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Open AccessArticle Analysis of the Dynamic Characteristics of a Micro-Piezoelectric Bimorph Beam Based on an Admittance Test

by Tianxiang Zheng, Shuo Chen, Linxu Lei, Zhanfeng Deng, Cheng Zhang, Xing Yang, Haodong Zou and Menghan Xu

Micromachines 2017, 8(7), 220; doi:10.3390/mi8070220 (registering DOI)

Received: 31 May 2017 / Revised: 9 July 2017 / Accepted: 11 July 2017 / Published: 14 July 2017

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Abstract

A piezoelectric bimorph beam, as an upgraded cantilever beam structure, can be used to detect gas content and build a micro-actuator, among other functions. Thus, this beam is widely applied to microelectromechanical systems (MEMS), transformers, and precision machinery. For example, when photoacoustic spectroscopy

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A piezoelectric bimorph beam, as an upgraded cantilever beam structure, can be used to detect gas content and build a micro-actuator, among other functions. Thus, this beam is widely applied to microelectromechanical systems (MEMS), transformers, and precision machinery. For example, when photoacoustic spectroscopy is performed to detect oil-soluble gas in transformers, a micro-cantilever beam can be used to detect gas content. The dynamic characteristics of piezoelectric bimorph beams, such as resonant frequency, are important indexes in the applications of these beams. The equivalent circuit model for a piezoelectric bimorph beam is examined in this study and an admittance test is performed on the beam to accurately, quickly, and economically measure and analyze its dynamic characteristics. Then, the least squares method is applied to obtain the characteristic curves of the admittance circle, amplitude frequency, and phase frequency; identify the dynamic characteristics of the piezoelectric bimorph beam (e.g., resonant frequency); and determine the parameters of the equivalent circuit. The resonant frequency of the piezoelectric bimorph beam is 207.67 Hz based on the result of the admittance circle test, which is basically consistent with the results of microscope image method (i.e., 207.85 Hz) and the theoretical calculation (i.e., 222.03 Hz). This finding proves the validity of the proposed test method. This method cannot only improve the detection speed of piezoelectric bimorph beams, but can also provide a fast detection strategy for testing the characteristics of such beams during photoacoustic spectroscopy. Full article

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Open AccessFeature PaperArticle Nearly Aberration-Free Multiphoton Polymerization into Thick Photoresist Layers

by Bence Horváth, Pál Ormos and Lóránd Kelemen

Micromachines 2017, 8(7), 219; doi:10.3390/mi8070219

Received: 22 May 2017 / Revised: 21 June 2017 / Accepted: 6 July 2017 / Published: 13 July 2017

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Abstract

In the era of lab-on-chip (LOC) devices, two-photon polymerization (TPP) is gaining more and more interest due to its capability of producing micrometer-sized 3D structures. With TPP, one may integrate functional structures into microfluidic systems by polymerizing them directly inside microchannels. When the

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In the era of lab-on-chip (LOC) devices, two-photon polymerization (TPP) is gaining more and more interest due to its capability of producing micrometer-sized 3D structures. With TPP, one may integrate functional structures into microfluidic systems by polymerizing them directly inside microchannels. When the feature of sub-micrometer size is a requirement, it is necessary to use high numerical aperture (NA) oil-immersion objectives that are optimized to work close to the glass substrate-photoresist interface. Further away from the substrate, that is, a few tens of micrometers into the photoresist, the focused beam undergoes focal spot elongation and focal position shift. These effects may eventually reduce the quality of the polymerized structures; therefore, it is desirable to eliminate them. We introduce a method that can highly improve the quality of structures polymerized tens of micrometers away from the substrate-photoresist interface by an oil-immersion, high NA objective. A spatial light-modulator is used to pre-compensate the phase-front distortion introduced by the interfacial refractive index jump on the strongly converging beam. Full article

(This article belongs to the Special Issue Ultrafast Laser Fabrication for Lab-on-a-Chip)

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Open AccessArticle Large-Area and High-Throughput PDMS Microfluidic Chip Fabrication Assisted by Vacuum Airbag Laminator

by Shuting Xie, Jun Wu, Biao Tang, Guofu Zhou, Mingliang Jin and Lingling Shui

Micromachines 2017, 8(7), 218; doi:10.3390/mi8070218

Received: 15 May 2017 / Revised: 23 June 2017 / Accepted: 29 June 2017 / Published: 12 July 2017

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Abstract

One of the key fabrication steps of large-area microfluidic devices is the flexible-to-hard sheet alignment and pre-bonding. In this work, the vacuum airbag laminator (VAL) which is commonly used for liquid crystal display (LCD) production has been applied for large-area microfluidic device fabrication.

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One of the key fabrication steps of large-area microfluidic devices is the flexible-to-hard sheet alignment and pre-bonding. In this work, the vacuum airbag laminator (VAL) which is commonly used for liquid crystal display (LCD) production has been applied for large-area microfluidic device fabrication. A straightforward, efficient, and low-cost method has been achieved for 400 × 500 mm² microfluidic device fabrication. VAL provides the advantages of precise alignment and lamination without bubbles. Thermal treatment has been applied to achieve strong PDMS–glass and PDMS–PDMS bonding with maximum breakup pressure of 739 kPa, which is comparable to interference-assisted thermal bonding method. The fabricated 152 × 152 mm² microfluidic chip has been successfully applied for droplet generation and splitting. Full article

(This article belongs to the Special Issue Insights and Advancements in Microfluidics)

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Open AccessArticle Effects of Environmental Gas and Trace Water on the Friction of DLC Sliding with Metals

by Yoshihiro Kurahashi, Hiroyoshi Tanaka, Masaya Terayama and Joichi Sugimura

Micromachines 2017, 8(7), 217; doi:10.3390/mi8070217

Received: 23 June 2017 / Accepted: 8 July 2017 / Published: 11 July 2017

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Abstract

This paper describes an experimental study on the friction of a-C:H diamond-like carbon (DLC) and ta-C DLC coatings in gas with different concentration of trace water. Pin-on-disk sliding experiments were conducted with DLC coated disks and aluminum pins in hydrogen, nitrogen, and argon.

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This paper describes an experimental study on the friction of a-C:H diamond-like carbon (DLC) and ta-C DLC coatings in gas with different concentration of trace water. Pin-on-disk sliding experiments were conducted with DLC coated disks and aluminum pins in hydrogen, nitrogen, and argon. Trace oxygen was eliminated to less than 0.1 ppm, while water in the gas was controlled between 0 and 160 ppm. Fourier transform infrared spectroscopy (FT-IR) and laser Raman spectroscopy were used to analyze the transfer films on the metal surfaces. It was found that trace water slightly increased friction in hydrogen gas, whereas trace water caused a significant decrease in the friction coefficient in nitrogen and argon, particularly with a-C:H DLC. The low friction in hydrogen was brought about by the formation of transfer films with structured amorphous carbon, but no differences in the structure and contents of the films were found in the tests with and without trace water. In nitrogen and argon, the low friction with a-C:H DLC was achieved by the gradual formation of transfer films containing structured amorphous carbon, and FT-IR spectra showed that the films contained CH, OH, C–O–C, and C–OH bonds. Full article

(This article belongs to the Special Issue Microtribology, Adhesion and Surface Engineering)

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Open AccessArticle Development of the Electric Equivalent Model for the Cytoplasmic Microinjection of Small Adherent Cells

by Florence Hiu Ling Chan, Runhuai Yang and King Wai Chiu Lai

Micromachines 2017, 8(7), 216; doi:10.3390/mi8070216

Received: 2 May 2017 / Revised: 25 June 2017 / Accepted: 4 July 2017 / Published: 8 July 2017

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Abstract

A novel approach utilizing current feedback for the cytoplasmic microinjection of biological cells is proposed. In order to realize the cytoplasmic microinjection on small adherent cells (diameter < 30 μm and thickness < 10 μm), an electrical model is built and analyzed according

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A novel approach utilizing current feedback for the cytoplasmic microinjection of biological cells is proposed. In order to realize the cytoplasmic microinjection on small adherent cells (diameter < 30 μm and thickness < 10 μm), an electrical model is built and analyzed according to the electrochemical properties of target cells. In this study, we have verified the effectiveness of the current measurement for monitoring the injection process and the study of ion channel activities for verifying the cell viability of the cells after the microinjection. Full article

(This article belongs to the Special Issue Microdevices and Microsystems for Cell Manipulation)

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Open AccessArticle PZT-Actuated and -Sensed Resonant Micromirrors with Large Scan Angles Applying Mechanical Leverage Amplification for Biaxial Scanning

by Shanshan Gu-Stoppel, Thorsten Giese, Hans-Joachim Quenzer, Ulrich Hofmann and Wolfgang Benecke

Micromachines 2017, 8(7), 215; doi:10.3390/mi8070215

Received: 9 April 2017 / Revised: 30 June 2017 / Accepted: 2 July 2017 / Published: 6 July 2017

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Abstract

This article presents design, fabrication and characterization of lead zirconate titanate (PZT)-actuated micromirrors, which enable extremely large scan angle of up to 106° and high frequency of 45 kHz simultaneously. Besides the high driving torque delivered by PZT actuators, mechanical leverage amplification has

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This article presents design, fabrication and characterization of lead zirconate titanate (PZT)-actuated micromirrors, which enable extremely large scan angle of up to 106° and high frequency of 45 kHz simultaneously. Besides the high driving torque delivered by PZT actuators, mechanical leverage amplification has been applied for the micromirrors in this work to reach large displacements consuming low power. Additionally, fracture strength and failure behavior of poly-Si, which is the basic material of the micromirrors, have been studied to optimize the designs and prevent the device from breaking due to high mechanical stress. Since comparing to using biaxial micromirror, realization of biaxial scanning using two independent single-axial micromirrors shows considerable advantages, a setup combining two single-axial micromirrors for biaxial scanning and the results will also be presented in this work. Moreover, integrated piezoelectric position sensors are implemented within the micromirrors, based on which closed-loop control has been developed and studied. Full article

(This article belongs to the Special Issue MEMS Mirrors)

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Open AccessArticle Designing a Tool System for Lowering Friction during the Ejection of In-Die Sintered Micro Gears

by Emanuele Cannella, Emil Krabbe Nielsen and Alessandro Stolfi

Micromachines 2017, 8(7), 214; doi:10.3390/mi8070214

Received: 29 May 2017 / Revised: 30 June 2017 / Accepted: 3 July 2017 / Published: 6 July 2017

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Abstract

The continuous improvements in micro-forging technologies generally involve process, material, and tool design. The field assisted sintering technique (FAST) is a process that makes possible the manufacture of near-net-shape components in a closed-die setup. However, the final part quality is affected by the

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The continuous improvements in micro-forging technologies generally involve process, material, and tool design. The field assisted sintering technique (FAST) is a process that makes possible the manufacture of near-net-shape components in a closed-die setup. However, the final part quality is affected by the influence of friction during the ejection phase, caused by radial expansion of the compacted and sintered powder. This paper presents the development of a pre-stressed tool system for the manufacture of micro gears made of aluminum. By using the hot isostatic pressing (HIP) sintering process and different combinations of process parameters, the designed tool system was compared to a similar tool system designed without a pre-stressing strategy. The comparison between the two tool systems was based on the ejection force and part fidelity. The ejection force was measured during the tests, while the part fidelity was documented using an optical microscope and computed tomography in order to obtain a multi-scale characterization. The results showed that the use of pre-stress reduced the porosity in the gear by 40% and improved the dimensional fidelity by more than 75% compared to gears produced without pre-stress. Full article

(This article belongs to the Special Issue Micro/Nano Manufacturing)

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Open AccessArticle Influences of Excitation on Dynamic Characteristics of Piezoelectric Micro-Jets

by Kai Li, Jun-Kao Liu, Wei-Shan Chen and Lu Zhang

Micromachines 2017, 8(7), 213; doi:10.3390/mi8070213

Received: 8 May 2017 / Revised: 14 June 2017 / Accepted: 30 June 2017 / Published: 5 July 2017

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Abstract

Piezoelectric micro-jets are based on piezoelectric ink-jet technology and can achieve the drop-on demand requirements. A piezoelectric micro-jet which is designed for bearing lubrication is presented in this paper. In order to analyze the fluid dynamic characteristics of the piezoelectric micro-jet so as

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Piezoelectric micro-jets are based on piezoelectric ink-jet technology and can achieve the drop-on demand requirements. A piezoelectric micro-jet which is designed for bearing lubrication is presented in this paper. In order to analyze the fluid dynamic characteristics of the piezoelectric micro-jet so as to obtain good injection performance, a direct coupling simulation method is proposed in this paper. The effects of inlet and viscous losses in the cavity are taken into account, which are close to the actual conditions in the direct coupling method. The effects of the pulse excitation parameters on the pinch-off time, tail length, velocity, and volume of the droplet are analyzed by the proposed direct coupling method. The pressure distribution inside the cavity of the micro-jet and the status of the droplet formation at different times are also given. In addition, the method is proved to be effective in predicting and analyzing the fluid dynamic characteristics of piezoelectric micro-jets by comparing the simulation results with the experimental results. Full article

(This article belongs to the Special Issue Piezoelectric MEMS)

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Open AccessArticle Simulation Analysis of Improving Microfluidic Heterogeneous Immunoassay Using Induced Charge Electroosmosis on a Floating Gate

by Qingming Hu, Yukun Ren, Weiyu Liu, Ye Tao and Hongyuan Jiang

Micromachines 2017, 8(7), 212; doi:10.3390/mi8070212

Received: 7 June 2017 / Revised: 2 July 2017 / Accepted: 3 July 2017 / Published: 4 July 2017

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Abstract

On-chip immuno-sensors are a hot topic in the microfluidic community, which is usually limited by slow diffusion-dominated transport of analytes in confined microchannels. Specifically, the antigen-antibody binding reaction at a functionalized area cannot be provided with enough antigen source near the reaction surface,

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On-chip immuno-sensors are a hot topic in the microfluidic community, which is usually limited by slow diffusion-dominated transport of analytes in confined microchannels. Specifically, the antigen-antibody binding reaction at a functionalized area cannot be provided with enough antigen source near the reaction surface, since a small diffusion flux cannot match with the quick rate of surface reaction, which influences the response time and sensitivity of on-chip heterogeneous immunoassay. In this work, we propose a method to enhance the transportation of biomolecules to the surface of an antibody-immobilized electrode with induce charge electroosmotic (ICEO) convection in a low concentration suspension, so as to improve the binding efficiency of microfluidic heterogeneous immunoassays. The circular stirring fluid motion of ICEO on the surface of a floating gate electrode at the channel bottom accelerates the transport of freely suspended antigen towards the wall-immobilized antibodies. We investigate the dependence of binding efficiency on voltage magnitude and field frequency of the applied alternate current (AC) electrical field. The binding rate yields a factor of 5.4 higher binding for an applied voltage of 4 V at 10 Hz when the Damkohler number is 1000. The proposed microfluidic immuno-sensor technology of a simple electrode structure using ICEO convective fluid flow around floating conductors could offer exciting opportunities for diffusion-limited on-chip bio-microfluidic sensors. Full article

(This article belongs to the Special Issue Micro/Nano-Chip Electrokinetics, Volume II)

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Open AccessArticle DC Microplasma Jet for Local a:C-H Deposition Operated in SEM Chamber

by Khanit Matra, Hiroshi Furuta and Akimitsu Hatta

Micromachines 2017, 8(7), 211; doi:10.3390/mi8070211

Received: 31 May 2017 / Revised: 21 June 2017 / Accepted: 1 July 2017 / Published: 3 July 2017

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Abstract

A DC micro plasma jet for local micro deposition of a:C-H film in the ambient vacuum of scanning electron microscope (SEM) chamber is proposed. Acetylene (C₂H₂) gas was locally fed into the chamber through an orifice shaped gas nozzle

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A DC micro plasma jet for local micro deposition of a:C-H film in the ambient vacuum of scanning electron microscope (SEM) chamber is proposed. Acetylene (C₂H₂) gas was locally fed into the chamber through an orifice shaped gas nozzle (OGN) at 6.6 sccm in flow rate by applying 80 kPa-inlet pressure with an additional direct pumping system equipped on the SEM chamber. As a cathode, a cut of n-type silicon (Si) wafer was placed right in front of the OGN at 200 μm gap distance. By applying a positive DC voltage to the OGN, C₂H₂ plasma was generated locally between the electrodes. During discharge, the voltage increased and the current decreased due to deposition of insulating film on the Si wafer with resulting in automatic termination of discharge at the constant source voltage. A symmetric mountain-shaped a:C-H film of 5 μm height was deposited at the center by operation for 15 s. Films were deposited with variation of gas flow rate, gap distance, voltage and current, and deposition time. The films were directly observed by SEM and analyzed by surface profiler and by Raman spectroscopy. Full article

(This article belongs to the Special Issue Microplasma Devices)

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Open AccessArticle New Endoscopic Imaging Technology Based on MEMS Sensors and Actuators

by Qiu Zhen and Wibool Piyawattanamatha

Micromachines 2017, 8(7), 210; doi:10.3390/mi8070210

Received: 31 December 2016 / Revised: 9 March 2017 / Accepted: 10 March 2017 / Published: 2 July 2017

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Abstract

Over the last decade, optical fiber-based forms of microscopy and endoscopy have extended the realm of applicability for many imaging modalities. Optical fiber-based imaging modalities permit the use of remote illumination sources and enable flexible forms supporting the creation of portable and hand-held

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Over the last decade, optical fiber-based forms of microscopy and endoscopy have extended the realm of applicability for many imaging modalities. Optical fiber-based imaging modalities permit the use of remote illumination sources and enable flexible forms supporting the creation of portable and hand-held imaging instrumentations to interrogate within hollow tissue cavities. A common challenge in the development of such devices is the design and integration of miniaturized optical and mechanical components. Until recently, microelectromechanical systems (MEMS) sensors and actuators have been playing a key role in shaping the miniaturization of these components. This is due to the precision mechanics of MEMS, microfabrication techniques, and optical functionality enabling a wide variety of movable and tunable mirrors, lenses, filters, and other optical structures. Many promising results from MEMS based optical fiber endoscopy have demonstrated great potentials for clinical translation. In this article, reviews of MEMS sensors and actuators for various fiber-optical endoscopy such as fluorescence, optical coherence tomography, confocal, photo-acoustic, and two-photon imaging modalities will be discussed. This advanced MEMS based optical fiber endoscopy can provide cellular and molecular features with deep tissue penetration enabling guided resections and early cancer assessment to better treatment outcomes. Full article

(This article belongs to the Special Issue MEMS/NEMS for Biomedical Imaging and Sensing)

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Open AccessArticle Analysis of the Diffusion Process by pH Indicator in Microfluidic Chips for Liposome Production

by Elisabetta Bottaro, Ali Mosayyebi, Dario Carugo and Claudio Nastruzzi

Micromachines 2017, 8(7), 209; doi:10.3390/mi8070209

Received: 28 April 2017 / Revised: 8 June 2017 / Accepted: 17 June 2017 / Published: 1 July 2017

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Abstract

In recent years, the development of nano- and micro-particles has attracted considerable interest from researchers and enterprises, because of the potential utility of such particles as drug delivery vehicles. Amongst the different techniques employed for the production of nanoparticles, microfluidic-based methods have proven

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In recent years, the development of nano- and micro-particles has attracted considerable interest from researchers and enterprises, because of the potential utility of such particles as drug delivery vehicles. Amongst the different techniques employed for the production of nanoparticles, microfluidic-based methods have proven to be the most effective for controlling particle size and dispersity, and for achieving high encapsulation efficiency of bioactive compounds. In this study, we specifically focus on the production of liposomes, spherical vesicles formed by a lipid bilayer encapsulating an aqueous core. The formation of liposomes in microfluidic devices is often governed by diffusive mass transfer of chemical species at the liquid interface between a solvent (i.e., alcohol) and a non-solvent (i.e., water). In this work, we developed a new approach for the analysis of mixing processes within microfluidic devices. The method relies on the use of a pH indicator, and we demonstrate its utility by characterizing the transfer of ethanol and water within two different microfluidic architectures. Our approach represents an effective route to experimentally characterize diffusion and advection processes governing the formation of vesicular/micellar systems in microfluidics, and can also be employed to validate the results of numerical modelling. Full article

(This article belongs to the Special Issue Microfluidic Technologies for Drug Delivery)

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Open AccessArticle Research on the Drilling Performance of a Helical Point Micro Drill with Different Geometry Parameters

by Zhiqiang Liang, Suyan Zhang, Xibin Wang, Haixin Guo, Tianfeng Zhou, Li Jiao and Pei Yan

Micromachines 2017, 8(7), 208; doi:10.3390/mi8070208

Received: 29 May 2017 / Revised: 18 June 2017 / Accepted: 22 June 2017 / Published: 29 June 2017

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Abstract

During the micro-drilling process of stainless steel, the wear, fracture, and breakage of the micro-drill easily occur. Micro-drill geometry parameters have significant influence on the drilling performance of the micro-drill. Nowadays, the helical point micro-drill is proposed and its improved drilling performance is

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During the micro-drilling process of stainless steel, the wear, fracture, and breakage of the micro-drill easily occur. Micro-drill geometry parameters have significant influence on the drilling performance of the micro-drill. Nowadays, the helical point micro-drill is proposed and its improved drilling performance is validated by some researchers. In this study, to analyze the effect of geometry parameters of the helical point micro-drill on drilling performance, the mathematical models of the helical flank and ground flute are proposed, and the cutting lip shape, rake angle, and uncut chip thickness are calculated using MATLAB software. Then, based on the orthogonal tests, nine kinds of micro-drills with different point angles, web thicknesses, and helix angles are fabricated using a six-axis CNC tool grinder, and micro-drilling experiments on 1Cr18Ni9Ti stainless steel are carried out. The drilling force, the burr height, and the hole wall quality are measured and observed. The results show that the point angle is the main contributing factor for the thrust force and burr height, and the web thickness is the main contributing factor for the micro hole wall quality. The increased point angle offers a larger thrust force, but gives rise to a smaller exit burr. A larger web thickness leads to a larger thrust force and burr height, and results in a poor surface quality. With the helix angle increased, the thrust force and burr height decreases, and the surface quality of micro-hole improves. The geometry parameters with a point angle 70°, a point angle of 40°, and web thickness ratio of 0.2 can used to improve the drilling performance of the helical point micro-drill. Full article

(This article belongs to the Special Issue State-Of-The-Art Micromachining)

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Open AccessArticle Electroceutical Approach for Impairing the Motility of Pathogenic Bacterium Using a Microfluidic Platform

by Ryan Berthelot, Kristina Doxsee and Suresh Neethirajan

Micromachines 2017, 8(7), 207; doi:10.3390/mi8070207

Received: 23 May 2017 / Revised: 20 June 2017 / Accepted: 27 June 2017 / Published: 29 June 2017

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Abstract

Electrotaxis, or galvanotaxis, refers to the migration pattern of cells induced in response to electrical potential. Electrotaxis has not been explored in detail in bacterial cells; information regarding the impact of current on pathogenic bacteria is severely lacking. Using microfluidic platforms and optical

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Electrotaxis, or galvanotaxis, refers to the migration pattern of cells induced in response to electrical potential. Electrotaxis has not been explored in detail in bacterial cells; information regarding the impact of current on pathogenic bacteria is severely lacking. Using microfluidic platforms and optical microscopy, we designed a series of single- and multi-cue experiments to assess the impact of varying electrical currents and acetic acid concentrations on bacterial motility dynamics in pathogenic multi-drug resistant (MDR) strains of Pseudomonas aeruginosa and Escherichia coli. The use of the microfluidic platform allows for single-cue experiments where electrical current is supplied at a range that is biocidal to bacteria and multi-cue experiments where acetic acid is combined with current to enhance disinfection. These strategies may offer substantial therapeutic benefits, specifically for the treatment of biofilm infections, such as those found in the wound environment. Our results showed that an application of current in combination with acetic acid has profound inhibitory effects on MDR strains of P. aeruginosa and E. coli, even with brief applications. Specifically, E. coli motility dynamics and cell survival were significantly impaired starting at a concentration of 0.125 mA of direct current (DC) and 0.31% acetic acid, while P. aeruginosa was impaired at 0.70 mA and 0.31% acetic acid. As these strains are relevant wound pathogens, it is likely that this strategy would be effective against similar strains in vivo and could represent a new approach to hasten wound healing. Full article

(This article belongs to the Special Issue Biomedical Microfluidic Devices)

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Open AccessArticle Flexural Properties and Fracture Behavior of Nanoporous Alumina film by Three-Point Bending Test

by Jung-Hsuan Chen and Wen-Shiang Luo

Micromachines 2017, 8(7), 206; doi:10.3390/mi8070206

Received: 30 May 2017 / Revised: 17 June 2017 / Accepted: 21 June 2017 / Published: 27 June 2017

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Abstract

This study investigated the influence of porosity on the flexural property of a nanoporous alumina film. When the porosity of the alumina film increased, both bending strength and modulus declined. The results from the bending test revealed that the setting of the film

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This study investigated the influence of porosity on the flexural property of a nanoporous alumina film. When the porosity of the alumina film increased, both bending strength and modulus declined. The results from the bending test revealed that the setting of the film during the bending test had significant influence on the flexural property. Fracture only occurred when the porous side of the alumina film suffered tensile stress. The ability to resist fracture in the barrier layer was higher than in the porous side; the magnitude of the bending strength was amplified when the barrier layer sustained tensile stress. When the porous layer suffered a tensile stress, the bending strength decreased from 182.4 MPa to 47.7 Mpa as the porosity increased from 22.7% to 51.7%; meanwhile, the modulus reduced from 82.7 GPa to 17.9 GPa. In this study, the most important finding from fractographic analysis suggested that there were a localized plastic deformations and layered ruptures at the porous side of the alumina film when a load was applied. The fracture behavior of the nanoporous alumina film observed in the present work was notably different from general ceramic materials and might be related to its asymmetric nanostructure. Full article

(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2017)

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Open AccessArticle Tuneable Liquid Crystal Micro-Lens Array for Image Contrast Enhancement in a Pixelated Thin Film Photo-Transistor Flat Panel Imager

by Kun Li, Daping Chu, Jiaqi Chu, Shuhei Kitajima, Tokiyoshi Matsuda and Mutsu Kimura

Micromachines 2017, 8(7), 205; doi:10.3390/mi8070205

Received: 12 June 2017 / Revised: 20 June 2017 / Accepted: 23 June 2017 / Published: 26 June 2017

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Abstract

We propose and demonstrate the concept of using a tuneable liquid crystal micro-lens (LCML) array to improve the image contrast of a pixelated thin film photo-transistor (TFPT) flat panel imager. Such a device can be used to image contents on paper-based media and

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We propose and demonstrate the concept of using a tuneable liquid crystal micro-lens (LCML) array to improve the image contrast of a pixelated thin film photo-transistor (TFPT) flat panel imager. Such a device can be used to image contents on paper-based media and display a magnified version on a flat panel display for elderly or visually impaired people. Practical aspects including device physical geometry, object scattering profile, LC material, and focusing effect of LCML on an object are considered during the design process with the support of ZEMAX simulations. An optimised effective focal length (EFL) has been calculated for the designed LCML to best relay the objects or contents on a paper to the TFPT pixel plane. The designed LCML devices are fabricated with the optimised EFL, and they have good phase depth profiles which are close to a spherical lens profile. Preliminary test results show that the combination of a TFPT imager with an LCML array can make the image contrast more than two times better than that using the TFPT imager alone. The tuneable EFL of the developed LCMLs are useful in the situation where the LCML is not in direct contact with the imaged object. Full article

(This article belongs to the collection Laser Micromachining and Microfabrication)

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Open AccessArticle Potential of Piezoelectric MEMS Resonators for Grape Must Fermentation Monitoring

by Georg Pfusterschmied, Javier Toledo, Martin Kucera, Wolfgang Steindl, Stefan Zemann, Víctor Ruiz-Díez, Michael Schneider, Achim Bittner, Jose Luis Sanchez-Rojas and Ulrich Schmid

Micromachines 2017, 8(7), 200; doi:10.3390/mi8070200

Received: 27 March 2017 / Revised: 8 June 2017 / Accepted: 20 June 2017 / Published: 26 June 2017

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Abstract

In this study grape must fermentation is monitored using a self-actuating/self-sensing piezoelectric micro-electromechanical system (MEMS) resonator. The sensor element is excited in an advanced roof tile-shaped vibration mode, which ensures high Q-factors in liquids (i.e., Q ~100 in isopropanol), precise resonance frequency

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In this study grape must fermentation is monitored using a self-actuating/self-sensing piezoelectric micro-electromechanical system (MEMS) resonator. The sensor element is excited in an advanced roof tile-shaped vibration mode, which ensures high Q-factors in liquids (i.e., Q ~100 in isopropanol), precise resonance frequency analysis, and a fast measurement procedure. Two sets of artificial model solutions are prepared, representing an ordinary and a stuck/sluggish wine fermentation process. The precision and reusability of the sensor are shown using repetitive measurements (10 times), resulting in standard deviations of the measured resonance frequencies of ~0.1%, Q-factor of ~11%, and an electrical conductance peak height of ~12%, respectively. With the applied evaluation procedure, moderate standard deviations of ~1.1% with respect to density values are achieved. Based on these results, the presented sensor concept is capable to distinguish between ordinary and stuck wine fermentation, where the evolution of the wine density associated with the decrease in sugar and the increase in ethanol concentrations during fermentation processes causes a steady increase in the resonance frequency for an ordinary fermentation. Finally, the first test measurements in real grape must are presented, showing a similar trend in the resonance frequency compared to the results of an artificial solutions, thus proving that the presented sensor concept is a reliable and reusable platform for grape must fermentation monitoring. Full article

(This article belongs to the Special Issue Piezoelectric MEMS)

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Open AccessArticle Design and Modeling of Polysilicon Electrothermal Actuators for a MEMS Mirror with Low Power Consumption

by Miguel Lara-Castro, Adrian Herrera-Amaya, Marco A. Escarola-Rosas, Moisés Vázquez-Toledo, Francisco López-Huerta, Luz A. Aguilera-Cortés and Agustín L. Herrera-May

Micromachines 2017, 8(7), 203; doi:10.3390/mi8070203

Received: 14 January 2017 / Revised: 19 June 2017 / Accepted: 20 June 2017 / Published: 25 June 2017

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Abstract

Endoscopic optical-coherence tomography (OCT) systems require low cost mirrors with small footprint size, out-of-plane deflections and low bias voltage. These requirements can be achieved with electrothermal actuators based on microelectromechanical systems (MEMS). We present the design and modeling of polysilicon electrothermal actuators for

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Endoscopic optical-coherence tomography (OCT) systems require low cost mirrors with small footprint size, out-of-plane deflections and low bias voltage. These requirements can be achieved with electrothermal actuators based on microelectromechanical systems (MEMS). We present the design and modeling of polysilicon electrothermal actuators for a MEMS mirror (100 μm × 100 μm × 2.25 μm). These actuators are composed by two beam types (2.25 μm thickness) with different cross-section area, which are separated by 2 μm gap. The mirror and actuators are designed through the Sandia Ultra-planar Multi-level MEMS Technology V (SUMMiT V^®) process, obtaining a small footprint size (1028 μm × 1028 µm) for actuators of 550 µm length. The actuators have out-of-plane displacements caused by low dc voltages and without use material layers with distinct thermal expansion coefficients. The temperature behavior along the actuators is calculated through analytical models that include terms of heat energy generation, heat conduction and heat energy loss. The force method is used to predict the maximum out-of-plane displacements in the actuator tip as function of supplied voltage. Both analytical models, under steady-state conditions, employ the polysilicon resistivity as function of the temperature. The electrothermal-and structural behavior of the actuators is studied considering different beams dimensions (length and width) and dc bias voltages from 0.5 to 2.5 V. For 2.5 V, the actuator of 550 µm length reaches a maximum temperature, displacement and electrical power of 115 °C, 10.3 µm and 6.3 mW, respectively. The designed actuation mechanism can be useful for MEMS mirrors of different sizes with potential application in endoscopic OCT systems that require low power consumption. Full article

(This article belongs to the Special Issue MEMS Mirrors)

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Open AccessReview Microfluidic and Nanofluidic Resistive Pulse Sensing: A Review

by Yongxin Song, Junyan Zhang and Dongqing Li

Micromachines 2017, 8(7), 204; doi:10.3390/mi8070204

Received: 17 April 2017 / Revised: 11 June 2017 / Accepted: 21 June 2017 / Published: 25 June 2017

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Abstract

The resistive pulse sensing (RPS) method based on the Coulter principle is a powerful method for particle counting and sizing in electrolyte solutions. With the advancement of micro- and nano-fabrication technologies, microfluidic and nanofluidic resistive pulse sensing technologies and devices have been developed.

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The resistive pulse sensing (RPS) method based on the Coulter principle is a powerful method for particle counting and sizing in electrolyte solutions. With the advancement of micro- and nano-fabrication technologies, microfluidic and nanofluidic resistive pulse sensing technologies and devices have been developed. Due to the unique advantages of microfluidics and nanofluidics, RPS sensors are enabled with more functions with greatly improved sensitivity and throughput and thus have wide applications in fields of biomedical research, clinical diagnosis, and so on. Firstly, this paper reviews some basic theories of particle sizing and counting. Emphasis is then given to the latest development of microfuidic and nanofluidic RPS technologies within the last 6 years, ranging from some new phenomena, methods of improving the sensitivity and throughput, and their applications, to some popular nanopore or nanochannel fabrication techniques. The future research directions and challenges on microfluidic and nanofluidic RPS are also outlined. Full article

(This article belongs to the Special Issue Insights and Advancements in Microfluidics)

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Open AccessOpinion Electronic Devices That Identify Individuals with Fever in Crowded Places: A Prototype

by Carlos Polanco González, Ignacio Islas Vazquez, Jorge Alberto Castañón González, Thomas Buhse and Miguel Arias-Estrada

Micromachines 2017, 8(7), 202; doi:10.3390/mi8070202

Received: 1 May 2017 / Revised: 14 June 2017 / Accepted: 16 June 2017 / Published: 24 June 2017

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Abstract

Most epidemiological surveillance systems for severe infections with epidemic potential are based on accumulated symptomatic cases in defined geographical areas. Eventually, all cases have to be clinically verified to confirm an outbreak. These patients will present high fever at the early stages of

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Most epidemiological surveillance systems for severe infections with epidemic potential are based on accumulated symptomatic cases in defined geographical areas. Eventually, all cases have to be clinically verified to confirm an outbreak. These patients will present high fever at the early stages of the disease. Here, we introduce a non-invasive low-cost electronic device (bracelet) that measures and reports 24/7, year-round information on the temperature, geographical location, and identification of the subject using the device. The data receiver can be installed in a tower (ground) or a drone (air) in densely populated or remote areas. The prototype was made with low-cost electronic components, and it was tested indoors and outdoors. The prototype shows efficient ground and air connectivity. This electronic device will allow health professionals to monitor the prevalence of fever in a geographical area and to reduce the time span between the presentation of the first cases of a potential outbreak and their medical evaluation by giving an early warning. Field tests of the device, programs, and technical diagrams of the prototype are available as ^{Supplementary Materials}. Full article

(This article belongs to the Special Issue Medical Microdevices and Micromachines)

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Open AccessArticle A Simple Extraction Method of Young’s Modulus for Multilayer Films in MEMS Applications

by Xin-Ge Guo, Zai-Fa Zhou, Chao Sun, Wei-Hua Li and Qing-An Huang

Micromachines 2017, 8(7), 201; doi:10.3390/mi8070201

Received: 8 May 2017 / Revised: 12 June 2017 / Accepted: 20 June 2017 / Published: 23 June 2017

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Abstract

Based on the first resonance frequency measurement of multilayer beams, a simple extraction method has been developed to extract the Young’s modulus of individual layers. To verify this method, the double-layer cantilever, as a typical example, is analyzed to simplify the situation and

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Based on the first resonance frequency measurement of multilayer beams, a simple extraction method has been developed to extract the Young’s modulus of individual layers. To verify this method, the double-layer cantilever, as a typical example, is analyzed to simplify the situation and finite element modeling (FEM) is used in consideration of the buckling and unbuckling situation of cantilevers. The first resonance frequencies, which are obtained by ANSYS (15.0, ANSYS Inc., Pittsburgh, PA, USA) with a group of thirteen setting values of Young’s modulus in the polysilicon layer are brought into the theoretical formulas to obtain a new group of Young’s modulus in the polysilicon layer. The reliability and feasibility of the theoretical method are confirmed, according to the slight differences between the setting values and the results of the theoretical model. In the experiment, a series of polysilicon-metal double-layer cantilevers were fabricated. Digital holographic microscopy (DHM) (Lyncée Tech, Lausanne, Switzerland) is used to distinguish the buckled from the unbuckled. A scanning laser Doppler vibrometer (LDV) (Polytech GmbH, Berlin, Germany) system is used to measure the first resonance frequencies of them. After applying the measurement results into the theoretical modulus, the average values of Young’s modulus in the polysilicon and gold layers are 151.78 GPa and 75.72 GPa, respectively. The extracted parameters are all within the rational ranges, compared with the available results. Full article

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Open AccessArticle Parametric Study of an Electroosmotic Micromixer with Heterogeneous Charged Surface Patches

by Faheem Ahmed and Kwang-Yong Kim

Micromachines 2017, 8(7), 199; doi:10.3390/mi8070199

Received: 4 May 2017 / Revised: 15 June 2017 / Accepted: 19 June 2017 / Published: 23 June 2017

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Abstract

A T-shaped micromixer featuring electroosmotic flow with heterogeneous charged surface patches on the channel walls was analyzed, and an improved design was proposed to enhance mixing performance. Numerical analysis was performed using steady Navier-Stokes equations with an additional electrokinetic body force. The numerical

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A T-shaped micromixer featuring electroosmotic flow with heterogeneous charged surface patches on the channel walls was analyzed, and an improved design was proposed to enhance mixing performance. Numerical analysis was performed using steady Navier-Stokes equations with an additional electrokinetic body force. The numerical results for species concentration were validated with available experimental data. A parametric analysis of the micromixer was performed by varying channel height, channel width, patch width, and externally applied voltage. The effects of these parameters on the flow structure and mixing performance were analyzed in detail. A quantitative measurement based upon the mass variance was employed to quantify the mixing performance. Numerical results of the parametric study were used to propose an improved micromixer design with spacing between adjacent charged patches. The proposed design provided a more favorable flow structure to allow for enhanced mixing performance. Full article

(This article belongs to the Special Issue Micro/Nano-Chip Electrokinetics, Volume II)

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Open AccessArticle A Viscosity-Based Model for Bubble-Propelled Catalytic Micromotors

by Zhen Wang, Qingjia Chi, Lisheng Liu, Qiwen Liu, Tao Bai and Qiang Wang

Micromachines 2017, 8(7), 198; doi:10.3390/mi8070198

Received: 28 March 2017 / Revised: 17 June 2017 / Accepted: 19 June 2017 / Published: 23 June 2017

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Abstract

Micromotors have shown significant potential for diverse future applications. However, a poor understanding of the propelling mechanism hampers its further applications. In this study, an accurate mechanical model of the micromotor has been proposed by considering the geometric asymmetry and fluid viscosity based

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Micromotors have shown significant potential for diverse future applications. However, a poor understanding of the propelling mechanism hampers its further applications. In this study, an accurate mechanical model of the micromotor has been proposed by considering the geometric asymmetry and fluid viscosity based on hydrodynamic principles. The results obtained from the proposed model are in a good agreement with the experimental results. The effects of the semi-cone angle on the micromotor are re-analyzed. Furthermore, other geometric parameters, like the length-radius aspect ratio, exert great impact on the velocity. It is also observed that micromotors travel much slower in highly viscous solutions and, hence, viscosity plays an important role. Full article

(This article belongs to the Special Issue Locomotion at Small Scales: From Biology to Artificial Systems)

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Open AccessArticle Analysis of Hydrodynamic Mechanism on Particles Focusing in Micro-Channel Flows

by Qikun Wang, Dan Yuan and Weihua Li

Micromachines 2017, 8(7), 197; doi:10.3390/mi8070197

Received: 5 May 2017 / Revised: 15 June 2017 / Accepted: 19 June 2017 / Published: 22 June 2017

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Abstract

In this paper, the hydrodynamic mechanism of moving particles in laminar micro-channel flows was numerically investigated. A hydrodynamic criterion was proposed to determine whether particles in channel flows can form a focusing pattern or not. A simple formula was derived to demonstrate how

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In this paper, the hydrodynamic mechanism of moving particles in laminar micro-channel flows was numerically investigated. A hydrodynamic criterion was proposed to determine whether particles in channel flows can form a focusing pattern or not. A simple formula was derived to demonstrate how the focusing position varies with Reynolds number and particle size. Based on this proposed criterion, a possible hydrodynamic mechanism was discussed as to why the particles would not be focused if their sizes were too small or the channel Reynolds number was too low. The Re-λ curve (Re, λ respectively represents the channel-based Reynolds number and the particle’s diameter scaled by the channel) was obtained using the data fitting with a least square method so as to obtain a parameter range of the focusing pattern. In addition, the importance of the particle rotation to the numerical modeling for the focusing of particles was discussed in view of the hydrodynamics. This research is expected to deepen the understanding of the particle transport phenomena in bounded flow, either in micro or macro fluidic scope. Full article

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Open AccessArticle 3-Dimensional Plasmonic Substrates Based on Chicken Eggshell Bio-Templates for SERS-Based Bio-Sensing

by Md Masud Parvez Arnob and Wei-Chuan Shih

Micromachines 2017, 8(6), 196; doi:10.3390/mi8060196

Received: 27 April 2017 / Revised: 14 June 2017 / Accepted: 15 June 2017 / Published: 21 June 2017

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Abstract

A simple technique is presented to fabricate stable and reproducible plasmonic substrates using chicken eggshell as bio-templates, an otherwise everyday waste material. The 3-dimensional (3D) submicron features on the outer shell (OS), inner shell (IS), and shell membrane (SM) regions are sputter coated

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A simple technique is presented to fabricate stable and reproducible plasmonic substrates using chicken eggshell as bio-templates, an otherwise everyday waste material. The 3-dimensional (3D) submicron features on the outer shell (OS), inner shell (IS), and shell membrane (SM) regions are sputter coated with gold and characterized for surface-enhanced Raman scattering (SERS) performance with respect to coating thickness, enhancement factor (EF), hot-spots distribution, and reproducibility. The OS and IS substrates have similar EF (2.6 × 10⁶ and 1.8 × 10⁶, respectively), while the SM provides smaller EF (1.5 × 10⁵) due to its larger characteristic feature size. The variability from them (calculated as relative standard deviation, %RSD) are less than 7, 15, and 9 for the OS, IS, and SM substrates, respectively. Due to the larger EF and better signal reproducibility, the OS region is used for label-free sensing and identification of Escherichia coli and Bacillus subtilis bacteria as an example of the potential SERS applications. It is demonstrated that the detection limit could reach the level of single bacterial cells. The OS and IS regions are also used as templates to fabricate 3D flexible SERS substrates using polydimethylsiloxane and characterized. The simple, low-cost, and green route of fabricating plasmonic substrates represents an innovative alternative approach without the needs for nanofabrication facilities. Coupled with hyperspectral Raman imaging, high-throughput bio-sensing can be carried out at the single pathogen level. Full article

(This article belongs to the Special Issue MEMS/NEMS for Biomedical Imaging and Sensing)

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Open AccessArticle Ink-Jet Printing of Micro-Electro-Mechanical Systems (MEMS)

by Gih-Keong Lau and Milan Shrestha

Micromachines 2017, 8(6), 194; doi:10.3390/mi8060194

Received: 21 March 2017 / Revised: 23 May 2017 / Accepted: 7 June 2017 / Published: 21 June 2017

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Abstract

Beyond printing text on paper, inkjet printing methods have recently been applied to print passive electrical and optical microparts, such as conductors, resistors, solder bumps and polymeric micro lenses. They are also useful to print micro-electro-mechanical systems (MEMS) as sub-millimeter sensor and actuator

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Beyond printing text on paper, inkjet printing methods have recently been applied to print passive electrical and optical microparts, such as conductors, resistors, solder bumps and polymeric micro lenses. They are also useful to print micro-electro-mechanical systems (MEMS) as sub-millimeter sensor and actuator arrays, such as multifunctional skins applicable to robotic application and ambient monitoring. This paper presents the latest review of a few successful cases of printable MEMS devices. This review shows that inkjet printing is good for printing two-dimensional or surface MEMS devices from a small unit to an array over a large area. In the future, three-dimensional printing of multi-materials, from metal, plastic, to ceramic, will open the possibility of realizing more variety and function of a large-areal MEMS array, for a mobile electro-mechanical systems. Full article

(This article belongs to the Special Issue Bioprinting and 3D Printing in MEMS Technology)

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Open AccessArticle On the Application of Replica Molding Technology for the Indirect Measurement of Surface and Geometry of Micromilled Components

by Federico Baruffi, Paolo Parenti, Francesco Cacciatore, Massimiliano Annoni and Guido Tosello

Micromachines 2017, 8(6), 195; doi:10.3390/mi8060195

Received: 24 May 2017 / Revised: 12 June 2017 / Accepted: 18 June 2017 / Published: 21 June 2017

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Abstract

The evaluation of micromilled parts quality requires detailed assessments of both geometry and surface topography. However, in many cases, the reduced accessibility caused by the complex geometry of the part makes it impossible to perform direct measurements. This problem can be solved by

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The evaluation of micromilled parts quality requires detailed assessments of both geometry and surface topography. However, in many cases, the reduced accessibility caused by the complex geometry of the part makes it impossible to perform direct measurements. This problem can be solved by adopting the replica molding technology. The method consists of obtaining a replica of the feature that is inaccessible for standard measurement devices and performing its indirect measurement. This paper examines the performance of a commercial replication media applied to the indirect measurement of micromilled components. Two specifically designed micromilled benchmark samples were used to assess the accuracy in replicating both surface texture and geometry. A 3D confocal microscope and a focus variation instrument were employed and the associated uncertainties were evaluated. The replication method proved to be suitable for characterizing micromilled surface texture even though an average overestimation in the nano-metric level of the Sa parameter was observed. On the other hand, the replicated geometry generally underestimated that of the master, often leading to a different measurement output considering the micrometric uncertainty. Full article

(This article belongs to the Special Issue Micro/Nano Manufacturing)

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Open AccessOpinion Commercial Value and Challenges of Drop-Based Microfluidic Screening Platforms–An Opinion

by Christian Holtze, Sebastian A. Weisse and Marcel Vranceanu

Micromachines 2017, 8(6), 193; doi:10.3390/mi8060193

Received: 13 February 2017 / Revised: 8 May 2017 / Accepted: 1 June 2017 / Published: 20 June 2017

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Abstract

Developments in High Throughput Screening aim at maximizing the number of samples per time and reducing the cost per sample, e.g., by applying very small sample volumes. The ultimate technological step in miniaturization is moving from microtiter plate wells to droplets, and from

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Developments in High Throughput Screening aim at maximizing the number of samples per time and reducing the cost per sample, e.g., by applying very small sample volumes. The ultimate technological step in miniaturization is moving from microtiter plate wells to droplets, and from batch-wise characterization to the continuous preparation and analysis of samples. A range of drop-based microfluidic screening platforms has emerged that benefit from drop-formation rates of thousands per second, perfect drop size uniformity, plug-flow and compartmentalization, and the possibility of continuously analyzing a train of drops. However, after many years of intensive research, only few commercial applications have been developed and substantial development in the field is still required to make them reliable and broadly applicable. Can academic research achieve this, given that most of the fundamental concepts have been described already, making it hard to publish a big story? Can start-up companies raise enough money to overcome the technical issues of drop-based screening platforms? This contribution addresses the question, focusing on how the different stakeholders in the field should interact so that disillusionment will not put a premature end to the development of drop-based screening technologies. Full article

(This article belongs to the Special Issue Droplet Microfluidics: Techniques and Technologies, Volume II)

Open AccessArticle Improvement of GNSS Carrier Phase Accuracy Using MEMS Accelerometer-Aided Phase-Locked Loops for Earthquake Monitoring

by Tisheng Zhang, Hengrong Liu, Qijin Chen, Hongping Zhang and Xiaoji Niu

Micromachines 2017, 8(6), 191; doi:10.3390/mi8060191

Received: 18 May 2017 / Revised: 6 June 2017 / Accepted: 16 June 2017 / Published: 19 June 2017

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Abstract

When strong earthquake occurs, global navigation satellite systems (GNSS) measurement errors increase significantly. Combined strategies of GNSS/accelerometer data can estimate better precision in displacement, but are of no help to carrier phase measurement. In this paper, strong-motion accelerometer-aided phase-locked loops (PLLs) are proposed

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When strong earthquake occurs, global navigation satellite systems (GNSS) measurement errors increase significantly. Combined strategies of GNSS/accelerometer data can estimate better precision in displacement, but are of no help to carrier phase measurement. In this paper, strong-motion accelerometer-aided phase-locked loops (PLLs) are proposed to improve carrier phase accuracy during strong earthquakes. To design PLLs for earthquake monitoring, the amplitude-frequency characteristics of the strong earthquake signals are studied. Then, the measurement errors of PLLs before and after micro electro mechanical systems (MEMS) accelerometer aiding are analyzed based on error models. Furthermore, tests based on a hardware simulator and a shake table are carried out. Results show that, with MEMS accelerometer aiding, the carrier phase accuracy of the PLL decreases little under strong earthquakes, which is consistent with the models analysis. Full article

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Open AccessArticle Three-Dimensional Calcium Alginate Hydrogel Assembly via TiOPc-Based Light-Induced Controllable Electrodeposition

by Yang Liu, Cong Wu, Hok Sum Sam Lai, Yan Ting Liu, Wen Jung Li and Ya Jing Shen

Micromachines 2017, 8(6), 192; doi:10.3390/mi8060192

Received: 31 March 2017 / Revised: 12 June 2017 / Accepted: 15 June 2017 / Published: 19 June 2017

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Abstract

Artificial reconstruction of three-dimensional (3D) hydrogel microstructures would greatly contribute to tissue assembly in vitro, and has been widely applied in tissue engineering and drug screening. Recent technological advances in the assembly of functional hydrogel microstructures such as microfluidic, 3D bioprinting, and micromold-based

[...] Read more.

Artificial reconstruction of three-dimensional (3D) hydrogel microstructures would greatly contribute to tissue assembly in vitro, and has been widely applied in tissue engineering and drug screening. Recent technological advances in the assembly of functional hydrogel microstructures such as microfluidic, 3D bioprinting, and micromold-based 3D hydrogel fabrication methods have enabled the formation of 3D tissue constructs. However, they still lack flexibility and high efficiency, which restrict their application in 3D tissue constructs. Alternatively, we report a feasible method for the fabrication and reconstruction of customized 3D hydrogel blocks. Arbitrary hydrogel microstructures were fabricated in situ via flexible and rapid light-addressable electrodeposition. To demonstrate the versatility of this method, the higher-order assembly of 3D hydrogel blocks was investigated using a constant direct current (DC) voltage (6 V) applied between two electrodes for 20–120 s. In addition to the plane-based two-dimensional (2D) assembly, hierarchical structures—including multi-layer 3D hydrogel structures and vessel-shaped structures—could be assembled using the proposed method. Overall, we developed a platform that enables researchers to construct complex 3D hydrogel microstructures efficiently and simply, which has the potential to facilitate research on drug screening and 3D tissue constructs. Full article

(This article belongs to the Special Issue Microdevices and Microsystems for Cell Manipulation)

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Open AccessArticle Electroosmotic Flow in a Rough Nanochannel with Surface Roughness Characterized by Fractal Cantor

by Pengfei Lu, Xiangdong Liu and Chengbin Zhang

Micromachines 2017, 8(6), 190; doi:10.3390/mi8060190

Received: 6 May 2017 / Revised: 7 June 2017 / Accepted: 15 June 2017 / Published: 19 June 2017

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Abstract

Molecular dynamics simulation is applied to study the electroosmotic flow in rough nanochannels, with particular attention given to the fluid–solid interactions. In the simulation, the surface roughness is characterized by a fractal Cantor. The roles of roughness height and fractal dimension on nanoscale

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Molecular dynamics simulation is applied to study the electroosmotic flow in rough nanochannels, with particular attention given to the fluid–solid interactions. In the simulation, the surface roughness is characterized by a fractal Cantor. The roles of roughness height and fractal dimension on nanoscale electroosmotic flow are examined and analyzed. The concentration distributions, zeta potential and electroosmotic velocity are presented and investigated. The results indicate that surface roughness plays a significant role in the fluid–solid interaction and nanoscale electroosmotic flow. The distribution of dipole angle for water molecules in both the near-wall region and middle region is almost unaffected by surface roughness; however, a significant difference of dipole angle distribution is observed in the fluid region away from the wall. Interestingly, the concentration distributions, electroosmotic velocity and zeta potential are highly affected by the surface fractal dimension, even with the same roughness height. Full article

(This article belongs to the Special Issue Micro/Nano-Chip Electrokinetics, Volume II)

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Open AccessArticle Parametric Analysis and Experimental Verification of a Hybrid Vibration Energy Harvester Combining Piezoelectric and Electromagnetic Mechanisms

by Zhenlong Xu, Xiaobiao Shan, Hong Yang, Wen Wang and Tao Xie

Micromachines 2017, 8(6), 189; doi:10.3390/mi8060189

Received: 11 May 2017 / Revised: 12 June 2017 / Accepted: 15 June 2017 / Published: 18 June 2017

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Considering coil inductance and the spatial distribution of the magnetic field, this paper developed an approximate distributed-parameter model of a hybrid energy harvester (HEH). The analytical solutions were compared with numerical solutions. The effects of load resistances, electromechanical coupling factors, mechanical damping ratio,

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Considering coil inductance and the spatial distribution of the magnetic field, this paper developed an approximate distributed-parameter model of a hybrid energy harvester (HEH). The analytical solutions were compared with numerical solutions. The effects of load resistances, electromechanical coupling factors, mechanical damping ratio, coil parameters and size scale on performance were investigated. A meso-scale HEH prototype was fabricated, tested and compared with a stand-alone piezoelectric energy harvester (PEH) and a stand-alone electromagnetic energy harvester (EMEH). The peak output power is 2.93% and 142.18% higher than that of the stand-alone PEH and EMEH, respectively. Moreover, its bandwidth is 108%- and 122.7%-times that of the stand-alone PEH and EMEH, respectively. The experimental results agreed well with the theoretical values. It is indicated that the linearized electromagnetic coupling coefficient is more suitable for low-level excitation acceleration. Hybrid energy harvesting contributes to widening the frequency bandwidth and improving energy conversion efficiency. However, only when the piezoelectric coupling effect is weak or medium can the HEH generate more power than the single-mechanism energy harvester. Hybrid energy harvesting can improve output power even at the microelectromechanical systems (MEMS) scale. This study presents a more effective model for the performance evaluation and structure optimization of the HEH. Full article

(This article belongs to the Special Issue Piezoelectric MEMS)

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Open AccessArticle Modeling the Influence of Tool Deflection on Cutting Force and Surface Generation in Micro-Milling

by Dehong Huo, Wanqun Chen, Xiangyu Teng, Chao Lin and Kai Yang

Micromachines 2017, 8(6), 188; doi:10.3390/mi8060188

Received: 24 May 2017 / Revised: 12 June 2017 / Accepted: 13 June 2017 / Published: 17 June 2017

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In micro-milling, cutting forces generate non-negligible tool deflection, which has a significant influence on the machining process and on workpiece accuracy. This paper investigates the tool deflection during micro-milling and its effect on cutting force and surface generation. The distribution of cutting forces

[...] Read more.

In micro-milling, cutting forces generate non-negligible tool deflection, which has a significant influence on the machining process and on workpiece accuracy. This paper investigates the tool deflection during micro-milling and its effect on cutting force and surface generation. The distribution of cutting forces acting on the tool is calculated with a mathematical model that considers tool elasticity and runout, and the tool deflection caused by the cutting forces is then obtained. Furthermore, an improved cutting force model and side wall surface generation model are established, including the tool deflection effect. Both cutting force and surface simulation models were verified by the micro-end-milling experiment, and the results show a very good agreement between the simulation and experiments. Full article

(This article belongs to the Special Issue State-Of-The-Art Micromachining)

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Open AccessArticle 3D Finite Element Simulation of Micro End-Milling by Considering the Effect of Tool Run-Out

by Ali Davoudinejad, Guido Tosello, Paolo Parenti and Massimiliano Annoni

Micromachines 2017, 8(6), 187; doi:10.3390/mi8060187

Received: 26 April 2017 / Revised: 6 June 2017 / Accepted: 12 June 2017 / Published: 16 June 2017

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Understanding the micro milling phenomena involved in the process is critical and difficult through physical experiments. This study presents a 3D finite element modeling (3D FEM) approach for the micro end-milling process on Al6082-T6. The proposed model employs a Lagrangian explicit finite element

[...] Read more.

Understanding the micro milling phenomena involved in the process is critical and difficult through physical experiments. This study presents a 3D finite element modeling (3D FEM) approach for the micro end-milling process on Al6082-T6. The proposed model employs a Lagrangian explicit finite element formulation to perform coupled thermo-mechanical transient analyses. FE simulations were performed at different cutting conditions to obtain realistic numerical predictions of chip formation, temperature distribution, and cutting forces by considering the effect of tool run-out in the model. The radial run-out is a significant issue in micro milling processes and influences the cutting stability due to chip load and force variations. The Johnson–Cook (JC) material constitutive model was applied and its constants were determined by an inverse method based on the experimental cutting forces acquired during the micro end-milling tests. The FE model prediction capability was validated by comparing the numerical model results with experimental tests. The maximum tool temperature was predicted in a different angular position of the cutter which is difficult or impossible to obtain in experiments. The predicted results of the model, involving the run-out influence, showed a good correlation with experimental chip formation and the signal shape of cutting forces. Full article

(This article belongs to the Special Issue Micro/Nano Manufacturing)

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Open AccessReview Recent Advances and Future Perspectives on Microfluidic Liquid Handling

by Nam-Trung Nguyen, Majid Hejazian, Chin Hong Ooi and Navid Kashaninejad

Micromachines 2017, 8(6), 186; doi:10.3390/mi8060186

Received: 23 May 2017 / Revised: 3 June 2017 / Accepted: 8 June 2017 / Published: 12 June 2017

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Abstract

The interdisciplinary research field of microfluidics has the potential to revolutionize current technologies that require the handling of a small amount of fluid, a fast response, low costs and automation. Microfluidic platforms that handle small amounts of liquid have been categorised as continuous-flow

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The interdisciplinary research field of microfluidics has the potential to revolutionize current technologies that require the handling of a small amount of fluid, a fast response, low costs and automation. Microfluidic platforms that handle small amounts of liquid have been categorised as continuous-flow microfluidics and digital microfluidics. The first part of this paper discusses the recent advances of the two main and opposing applications of liquid handling in continuous-flow microfluidics: mixing and separation. Mixing and separation are essential steps in most lab-on-a-chip platforms, as sample preparation and detection are required for a variety of biological and chemical assays. The second part discusses the various digital microfluidic strategies, based on droplets and liquid marbles, for the manipulation of discrete microdroplets. More advanced digital microfluidic devices combining electrowetting with other techniques are also introduced. The applications of the emerging field of liquid-marble-based digital microfluidics are also highlighted. Finally, future perspectives on microfluidic liquid handling are discussed. Full article

(This article belongs to the Special Issue Insights and Advancements in Microfluidics)

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Open AccessArticle Lithium Niobate Micromachining for the Fabrication of Microfluidic Droplet Generators

by Giacomo Bettella, Gianluca Pozza, Sebastian Kroesen, Riccardo Zamboni, Enrico Baggio, Carlo Montevecchi, Annamaria Zaltron, Ludovic Gauthier-Manuel, Giampaolo Mistura, Claudio Furlan, Mathieu Chauvet, Cornelia Denz and Cinzia Sada

Micromachines 2017, 8(6), 185; doi:10.3390/mi8060185

Received: 9 March 2017 / Revised: 22 May 2017 / Accepted: 31 May 2017 / Published: 9 June 2017

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Abstract

In this paper, we present the first microfluidic junctions for droplet generation directly engraved on lithium niobate crystals by micromachining techniques, preparatory to a fully integrated opto-microfluidics lab-on-chip system. In particular, laser ablation technique and the mechanical micromachining technique are exploited to realise

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In this paper, we present the first microfluidic junctions for droplet generation directly engraved on lithium niobate crystals by micromachining techniques, preparatory to a fully integrated opto-microfluidics lab-on-chip system. In particular, laser ablation technique and the mechanical micromachining technique are exploited to realise microfluidic channels in T- and cross junction configurations. The quality of both lateral and bottom surfaces of the channels are therefore compared together with a detailed study of their roughness measured by means of atomic force microscopy in order to evaluate the final performance achievable in an optofluidic device. Finally, the microfluidics performances of these water-in-oil droplets generators are investigated depending on these micromachining techniques, with particular focus on a wide range of droplet generation rates. Full article

(This article belongs to the Special Issue Ultrafast Laser Fabrication for Lab-on-a-Chip)

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Open AccessEditorial Editorial for Special Issue: Advances in Microfluidic Devices for Cell Handling and Analysis

by Abel Martin Gonzalez Oliva

Micromachines 2017, 8(6), 184; doi:10.3390/mi8060184

Received: 6 June 2017 / Revised: 6 June 2017 / Accepted: 7 June 2017 / Published: 9 June 2017

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Abstract Microfluidics is a technology that is expanding rapidly in many areas of research, especially in the biological areas of cell handling and analysis.[...] Full article

(This article belongs to the Special Issue Advances in Microfluidic Devices for Cell Handling and Analysis)

Open AccessArticle “Z”-Shaped Rotational Au/Pt Micro-Nanorobot

by Kai Chen, Chenyi Gu, Zhan Yang, Masahiro Nakajima, Tao Chen and Toshio Fukuda

Micromachines 2017, 8(6), 183; doi:10.3390/mi8060183

Received: 15 March 2017 / Revised: 27 May 2017 / Accepted: 29 May 2017 / Published: 8 June 2017

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Abstract

Drug delivery, minimally-invasive surgery, and a hospital-in-the-body are highly desirable for meeting the rapidly growing needs of nanorobot. This paper reports a Z-shaped gold/platinum (Au/Pt) hybrid nanorobot which realizes the self-rotational movement without an external force field. The Z-shaped Au/Pt hybrid nanorobot was

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Drug delivery, minimally-invasive surgery, and a hospital-in-the-body are highly desirable for meeting the rapidly growing needs of nanorobot. This paper reports a Z-shaped gold/platinum (Au/Pt) hybrid nanorobot which realizes the self-rotational movement without an external force field. The Z-shaped Au/Pt hybrid nanorobot was fabricated by focused ion beam (FIB) and plasma sputtering. The purity of the nanorobot was tested by energy dispersive X-ray analysis (EDS). The weight percentage of Pt and Au at the tip were 94.28% and 5.72%, respectively. The weight percentage of Pt and Au at the bottom were 17.39% and 82.75%, respectively. The size of the nanorobot was 2.58 × 10⁻¹⁶ m² and the mass of the nanorobot was 8.768 × 10⁻⁸ kg. The driving force of the nanorobot was 9.76 × 10⁻¹⁴ N at the 6.9% concentration of hydrogen peroxide solution. The rotation speed was 13 rpm, 14 rpm, and 19 rpm at 5.6%, 6.2%, and 7.8% concentrations, respectively. Full article

(This article belongs to the Special Issue Micro/Nano Robotics, Volume II)

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Open AccessArticle Reliable and Accurate Release of Micro-Sized Objects with a Gripper that Uses the Capillary-Force Method

by Suzana Uran, Riko Šafarič and Božidar Bratina

Micromachines 2017, 8(6), 182; doi:10.3390/mi8060182

Received: 22 March 2017 / Revised: 30 May 2017 / Accepted: 3 June 2017 / Published: 8 June 2017

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Abstract

There have been recent developments in grippers that are based on capillary force and condensed water droplets. These are used for manipulating micro-sized objects. Recently, one-finger grippers have been produced that are able to reliably grip using the capillary force. To release objects,

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There have been recent developments in grippers that are based on capillary force and condensed water droplets. These are used for manipulating micro-sized objects. Recently, one-finger grippers have been produced that are able to reliably grip using the capillary force. To release objects, either the van der Waals, gravitational or inertial-forces method is used. This article presents methods for reliably gripping and releasing micro-objects using the capillary force. The moisture from the surrounding air is condensed into a thin layer of water on the contact surfaces of the objects. From the thin layer of water, a water meniscus between the micro-sized object, the gripper and the releasing surface is created. Consequently, the water meniscus between the object and the releasing surface produces a high enough capillary force to release the micro-sized object from the tip of the one-finger gripper. In this case, either polystyrene, glass beads with diameters between 5–60 µm, or irregularly shaped dust particles of similar sizes were used. 3D structures made up of micro-sized objects could be constructed using this method. This method is reliable for releasing during assembly and also for gripping, when the objects are removed from the top of the 3D structure—the so-called “disassembling gripping” process. The accuracy of the release was lower than 0.5 µm. Full article

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Open AccessArticle Chiral Orientation of Skeletal Muscle Cells Requires Rigid Substrate

by Ninghao Zhu, Hoi Kwan Kwong, Yuanye Bao and Ting-Hsuan Chen

Micromachines 2017, 8(6), 181; doi:10.3390/mi8060181

Received: 11 February 2017 / Revised: 31 May 2017 / Accepted: 2 June 2017 / Published: 8 June 2017

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Abstract

Reconstitution of tissue morphology with inherent left–right (LR) asymmetry is essential for tissue/organ functions. For skeletal muscle, the largest tissue in mammalian organisms, successful myogenesis requires the regulation of the LR asymmetry to form the appropriate muscle alignment. However, the key factor for

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Reconstitution of tissue morphology with inherent left–right (LR) asymmetry is essential for tissue/organ functions. For skeletal muscle, the largest tissue in mammalian organisms, successful myogenesis requires the regulation of the LR asymmetry to form the appropriate muscle alignment. However, the key factor for reproducing the LR asymmetry of skeletal tissues in a controllable, engineering context remains largely unknown. Recent reports indicate that cell chirality may underlie the LR development in tissue morphogenesis. Here, we report that a rigid substrate is required for the chirality of skeletal muscle cells. By using alternating micropatterned cell-adherent and cell-repellent stripes on a rigid substrate, we found that C2C12 skeletal muscle myoblasts exhibited a unidirectional tilted orientation with respect to the stripe boundary. Importantly, such chiral orientation was reduced when soft substrates were used instead. In addition, we demonstrated the key role of actin stress fibers in the formation of the chiral orientation. This study reveals that a rigid substrate is required for the chiral pattern of myoblasts, paving the way for reconstructing damaged muscle tissue with inherent LR asymmetry in the future. Full article

(This article belongs to the Special Issue Optofluidics 2016)

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Open AccessFeature PaperArticle Development of Temperature Control Solutions for Non-Instrumented Nucleic Acid Amplification Tests (NINAAT)

by Tamás Pardy, Toomas Rang and Indrek Tulp

Micromachines 2017, 8(6), 180; doi:10.3390/mi8060180

Received: 24 April 2017 / Revised: 23 May 2017 / Accepted: 1 June 2017 / Published: 7 June 2017

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Abstract

Non-instrumented nucleic acid amplification tests (NINAAT) are a novel paradigm in portable molecular diagnostics. They offer the high detection accuracy characteristic of nucleic acid amplification tests (NAAT) in a self-contained device, without the need for any external instrumentation. These Point-of-Care tests typically employ

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Non-instrumented nucleic acid amplification tests (NINAAT) are a novel paradigm in portable molecular diagnostics. They offer the high detection accuracy characteristic of nucleic acid amplification tests (NAAT) in a self-contained device, without the need for any external instrumentation. These Point-of-Care tests typically employ a Lab-on-a-Chip for liquid handling functionality, and perform isothermal nucleic acid amplification protocols that require low power but high accuracy temperature control in a single well-defined temperature range. We propose temperature control solutions based on commercially available heating elements capable of meeting these challenges, as well as demonstrate the process by which such elements can be fitted to a NINAAT system. Self-regulated and thermostat-controlled resistive heating elements were evaluated through experimental characterization as well as thermal analysis using the finite element method (FEM). We demonstrate that the proposed solutions can support various NAAT protocols, as well as demonstrate an optimal solution for the loop-mediated isothermal amplification (LAMP) protocol. Furthermore, we present an Arduino-compatible open-source thermostat developed for NINAAT applications. Full article

(This article belongs to the Special Issue Application of Microfluidic Methodology for the Analysis of DNA)

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Open AccessArticle Fabrication of Functional Plastic Parts Using Nanostructured Steel Mold Inserts

by Nicolas Blondiaux, Raphaël Pugin, Gaëlle Andreatta, Lionel Tenchine, Stéphane Dessors, Pierre-François Chauvy, Matthieu Diserens and Philippe Vuillermoz

Micromachines 2017, 8(6), 179; doi:10.3390/mi8060179

Received: 6 April 2017 / Revised: 15 May 2017 / Accepted: 25 May 2017 / Published: 6 June 2017

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We report on the fabrication of sub-micro and nanostructured steel mold inserts for the replication of nanostructured immunoassay biochips. Planar and microstructured stainless steel inserts were textured at the sub-micron and nanoscale by combining nanosphere lithography and electrochemical etching. This allowed the fabrication

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We report on the fabrication of sub-micro and nanostructured steel mold inserts for the replication of nanostructured immunoassay biochips. Planar and microstructured stainless steel inserts were textured at the sub-micron and nanoscale by combining nanosphere lithography and electrochemical etching. This allowed the fabrication of structures with lateral dimensions of hundreds of nanometers and aspect ratios of up to 1:2. Nanostructured plastic parts were produced by means of hot embossing and injection molding. Surface nanostructuring was used to control wettability and increase the sensitivity of an immunoassay. Full article

(This article belongs to the Special Issue Micro/Nano Manufacturing)

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Open AccessCorrection Correction: Liu, W. et al. A Highly Sensitive Humidity Sensor Based on Ultrahigh-Frequency Microelectromechanical Resonator Coated with Nano-Assembled Polyelectrolyte Thin Films. Micromachines, 2017, 8, 116

by Wenpeng Liu, Hemi Qu, Jizhou Hu, Wei Pang, Hao Zhang and Xuexin Duan

Micromachines 2017, 8(6), 178; doi:10.3390/mi8060178

Received: 26 May 2017 / Accepted: 30 May 2017 / Published: 5 June 2017

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Abstract In the published paper [1], there is an error in Figure 3 [...] Full article

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Open AccessArticle Motor Power Signal Analysis for End-Point Detection of Chemical Mechanical Planarization

by Hongkai Li, Xinchun Lu and Jianbin Luo

Micromachines 2017, 8(6), 177; doi:10.3390/mi8060177

Received: 9 April 2017 / Revised: 11 May 2017 / Accepted: 21 May 2017 / Published: 5 June 2017

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Abstract

In the integrated circuit (IC) manufacturing, in-situ end-point detection (EPD) is an important issue in the chemical mechanical planarization (CMP) process. In the paper, we chose the motor power signal of the polishing platen as the monitoring object. We then used the moving

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In the integrated circuit (IC) manufacturing, in-situ end-point detection (EPD) is an important issue in the chemical mechanical planarization (CMP) process. In the paper, we chose the motor power signal of the polishing platen as the monitoring object. We then used the moving average method, which was appropriate for in-situ calculation process and made it easy to code for software development, to smooth the signal curve, and then studied the signal variation during the actual CMP process. The results demonstrated that the motor power signal contained the end-point feature of the metal layer removal, and the processed signal curve facilitated the feature extraction and it was relatively steady before and after the layer transition stage. In addition, the motor power signal variation of the polishing head was explored and further analysis of time delay was performed. Full article

(This article belongs to the Special Issue Microtribology, Adhesion and Surface Engineering)

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Open AccessArticle Hollow Hydrogel Microfiber Encapsulating Microorganisms for Mass-Cultivation in Open Systems

by Kazuhiko Higashi, Miho Ogawa, Kazuma Fujimoto, Hiroaki Onoe and Norihisa Miki

Micromachines 2017, 8(6), 176; doi:10.3390/mi8060176

Received: 25 April 2017 / Revised: 23 May 2017 / Accepted: 1 June 2017 / Published: 3 June 2017

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Open cultivation systems to monoculture microorganisms are promising for the commercialization of low-value commodities because they reduce the cultivation cost. However, contamination from biological pollutants frequently impedes the process. Here we propose a cultivation method using hollow hydrogel microfibers encapsulating microorganisms. Due to

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Open cultivation systems to monoculture microorganisms are promising for the commercialization of low-value commodities because they reduce the cultivation cost. However, contamination from biological pollutants frequently impedes the process. Here we propose a cultivation method using hollow hydrogel microfibers encapsulating microorganisms. Due to the pore size, hydrogels allow nutrients and waste to pass through while preventing invading microorganisms from entering the microfiber. Experimental cultivation shows the growth of target bacteria inside the alginate hydrogel microfiber during exposure to invading bacteria. The membrane thickness of the microfiber greatly affects the bacterial growth due to changes in membrane permeability. The enhancement of mechanical toughness is also demonstrated by employing a double-network hydrogel for long-term cultivation. The hollow hydrogel microfiber has the potential to become a mainstream solution for mass-cultivation of microorganisms in an open system. Full article

(This article belongs to the Special Issue Biomedical Microfluidic Devices)

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Open AccessArticle Rapid Screening of Graphitic Carbon Nitrides for Photocatalytic Cofactor Regeneration Using a Drop Reactor

by Xiaowen Huang, Huimin Hao, Yang Liu, Yujiao Zhu and Xuming Zhang

Micromachines 2017, 8(6), 175; doi:10.3390/mi8060175

Received: 1 April 2017 / Revised: 24 May 2017 / Accepted: 31 May 2017 / Published: 2 June 2017

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Abstract

Artificial photosynthesis is the imitation of natural photosynthesis, which promises an efficient way to use solar energy to synthesize organic matters, in which the key step is the coenzyme regeneration (NADH/NADPH). To achieve an efficient regeneration rate, various photocatalysts have been developed, such

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Artificial photosynthesis is the imitation of natural photosynthesis, which promises an efficient way to use solar energy to synthesize organic matters, in which the key step is the coenzyme regeneration (NADH/NADPH). To achieve an efficient regeneration rate, various photocatalysts have been developed, such as g-C₃N₄ and mesoporous carbon nitride (mpg-C₃N₄). Generally, efficiency determination of different photocatalysts requires laborious experiments, high consumption of reagents, and a considerable amount of time. Here, based on the one-step artificial photosystem I method, we processed the analytical experiment in a very simple PDMS well (20 μL, a drop) to achieve a rapid screening of photocatalysts. For comparison, we used two types of graphitic carbon nitrides, few-layer g-C₃N₄ and mpg-C₃N₄. Compared with the slurry systems, firstly, the regeneration rate of mpg-C₃N₄ drop-reactor system is 4.3 times and 7.1 times those of the few-layer g-C₃N₄-slurry system and mpg-C₃N₄-slurry system, respectively. Secondly, this one-drop method reduces the typical verification time from 90 min to 5 min and lowers the liquid volume from 20 mL to 20 μL. Thirdly, this operation is a pump-free and soft lithography technique-free process. The miniaturization of the photocatalytic reaction in the PDMS well improves the regeneration rates, saves samples, and achieves high-throughput screening of multiple photocatalysts. Full article

(This article belongs to the Special Issue Photonic MEMS and Optofluidic Devices)

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Open AccessArticle Rapid Prototyping of a Micromotor with an Optical Rotary Encoder

by Da-Chen Pang and Yi-Wei Lai

Micromachines 2017, 8(6), 174; doi:10.3390/mi8060174

Received: 28 April 2017 / Revised: 24 May 2017 / Accepted: 29 May 2017 / Published: 2 June 2017

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This study proposed a rapid prototyping fabrication method for micromotors that allowed us to develop both 1 mm and 1.5 mm diameter permanent-magnet synchronous motors (PMSMs) with an optical rotary encoder. First, an integrated electroforming method was proposed for combining stator housing and

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This study proposed a rapid prototyping fabrication method for micromotors that allowed us to develop both 1 mm and 1.5 mm diameter permanent-magnet synchronous motors (PMSMs) with an optical rotary encoder. First, an integrated electroforming method was proposed for combining stator housing and flexible print circuit (FPC) coils to ease the manufacturing and assembly of micromotor components. This is particularly useful in the production of prototypes or small volumes of units. Second, an optical encoder was used to detect the rotational angle by means of a reflective code disk, an optical fiber, and a photo-detector. The micromotor was built with a code disk and an optical fiber. The code disk was designed to match the optical fiber and was made by photolithography and sputtering. Both the 1 mm and 1.5 mm diameter motors successfully achieved a rotational speed over 20,000 RPM and due to a 50 µm diameter optical fiber core, the encoders showed a resolution of 12 and 18 pulses per revolution (PPR), respectively. Full article

(This article belongs to the Special Issue State-Of-The-Art Micromachining)

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Open AccessArticle Separated Type Atmospheric Pressure Plasma Microjets Array for Maskless Microscale Etching

by Yichuan Dai, Man Zhang, Qiang Li, Li Wen, Hai Wang and Jiaru Chu

Micromachines 2017, 8(6), 173; doi:10.3390/mi8060173

Received: 26 March 2017 / Revised: 26 April 2017 / Accepted: 10 May 2017 / Published: 1 June 2017

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Maskless etching approaches such as microdischarges and atmospheric pressure plasma jets (APPJs) have been studied recently. Nonetheless, a simple, long lifetime, and efficient maskless etching method is still a challenge. In this work, a separated type maskless etching system based on atmospheric pressure

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Maskless etching approaches such as microdischarges and atmospheric pressure plasma jets (APPJs) have been studied recently. Nonetheless, a simple, long lifetime, and efficient maskless etching method is still a challenge. In this work, a separated type maskless etching system based on atmospheric pressure He/O₂ plasma jet and microfabricated Micro Electro Mechanical Systems (MEMS) nozzle have been developed with advantages of simple-structure, flexibility, and parallel processing capacity. The plasma was generated in the glass tube, forming the micron level plasma jet between the nozzle and the surface of polymer. The plasma microjet was capable of removing photoresist without masks since it contains oxygen reactive species verified by spectra measurement. The experimental results illustrated that different features of microholes etched by plasma microjet could be achieved by controlling the distance between the nozzle and the substrate, additive oxygen ratio, and etch time, the result of which is consistent with the analysis result of plasma spectra. In addition, a parallel etching process was also realized by plasma microjets array. Full article

(This article belongs to the Special Issue Microplasma Devices)

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Open AccessArticle Automatic and Selective Single Cell Manipulation in a Pressure-Driven Microfluidic Lab-On-Chip Device

by Yigang Shen, Zhenyu Song, Yimo Yan, Yongxin Song, Xinxiang Pan and Qi Wang

Micromachines 2017, 8(6), 172; doi:10.3390/mi8060172

Received: 7 April 2017 / Revised: 9 May 2017 / Accepted: 16 May 2017 / Published: 1 June 2017

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Abstract

A microfluidic lab-on-chip device was developed to automatically and selectively manipulate target cells at the single cell level. The device is composed of a microfluidic chip, mini solenoid valves with negative-pressurized soft tubes, and a LabView^®-based data acquisition device. Once a

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A microfluidic lab-on-chip device was developed to automatically and selectively manipulate target cells at the single cell level. The device is composed of a microfluidic chip, mini solenoid valves with negative-pressurized soft tubes, and a LabView^®-based data acquisition device. Once a target cell passes the resistive pulse sensing gate of the microfluidic chip, the solenoid valves are automatically actuated and open the negative-pressurized tubes placed at the ends of the collecting channels. As a result, the cell is transported to that collecting well. Numerical simulation shows that a 0.14 mm³ volume change of the soft tube can result in a 1.58 mm/s moving velocity of the sample solution. Experiments with single polystyrene particles and cancer cells samples were carried out to demonstrate the effectiveness of this method. Selectively manipulating a certain size of particles from a mixture solution was also achieved. Due to the very high pressure-driven flow switching, as many as 300 target cells per minute can be isolated from the sample solution and thus is particularly suitable for manipulating very rare target cells. The device is simple, automatic, and label-free and particularly suitable for isolating single cells off the chip one by one for downstream analysis. Full article

(This article belongs to the Special Issue Selected Papers from 2016 International Conference of Microfluidics, Nanofluidics and Lab-on-a-Chip)

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Open AccessArticle Dynamical Modeling and Analysis of Viscoelastic Properties of Single Cells

by Bo Wang, Wenxue Wang, Yuechao Wang, Bin Liu and Lianqing Liu

Micromachines 2017, 8(6), 171; doi:10.3390/mi8060171

Received: 14 April 2017 / Revised: 13 May 2017 / Accepted: 22 May 2017 / Published: 1 June 2017

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A single cell can be regarded as a complex network that contains thousands of overlapping signaling pathways. The traditional methods for describing the dynamics of this network are extremely complicated. The mechanical properties of a cell reflect the cytoskeletal structure and composition and

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A single cell can be regarded as a complex network that contains thousands of overlapping signaling pathways. The traditional methods for describing the dynamics of this network are extremely complicated. The mechanical properties of a cell reflect the cytoskeletal structure and composition and are closely related to the cellular biological functions and physiological activities. Therefore, modeling the mechanical properties of single cells provides the basis for analyzing and controlling the cellular state. In this study, we developed a dynamical model with cellular viscoelasticity properties as the system parameters to describe the stress-relaxation phenomenon of a single cell indented by an atomic force microscope (AFM). The system order and parameters were identified and analyzed. Our results demonstrated that the parameters identified using this model represent the cellular mechanical elasticity and viscosity and can be used to classify cell types. Full article

(This article belongs to the Special Issue Microdevices and Microsystems for Cell Manipulation)

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