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Micromachines, Volume 7, Issue 9 (September 2016)

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Editorial

Jump to: Research, Review

Open AccessEditorial Micro/Nano Devices for Chemical Analysis
Micromachines 2016, 7(9), 164; doi:10.3390/mi7090164
Received: 31 August 2016 / Revised: 1 September 2016 / Accepted: 1 September 2016 / Published: 9 September 2016
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Abstract
Since the concept of micro total analysis systems (µ-TAS) has been advocated, various kinds of micro/nano devices have been developed by researchers in many fields, such as in chemistry, chemical engineering, mechanical engineering, electric engineering, biology, and medicine, among others.[...] Full article
(This article belongs to the Special Issue Micro/Nano Devices for Chemical Analysis)

Research

Jump to: Editorial, Review

Open AccessArticle A Novel Classification Technique of Arteriovenous Fistula Stenosis Evaluation Using Bilateral PPG Analysis
Micromachines 2016, 7(9), 147; doi:10.3390/mi7090147
Received: 23 June 2016 / Revised: 16 August 2016 / Accepted: 18 August 2016 / Published: 23 August 2016
Cited by 1 | PDF Full-text (2966 KB) | HTML Full-text | XML Full-text
Abstract
The most common treatment for end-stage renal disease (ESRD) patients is the hemodialysis (HD). For this kind of treatment, the functional vascular access that called arteriovenous fistula (AVF) is done by surgery to connect the vein and artery. Stenosis is considered the major
[...] Read more.
The most common treatment for end-stage renal disease (ESRD) patients is the hemodialysis (HD). For this kind of treatment, the functional vascular access that called arteriovenous fistula (AVF) is done by surgery to connect the vein and artery. Stenosis is considered the major cause of dysfunction of AVF. In this study, a noninvasive approach based on asynchronous analysis of bilateral photoplethysmography (PPG) with error correcting output coding support vector machine one versus rest (ESVM-OVR) for the degree of stenosis (DOS) evaluation is proposed. An artificial neural network (ANN) classifier is also applied to compare the performance with the proposed system. The testing data has been collected from 22 patients at the right and left thumb of the hand. The experimental results indicated that the proposed system could provide positive predictive value (PPV) reaching 91.67% and had higher noise tolerance. The system has the potential for providing diagnostic assistance in a wearable device for evaluation of AVF stenosis. Full article
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Open AccessArticle Design and Analysis of a New Tuning Fork Structure for Resonant Pressure Sensor
Micromachines 2016, 7(9), 148; doi:10.3390/mi7090148
Received: 18 July 2016 / Revised: 18 August 2016 / Accepted: 18 August 2016 / Published: 24 August 2016
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Abstract
This paper presents a micromachined resonant pressure sensor. The sensor is designed to optimize the sensitivity and reduce the cross-talk between the driving electrodes and sensing electrodes. The relationship between the sensitivity of the sensor and the main design parameters is analyzed both
[...] Read more.
This paper presents a micromachined resonant pressure sensor. The sensor is designed to optimize the sensitivity and reduce the cross-talk between the driving electrodes and sensing electrodes. The relationship between the sensitivity of the sensor and the main design parameters is analyzed both theoretically and numerically. The sensing and driving electrodes are optimized to get both high sensing capacitance and low cross-talk. This sensor is fabricated using a micromachining process based on a silicon-on-insulator (SOI) wafer. An open-loop measurement system and a closed-loop self-oscillation system is employed to measure the characteristics of the sensor. The experiment result shows that the sensor has a pressure sensitivity of about 29 Hz/kPa, a nonlinearity of 0.02%FS, a hysteresis error of 0.05%FS, and a repeatability error of 0.01%FS. The temperature coefficient is less than 2 Hz/°C in the range of −40 to 80 °C and the short-term stability of the sensor is better than 0.005%FS. Full article
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Open AccessArticle 21.69–24.36 GHz MEMS Tunable Band-Pass Filter
Micromachines 2016, 7(9), 149; doi:10.3390/mi7090149
Received: 24 June 2016 / Revised: 8 August 2016 / Accepted: 18 August 2016 / Published: 24 August 2016
Cited by 1 | PDF Full-text (3237 KB) | HTML Full-text | XML Full-text
Abstract
The K-band microelectromechanical systems (MEMS) tunable band-pass filter, with a wide-frequency tunable range and miniature size, is able to fulfill the requirements of the multiband satellite communication systems. A novel 21.69–24.36 GHz MEMS tunable band-pass filter is designed, analyzed, fabricated and measured. This
[...] Read more.
The K-band microelectromechanical systems (MEMS) tunable band-pass filter, with a wide-frequency tunable range and miniature size, is able to fulfill the requirements of the multiband satellite communication systems. A novel 21.69–24.36 GHz MEMS tunable band-pass filter is designed, analyzed, fabricated and measured. This paper also designs and analyzes an inductively tuned slow-wave resonator, which consists of the MEMS capacitive switch, the MEMS capacitor and the short metal line. The proposed filter has four different work states by changing the capacitance values of the MEMS switches. Measured results demonstrate that, for all four states, the insertion loss is 2.81, 3.27, 3.65 and 4.03 dB at 24.36, 23.2, 22.24 and 21.69 GHz, respectively. The actuation voltage is 0, 20, 16 and 26 V, respectively. The 3 dB bandwidth of the tunable filter is 5.4%, 6.2%, 5.7% and 5.9%, respectively. This study contributes to the design of miniature millimeter tunable filters with a wide-frequency tunable range. Full article
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Open AccessFeature PaperArticle Controllable Acoustic Mixing of Fluids in Microchannels for the Fabrication of Therapeutic Nanoparticles
Micromachines 2016, 7(9), 150; doi:10.3390/mi7090150
Received: 27 July 2016 / Revised: 11 August 2016 / Accepted: 16 August 2016 / Published: 2 September 2016
Cited by 3 | PDF Full-text (3923 KB) | HTML Full-text | XML Full-text
Abstract
Fifteen years ago, surface acoustic waves (SAW) were found to be able to drive fluids and numerous applications in microfluidics have been developed since. Here, we review the progress made and report on new approaches in setting-up microfluidic, continuous flow acoustic mixing. In
[...] Read more.
Fifteen years ago, surface acoustic waves (SAW) were found to be able to drive fluids and numerous applications in microfluidics have been developed since. Here, we review the progress made and report on new approaches in setting-up microfluidic, continuous flow acoustic mixing. In a microchannel, chaotic advection is achieved by generation of a SAW driven fluid jet perpendicular to the mean flow direction. Using a high speed video camera and particle image velocimetry, we measure the flow velocities and show that mixing is achieved in a particularly controllable and fast way. The mixing quality is determined as a function of system parameters: SAW power, volume flux and fluid viscosity. Exploring the parameter space of mixing provides a practical guide for acoustic mixing in microchannels and allows for adopting conditions to different solvents, as e.g., required for the generation of nanoscale particles from alcoholic phases. We exemplarily demonstrate the potential of SAW based continuous flow mixing for the production of therapeutic nucleic acid nanoparticles assembled from polymer and lipid solutions. Full article
(This article belongs to the Special Issue Surface Acoustic Wave Microfluidics)
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Open AccessArticle Investigation of Antireflection Nb2O5 Thin Films by the Sputtering Method under Different Deposition Parameters
Micromachines 2016, 7(9), 151; doi:10.3390/mi7090151
Received: 11 July 2016 / Revised: 23 August 2016 / Accepted: 24 August 2016 / Published: 1 September 2016
Cited by 2 | PDF Full-text (1861 KB) | HTML Full-text | XML Full-text
Abstract
In this study, Nb2O5 ceramic was used as the target to deposit the Nb2O5 thin films on glass substrates with the radio frequency (RF) magnetron sputtering method. Different deposition temperatures and O2 ratios were used as
[...] Read more.
In this study, Nb2O5 ceramic was used as the target to deposit the Nb2O5 thin films on glass substrates with the radio frequency (RF) magnetron sputtering method. Different deposition temperatures and O2 ratios were used as parameters to investigate the optical properties of Nb2O5 thin films. The deposition parameters were a pressure of 5 × 10−3 Torr, a deposition power of 100 W, a deposition time of 30 min, an O2 ratio (O2/(O2 + Ar), in sccm) of 10% and 20%, and deposition temperatures of room temperature (RT), 200, 300 and 400 °C, respectively. We found that even if the deposition temperature was 400 °C, the deposited Nb2O5 thin films revealed an amorphous phase and no crystallization phase was observed. The optical properties of transmittance of Nb2O5 thin films deposited on glass substrates were determined by using a ultraviolet-visible (UV-vis) spectrophotometer (transmittance) and reflectance spectra transmittance (reflectance, refractive index, and extinction coefficient) in the light wavelength range of 250–1000 nm. When the O2 ratio was 10% and the deposition temperature increased from RT to 200 °C, the red-shift was clearly observed in the transmittance curve and the transmission ratio had no apparent change with the increasing deposition temperature. When the O2 ratio was 20%, the red-shift was not observed in the transmittance curve and the transmission ratio apparently decreased with the increasing deposition temperature. The variations in the optical band gap (Eg) values of Nb2O5 thin films were evaluated from the Tauc plot by using the quantity (the photon energy) on the abscissa and the quantity (α)r on the ordinate, where α is the optical absorption coefficient, c is the constant for direct transition, h is Planck’s constant, ν is the frequency of the incident photon, and the exponent r denotes the nature of the transition. As the O2 ratio of 10% or 20% was used as the deposition atmosphere, the measured Eg values decreased with the increase of the deposition temperature. The reflectance ratio, extinction coefficient, and refractive index curves of Nb2O5 thin films were also investigated in this study. We would show that those results were influenced by the deposition temperature and O2 ratio. Full article
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Open AccessArticle Antireflective SiC Surface Fabricated by Scalable Self-Assembled Nanopatterning
Micromachines 2016, 7(9), 152; doi:10.3390/mi7090152
Received: 22 June 2016 / Revised: 15 August 2016 / Accepted: 24 August 2016 / Published: 1 September 2016
Cited by 2 | PDF Full-text (3100 KB) | HTML Full-text | XML Full-text
Abstract
An approach for fabricating sub-wavelength antireflective structures on SiC material is demonstrated. A time-efficient scalable nanopatterning method by rapid thermal annealing of thin metal film is applied followed by a dry etching process. Size-dependent optical properties of the antireflective SiC structures have been
[...] Read more.
An approach for fabricating sub-wavelength antireflective structures on SiC material is demonstrated. A time-efficient scalable nanopatterning method by rapid thermal annealing of thin metal film is applied followed by a dry etching process. Size-dependent optical properties of the antireflective SiC structures have been investigated. It is found that the surface reflection of SiC in the visible spectral range is significantly suppressed by applying the antireflective structures. Meanwhile, optical transmission and absorption could be tuned by modifying the feature size of the structure. It is believed that this effective fabrication method of antireflective structures could also be realized on other semiconductor materials or devices. Full article
(This article belongs to the Special Issue Scalable Micro/Nano Patterning)
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Open AccessArticle Integration of an Optical Ring Resonator Biosensor into a Self-Contained Microfluidic Cartridge with Active, Single-Shot Micropumps
Micromachines 2016, 7(9), 153; doi:10.3390/mi7090153
Received: 4 August 2016 / Revised: 24 August 2016 / Accepted: 29 August 2016 / Published: 13 September 2016
Cited by 1 | PDF Full-text (6181 KB) | HTML Full-text | XML Full-text
Abstract
While there have been huge advances in the field of biosensors during the last decade, their integration into a microfluidic environment avoiding external tubing and pumping is still neglected. Herein, we show a new microfluidic design that integrates multiple reservoirs for reagent storage
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While there have been huge advances in the field of biosensors during the last decade, their integration into a microfluidic environment avoiding external tubing and pumping is still neglected. Herein, we show a new microfluidic design that integrates multiple reservoirs for reagent storage and single-use electrochemical pumps for time-controlled delivery of the liquids. The cartridge has been tested and validated with a silicon nitride-based photonic biosensor incorporating multiple optical ring resonators as sensing elements and an immunoassay as a potential target application. Based on experimental results obtained with a demonstration model, subcomponents were designed and existing protocols were adapted. The newly-designed microfluidic cartridges and photonic sensors were separately characterized on a technical basis and performed well. Afterwards, the sensor was functionalized for a protein detection. The microfluidic cartridge was loaded with the necessary assay reagents. The integrated pumps were programmed to drive the single process steps of an immunoassay. The prototype worked selectively, but only with a low sensitivity. Further work must be carried out to optimize biofunctionalization of the optical ring resonators and to have a more suitable flow velocity progression to enhance the system’s reproducibility. Full article
(This article belongs to the collection Lab-on-a-Chip)
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Open AccessArticle Fabrication and Microassembly of a mm-Sized Floating Probe for a Distributed Wireless Neural Interface
Micromachines 2016, 7(9), 154; doi:10.3390/mi7090154
Received: 2 July 2016 / Revised: 15 August 2016 / Accepted: 22 August 2016 / Published: 1 September 2016
Cited by 2 | PDF Full-text (4618 KB) | HTML Full-text | XML Full-text
Abstract
A new class of wireless neural interfaces is under development in the form of tens to hundreds of mm-sized untethered implants, distributed across the target brain region(s). Unlike traditional interfaces that are tethered to a centralized control unit and suffer from micromotions that
[...] Read more.
A new class of wireless neural interfaces is under development in the form of tens to hundreds of mm-sized untethered implants, distributed across the target brain region(s). Unlike traditional interfaces that are tethered to a centralized control unit and suffer from micromotions that may damage the surrounding neural tissue, the new free-floating wireless implantable neural recording (FF-WINeR) probes will be stand-alone, directly communicating with an external interrogator. Towards development of the FF-WINeR, in this paper we describe the micromachining, microassembly, and hermetic packaging of 1-mm3 passive probes, each of which consists of a thinned micromachined silicon die with a centered Ø(diameter) 130 μm through-hole, an Ø81 μm sharpened tungsten electrode, a 7-turn gold wire-wound coil wrapped around the die, two 0201 surface mount capacitors on the die, and parylene-C/Polydimethylsiloxane (PDMS) coating. The fabricated passive probe is tested under a 3-coil inductive link to evaluate power transfer efficiency (PTE) and power delivered to a load (PDL) for feasibility assessment. The minimum PTE/PDL at 137 MHz were 0.76%/240 μW and 0.6%/191 μW in the air and lamb head medium, respectively, with coil separation of 2.8 cm and 9 kΩ receiver (Rx) loading. Six hermetically sealed probes went through wireless hermeticity testing, using a 2-coil inductive link under accelerated lifetime testing condition of 85 °C, 1 atm, and 100%RH. The mean-time-to-failure (MTTF) of the probes at 37 °C is extrapolated to be 28.7 years, which is over their lifetime. Full article
(This article belongs to the Special Issue Implantable Microsystems)
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Open AccessArticle Investigation of the Influence of Glucose Concentration on Cancer Cells by Using a Microfluidic Gradient Generator without the Induction of Large Shear Stress
Micromachines 2016, 7(9), 155; doi:10.3390/mi7090155
Received: 20 July 2016 / Revised: 23 August 2016 / Accepted: 24 August 2016 / Published: 1 September 2016
PDF Full-text (14795 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A microfluidic device capable of precise chemical control is helpful to mimic tumor microenvironments in vitro, which are closely associated with malignant progression, including metastasis. Cancer cells under a concentration gradient of oxygen and other sustenance materials inside a tumor in vivo have
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A microfluidic device capable of precise chemical control is helpful to mimic tumor microenvironments in vitro, which are closely associated with malignant progression, including metastasis. Cancer cells under a concentration gradient of oxygen and other sustenance materials inside a tumor in vivo have recently been reported to increase the probability of metastasis. The influence of glucose concentration on cancer cells has not been measured well, whereas that of oxygen concentration has been thoroughly examined using microfluidic devices. This is because glucose concentrations can be controlled using microfluidic concentration gradient generators, which trade off temporal stability of the glucose concentration and shear stress on the cells; by contrast, oxygen concentration can be easily controlled without microfluidic device-induced shear stresses. To study cell division and migration responses as a function of glucose concentration, we developed a microfluidic device to observe cell behaviors under various chemical conditions. The device has small-cross-section microchannels for generating a concentration gradient and a large-cross-section chamber for cell culture. With this design, the device can achieve both a cell culture with sufficiently low shear stress on cell activity and a stable glucose concentration gradient. Experiments revealed that a low glucose concentration increased the total migration length of HeLa cells and that HeLa cells under a glucose concentration gradient exhibit random motion rather than chemotaxis. Full article
(This article belongs to the collection Lab-on-a-Chip)
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Open AccessArticle Enhanced Throughput for Electrokinetic Manipulation of Particles and Cells in a Stacked Microfluidic Device
Micromachines 2016, 7(9), 156; doi:10.3390/mi7090156
Received: 27 July 2016 / Revised: 23 August 2016 / Accepted: 29 August 2016 / Published: 1 September 2016
Cited by 2 | PDF Full-text (3927 KB) | HTML Full-text | XML Full-text
Abstract
Electrokinetic manipulation refers to the control of particle and cell motions using an electric field. It is an efficient technique for microfluidic applications with the ease of operation and integration. It, however, suffers from an intrinsic drawback of low throughput due to the
[...] Read more.
Electrokinetic manipulation refers to the control of particle and cell motions using an electric field. It is an efficient technique for microfluidic applications with the ease of operation and integration. It, however, suffers from an intrinsic drawback of low throughput due to the linear dependence of the typically very low fluid permittivity. We demonstrate in this work a significantly enhanced throughput for electrokinetic manipulation of particles and cells by the use of multiple parallel microchannels in a two-layer stacked microfluidic device. The fabrication of this device is simple without the need of a precise alignment of the two layers. The number of layers and the number of microchannels in each layer can thus be further increased for a potentially high throughput electrokinetic particle and cell manipulations. Full article
(This article belongs to the Special Issue Micro/Nano-Chip Electrokinetics) Printed Edition available
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Open AccessArticle Resonance Spectrum Characteristics of Effective Electromechanical Coupling Coefficient of High-Overtone Bulk Acoustic Resonator
Micromachines 2016, 7(9), 159; doi:10.3390/mi7090159
Received: 10 June 2016 / Revised: 26 August 2016 / Accepted: 29 August 2016 / Published: 6 September 2016
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Abstract
A high-overtone bulk acoustic resonator (HBAR) consisting of a piezoelectric film with two electrodes on a substrate exhibits a high quality factor (Q) and multi-mode resonance spectrum. By analyzing the influences of each layer’s material and structure (thickness) parameters on the
[...] Read more.
A high-overtone bulk acoustic resonator (HBAR) consisting of a piezoelectric film with two electrodes on a substrate exhibits a high quality factor (Q) and multi-mode resonance spectrum. By analyzing the influences of each layer’s material and structure (thickness) parameters on the effective electromechanical coupling coefficient (Keff2), the resonance spectrum characteristics of Keff2 have been investigated systematically, and the optimal design of HBAR has been provided. Besides, a device, corresponding to one of the theoretical cases studied, is fabricated and evaluated. The experimental results are basically consistent with the theoretical results. Finally, the effects of Keff2 on the function of the crystal oscillators constructed with HBARs are proposed. The crystal oscillators can operate in more modes and have a larger frequency hopping bandwidth by using the HBARs with a larger Keff2·Q. Full article
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Open AccessArticle Operation of Droplet-Microfluidic Devices with a Lab Centrifuge
Micromachines 2016, 7(9), 161; doi:10.3390/mi7090161
Received: 7 June 2016 / Revised: 12 August 2016 / Accepted: 18 August 2016 / Published: 6 September 2016
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Abstract
Microfluidic devices are valuable for a variety of biotechnology applications, such as synthesizing biochemical libraries, screening enzymes, and analyzing single cells. However, normally, the devices are controlled using specialized pumps, which require expert knowledge to operate. Here, we demonstrate operation of poly(dimethylsiloxane) devices
[...] Read more.
Microfluidic devices are valuable for a variety of biotechnology applications, such as synthesizing biochemical libraries, screening enzymes, and analyzing single cells. However, normally, the devices are controlled using specialized pumps, which require expert knowledge to operate. Here, we demonstrate operation of poly(dimethylsiloxane) devices without pumps. We build a scaffold that holds the device and reagents to be infused in a format that can be inserted into a 50 mL falcon tube and spun in a common lab centrifuge. By controlling the device design and centrifuge spin speed, we infuse the reagents at controlled flow rates. We demonstrate the encapsulation and culture of clonal colonies of red and green Escherichia coli in droplets seeded from single cells. Full article
(This article belongs to the Special Issue Droplet Microfluidics: Techniques and Technologies, Volume II)
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Open AccessArticle Direct Growth of Carbon Nanotubes on New High-Density 3D Pyramid-Shaped Microelectrode Arrays for Brain-Machine Interfaces
Micromachines 2016, 7(9), 163; doi:10.3390/mi7090163
Received: 7 June 2016 / Revised: 26 August 2016 / Accepted: 30 August 2016 / Published: 8 September 2016
Cited by 1 | PDF Full-text (6284 KB) | HTML Full-text | XML Full-text
Abstract
Silicon micromachined, high-density, pyramid-shaped neural microelectrode arrays (MEAs) have been designed and fabricated for intracortical 3D recording and stimulation. The novel architecture of this MEA has made it unique among the currently available micromachined electrode arrays, as it has provided higher density contacts
[...] Read more.
Silicon micromachined, high-density, pyramid-shaped neural microelectrode arrays (MEAs) have been designed and fabricated for intracortical 3D recording and stimulation. The novel architecture of this MEA has made it unique among the currently available micromachined electrode arrays, as it has provided higher density contacts between the electrodes and targeted neural tissue facilitating recording from different depths of the brain. Our novel masking technique enhances uniform tip-exposure for variable-height electrodes and improves process time and cost significantly. The tips of the electrodes have been coated with platinum (Pt). We have reported for the first time a selective direct growth of carbon nanotubes (CNTs) on the tips of 3D MEAs using the Pt coating as a catalyzer. The average impedance of the CNT-coated electrodes at 1 kHz is 14 kΩ. The CNT coating led to a 5-fold decrease of the impedance and a 600-fold increase in charge transfer compared with the Pt electrode. Full article
(This article belongs to the Special Issue Implantable Microsystems)
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Open AccessArticle Development of a Multi-Stage Electroosmotic Flow Pump Using Liquid Metal Electrodes
Micromachines 2016, 7(9), 165; doi:10.3390/mi7090165
Received: 27 July 2016 / Revised: 28 August 2016 / Accepted: 7 September 2016 / Published: 14 September 2016
Cited by 2 | PDF Full-text (2396 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Injection of liquid metal into a polydimethylsiloxane (PDMS) channel can provide a simple, cheap, and fast method to fabricate a noncontact electrode for micro electroosmotic flow (EOF) pumps. In this study, a multi-stage EOF pump using liquid metal noncontact electrodes was proposed and
[...] Read more.
Injection of liquid metal into a polydimethylsiloxane (PDMS) channel can provide a simple, cheap, and fast method to fabricate a noncontact electrode for micro electroosmotic flow (EOF) pumps. In this study, a multi-stage EOF pump using liquid metal noncontact electrodes was proposed and demonstrated for high-flow-velocity applications. To test the pumping performance of this EOF pump and measure the flow velocity, fluorescent particles were added into deionized (DI) water to trace the flow. According to the experimental results, the pump with a five-stage design can drive a water flow of 5.57 μm/s at 10 V, while the PDMS gap between the electrode and the pumping channel is 20 μm. To provide the guidance for the pump design, parametric studies were performed and fully discussed, such as the PDMS gap, pumping channel dimension, and stage number. This multi-stage EOF pump shows potential for many high-flow-velocity microfluidic applications. Full article
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Open AccessArticle Reliability Design and Electro-Thermal-Optical Simulation of Bridge-Style Infrared Thermal Emitters
Micromachines 2016, 7(9), 166; doi:10.3390/mi7090166
Received: 7 July 2016 / Revised: 1 September 2016 / Accepted: 5 September 2016 / Published: 13 September 2016
PDF Full-text (12721 KB) | HTML Full-text | XML Full-text
Abstract
Designs and simulations of silicon-based micro-electromechanical systems (MEMS) infrared (IR) thermal emitters for gas sensing application are presented. The IR thermal emitter is designed as a bridge-style hotplate (BSH) structure suspended on a silicon frame for realizing a good thermal isolation between hotplate
[...] Read more.
Designs and simulations of silicon-based micro-electromechanical systems (MEMS) infrared (IR) thermal emitters for gas sensing application are presented. The IR thermal emitter is designed as a bridge-style hotplate (BSH) structure suspended on a silicon frame for realizing a good thermal isolation between hotplate and frame. For investigating the reliability of BSH structure, three kinds of fillet structures were designed in the contact corner between hotplate and frame. A 3-dimensional finite element method (3D-FEM) is used to investigate the electro-thermal, thermal-mechanical, and thermal-optical properties of BSH IR emitter using software COMSOLTM (COMSOL 4.3b, COMSOL Inc., Stockholm, Sweden). The simulation results show that the BSH with oval fillet has the lowest stress distribution and smoothest flows of stress streamlines, while the BSH with square fillet has the highest temperature and stress distribution. The thermal-optical and thermal-response simulations further indicate that the BSH with oval fillet is the optimal design for a reliable IR thermal emitter in spite of having slight inadequacies in emission intensity and modulation bandwidth in comparison with other two structures. Full article
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Open AccessArticle Novel Capacitive Sensing System Design of a Microelectromechanical Systems Accelerometer for Gravity Measurement Applications
Micromachines 2016, 7(9), 167; doi:10.3390/mi7090167
Received: 15 June 2016 / Revised: 22 August 2016 / Accepted: 26 August 2016 / Published: 14 September 2016
Cited by 3 | PDF Full-text (7069 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an in-plane sandwich nano-g microelectromechanical systems (MEMS) accelerometer. The proof-mass fabrication is based on silicon etching through technology using inductive coupled plasma (ICP) etching. The capacitive detection system, which employs the area-changing sensing method, combines elementary capacitive pickup electrodes with
[...] Read more.
This paper presents an in-plane sandwich nano-g microelectromechanical systems (MEMS) accelerometer. The proof-mass fabrication is based on silicon etching through technology using inductive coupled plasma (ICP) etching. The capacitive detection system, which employs the area-changing sensing method, combines elementary capacitive pickup electrodes with periodic-sensing-array transducers. In order to achieve a large dynamic range with an ultrahigh resolution, the capacitive detection system employs two periodic-sensing-array transducers. Each of them can provide numbers for the signal period in the entire operating range. The suspended proof-mass is encapsulated between two glass caps, which results in a three dimensional structure. The measured resonant frequency and quality factor (Q) are 13.2 Hz and 47, respectively. The calibration response of a ±0.7 g input acceleration is presented, and the accelerometer system presents a sensitivity of 122 V/g and a noise floor of 30 ng/√Hz (at 1 Hz, and 1 atm). The bias stability for a period of 10 h is 30 μg. The device has endured a shock up to ±2.6 g, and the full scale output appears to be approximately ±1.4 g presently. This work presents a new opportunity for highly sensitive MEMS fabrication to enable future high-precision measurement applications, such as for gravity measurements. Full article
(This article belongs to the Special Issue 3D Integration Technologies for MEMS)
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Open AccessArticle PSO-Based Algorithm Applied to Quadcopter Micro Air Vehicle Controller Design
Micromachines 2016, 7(9), 168; doi:10.3390/mi7090168
Received: 1 July 2016 / Revised: 30 August 2016 / Accepted: 1 September 2016 / Published: 15 September 2016
Cited by 3 | PDF Full-text (1479 KB) | HTML Full-text | XML Full-text
Abstract
Due to the rapid development of science and technology in recent times, many effective controllers are designed and applied successfully to complicated systems. The significant task of controller design is to determine optimized control gains in a short period of time. With this
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Due to the rapid development of science and technology in recent times, many effective controllers are designed and applied successfully to complicated systems. The significant task of controller design is to determine optimized control gains in a short period of time. With this purpose in mind, a combination of the particle swarm optimization (PSO)-based algorithm and the evolutionary programming (EP) algorithm is introduced in this article. The benefit of this integration algorithm is the creation of new best-parameters for control design schemes. The proposed controller designs are then demonstrated to have the best performance for nonlinear micro air vehicle models. Full article
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Open AccessArticle Rapid Capture and Analysis of Airborne Staphylococcus aureus in the Hospital Using a Microfluidic Chip
Micromachines 2016, 7(9), 169; doi:10.3390/mi7090169
Received: 3 August 2016 / Revised: 1 September 2016 / Accepted: 12 September 2016 / Published: 15 September 2016
Cited by 2 | PDF Full-text (1276 KB) | HTML Full-text | XML Full-text
Abstract
In this study we developed a microfluidic chip for the rapid capture, enrichment and detection of airborne Staphylococcus (S.) aureus. The whole analysis took about 4 h and 40 min from airborne sample collection to loop-mediated isothermal amplification (LAMP), with
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In this study we developed a microfluidic chip for the rapid capture, enrichment and detection of airborne Staphylococcus (S.) aureus. The whole analysis took about 4 h and 40 min from airborne sample collection to loop-mediated isothermal amplification (LAMP), with a detection limit down to about 27 cells. The process did not require DNA purification. The chip was validated using standard bacteria bioaerosol and was directly used for clinical airborne pathogen sampling in hospital settings. This is the first report on the capture and analysis of airborne S. aureus using a novel microfluidic technique, a process that could have a very promising platform for hospital airborne infection prevention (HAIP). Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics)
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Open AccessArticle Deformability-Based Electrokinetic Particle Separation
Micromachines 2016, 7(9), 170; doi:10.3390/mi7090170
Received: 14 July 2016 / Revised: 5 September 2016 / Accepted: 7 September 2016 / Published: 20 September 2016
Cited by 7 | PDF Full-text (3675 KB) | HTML Full-text | XML Full-text
Abstract
Deformability is an effective property that can be used in the separation of colloidal particles and cells. In this study, a microfluidic device is proposed and tested numerically for the sorting of deformable particles of various degrees. The separation process is numerically investigated
[...] Read more.
Deformability is an effective property that can be used in the separation of colloidal particles and cells. In this study, a microfluidic device is proposed and tested numerically for the sorting of deformable particles of various degrees. The separation process is numerically investigated by a direct numerical simulation of the fluid–particle–electric field interactions with an arbitrary Lagrangian–Eulerian finite-element method. The separation performance is investigated with the shear modulus of particles, the strength of the applied electric field, and the design of the contracted microfluidic devices as the main parameters. The results show that the particles with different shear moduli take different shapes and trajectories when passing through a microchannel contraction, enabling the separation of particles based on their difference in deformability. Full article
(This article belongs to the Special Issue Micro/Nano-Chip Electrokinetics) Printed Edition available
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Open AccessReview Free-Standing Self-Assemblies of Gallium Nitride Nanoparticles: A Review
Micromachines 2016, 7(9), 121; doi:10.3390/mi7090121
Received: 6 April 2016 / Revised: 23 June 2016 / Accepted: 12 July 2016 / Published: 23 August 2016
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Abstract
Gallium nitride (GaN) is an III-V semiconductor with a direct band-gap of 3.4eV. GaN has important potentials in white light-emitting diodes, blue lasers, and field effect transistors because of its super thermal stability and excellent optical properties, playing
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Gallium nitride (GaN) is an III-V semiconductor with a direct band-gap of 3 . 4 e V . GaN has important potentials in white light-emitting diodes, blue lasers, and field effect transistors because of its super thermal stability and excellent optical properties, playing main roles in future lighting to reduce energy cost and sensors to resist radiations. GaN nanomaterials inherit bulk properties of the compound while possess novel photoelectric properties of nanomaterials. The review focuses on self-assemblies of GaN nanoparticles without templates, growth mechanisms of self-assemblies, and potential applications of the assembled nanostructures on renewable energy. Full article
(This article belongs to the Special Issue Building by Self-Assembly)
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Open AccessFeature PaperReview Neural Circuits on a Chip
Micromachines 2016, 7(9), 157; doi:10.3390/mi7090157
Received: 22 July 2016 / Revised: 20 August 2016 / Accepted: 29 August 2016 / Published: 5 September 2016
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Abstract
Neural circuits are responsible for the brain’s ability to process and store information. Reductionist approaches to understanding the brain include isolation of individual neurons for detailed characterization. When maintained in vitro for several days or weeks, dissociated neurons self-assemble into randomly connected networks
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Neural circuits are responsible for the brain’s ability to process and store information. Reductionist approaches to understanding the brain include isolation of individual neurons for detailed characterization. When maintained in vitro for several days or weeks, dissociated neurons self-assemble into randomly connected networks that produce synchronized activity and are capable of learning. This review focuses on efforts to control neuronal connectivity in vitro and construct living neural circuits of increasing complexity and precision. Microfabrication-based methods have been developed to guide network self-assembly, accomplishing control over in vitro circuit size and connectivity. The ability to control neural connectivity and synchronized activity led to the implementation of logic functions using living neurons. Techniques to construct and control three-dimensional circuits have also been established. Advances in multiple electrode arrays as well as genetically encoded, optical activity sensors and transducers enabled highly specific interfaces to circuits composed of thousands of neurons. Further advances in on-chip neural circuits may lead to better understanding of the brain. Full article
(This article belongs to the Special Issue MEMS/NEMS for Neuroscience)
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Open AccessFeature PaperReview Energy Dissipation in Graphene Mechanical Resonators with and without Free Edges
Micromachines 2016, 7(9), 158; doi:10.3390/mi7090158
Received: 31 July 2016 / Revised: 25 August 2016 / Accepted: 31 August 2016 / Published: 5 September 2016
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Abstract
Graphene-based nanoelectromechanical systems (NEMS) have high future potential to realize sensitive mass and force sensors owing to graphene’s low mass density and exceptional mechanical properties. One of the important remaining issues in this field is how to achieve mechanical resonators with a high
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Graphene-based nanoelectromechanical systems (NEMS) have high future potential to realize sensitive mass and force sensors owing to graphene’s low mass density and exceptional mechanical properties. One of the important remaining issues in this field is how to achieve mechanical resonators with a high quality factor (Q). Energy dissipation in resonators decreases Q, and suppressing it is the key to realizing sensitive sensors. In this article, we review our recent work on energy dissipation in doubly-clamped and circular drumhead graphene resonators. We examined the temperature (T) dependence of the inverse of a quality factor ( Q - 1 ) to reveal what the dominant dissipation mechanism is. Our doubly-clamped trilayer resonators show a characteristic Q - 1 -T curve similar to that observed in monolayer resonators: Q - 1 T 2 above ∼100 K and ∝ T 0.3 below ∼100 K. By comparing our results with previous experimental and theoretical results, we determine that the T 2 and T 0.3 dependences can be attributed to tensile strain induced by clamping metals and vibrations at the free edges in doubly-clamped resonators, respectively. The Q - 1 -T curve in our circular drumhead resonators indicates that removing free edges and clamping metal suppresses energy dissipation in the resonators, resulting in a linear T dependence of Q - 1 in a wide temperature range. Full article
(This article belongs to the Special Issue Graphene Nano-Electro-Mechanical (NEM) Devices and Applications)
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Open AccessReview Micromachined Resonators: A Review
Micromachines 2016, 7(9), 160; doi:10.3390/mi7090160
Received: 2 June 2016 / Revised: 24 July 2016 / Accepted: 25 July 2016 / Published: 8 September 2016
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Abstract
This paper is a review of the remarkable progress that has been made during the past few decades in design, modeling, and fabrication of micromachined resonators. Although micro-resonators have come a long way since their early days of development, they are yet to
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This paper is a review of the remarkable progress that has been made during the past few decades in design, modeling, and fabrication of micromachined resonators. Although micro-resonators have come a long way since their early days of development, they are yet to fulfill the rightful vision of their pervasive use across a wide variety of applications. This is partially due to the complexities associated with the physics that limit their performance, the intricacies involved in the processes that are used in their manufacturing, and the trade-offs in using different transduction mechanisms for their implementation. This work is intended to offer a brief introduction to all such details with references to the most influential contributions in the field for those interested in a deeper understanding of the material. Full article
(This article belongs to the Special Issue Microresonators)
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Open AccessReview Microfluidic-Based Multi-Organ Platforms for Drug Discovery
Micromachines 2016, 7(9), 162; doi:10.3390/mi7090162
Received: 24 May 2016 / Revised: 23 August 2016 / Accepted: 24 August 2016 / Published: 8 September 2016
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Abstract
Development of predictive multi-organ models before implementing costly clinical trials is central for screening the toxicity, efficacy, and side effects of new therapeutic agents. Despite significant efforts that have been recently made to develop biomimetic in vitro tissue models, the clinical application of
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Development of predictive multi-organ models before implementing costly clinical trials is central for screening the toxicity, efficacy, and side effects of new therapeutic agents. Despite significant efforts that have been recently made to develop biomimetic in vitro tissue models, the clinical application of such platforms is still far from reality. Recent advances in physiologically-based pharmacokinetic and pharmacodynamic (PBPK-PD) modeling, micro- and nanotechnology, and in silico modeling have enabled single- and multi-organ platforms for investigation of new chemical agents and tissue-tissue interactions. This review provides an overview of the principles of designing microfluidic-based organ-on-chip models for drug testing and highlights current state-of-the-art in developing predictive multi-organ models for studying the cross-talk of interconnected organs. We further discuss the challenges associated with establishing a predictive body-on-chip (BOC) model such as the scaling, cell types, the common medium, and principles of the study design for characterizing the interaction of drugs with multiple targets. Full article
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