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Micromachines, Volume 8, Issue 10 (October 2017)

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Cover Story We propose a microrobotic platform for single motile microorganism observation and investigation. [...] Read more.
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Editorial

Jump to: Research, Review, Other

Open AccessEditorial Micro/Nano Manufacturing
Micromachines 2017, 8(10), 297; doi:10.3390/mi8100297
Received: 30 September 2017 / Accepted: 30 September 2017 / Published: 2 October 2017
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Abstract
Micro- and nano-scale manufacturing has been the subject of an increasing amount of interest and research effort worldwide in both academia and industry over the past 10 years.[...] Full article
(This article belongs to the Special Issue Micro/Nano Manufacturing)
Open AccessEditorial Biomedical Applications of Nanotechnology and Nanomaterials
Micromachines 2017, 8(10), 298; doi:10.3390/mi8100298
Received: 29 September 2017 / Accepted: 29 September 2017 / Published: 2 October 2017
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Abstract
The spurring growth and clinical adoption of nanomaterials and nanotechnology in medicine, i.e. “nanomedicine”, to shape global health care system is a collective effort that comprises academia research, industrial drive, and political and financial support from government.[...] Full article
(This article belongs to the Special Issue Biomedical Applications of Nanotechnology and Nanomaterials)

Research

Jump to: Editorial, Review, Other

Open AccessArticle Milling Positive Master for Polydimethylsiloxane Microfluidic Devices: The Microfabrication and Roughness Issues
Micromachines 2017, 8(10), 287; doi:10.3390/mi8100287
Received: 3 August 2017 / Revised: 12 September 2017 / Accepted: 18 September 2017 / Published: 21 September 2017
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Abstract
We provide a facile and low-cost method (F-L) to fabricate a two-dimensional positive master using a milling technique for polydimethylsiloxane (PDMS)-based microchannel molding. This method comprises the following steps: (1) a positive microscale master of the geometry is milled on to an acrylic
[...] Read more.
We provide a facile and low-cost method (F-L) to fabricate a two-dimensional positive master using a milling technique for polydimethylsiloxane (PDMS)-based microchannel molding. This method comprises the following steps: (1) a positive microscale master of the geometry is milled on to an acrylic block; (2) pre-cured PDMS is used to mold the microscale positive master; (3) the PDMS plate is peeled off from the master and punctured with a blunt needle; and (4) the PDMS plate is O2 plasma bonded to a glass slide. Using this technique, we can fabricate microchannels with very simple protocols quickly and inexpensively. This method also avoids breakage of the end mill (ϕ = 0.4 mm) of the computerized numerical control (CNC) system when fabricating the narrow channels (width < 50 µm). The prominent surface roughness of the milled bottom-layer could be overcomed by pre-cured PDMS with size trade-off in design. Finally, emulsion formation successfully demonstrates the validity of the proposed fabrication protocol. This work represents an important step toward the use of a milling technique for PDMS-based microfabrication. Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)
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Open AccessArticle Electromagnetic Linear Vibration Energy Harvester Using Sliding Permanent Magnet Array and Ferrofluid as a Lubricant
Micromachines 2017, 8(10), 288; doi:10.3390/mi8100288
Received: 5 September 2017 / Revised: 18 September 2017 / Accepted: 19 September 2017 / Published: 22 September 2017
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Abstract
We present an electromagnetic linear vibration energy harvester with an array of rectangular permanent magnets as a springless proof mass. Instead of supporting the magnet assembly with spring element, ferrofluid has been used as a lubricating material. When external vibration is applied laterally
[...] Read more.
We present an electromagnetic linear vibration energy harvester with an array of rectangular permanent magnets as a springless proof mass. Instead of supporting the magnet assembly with spring element, ferrofluid has been used as a lubricating material. When external vibration is applied laterally to the harvester, magnet assembly slides back and forth on the channel with reduced friction and wear due to ferrofluid, which significantly improves the long-term reliability of the device. Electric power is generated across an array of copper windings formed at the bottom of the aluminum housing. A proof-of-concept harvester has been fabricated and tested with a vibration exciter at various input frequencies and accelerations. For the device where 5 μL of ferrofluid was used for lubrication, maximum output power of 493 μW has been generated, which was 4.37% higher than that without ferrofluid. Long-term reliability improvement due to ferrofluid lubrication has also been verified. For the device with ferrofluid, 1.02% decrease of output power has been observed, in contrast to 59.73% decrease of output power without ferrofluid after 93,600 cycles. Full article
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Open AccessFeature PaperArticle Modelling and Experimental Verification of Step Response Overshoot Removal in Electrothermally-Actuated MEMS Mirrors
Micromachines 2017, 8(10), 289; doi:10.3390/mi8100289
Received: 1 September 2017 / Revised: 16 September 2017 / Accepted: 20 September 2017 / Published: 25 September 2017
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Abstract
Micro-electro-mechanical system (MEMS) mirrors are widely used for optical modulation, attenuation, steering, switching and tracking. In most cases, MEMS mirrors are packaged in air, resulting in overshoot and ringing upon actuation. In this paper, an electrothermal bimorph MEMS mirror that does not generate
[...] Read more.
Micro-electro-mechanical system (MEMS) mirrors are widely used for optical modulation, attenuation, steering, switching and tracking. In most cases, MEMS mirrors are packaged in air, resulting in overshoot and ringing upon actuation. In this paper, an electrothermal bimorph MEMS mirror that does not generate overshoot in step response, even operating in air, is reported. This is achieved by properly designing the thermal response time and the mechanical resonance without using any open-loop or closed-loop control. Electrothermal and thermomechanical lumped-element models are established. According to the analysis, when setting the product of the thermal response time and the fundamental resonance frequency to be greater than Q/2π, the mechanical overshoot and oscillation caused by a step signal can be eliminated effectively. This method is verified experimentally with fabricated electrothermal bimorph MEMS mirrors. Full article
(This article belongs to the Special Issue MEMS Mirrors)
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Open AccessArticle Acoustic Manipulation of Bio-Particles at High Frequencies: An Analytical and Simulation Approach
Micromachines 2017, 8(10), 290; doi:10.3390/mi8100290
Received: 21 August 2017 / Revised: 16 September 2017 / Accepted: 21 September 2017 / Published: 27 September 2017
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Abstract
Manipulation of micro and nano particles in microfluidic devices with high resolution is a challenge especially in bioengineering applications where bio-particles (BPs) are separated or patterned. While acoustic forces have been used to control the position of BPs, its theoretical aspects need further
[...] Read more.
Manipulation of micro and nano particles in microfluidic devices with high resolution is a challenge especially in bioengineering applications where bio-particles (BPs) are separated or patterned. While acoustic forces have been used to control the position of BPs, its theoretical aspects need further investigation particularly for high-resolution manipulation where the wavelength and particle size are comparable. In this study, we used a finite element method (FEM) to amend analytical calculations of acoustic radiation force (ARF) arising from an imposed standing ultrasound field. First, an acoustic solid interaction (ASI) approach was implemented to calculate the ARF exerted on BPs and resultant deformation induced to them. The results were then used to derive a revised expression for the ARF beyond the small particle assumption. The expression was further assessed in numerical simulations of one- and multi-directional standing acoustic waves (SAWs). Furthermore, a particle tracing scheme was used to investigate the effect of actual ARF on separation and patterning applications under experimentally-relevant conditions. The results demonstrated a significant mismatch between the actual force and previous analytical predictions especially for high frequencies of manipulation. This deviation found to be not only because of the shifted ARF values but also due to the variation in force maps in multidirectional wave propagation. Findings of this work can tackle the simulation limitations for spatiotemporal control of BPs using a high resolution acoustic actuation. Full article
(This article belongs to the Special Issue Acoustofluidics in Medicine and Biology)
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Open AccessArticle A Method to Encapsulate Small Organic Molecules in Calcium Phosphate Nanoparticles Based on the Supramolecular Chemistry of Cyclodextrin
Micromachines 2017, 8(10), 291; doi:10.3390/mi8100291
Received: 3 September 2017 / Revised: 19 September 2017 / Accepted: 19 September 2017 / Published: 27 September 2017
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Abstract
Calcium phosphate nanoparticles (CPNPs) encapsulating small organic molecules, such as imaging agents and drugs, are considered to be ideal devices for cancer diagnosis or therapy. However, it is generally difficult to encapsulate small organic molecules in CPNPs because of the lack of solubility
[...] Read more.
Calcium phosphate nanoparticles (CPNPs) encapsulating small organic molecules, such as imaging agents and drugs, are considered to be ideal devices for cancer diagnosis or therapy. However, it is generally difficult to encapsulate small organic molecules in CPNPs because of the lack of solubility in water or binding affinity to calcium phosphate. To solve these issues, we utilized the carboxymethyl β-cyclodextrin (CM-β-CD) to increase the solubility and binding affinity to small organic molecules for the encapsulation into CPNPs in this work. The results indicated that the model molecules, hydrophilic rhodamine B (RB) and hydrophobic docetaxel (Dtxl), are successfully encapsulated into CPNPs with the assistance of CM-β-CD. We also demonstrated the CPNPs could be remarkably internalized into A549 cells, resulting in the efficient inhibition of tumor cells’ growth. Full article
(This article belongs to the Special Issue Biomedical Applications of Nanotechnology and Nanomaterials)
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Open AccessArticle Real Time Monitoring of Children, and Adults with Mental Disabilities Using a Low-Cost Non-Invasive Electronic Device
Micromachines 2017, 8(10), 292; doi:10.3390/mi8100292
Received: 28 June 2017 / Revised: 11 September 2017 / Accepted: 26 September 2017 / Published: 28 September 2017
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Abstract
There are a growing number of small children—as well as adults—with mental disabilities (including elderly citizens with Alzheimer’s disease or other forms of age-related dementia) that are getting lost in rural and urban areas for various reasons. Establishing their location within the first
[...] Read more.
There are a growing number of small children—as well as adults—with mental disabilities (including elderly citizens with Alzheimer’s disease or other forms of age-related dementia) that are getting lost in rural and urban areas for various reasons. Establishing their location within the first 72 h is crucial because lost people are exposed to all kinds of adverse conditions and in the case of the elderly, this is further aggravated if prescribed medication is needed. Herein we describe a non-invasive, low-cost electronic device that operates constantly, keeping track of time, the geographical location and the identification of the subject using it. The prototype was made using commercial low-cost electronic components. This electronic device shows high connectivity in open and closed areas and identifies the geographical location of a lost subject. We freely provide the software and technical diagrams of the prototypes. Full article
(This article belongs to the Special Issue Medical Microdevices and Micromachines)
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Open AccessArticle Development of a Cantilever-Type Electrostatic Energy Harvester and Its Charging Characteristics on a Highway Viaduct
Micromachines 2017, 8(10), 293; doi:10.3390/mi8100293
Received: 11 August 2017 / Revised: 8 September 2017 / Accepted: 14 September 2017 / Published: 28 September 2017
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Abstract
We have developed a micro-electro-mechanical systems (MEMS) electrostatic vibratory power generator with over 100 μWRMS of (root-mean-square) output electric power under 0.03 GRMS (G: the acceleration of gravity) accelerations. The device is made of a silicon-on-insulator (SOI) wafer and is
[...] Read more.
We have developed a micro-electro-mechanical systems (MEMS) electrostatic vibratory power generator with over 100 μ W RMS of (root-mean-square) output electric power under 0.03 G RMS (G: the acceleration of gravity) accelerations. The device is made of a silicon-on-insulator (SOI) wafer and is fabricated by silicon micromachining technology. An electret built-in potential is given to the device by electrothermal polarization in silicon oxide using potassium ions. The force factor, which is defined by a proportional coefficient of the output current with respect to the vibration velocity, is 2.34 × 10 4 C/m; this large value allows the developed vibration power generator to have a very high power efficiency of 80.7%. We have also demonstrated a charging experiment by using an environmental acceleration waveform with an average amplitude of about 0.03 G RMS taken at a viaduct of a highway, and we obtained 4.8 mJ of electric energy stored in a 44 μ F capacitor in 90 min. Full article
(This article belongs to the Special Issue MEMS Energy Harvesters)
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Open AccessArticle Stress Distribution Profile Imaging With Spectral Fabry-Perot Interferometry in Thin Layer Substrates for Surface Micromachining
Micromachines 2017, 8(10), 294; doi:10.3390/mi8100294
Received: 21 August 2017 / Revised: 25 September 2017 / Accepted: 27 September 2017 / Published: 30 September 2017
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Abstract
We have used spectral two-layer interferometry (STLI) imaging for estimation of the stress distribution profiles (SDPs) in thin film substrates, enabling fast and reliable all-optical methodology for the evaluation of pre-stress topography profiles in silicon wafers deposited with thin films. Specifically, in polycrystalline
[...] Read more.
We have used spectral two-layer interferometry (STLI) imaging for estimation of the stress distribution profiles (SDPs) in thin film substrates, enabling fast and reliable all-optical methodology for the evaluation of pre-stress topography profiles in silicon wafers deposited with thin films. Specifically, in polycrystalline silicon (PS) and silicon nitride (SN) thin films, we demonstrate a nondestructive, systematic, and robust capability for consistent stress distribution profile (SDP) evaluation relying on STLI. In particular, for PS and SN devices, the SDP estimation is consistent and is compared with complementary characterization of the films. Full article
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Open AccessArticle Microrobotic Platform for Single Motile Microorganism Investigation
Micromachines 2017, 8(10), 295; doi:10.3390/mi8100295
Received: 7 September 2017 / Revised: 28 September 2017 / Accepted: 28 September 2017 / Published: 30 September 2017
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Abstract
We propose a microrobotic platform for single motile microorganism observation and investigation. The platform utilizes a high-speed online vision sensor to realize real-time observation of a microorganism under a microscopic environment with a relatively high magnification ratio. A microfluidic chip was used to
[...] Read more.
We propose a microrobotic platform for single motile microorganism observation and investigation. The platform utilizes a high-speed online vision sensor to realize real-time observation of a microorganism under a microscopic environment with a relatively high magnification ratio. A microfluidic chip was used to limit the vertical movement of the microorganism and reduce the tracking system complexity. We introduce a simple image processing method, which utilizes high-speed online vision characteristics and shows robustness against image noise to increase the overall tracking performance with low computational time consumption. The design also considers the future integration of a stimulation system using microtools. Successful long-time tracking of a freely swimming microorganism inside of a microfluidic chip for more than 30 min was achieved notwithstanding the presence of noises in the environment of the cell. The specific design of the platform, particularly the tracking system, is described, and the performance is evaluated and confirmed through basic experiments. The potential of the platform to apply mechanical stimulation to a freely swimming microorganism is demonstrated by using a 50-µm-thick microtool. The proposed platform can be used for long-term observation and to achieve different kinds of stimulations, which can induce new behavior of the cells and lead to unprecedented discoveries in biological fields. Full article
(This article belongs to the Special Issue Micro/Nano Robotics, Volume II)
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Open AccessArticle Structural Analysis of Disk Resonance Gyroscope
Micromachines 2017, 8(10), 296; doi:10.3390/mi8100296
Received: 27 July 2017 / Revised: 9 September 2017 / Accepted: 29 September 2017 / Published: 30 September 2017
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Abstract
In this paper, we present two design methods to improve the performance of disk resonator gyroscope (DRG), including decreasing the frequency split and increasing the quality factor (Q). The structure parameters, which can affect the frequency split and Q value were
[...] Read more.
In this paper, we present two design methods to improve the performance of disk resonator gyroscope (DRG), including decreasing the frequency split and increasing the quality factor (Q). The structure parameters, which can affect the frequency split and Q value were concluded with the help of the FEM software. Meanwhile, devices with different parameters were designed, fabricated, and tested, and the experimental result was in accordance with the simulation. With the proposed methods, the DRG was selected with a high Q value and a low frequency split to satisfy the demand of high performance. The weakness and future works were pointed at last. Full article
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Open AccessArticle Laser-Induced-Plasma-Assisted Ablation and Metallization on C-Plane Single Crystal Sapphire (c-Al2O3)
Micromachines 2017, 8(10), 300; doi:10.3390/mi8100300
Received: 20 August 2017 / Revised: 12 September 2017 / Accepted: 28 September 2017 / Published: 7 October 2017
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Abstract
Laser-induced-plasma-assisted ablation (LIPAA) is a promising micro-machining method that can fabricate microstructure on hard and transparent double-polished single crystal sapphire (SCS). While ablating, a nanosecond pulse 1064 nm wavelength laser beam travels through the SCS substrate and bombards the copper target lined up
[...] Read more.
Laser-induced-plasma-assisted ablation (LIPAA) is a promising micro-machining method that can fabricate microstructure on hard and transparent double-polished single crystal sapphire (SCS). While ablating, a nanosecond pulse 1064 nm wavelength laser beam travels through the SCS substrate and bombards the copper target lined up behind the substrate, which excites the ablating plasma. When laser fluence rises and is above the machining threshold of copper but below that of SCS, the kinetic energy of the copper plasma generated from the bombardment is mainly determined by the laser fluence, the repetition rate, and the substrate-to-target distance. With a lower repetition rate, SCS becomes metallized and gains conductivity. When micro-machining SCS with a pulsed laser are controlled by properly controlling laser machining parameters, such as laser fluence, repetition rate, and substrate-to-target distance, LIPAA can ablate certain line widths and depths of the microstructure as well as the resistance of SCS. On the contrary, conductivity resistance of metalized sapphire depends on laser parameters and distance in addition to lower repetition rate. Full article
(This article belongs to the Special Issue Plasma-Based Surface Engineering)
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Open AccessArticle AlN-Based Ceramic Patch Antenna-Type Wireless Passive High-Temperature Sensor
Micromachines 2017, 8(10), 301; doi:10.3390/mi8100301
Received: 22 September 2017 / Revised: 5 October 2017 / Accepted: 5 October 2017 / Published: 10 October 2017
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Abstract
An aluminum nitride (AlN) based patch antenna-type high-temperature wireless passive sensor is reported to operate as both a sensor and an antenna, which integrates in situ measurement/sensing with remote wireless communication at the same time. The sensor is small, easy to manufacture, highly
[...] Read more.
An aluminum nitride (AlN) based patch antenna-type high-temperature wireless passive sensor is reported to operate as both a sensor and an antenna, which integrates in situ measurement/sensing with remote wireless communication at the same time. The sensor is small, easy to manufacture, highly sensitive and has a high operating temperature; it can be used in high-temperature, chemically corrosive and other harsh environments. The sensing mechanism of the sensor, the dielectric constant of the AlN ceramic substrate, increases with rising temperature, which reduces the resonant frequency of the sensor. Thus, the temperature can be measured by detecting changes in the sensor’s resonant frequency. High-Frequency Simulation Structure (HFSS) software is used to determine the structure and size of the sensor, which is then fabricated using thick-film technology. The substrate of the sensor is AlN ceramic due to its outstanding thermal resistance at high temperature; and its conductors (the radiation patch and the ground under the substrate) are silver-palladium alloy sintered form silver–palladium paste. A vector network analyzer reveals that the sensor’s operating range extends to 700 °C. Furthermore, its resonant frequency decreases from 2.20 GHz to 2.13 GHz with increasing temperature from room temperature (25 °C) to 700 °C, with an absolute sensitivity of 104.77 KHz/°C. Our work verifies the feasibility of measuring high temperatures using AlN-based patch antenna wireless passive temperature sensors, and provides a new material and temperature sensitive structure for high-temperature measurement in harsh environments. Full article
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Open AccessArticle The Analysis of Three-Body Contact Temperature under the Different Third Particle Size, Density, and Value of Friction
Micromachines 2017, 8(10), 302; doi:10.3390/mi8100302
Received: 24 July 2017 / Revised: 26 September 2017 / Accepted: 6 October 2017 / Published: 11 October 2017
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Abstract
Recently, many studies have investigated the friction, wear, and temperature characteristics of the interface between two relative movements. Such analyses often set the coefficient of friction as a fixed value and are analyzed in cases of two-body contact; however, the interface is often
[...] Read more.
Recently, many studies have investigated the friction, wear, and temperature characteristics of the interface between two relative movements. Such analyses often set the coefficient of friction as a fixed value and are analyzed in cases of two-body contact; however, the interface is often a three-body contact and the coefficient of friction varies depending on the operating conditions. This is a significant error in the analysis of contact characteristics, therefore, in this study, the actual interface and the change of the coefficient of friction were analyzed based on three-body micro-contact theory where the contact temperature was also analyzed and the difference between the generally assumed values were compared. The results showed that under three-body contact, the coefficient of total friction increased with an increase in particle size; and at a different particle size and area density of particles, the surface contact temperature increased with the plasticity index and load increases, and the particle contact temperature increased with the increasing particle size. The surface temperature rise was mainly affected by the ratio of the average temperature between surface 1 and surface 2 to the multiplication between the 100th root of the area density of particles and the square root of the equivalent surface roughness (Ts1s2_ave*/ηa0.01σ0.5) and the ratio of the 10th root of the mean particle diameter to the 100th root of the equivalent surface roughness (xa0.1/σ0.001). Particle temperature was mainly affected by the ratio of the 10th root of the mean particle diameter to the 100th root of the equivalent surface roughness (xa0.1/σ0.001) and the area density of particles ηa. Our study indicated that when the contact of surface with surface and the contact of the particles with the surface, the resulting heat balance was assigned to the particles and the surface in a three-body contact situation. Under this contact behavior, it could avoid a too high a rise in micro-contact temperature to achieve the material failure temperature. Full article
(This article belongs to the Special Issue Microtribology, Adhesion and Surface Engineering)
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Open AccessArticle A Micro-Force Sensor with Beam-Membrane Structure for Measurement of Friction Torque in Rotating MEMS Machines
Micromachines 2017, 8(10), 304; doi:10.3390/mi8100304
Received: 20 July 2017 / Revised: 9 October 2017 / Accepted: 10 October 2017 / Published: 12 October 2017
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Abstract
In this paper, a beam-membrane (BM) sensor for measuring friction torque in micro-electro-mechanical system (MEMS) gas bearings is presented. The proposed sensor measures the force-arm-transformed force using a detecting probe and the piezoresistive effect. This solution incorporates a membrane into a conventional four-beam
[...] Read more.
In this paper, a beam-membrane (BM) sensor for measuring friction torque in micro-electro-mechanical system (MEMS) gas bearings is presented. The proposed sensor measures the force-arm-transformed force using a detecting probe and the piezoresistive effect. This solution incorporates a membrane into a conventional four-beam structure to meet the range requirements for the measurement of both the maximum static friction torque and the kinetic friction torque in rotating MEMS machines, as well as eliminate the problem of low sensitivity with neat membrane structure. A glass wafer is bonded onto the bottom of the sensor chip with a certain gap to protect the sensor when overloaded. The comparisons between the performances of beam-based sensor, membrane-based sensor and BM sensor are conducted by finite element method (FEM), and the final sensor dimensions are also determined. Calibration of the fabricated and packaged device is experimentally performed. The practical verification is also reported in the paper for estimating the friction torque in micro gas bearings by assembling the proposed sensor into a rotary table-based measurement system. The results demonstrate that the proposed force sensor has a potential application in measuring micro friction or force in MEMS machines. Full article
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Open AccessArticle Design and Performance Testing of a Novel Three-Dimensional Elliptical Vibration Turning Device
Micromachines 2017, 8(10), 305; doi:10.3390/mi8100305
Received: 18 September 2017 / Revised: 6 October 2017 / Accepted: 10 October 2017 / Published: 12 October 2017
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Abstract
A novel three-dimensional (3D) elliptical vibration turning device which is on the basis of the leaf-spring-flexure-hinges-based (LSFH-based) double parallel four-bar linkages (DPFLMs) has been proposed. In order to evaluate the performance of the developed 3D elliptical vibration cutting generator (EVCG), the off-line tests
[...] Read more.
A novel three-dimensional (3D) elliptical vibration turning device which is on the basis of the leaf-spring-flexure-hinges-based (LSFH-based) double parallel four-bar linkages (DPFLMs) has been proposed. In order to evaluate the performance of the developed 3D elliptical vibration cutting generator (EVCG), the off-line tests were carried out to investigate the stroke, dynamic performance, resolution, tracking accuracy and hysteresis along the three vibration axes. Experimental results indicate that the maximum stroke of three vibration axes can reach up to 26 μm. The working bandwidth can reach up to 1889 Hz. The resolution and hysteresis tests show that the developed 3D EVCG has a good tracking accuracy, relative high resolution and low hysteresis, which is appropriate for micro/nano machining. Kinematical modeling is carried out to investigate the tool vibration trajectory. Experimental results shown that the simulation results agree well with the experimental one, which indicate that the developed 3D EVCG can be used as an option for micro/nano machining. Full article
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Open AccessArticle Study on Ti-6Al-4V Alloy Machining Applying the Non-Resonant Three-Dimensional Elliptical Vibration Cutting
Micromachines 2017, 8(10), 306; doi:10.3390/mi8100306
Received: 30 August 2017 / Revised: 6 October 2017 / Accepted: 10 October 2017 / Published: 13 October 2017
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Abstract
The poor machinability of Ti-6Al-4V alloy makes it hard to process by conventional processing methods even though it has been widely used in military and civilian enterprise fields. Non-resonant three-dimensional elliptical vibration cutting (3D-EVC) is a novel cutting technique which is a significant
[...] Read more.
The poor machinability of Ti-6Al-4V alloy makes it hard to process by conventional processing methods even though it has been widely used in military and civilian enterprise fields. Non-resonant three-dimensional elliptical vibration cutting (3D-EVC) is a novel cutting technique which is a significant development potential for difficult-to-cut materials. However, few studies have been conducted on processing the Ti-6Al-4V alloy using the non-resonant 3D-EVC technique, the effect of surface quality, roughness, topography and freeform surface has not been clearly researched yet. Therefore, the machinability of Ti-6Al-4V alloy using the non-resonant 3D-EVC apparatus is studied in this paper. Firstly, the principle of non-resonant 3D-EVC technique and the model of cutter motion are introduced. Then the tool path is synthesized. The comparison experiments are carried out with traditional continuous cutting (TCC), two-dimension elliptical vibration cutting (2D-EVC), and the non-resonant 3D-EVC method. The experimental results shown that the excellent surface and lower roughness (77.3 nm) could be obtained using the non-resonant 3D-EVC method; the shape and dimension of elliptical cutting mark also relates to the cutting speed and vibration frequency, and the concave/convex spherical surface topography are achieved by non-resonant 3D-EVC in the Ti-6Al-4V alloy. This proved that the non-resonant 3D-EVC technique has the better machinability compared with the TCC and 2D-EVC methods. Full article
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Open AccessArticle Controlled Solvent-Free Formation of Embedded PDMS-Derived Carbon Nanodomains with Tunable Fluorescence Using Selective Laser Ablation with A Low-Power CD Laser
Micromachines 2017, 8(10), 307; doi:10.3390/mi8100307
Received: 16 September 2017 / Revised: 30 September 2017 / Accepted: 4 October 2017 / Published: 17 October 2017
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Abstract
We present a study of the application of a single-step and solvent-free laser-based strategy to control the formation of polymer-derived fluorescent carbon nanodomains embedded in poly-dimethylsiloxane (PDMS) microchannels. A low-power, laser-induced microplasma was used to produce a localised combustion of a PDMS surface
[...] Read more.
We present a study of the application of a single-step and solvent-free laser-based strategy to control the formation of polymer-derived fluorescent carbon nanodomains embedded in poly-dimethylsiloxane (PDMS) microchannels. A low-power, laser-induced microplasma was used to produce a localised combustion of a PDMS surface and confine nanocarbon byproducts within the exposed microregions. Patterns with on-demand geometries were achieved under dry environmental conditions thanks to a low-cost 3-axis CD-DVD platform motorised in a selective laser ablation fashion. The high temperature required for combustion of PDMS was achieved locally by strongly focusing the laser spot on the desired areas, and the need for high-power laser was bypassed by coating the surface with an absorbing carbon additive layer, hence making the etching of a transparent material possible. The simple and repeatable fabrication process and the spectroscopic characterisation of resulting fluorescent microregions are reported. In situ Raman and fluorescence spectroscopy were used to identify the nature of the nanoclusters left inside the modified areas and their fluorescence spectra as a function of excitation wavelength. Interestingly, the carbon nanodomains left inside the etched micropatterns showed a strong dependency on the additive materials and laser energy that were used to achieve the incandescence and etch microchannels on the surface of the polymer. This dependence on the lasing conditions indicates that our cost-effective laser ablation technique may be used to tune the nature of the polymer-derived nanocarbons, useful for photonics applications in transparent silicones in a rapid-prototyping fashion. Full article
(This article belongs to the Special Issue Carbon Based Materials for MEMS/NEMS)
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Open AccessArticle A Fluidic Interface with High Flow Uniformity for Reusable Large Area Resonant Biosensors
Micromachines 2017, 8(10), 308; doi:10.3390/mi8100308
Received: 16 August 2017 / Revised: 6 October 2017 / Accepted: 11 October 2017 / Published: 14 October 2017
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Abstract
Resonant biosensors are known for their high accuracy and high level of miniaturization. However, their fabrication costs prevent them from being used as disposable sensors and their effective commercial success will depend on their ability to be reused repeatedly. Accordingly, all the parts
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Resonant biosensors are known for their high accuracy and high level of miniaturization. However, their fabrication costs prevent them from being used as disposable sensors and their effective commercial success will depend on their ability to be reused repeatedly. Accordingly, all the parts of the sensor in contact with the fluid need to tolerate the regenerative process which uses different chemicals (H3PO4, H2SO4 based baths) without degrading the characteristics of the sensor. In this paper, we propose a fluidic interface that can meet these requirements, and control the liquid flow uniformity at the surface of the vibrating area. We study different inlet and outlet channel configurations, estimating their performance using numerical simulations based on finite element method (FEM). The interfaces were fabricated using wet chemical etching on Si, which has all the desirable characteristics for a reusable biosensor circuit. Using a glass cover, we could observe the circulation of liquid near the active surface, and by using micro-particle image velocimetry (μPIV) on large surface area we could verify experimentally the effectiveness of the different designs and compare with simulation results. Full article
(This article belongs to the Special Issue Biomedical Microfluidic Devices)
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Open AccessArticle Dislocation Dynamics-Based Modeling and Simulations of Subsurface Damages Microstructure of Orthogonal Cutting of Titanium Alloy
Micromachines 2017, 8(10), 309; doi:10.3390/mi8100309
Received: 18 August 2017 / Revised: 7 October 2017 / Accepted: 12 October 2017 / Published: 16 October 2017
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Abstract
In this work, a novel method is put forward to quantitatively simulate the subsurface damages microstructural alteration of titanium alloy components subjected to microscale cutting. A trans-scale numerical framework is conducted with the purpose of revealing the underlying influence mechanism of tool structure
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In this work, a novel method is put forward to quantitatively simulate the subsurface damages microstructural alteration of titanium alloy components subjected to microscale cutting. A trans-scale numerical framework is conducted with the purpose of revealing the underlying influence mechanism of tool structure parameters on subsurface dislocation configurations using a dislocation dynamics-based model, which considers both dislocation structural transformation and grain refining. Results showed that the developed framework not only captured the essential features of workpiece microstructure, but also predicted the subsurface damages layer states and their modifications. A series of defects were found in the material subsurface during the orthogonal cutting of titanium alloy, such as edge and screw dislocations, junctions, parallel slip lines, intersection dislocation bands, vacancy defects, and refinement grains. Particularly, in the process of micro-cutting, the depth of subsurface damages layer increased significantly with cutting length at the beginning, and then remained unchanged in the stable removal phase. Moreover, smaller edge radius and larger rake angle can greatly weaken the squeezing action and heat diffusion effect between the tool tip and workpiece, which further prevents the formation of subsurface defects and enhances finished surface quality. In addition, although increasing tool clearance angle could drastically lighten the thickness of subsurface damages layer, it is noteworthy that its performance would be decreased significantly when the clearance angle was greater than or equal to 5°. The micro-end-milling experiment was performed to validate the existing simulation results, and the results show very good agreement. Full article
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Open AccessArticle Coupling Mechanism Analysis and Fabrication of Triaxial Gyroscopes in Monolithic MIMU
Micromachines 2017, 8(10), 310; doi:10.3390/mi8100310
Received: 31 July 2017 / Revised: 9 September 2017 / Accepted: 10 October 2017 / Published: 16 October 2017
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Abstract
A novel fully decoupled micro inertial measurement unit (MIMU) is presented in this paper. The proposed MIMU structure, mostly focusing on the gyroscope unit, is highly symmetrical and can be limited to an area of 10,000 μm × 10,000 μm. Both the tri-axis
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A novel fully decoupled micro inertial measurement unit (MIMU) is presented in this paper. The proposed MIMU structure, mostly focusing on the gyroscope unit, is highly symmetrical and can be limited to an area of 10,000 μm × 10,000 μm. Both the tri-axis gyroscope and tri-axis accelerometer structures are fabricated on the same single silicon chip, which can differentially detect three axes’ angular velocities and linear accelerated velocities at the same time. By elaborately arranging different decoupling beams, anchors and sensing frames, the drive and sense modes of the tri-axis gyroscope are fully decoupled from each other. Several dynamic models, including decoupling beams with fabrication imperfections, are established for theoretical analysis. The numerical simulation made by MATLAB shows the structural decoupling of three sense modes, and indicates that the key decoupling beams, which affect the quadrature error, can be improved in design. The whole fabrication process, including silicon on glass (SOG) process, dry/wet etching as well as the methods for improving the fabrication quality, is then shown. Experiments for mode frequency and quality factors of four modes (drive, yaw, pitch and roll) have been performed, and are found to be 455 (6950.2 Hz), 66 (7054.4 Hz), 109 (7034.2 Hz) and 107 (7040.5 Hz) respectively. The analysis and experiment both prove that this novel MIMU has the potential value of further intensive investigation. Full article
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Open AccessFeature PaperArticle Spiral-Shaped Piezoelectric MEMS Cantilever Array for Fully Implantable Hearing Systems
Micromachines 2017, 8(10), 311; doi:10.3390/mi8100311
Received: 6 September 2017 / Revised: 30 September 2017 / Accepted: 12 October 2017 / Published: 18 October 2017
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Abstract
Fully implantable, self-powered hearing aids with no external unit could significantly increase the life quality of patients suffering severe hearing loss. This highly demanding concept, however, requires a strongly miniaturized device which is fully implantable in the middle/inner ear and includes the following
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Fully implantable, self-powered hearing aids with no external unit could significantly increase the life quality of patients suffering severe hearing loss. This highly demanding concept, however, requires a strongly miniaturized device which is fully implantable in the middle/inner ear and includes the following components: frequency selective microphone or accelerometer, energy harvesting device, speech processor, and cochlear multielectrode. Here we demonstrate a low volume, piezoelectric micro-electromechanical system (MEMS) cantilever array which is sensitive, even in the lower part of the voice frequency range (300–700 Hz). The test array consisting of 16 cantilevers has been fabricated by standard bulk micromachining using a Si-on-Insulator (SOI) wafer and aluminum nitride (AlN) as a complementary metal-oxide-semiconductor (CMOS) and biocompatible piezoelectric material. The low frequency and low device footprint are ensured by Archimedean spiral geometry and Si seismic mass. Experimentally detected resonance frequencies were validated by an analytical model. The generated open circuit voltage (3–10 mV) is sufficient for the direct analog conversion of the signals for cochlear multielectrode implants. Full article
(This article belongs to the Special Issue Piezoelectric MEMS)
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Open AccessFeature PaperArticle Design and Fabrication of Capacitive Silicon Nanomechanical Resonators with Selective Vibration of a High-Order Mode
Micromachines 2017, 8(10), 312; doi:10.3390/mi8100312
Received: 25 September 2017 / Revised: 11 October 2017 / Accepted: 16 October 2017 / Published: 20 October 2017
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Abstract
This paper reports the design and fabrication of capacitive silicon nanomechanical resonators with the selective vibration of a high-order mode. Fixed-fixed beam capacitive silicon resonators have been successfully produced by the use of electron beam lithography, photolithography, deep reactive ion etching, and anodic
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This paper reports the design and fabrication of capacitive silicon nanomechanical resonators with the selective vibration of a high-order mode. Fixed-fixed beam capacitive silicon resonators have been successfully produced by the use of electron beam lithography, photolithography, deep reactive ion etching, and anodic bonding methods. All resonators with different vibration modes are designed to have the same resonant frequency for performance comparison. Measurement results show that higher-order mode capacitive silicon resonators can achieve lower insertion loss compared to that of lower-order mode capacitive silicon resonators. The motional resistance of the fourth mode vibration resonator is improved by 83%, 90%, and 93% over the third, second, and first mode vibration resonators, respectively. Full article
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Open AccessArticle Transparent Ferroelectric Capacitors on Glass
Micromachines 2017, 8(10), 313; doi:10.3390/mi8100313
Received: 6 September 2017 / Revised: 8 October 2017 / Accepted: 17 October 2017 / Published: 20 October 2017
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Abstract
We deposited transparent ferroelectric lead zirconate titanate thin films on fused silica and contacted them via Al-doped zinc oxide (AZO) transparent electrodes with an interdigitated electrode (IDE) design. These layers, together with a TiO2 buffer layer on the fused silica substrate, are
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We deposited transparent ferroelectric lead zirconate titanate thin films on fused silica and contacted them via Al-doped zinc oxide (AZO) transparent electrodes with an interdigitated electrode (IDE) design. These layers, together with a TiO2 buffer layer on the fused silica substrate, are highly transparent (>60% in the visible optical range). Fully crystallized Pb(Zr0.52Ti0.48)O3 (PZT) films are dielectrically functional and exhibit a typical ferroelectric polarization loop with a remanent polarization of 15 μC/cm2. The permittivity value of 650, obtained with IDE AZO electrodes is equivalent to the one measured with Pt electrodes patterned with the same design, which proves the high quality of the developed transparent structures. Full article
(This article belongs to the Special Issue Piezoelectric MEMS)
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Open AccessArticle Fabrication of Micro-Optics Elements with Arbitrary Surface Profiles Based on One-Step Maskless Grayscale Lithography
Micromachines 2017, 8(10), 314; doi:10.3390/mi8100314
Received: 1 September 2017 / Revised: 15 October 2017 / Accepted: 17 October 2017 / Published: 23 October 2017
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Abstract
A maskless lithography method to realize the rapid and cost-effective fabrication of micro-optics elements with arbitrary surface profiles is reported. A digital micro-mirror device (DMD) is applied to flexibly modulate that the exposure dose according to the surface profile of the structure to
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A maskless lithography method to realize the rapid and cost-effective fabrication of micro-optics elements with arbitrary surface profiles is reported. A digital micro-mirror device (DMD) is applied to flexibly modulate that the exposure dose according to the surface profile of the structure to be fabricated. Due to the fact that not only the relationship between the grayscale levels of the DMD and the exposure dose on the surface of the photoresist, but also the dependence of the exposure depth on the exposure dose, deviate from a linear relationship arising from the DMD and photoresist, respectively, and cannot be systemically eliminated, complicated fabrication art and large fabrication error will results. A method of compensating the two nonlinear effects is proposed that can be used to accurately design the digital grayscale mask and ensure a precise control of the surface profile of the structure to be fabricated. To testify to the reliability of this approach, several typical array elements with a spherical surface, aspherical surface, and conic surface have been fabricated and tested. The root-mean-square (RMS) between the test and design value of the surface height is about 0.1 μm. The proposed method of compensating the nonlinear effect in maskless lithography can be directly used to control the grayscale levels of the DMD for fabricating the structure with an arbitrary surface profile. Full article
(This article belongs to the Special Issue MEMS Mirrors)
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Open AccessReview Bio-Inspired Microdevices that Mimic the Human Vasculature
Micromachines 2017, 8(10), 299; doi:10.3390/mi8100299
Received: 30 August 2017 / Revised: 25 September 2017 / Accepted: 26 September 2017 / Published: 7 October 2017
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Abstract
Blood vessels may be found throughout the entire body and their importance to human life is undeniable. This is evident in the fact that a malfunctioning blood vessel can result in mild symptoms such as shortness of breath or chest pain to more
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Blood vessels may be found throughout the entire body and their importance to human life is undeniable. This is evident in the fact that a malfunctioning blood vessel can result in mild symptoms such as shortness of breath or chest pain to more severe symptoms such as a heart attack or stroke, to even death in the severest of cases. Furthermore, there are a host of pathologies that have been linked to the human vasculature. As a result many researchers have attempted to unlock the mysteries of the vasculature by performing studies that duplicate the physiological structural, chemical, and mechanical properties known to exist. While the ideal study would consist of utilizing living, blood vessels derived from human tissue, such studies are not always possible since intact human blood vessels are not readily accessible and there are immense technical difficulties associated with such studies. These limitations have opened the door for the development of microdevices modeled after the human vasculature as it is believed by many researchers in the field that such devices can one day replace tissue models. In this review we present an overview of microdevices developed to mimic various types of vasculature found throughout the human body. Although the human body contains a diverse array of vascular systems for this review we limit our discussion to the cardiovascular system and cerebrovascular system and discuss such systems that have been fabricated in both 2D and 3D configurations. Full article
(This article belongs to the Special Issue Bio-Inspired Micro/Nano Devices and Systems)
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Other

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Open AccessCorrection Correction: Li, H. et al. Research on Design and Simulation of Biaxial Tensile-Bending Complex Mechanical Performance Test Apparatus. Micromachines, 2017, 8, 286
Micromachines 2017, 8(10), 303; doi:10.3390/mi8100303
Received: 10 October 2017 / Accepted: 10 October 2017 / Published: 12 October 2017
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Abstract
In the published paper [1], there is an error in Figure 8. The labels in Figure 8 was incorrect, it should be corrected as follows [...]
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