor cortex for 13 weeks. SMPs are a class of material that exhibit modulus changes when exposed to specific conditions. The formulation used in these devices softens by an order of magnitude after implantation compared to its dry, room-temperature modulus of ~2 GPa. Full article
(This article belongs to the Special Issue Neural Microelectrodes: Design and Applications)
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Open AccessArticle Vibration-Assisted Roll-Type Polishing System Based on Compliant Micro-Motion Stage
Micromachines 2018, 9(10), 499; https://doi.org/10.3390/mi9100499
Received: 3 September 2018 / Revised: 24 September 2018 / Accepted: 27 September 2018 / Published: 29 September 2018
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Abstract
This paper aims to create a high-quality surface based on the linear contact material removal mechanism. For this paper, a piezo-driven, flexure-based micro-motion stage was developed for the vibration-assisted roll-type precision polishing system. Meanwhile, the compliance matrix method was employed to establish the
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This paper aims to create a high-quality surface based on the linear contact material removal mechanism. For this paper, a piezo-driven, flexure-based micro-motion stage was developed for the vibration-assisted roll-type precision polishing system. Meanwhile, the compliance matrix method was employed to establish the amplification ratio and compliance model of the flexure mechanism. The dimensions of the mechanism were optimized using the grey wolves optimization (GWO) algorithm, aiming to maximize the natural frequencies. Using the optimal parameters, the established models for the mechanical performance evaluation of the flexure stage were verified with the finite-element method. Through closed-loop test, it was proven that the proposed micro-motion stage performs well in positioning micro motions. Finally, high quality surface using silicon carbide (SiC) ceramic with 36 nm Sa was generated by the independently developed vibration-assisted roll-type polishing machine to validate the performance of the established polishing system. Full article
(This article belongs to the Section Micro-/Nano-system and Technology)
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