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Micromachines, Volume 9, Issue 2 (February 2018)

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Open AccessArticle The Application of Chemical Foaming Method in the Fabrication of Micro Glass Hemisphere Resonator
Micromachines 2018, 9(2), 42; doi:10.3390/mi9020042
Received: 20 November 2017 / Revised: 18 January 2018 / Accepted: 19 January 2018 / Published: 24 January 2018
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Abstract
Many researchers have studied the miniaturization of the hemisphere resonator gyroscope for decades. The hemisphere resonator (HSR), as the core component, has a size that has been reduced to the submillimeter level. We developed a method of batch production of micro-hemisphere shell resonators
[...] Read more.
Many researchers have studied the miniaturization of the hemisphere resonator gyroscope for decades. The hemisphere resonator (HSR), as the core component, has a size that has been reduced to the submillimeter level. We developed a method of batch production of micro-hemisphere shell resonators based on a glass-blowing process to obtain larger hemisphere shells with a higher ratio of height to diameter (H/D), we introduced the chemical foaming process (CFP) and acquired an optimized hemisphere shell; the contrasted and improved H/D of the hemisphere shell are 0.61 and 0.80, respectively. Finally, we increased the volume of glass shell resonator by 51.48 times while decreasing the four-node wineglass resonant frequencies from 7.24 MHz to 0.98 MHz. The larger HSR with greater surface area is helpful for setting larger surrounding drive and sense capacitive electrodes, thereby enhancing the sensitivity of HSR to the rotation. This CFP method not only provides more convenience to control the shape of a hemisphere shell but also reduces non-negligible cost in the fabrication process. In addition, this method may inspire some other research fields, e.g., microfluidics, chemical analysis, and wafer level package (WLP). Full article
(This article belongs to the Special Issue Micro-Resonators: The Quest for Superior Performance)
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Open AccessArticle Nanocomposite-Based Microstructured Piezoresistive Pressure Sensors for Low-Pressure Measurement Range
Micromachines 2018, 9(2), 43; doi:10.3390/mi9020043
Received: 30 December 2017 / Revised: 23 January 2018 / Accepted: 24 January 2018 / Published: 26 January 2018
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Abstract
Piezoresistive pressure sensors capable of detecting ranges of low compressive stresses have been successfully fabricated and characterised. The 5.5 × 5 × 1.6 mm3 sensors consist of a planar aluminium top electrode and a microstructured bottom electrode containing a two-by-two array of
[...] Read more.
Piezoresistive pressure sensors capable of detecting ranges of low compressive stresses have been successfully fabricated and characterised. The 5.5 × 5 × 1.6 mm3 sensors consist of a planar aluminium top electrode and a microstructured bottom electrode containing a two-by-two array of truncated pyramids with a piezoresistive composite layer sandwiched in-between. The responses of two different piezocomposite materials, a Multiwalled Carbon Nanotube (MWCNT)-elastomer composite and a Quantum Tunneling Composite (QTC), have been characterised as a function of applied pressure and effective contact area. The MWCNT piezoresistive composite-based sensor was able to detect pressures as low as 200 kPa. The QTC-based sensor was capable of detecting pressures as low as 50 kPa depending on the contact area of the bottom electrode. Such sensors could find useful applications requiring the detection of small compressive loads such as those encountered in haptic sensing or robotics. Full article
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Open AccessArticle Compensation of Hysteresis on Piezoelectric Actuators Based on Tripartite PI Model
Micromachines 2018, 9(2), 44; doi:10.3390/mi9020044
Received: 7 December 2017 / Revised: 24 January 2018 / Accepted: 24 January 2018 / Published: 26 January 2018
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Abstract
Piezoelectric ceramic actuators have been widely used in nanopositioning applications owing to their fast response, high stiffness, and ability to generate large forces. However, the existence of nonlinearities such as hysteresis can greatly deteriorate the accuracy of the manipulation, even causing instability of
[...] Read more.
Piezoelectric ceramic actuators have been widely used in nanopositioning applications owing to their fast response, high stiffness, and ability to generate large forces. However, the existence of nonlinearities such as hysteresis can greatly deteriorate the accuracy of the manipulation, even causing instability of the whole system. In this article, we have explained the causes of hysteresis based on the micropolarization theory and proposed a piezoelectric ceramic deformation speed law. For this, we analyzed the piezoelectric ceramic actuator deformation speed law based on the domain wall theory. Based on this analysis, a three-stage Prandtl–Ishlinskii (PI) model (hereafter referred to as tripartite PI model) was designed and implemented. According to the piezoelectric ceramic deformation speed law, this model makes separate local PI models in different parts of piezoelectric ceramics’ hysteresis curve. The weighting values and threshold values of the tripartite PI model were obtained through a quadratic programming optimization algorithm. Compared to the classical PI model, the tripartite PI model can describe the asymmetry of hysteresis curves more accurately. A tripartite PI inverse controller, PI inverse controller, and Preisach inverse controller were used to compensate for the piezoelectric ceramic actuator in the experiment. The experimental results show that the inclusion of the PI inverse controller and the Preisach inverse controller improved the tracking performance of the tripartite PI inverse model by more than 80%. Full article
(This article belongs to the Special Issue Piezoelectric MEMS)
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Open AccessArticle Three-Dimensional Fractal Geometry for Gas Permeation in Microchannels
Micromachines 2018, 9(2), 45; doi:10.3390/mi9020045
Received: 21 December 2017 / Revised: 23 January 2018 / Accepted: 24 January 2018 / Published: 27 January 2018
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Abstract
The novel concept of a microfluidic chip with an integrated three-dimensional fractal geometry with nanopores, acting as a gas transport membrane, is presented. The method of engineering the 3D fractal structure is based on a combination of anisotropic etching of silicon and corner
[...] Read more.
The novel concept of a microfluidic chip with an integrated three-dimensional fractal geometry with nanopores, acting as a gas transport membrane, is presented. The method of engineering the 3D fractal structure is based on a combination of anisotropic etching of silicon and corner lithography. The permeation of oxygen and carbon dioxide through the fractal membrane is measured and validated theoretically. The results show high permeation flux due to low resistance to mass transfer because of the hierarchical branched structure of the fractals, and the high number of the apertures. This approach offers an advantage of high surface to volume ratio and pores in the range of nanometers. The obtained results show that the gas permeation through the nanonozzles in the form of fractal geometry is remarkably enhanced in comparison to the commonly-used polydimethylsiloxane (PDMS) dense membrane. The developed chip is envisioned as an interesting alternative for gas-liquid contactors that require harsh conditions, such as microreactors or microdevices, for energy applications. Full article
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Open AccessArticle Reactive Inkjet Printing of Regenerated Silk Fibroin Films for Use as Dental Barrier Membranes
Micromachines 2018, 9(2), 46; doi:10.3390/mi9020046
Received: 8 December 2017 / Revised: 19 January 2018 / Accepted: 23 January 2018 / Published: 27 January 2018
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Abstract
Current commercially available barrier membranes for oral surgery have yet to achieve a perfect design. Existing materials used are either non-resorbable and require a second surgery for their extraction, or alternatively are resorbable but suffer from poor structural integrity or degrade into acidic
[...] Read more.
Current commercially available barrier membranes for oral surgery have yet to achieve a perfect design. Existing materials used are either non-resorbable and require a second surgery for their extraction, or alternatively are resorbable but suffer from poor structural integrity or degrade into acidic by-products. Silk has the potential to overcome these issues and has yet to be made into a commercially available dental barrier membrane. Reactive inkjet printing (RIJ) has recently been demonstrated to be a suitable method for assembling silk in its regenerated silk fibroin (RSF) form into different constructs. This paper will establish the properties of RSF solutions for RIJ and the suitability of RIJ for the construction of RSF barrier membranes. Printed RSF films were characterised by their crystallinity and surface properties, which were shown to be controllable via RIJ. RSF films degraded in either phosphate buffered saline or protease XIV solutions had degradation rates related to RSF crystallinity. RSF films were also printed with the inclusion of nano-hydroxyapatite (nHA). As reactive inkjet printing could control RSF crystallinity and hence its degradation rate, as well as offering the ability to incorporate bioactive nHA inclusions, reactive inkjet printing is deemed a suitable alternative method for RSF processing and the production of dental barrier membranes. Full article
(This article belongs to the Special Issue Additive Manufacturing for Medical Applications)
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Open AccessArticle Design and Performance Assessment of a Solid-State Microcooler for Thermal Neuromodulation
Micromachines 2018, 9(2), 47; doi:10.3390/mi9020047
Received: 14 November 2017 / Revised: 25 January 2018 / Accepted: 26 January 2018 / Published: 27 January 2018
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Abstract
It is well known that neural activity can be modulated using a cooling device. The applications of this technique range from the treatment of medication-resistant cerebral diseases to brain functional mapping. Despite the potential benefits of such technique, its use has been limited
[...] Read more.
It is well known that neural activity can be modulated using a cooling device. The applications of this technique range from the treatment of medication-resistant cerebral diseases to brain functional mapping. Despite the potential benefits of such technique, its use has been limited due to the lack of suitable thermal modulators. This paper presents the design and validation of a solid-state cooler that was able to modulate the neural activity of rodents without the use of large and unpractical water pipes. A miniaturized thermal control solution based exclusively on solid-state devices was designed, occupying only 5 mm × 5 mm × 3 mm, and featuring the potential for wireless power and communications. The cold side of the device was cooled to 26 °C, while the hot side was kept below 43 °C. This range of temperatures is compatible with brain cooling and efficient enough for achieving some control of neural activity. Full article
(This article belongs to the Special Issue Wireless Microdevices and Systems for Biomedical Applications)
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Open AccessArticle Analysis of PCR Kinetics inside a Microfluidic DNA Amplification System
Micromachines 2018, 9(2), 48; doi:10.3390/mi9020048
Received: 1 December 2017 / Revised: 18 January 2018 / Accepted: 25 January 2018 / Published: 28 January 2018
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Abstract
In order to analyze the DNA amplification numerically with integration of the DNA kinetics, three-dimensional simulations, including flow and thermal fields, and one-dimensional polymerase chain reaction (PCR) kinetics are presented. The simulated results are compared with experimental data that have been applied to
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In order to analyze the DNA amplification numerically with integration of the DNA kinetics, three-dimensional simulations, including flow and thermal fields, and one-dimensional polymerase chain reaction (PCR) kinetics are presented. The simulated results are compared with experimental data that have been applied to the operation of a continuous-flow PCR device. Microchannels fabricated by Micro Electro-Mechanical Systems (MEMS) technologies are shown. Comprehensive simulations of the flow and thermal fields and experiments measuring temperatures during thermal cycling are presented first. The resultant velocity and temperature profiles from the simulations are introduced to the mathematical models of PCR kinetics. Then kinetic equations are utilized to determine the evolution of the species concentrations inside the DNA mixture along the microchannel. The exponential growth of the double-stranded DNA concentration is investigated numerically with the various operational parameters during PCR. Next a 190-bp segment of Bartonella DNA is amplified to evaluate the PCR performance. The trends of the experimental results and numerical data regarding the DNA amplification are similar. The unique architecture built in this study can be applied to a low-cost portable PCR system in the future. Full article
(This article belongs to the Special Issue Biomedical Microdevices: Design, Fabrication and Application)
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Open AccessArticle A Study of Mechanics in Brittle–Ductile Cutting Mode Transition
Micromachines 2018, 9(2), 49; doi:10.3390/mi9020049
Received: 10 December 2017 / Revised: 19 January 2018 / Accepted: 24 January 2018 / Published: 29 January 2018
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Abstract
This paper presents an investigation of the mechanism of the brittle–ductile cutting mode transition from the perspective of the mechanics. A mechanistic model is proposed to analyze the relationship between undeformed chip thickness, deformation, and stress levels in the elastic stage of the
[...] Read more.
This paper presents an investigation of the mechanism of the brittle–ductile cutting mode transition from the perspective of the mechanics. A mechanistic model is proposed to analyze the relationship between undeformed chip thickness, deformation, and stress levels in the elastic stage of the periodic chip formation process, regarding whether brittle or ductile mode deformation is to follow the elastic stage. It is revealed that, the distance of tool advancement required to induce the same level of compressive stress decreases with undeformed chip thickness, and thereby the tensile stress below and behind the tool decreases with undeformed chip thickness. As a result, the tensile stress becomes lower than the critical tensile stress for brittle fracture when the undeformed chip thickness becomes sufficiently small, enabling the brittle–ductile cutting mode transition. The finite element method is employed to verify the analysis of the mechanics on a typical brittle material 6H silicon carbide, and confirmed that the distance of the tool advancement required to induce the same level of compressive stress becomes smaller when the undeformed chip thickness decreases, and consequently smaller tensile stress is induced below and behind the tool. The critical undeformed chip thicknesses for brittle–ductile cutting mode transition are estimated according to the proposed mechanics, and are verified by plunge cutting experiments in a few crystal directions. This study should contribute to better understanding of the mechanism of brittle–ductile cutting mode transition and the ultra-precision machining of brittle materials. Full article
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Open AccessArticle Manipulating Microrobots Using Balanced Magnetic and Buoyancy Forces
Micromachines 2018, 9(2), 50; doi:10.3390/mi9020050
Received: 9 December 2017 / Revised: 16 January 2018 / Accepted: 24 January 2018 / Published: 29 January 2018
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Abstract
We present a novel method for the three-dimensional (3D) control of microrobots within a microfluidic chip. The microrobot body contains a hollow space, producing buoyancy that allows it to float in a microfluidic environment. The robot moves in the z direction by balancing
[...] Read more.
We present a novel method for the three-dimensional (3D) control of microrobots within a microfluidic chip. The microrobot body contains a hollow space, producing buoyancy that allows it to float in a microfluidic environment. The robot moves in the z direction by balancing magnetic and buoyancy forces. In coordination with the motion of stages in the xy plane, we achieved 3D microrobot control. A microgripper designed to grasp micron-scale objects was attached to the front of the robot, allowing it to hold and deliver micro-objects in three dimensions. The microrobot had four degrees of freedom and generated micronewton-order forces. We demonstrate the microrobot’s utility in an experiment in which it grips a 200 μm particle and delivers it in a 3D space. Full article
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Open AccessArticle Development of an AVF Stenosis Assessment Tool for Hemodialysis Patients Using Robotic Ultrasound System
Micromachines 2018, 9(2), 51; doi:10.3390/mi9020051
Received: 30 November 2017 / Revised: 24 January 2018 / Accepted: 25 January 2018 / Published: 29 January 2018
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Abstract
With the aging population and lifestyle changes, the number of hemodialysis (HD) patients increases year by year. The arteriovenous fistula (AVF) is the gold standard vascular access used to access the blood for HD treatment. Since the status of stenosis affects HD efficiency,
[...] Read more.
With the aging population and lifestyle changes, the number of hemodialysis (HD) patients increases year by year. The arteriovenous fistula (AVF) is the gold standard vascular access used to access the blood for HD treatment. Since the status of stenosis affects HD efficiency, current clinical practices usually use a Doppler ultrasound imaging system to assess the parameters of the stenosis, such as the degree of stenosis (DOS). Unfortunately, this is a very time-consuming task. Furthermore, it is difficult to stably maintain the ultrasound probe for a prolonged period to give doctors clearer or reproducible images. In this study, a robotic ultrasound system (RUS) with ultrasound sequential imaging analysis was designed to evaluate the DOS of the AVF. The sequential imaging analysis was capable of image smoothing and vessel boundary detection. It enabled clinicians to mark the thickness of the plaque for further processing. Finally, the system was used to reconstruct 3D models of fistulas and calculated the DOS for clinical assessment. We also designed a pressure sensing module attached to the ultrasound probe to prevent the probe from coming loose, vibrating, and exerting abnormal pressure on the skin. In the phantom test, the results showed that the error of the DOS that was calculated by RUS was less than 3%. The results of clinical trials obtained from ten patients show that the error between the RUS and clinicians’ measurement was about 10% and had a highly linear correlation (R Square > 0.95). In addition, the reproducibility error was about 3% and could effectively save about 46% of the time during clinical examinations. Full article
(This article belongs to the Special Issue Selected Papers from IEEE ICICE 2017)
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Open AccessArticle Fiducial-Aided Robust Positioning of Optical Freeform Surfaces
Micromachines 2018, 9(2), 52; doi:10.3390/mi9020052
Received: 2 December 2017 / Revised: 25 January 2018 / Accepted: 26 January 2018 / Published: 30 January 2018
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Abstract
Form characterization of a machined optical freeform surface demands accurate alignment of the sampled measured data points on the machined surface, and they are compared with the designed geometry of the surface through positioning. In this paper, a fiducial-aided robust positioning method (FAPM)
[...] Read more.
Form characterization of a machined optical freeform surface demands accurate alignment of the sampled measured data points on the machined surface, and they are compared with the designed geometry of the surface through positioning. In this paper, a fiducial-aided robust positioning method (FAPM) is developed which attempts to evaluate freeform surfaces with high efficiency and precision. The FAPM method makes use of fiducials as reference datum to form a fiducial-aided computer-aided design (FA-CAD) of the freeform surface which not only establishes an inherent surface feature, but also links the different coordinate systems among design coordinate frame, machine tool, and measurement instrument. To verify the capability of the proposed method, a series of experiments were conducted. Compared with the traditional freeform measurement method (e.g., least squares method), the results indicate that the robustness and accuracy of the measurement is significantly enhanced by the FAPM. Full article
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Open AccessArticle Statistical Investigation of the Mechanical and Geometrical Properties of Polysilicon Films through On-Chip Tests
Micromachines 2018, 9(2), 53; doi:10.3390/mi9020053
Received: 13 November 2017 / Revised: 23 January 2018 / Accepted: 28 January 2018 / Published: 30 January 2018
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Abstract
In this work, we provide a numerical/experimental investigation of the micromechanics-induced scattered response of a polysilicon on-chip MEMS testing device, whose moving structure is constituted by a slender cantilever supporting a massive perforated plate. The geometry of the cantilever was specifically designed to
[...] Read more.
In this work, we provide a numerical/experimental investigation of the micromechanics-induced scattered response of a polysilicon on-chip MEMS testing device, whose moving structure is constituted by a slender cantilever supporting a massive perforated plate. The geometry of the cantilever was specifically designed to emphasize the micromechanical effects, in compliance with the process constraints. To assess the effects of the variability of polysilicon morphology and of geometrical imperfections on the experimentally observed nonlinear sensor response, we adopt statistical Monte Carlo analyses resting on a coupled electromechanical finite element model of the device. For each analysis, the polysilicon morphology was digitally built through a Voronoi tessellation of the moving structure, whose geometry was in turn varied by sampling out of a uniform probability density function the value of the over-etch, considered as the main source of geometrical imperfections. The comparison between the statistics of numerical and experimental results is adopted to assess the relative significance of the uncertainties linked to variations in the micro-fabrication process, and the mechanical film properties due to the polysilicon morphology. Full article
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Open AccessArticle High-Q Fabry–Pérot Micro-Cavities for High-Sensitivity Volume Refractometry
Micromachines 2018, 9(2), 54; doi:10.3390/mi9020054
Received: 25 November 2017 / Revised: 22 December 2017 / Accepted: 24 January 2018 / Published: 31 January 2018
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Abstract
This work reports a novel structure for a Fabry–Pérot micro cavity that combines the highest reported quality factor for an on-chip Fabry–Pérot resonator that exceeds 9800, and a very high sensitivity for an on-chip volume refractometer based on a Fabry–Pérot cavity that is
[...] Read more.
This work reports a novel structure for a Fabry–Pérot micro cavity that combines the highest reported quality factor for an on-chip Fabry–Pérot resonator that exceeds 9800, and a very high sensitivity for an on-chip volume refractometer based on a Fabry–Pérot cavity that is about 1000 nm/refractive index unit (RIU). The structure consists of two cylindrical Bragg micromirrors that achieve confinement of the Gaussian beam in the plan parallel to the chip substrate, while for the perpendicular plan, external fiber rod lenses (FRLs) are placed in the optical path of the input and the output of the cavity. This novel structure overcomes number of the drawbacks presented in previous designs. The analyte is passed between the mirrors, enabling its detection from the resonance peak wavelengths of the transmission spectra. Mixtures of ethanol and deionized (DI)-water with different ratios are used as analytes with different refractive indices to exploit the device as a micro-opto-fluidic refractometer. The design criteria are detailed and the modeling is based on Gaussian-optics equations, which depicts a scenario closer to reality than the usually used ray-optics modeling. Full article
(This article belongs to the Special Issue Photonic MEMS and Optofluidic Devices)
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Open AccessArticle The Fabrication of Micro-Array Channels with the Ultrafine-Grained LZ91 Mg-Li Alloy by Micro-Embossing
Micromachines 2018, 9(2), 55; doi:10.3390/mi9020055
Received: 15 January 2018 / Revised: 28 January 2018 / Accepted: 29 January 2018 / Published: 31 January 2018
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Abstract
The fabrication of the micro-channel array through micro-embossing on an ultrafine-grained (UFG) LZ91 Mg-Li alloy was investigated in this paper. Micro-embossing tests indicated that the depth of the channels increase with increasing temperatures. Micro-array channels with widths ranging from 50 μm to 200
[...] Read more.
The fabrication of the micro-channel array through micro-embossing on an ultrafine-grained (UFG) LZ91 Mg-Li alloy was investigated in this paper. Micro-embossing tests indicated that the depth of the channels increase with increasing temperatures. Micro-array channels with widths ranging from 50 μm to 200 μm were performed with an applied force of 2 kN at 423 K, following by a dwell time of 60 s on the UFG LZ91 Mg-Li alloy. The surface topography indicates that embossed micro-channels for UFG LZ91 Mg-Li with all widths are clearly printed well with good geometrical transferability and no obvious defects. The comparison filling behavior of UFG and the CG LZ91 Mg-Li alloy reveals that grain sizes mainly affect the filling quality of micro-embossing. The results indicate a potential application of the UFG Mg-Li alloy in the mass fabrication of micro-electro-mechanical system (MEMS) components. Full article
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Open AccessArticle Continuous Near-Field Electrospraying Using a Glass Capillary Nozzle
Micromachines 2018, 9(2), 56; doi:10.3390/mi9020056
Received: 24 December 2017 / Revised: 25 January 2018 / Accepted: 30 January 2018 / Published: 31 January 2018
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Abstract
A continuous near-field electrospray process has been developed to deposit micropatterns. Different from traditional electrospray technologies, the nozzle-to-substrate distance was shortened to less than 5 mm, and a glass capillary nozzle with a diameter of tens of microns was used. Steady and continuous
[...] Read more.
A continuous near-field electrospray process has been developed to deposit micropatterns. Different from traditional electrospray technologies, the nozzle-to-substrate distance was shortened to less than 5 mm, and a glass capillary nozzle with a diameter of tens of microns was used. Steady and continuous ejection was achieved, and patterns with line widths of sub-100 μm were generated. The influence of experimental parameters was investigated. The critical voltage for electrospray increased with nozzle-to-substrate distance and flow rate. The line width of electrosprayed patterns increased with the increases in applied voltage, flow rate, nozzle diameter, and deposition time. This work provides a simple and potential route for on-demand deposition of micro-/nano-patterns in the electrospray process. Full article
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Open AccessArticle Droplet Breakup Dynamics in Bi-Layer Bifurcating Microchannel
Micromachines 2018, 9(2), 57; doi:10.3390/mi9020057
Received: 30 November 2017 / Revised: 20 January 2018 / Accepted: 28 January 2018 / Published: 31 January 2018
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Abstract
Breakup of droplets at bi-layer bifurcating junction in polydimethylsiloxane (PDMS) microchannel has been investigated by experiments and numerical simulation. The pressure drop in bi-layer bifurcating channel was investigated and compared with single-layer bifurcating channel. Daughter droplet size variation generated in bi-layer bifurcating microchannel
[...] Read more.
Breakup of droplets at bi-layer bifurcating junction in polydimethylsiloxane (PDMS) microchannel has been investigated by experiments and numerical simulation. The pressure drop in bi-layer bifurcating channel was investigated and compared with single-layer bifurcating channel. Daughter droplet size variation generated in bi-layer bifurcating microchannel was analyzed. The correlation was proposed to predict the transition between breakup and non-breakup conditions of droplets in bi-layer bifurcating channel using a phase diagram. In the non-breakup regime, droplets exiting port can be switched via tuning flow resistance by controlling radius of curvature, and or channel height ratio. Compared with single-layer bifurcating junction, 3-D cutting in diagonal direction from bi-layer bifurcating junction induces asymmetric fission to form daughter droplets with distinct sizes while each size has good monodispersity. Lower pressure drop is required in the new microsystem. The understanding of the droplet fission in the novel microstructure will enable more versatile control over the emulsion formation, fission and sorting. The model system can be developed to investigate the encapsulation and release kinetics of emulsion templated particles such as drug encapsulated microcapsules as they flow through complex porous media structures, such as blood capillaries or the porous tissue structures, which feature with bifurcating junctions. Full article
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Open AccessArticle Effect of Process Parameters on Flow Length and Flash Formation in Injection Moulding of High Aspect Ratio Polymeric Micro Features
Micromachines 2018, 9(2), 58; doi:10.3390/mi9020058
Received: 14 December 2017 / Revised: 26 January 2018 / Accepted: 29 January 2018 / Published: 31 January 2018
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Abstract
This paper reports an investigation of the effects of process parameters on the quality characteristics of polymeric parts produced by micro injection moulding (μIM) with two different materials. Four injection moulding process parameters (injection velocity, holding pressure, melt temperature and mould temperature) were
[...] Read more.
This paper reports an investigation of the effects of process parameters on the quality characteristics of polymeric parts produced by micro injection moulding (μIM) with two different materials. Four injection moulding process parameters (injection velocity, holding pressure, melt temperature and mould temperature) were investigated using Polypropylene (PP) and Acrylonitrile Butadiene Styrene (ABS). Three key characteristics of the mouldings were evaluated with respect to process settings and the material employed: part mass, flow length and flash formation. The experimentation employs a test part with four micro fingers with different aspect ratios (from 21 up to 150) and was carried out according to the Design of Experiments (DOE) statistical technique. The results show that holding pressure and injection velocity are the most influential parameters on part mass with a direct effect for both materials. Both parameters have a similar effect on flow length for both PP and ABS at all aspect ratios and have higher effects as the feature thickness decreased below 300 μm. The study shows that for the investigated materials the injection speed and packing pressure were the most influential parameters for increasing the amount of flash formation, with relative effects consistent for both materials. Higher melt and mould temperatures settings were less influential parameters for increasing the flash amount when moulding with both materials. Of the two investigated materials, PP was the one exhibiting more flash formation as compared with ABS, when corresponding injection moulding parameters settings for both materials were considered. Full article
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Open AccessArticle Sinusoidal Microchannel with Descending Curves for Varicose Veins Implantation
Micromachines 2018, 9(2), 59; doi:10.3390/mi9020059
Received: 18 October 2017 / Revised: 22 January 2018 / Accepted: 25 January 2018 / Published: 31 January 2018
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Abstract
Approximately 26% of adult people, mostly females, are affected by varicose veins in old age. It is a common reason for distress, loss of efficiency, and worsening living conditions. Several traditional treatment techniques (sclerotherapy and foam sclerotherapy of large veins, laser surgeries and
[...] Read more.
Approximately 26% of adult people, mostly females, are affected by varicose veins in old age. It is a common reason for distress, loss of efficiency, and worsening living conditions. Several traditional treatment techniques (sclerotherapy and foam sclerotherapy of large veins, laser surgeries and radiofrequency ablation, vein ligation and stripping, ambulatory phlebectomy, and endoscopic vein surgery) have failed to handle this disease effectively. Herein, authors have presented an alternative varicose vein implant method—the descending sinusoidal microchannel (DSMC). DSMC was simulated by Fuzzy logic MATLAB (The MathWorks, Natick, MA, USA) and ANSYS (ANSYS 18.2, perpetual license purchased by Ibadat Education Trust, The University of Lahore, Pakistan) with real and actual conditions. After simulations of DSMC, fabrication and testing were performed. The silver DSMC was manufactured by utilizing a micromachining procedure. The length, width, and depth of the silver substrate were 51 mm, 25 mm, and 1.1 mm, respectively. The measurements of the DSMC channel in the silver wafer substrate were 0.9 mm in width and 0.9 mm in depth. The three descending curves of the DSMC were 7 mm, 6 mm, and 5 mm in height. For pressure, actual conditions were carefully taken as 1.0 kPa to 1.5 kPa for varicose veins. For velocity, actual conditions were carefully taken as 0.02 m/s to 0.07 m/s for these veins. These are real and standard values used in simulations and experiments. At Reynolds number 323, the flow rate and velocity were determined as 1001.0 (0.1 nL/s), 11.4 cm/s and 1015.3 (0.1 nL/s), 12.19 cm/s by MATLAB (The MathWorks, Natick, MA, USA) and ANSYS simulations, respectively. The flow rate and velocity were determined to be 995.3 (0.1 nL/s) and 12.2 cm/s, respectively, at the same Reynolds number (323) in the experiment. Moreover, the Dean number was also calculated to observe Dean vortices. All simulated and experimental results were in close agreement. Consequently, DSMC can be implanted in varicose veins as a new treatment to preserve excellent blood flow in human legs from the original place to avoid tissue damage and other problems. Full article
(This article belongs to the Special Issue Medical Microdevices and Micromachines)
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Open AccessArticle 3D Fractals as SERS Active Platforms: Preparation and Evaluation for Gas Phase Detection of G-Nerve Agents
Micromachines 2018, 9(2), 60; doi:10.3390/mi9020060
Received: 15 December 2017 / Revised: 26 January 2018 / Accepted: 28 January 2018 / Published: 31 January 2018
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Abstract
One of the main limitations of the technique surface-enhanced Raman scattering (SERS) for chemical detection relies on the homogeneity, reproducibility and reusability of the substrates. In this work, SERS active platforms based on 3D-fractal microstructures is developed by combining corner lithography and anisotropic
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One of the main limitations of the technique surface-enhanced Raman scattering (SERS) for chemical detection relies on the homogeneity, reproducibility and reusability of the substrates. In this work, SERS active platforms based on 3D-fractal microstructures is developed by combining corner lithography and anisotropic wet etching of silicon, to extend the SERS-active area into 3D, with electrostatically driven Au@citrate nanoparticles (NPs) assembly, to ensure homogeneous coating of SERS active NPs over the entire microstructured platforms. Strong SERS intensities are achieved using 3D-fractal structures compared to 2D-planar structures; leading to SERS enhancement factors for R6G superior than those merely predicted by the enlarged area effect. The SERS performance of Au monolayer-over-mirror configuration is demonstrated for the label-free real-time gas phase detection of 1.2 ppmV of dimethyl methylphosphonate (DMMP), a common surrogate of G-nerve agents. Thanks to the hot spot accumulation on the corners and tips of the 3D-fractal microstructures, the main vibrational modes of DMMP are clearly identified underlying the spectral selectivity of the SERS technique. The Raman acquisition conditions for SERS detection in gas phase have to be carefully chosen to avoid photo-thermal effects on the irradiated area. Full article
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Open AccessArticle Fabrication of Electromagnetically-Driven Tilted Microcoil on Polyimide Capillary Surface for Potential Single-Fiber Endoscope Scanner Application
Micromachines 2018, 9(2), 61; doi:10.3390/mi9020061
Received: 25 December 2017 / Revised: 17 January 2018 / Accepted: 26 January 2018 / Published: 1 February 2018
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Abstract
The design and fabrication of a Micro-electromechanical Systems (MEMS)-based tilted microcoil on a polyimide capillary are reported in this paper, proposed for an electromagnetically-driven single-fiber endoscope scanner application. The parameters of the tilted microcoil were optimized by simulation. It is proved that the
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The design and fabrication of a Micro-electromechanical Systems (MEMS)-based tilted microcoil on a polyimide capillary are reported in this paper, proposed for an electromagnetically-driven single-fiber endoscope scanner application. The parameters of the tilted microcoil were optimized by simulation. It is proved that the largest driving force could be achieved when the tilt-angle, the pitch and the coil turns of the designed microcoil were 60°, 80 µm and 20, respectively. The modal simulation of the designed fiber scanner was carried out. The prototypes of the tilted microcoils were fabricated on the surface of polyimide capillary with 1 mm-diameter using our developed cylindrical projection lithography system. The dimensions of the two tilted microcoils were as follows: one was tilt-angle 45°, line width 10 ± 0.2 µm, coil pitch 78.5 ± 0.5 µm, and the other was tilt-angle 60°, line width 10 ± 0.2 µm, coil pitch 81.5 ± 0.5 µm. Finally, a direct mask-less electroplating process was employed to fabricate the copper microcoil with 15 µm thickness on the gold (Au) seed-layer, and the corresponding line width was expanded to 40 µm. Full article
(This article belongs to the Special Issue MEMS Technology for Biomedical Imaging Applications)
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Open AccessArticle Micro-Electromechanical Acoustic Resonator Coated with Polyethyleneimine Nanofibers for the Detection of Formaldehyde Vapor
Micromachines 2018, 9(2), 62; doi:10.3390/mi9020062
Received: 19 December 2017 / Revised: 22 January 2018 / Accepted: 26 January 2018 / Published: 1 February 2018
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Abstract
We demonstrate a promising strategy to combine the micro-electromechanical film bulk acoustic resonator and the nanostructured sensitive fibers for the detection of low-concentration formaldehyde vapor. The polyethyleneimine nanofibers were directly deposited on the resonator surface by a simple electrospinning method. The film bulk
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We demonstrate a promising strategy to combine the micro-electromechanical film bulk acoustic resonator and the nanostructured sensitive fibers for the detection of low-concentration formaldehyde vapor. The polyethyleneimine nanofibers were directly deposited on the resonator surface by a simple electrospinning method. The film bulk acoustic resonator working at 4.4 GHz acted as a sensitive mass loading platform and the three-dimensional structure of nanofibers provided a large specific surface area for vapor adsorption and diffusion. The ultra-small mass change induced by the absorption of formaldehyde molecules onto the amine groups in polyethyleneimine was detected by measuring the frequency downshift of the film bulk acoustic resonator. The proposed sensor exhibits a fast, reversible and linear response towards formaldehyde vapor with an excellent selectivity. The gas sensitivity and the detection limit were 1.216 kHz/ppb and 37 ppb, respectively. The study offers a great potential for developing sensitive, fast-response and portable sensors for the detection of indoor air pollutions. Full article
(This article belongs to the Special Issue Micro-Resonators: The Quest for Superior Performance)
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Open AccessArticle Fundamental Study for a Graphite-Based Microelectromechanical System
Micromachines 2018, 9(2), 64; doi:10.3390/mi9020064
Received: 29 December 2017 / Revised: 29 January 2018 / Accepted: 31 January 2018 / Published: 2 February 2018
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Abstract
We aimed to develop a process for constructing a carbon-based microelectromechanical system (MEMS). First, we prepared a highly oriented pyrolytic graphite (HOPG) crystal microsheet by exfoliation. We fabricated cantilevers and a double-clamped beam by controlling the thickness of the HOPG microsheet using a
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We aimed to develop a process for constructing a carbon-based microelectromechanical system (MEMS). First, we prepared a highly oriented pyrolytic graphite (HOPG) crystal microsheet by exfoliation. We fabricated cantilevers and a double-clamped beam by controlling the thickness of the HOPG microsheet using a MEMS process. Second, we used a graphite sheet with contour line adhesion by metal sputter deposition. Third, we used a highly accurate graphite sheet with face adhesion and laser cutting. The first resonance frequencies were evaluated. We confirmed improvement in Q values to 1/10 level of a quarts vibrator, high performance, and a simple structure. Full article
(This article belongs to the Special Issue Carbon Based Materials for MEMS/NEMS)
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Open AccessArticle Strategy for Monitoring Cardiac Interventions with an Intelligent Robotic Ultrasound Device
Micromachines 2018, 9(2), 65; doi:10.3390/mi9020065
Received: 5 December 2017 / Revised: 17 January 2018 / Accepted: 31 January 2018 / Published: 2 February 2018
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Abstract
In recent years, 3D trans-oesophageal echocardiography (TOE) has become widely used for monitoring cardiac interventions. The control of the TOE probe during the procedure is a manual task which is tedious and harmful for the operator when exposed to radiation. To improve this
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In recent years, 3D trans-oesophageal echocardiography (TOE) has become widely used for monitoring cardiac interventions. The control of the TOE probe during the procedure is a manual task which is tedious and harmful for the operator when exposed to radiation. To improve this technique, an add-on robotic system has been developed for holding and manipulating a commercial TOE probe. This paper focuses on the probe adjustment strategy in order to accurately monitor the moving intra-operative catheters. The positioning strategy is divided into an initialization step based on a pre-planning method, and a localized adjustment step based on the robotic differential kinematics. A series of experiments was performed to evaluate the initialization and the localized adjustment steps. The results indicate a mean error less than 10 mm from the phantom experiments for the initialization step, and a median error less than 1.5 mm from the computer-based simulation experiments for the localized adjustment step. Compared to the much bigger image volume, it is concluded that the proposed methods are feasible for this application. Future work will focus on evaluating the method in a more realistic TOE scanning scenario. Full article
(This article belongs to the Special Issue Selected Papers from ICMEAS 2017)
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Open AccessArticle Electrospray Deposition of ZnO Thin Films and Its Application to Gas Sensors
Micromachines 2018, 9(2), 66; doi:10.3390/mi9020066
Received: 24 December 2017 / Revised: 18 January 2018 / Accepted: 1 February 2018 / Published: 2 February 2018
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Abstract
Electrospray is a simple and cost-effective method to fabricate micro-structured thin films. This work investigates the electrospray process of ZnO patterns. The effects of experimental parameters on jet characteristics and electrosprayed patterns are studied. The length of stable jets increases with increasing applied
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Electrospray is a simple and cost-effective method to fabricate micro-structured thin films. This work investigates the electrospray process of ZnO patterns. The effects of experimental parameters on jet characteristics and electrosprayed patterns are studied. The length of stable jets increases with increasing applied voltage and flow rate, and decreases with increasing nozzle-to-substrate distance, while electrospray angles exhibit an opposite trend with respect to the stable jet lengths. The diameter of electrosprayed particles decreases with increasing applied voltage, and increases with flow rate. Furthermore, an alcohol gas sensor is presented. The ZnAc is calcined into ZnO, which reveals good repeatability and stability of response in target gas. The sensing response, defined as the resistance ratio of R0/Rg, where R0 and Rg are resistance of ZnO in air and alcohol gas, increases with the concentration of alcohol vapors and electrospray deposition time. Full article
(This article belongs to the Special Issue Nanostructure Based Sensors for Gas Sensing: from Devices to Systems)
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Open AccessArticle Design of Microscale Magnetic Tumbling Robots for Locomotion in Multiple Environments and Complex Terrains
Micromachines 2018, 9(2), 68; doi:10.3390/mi9020068
Received: 5 December 2017 / Revised: 25 January 2018 / Accepted: 30 January 2018 / Published: 3 February 2018
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Abstract
This paper presents several variations of a microscale magnetic tumbling (μTUM) robot capable of traversing complex terrains in dry and wet environments. The robot is fabricated by photolithography techniques and consists of a polymeric body with two sections with embedded magnetic
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This paper presents several variations of a microscale magnetic tumbling ( μ TUM) robot capable of traversing complex terrains in dry and wet environments. The robot is fabricated by photolithography techniques and consists of a polymeric body with two sections with embedded magnetic particles aligned at the ends and a middle nonmagnetic bridge section. The robot’s footprint dimensions are 400 μ m × 800 μ m. Different end geometries are used to test the optimal conditions for low adhesion and increased dynamic response to an actuating external rotating magnetic field. When subjected to a magnetic field as low as 7 mT in dry conditions, this magnetic microrobot is able to operate with a tumbling locomotion mode and translate with speeds of over 60 body lengths/s (48 mm/s) in dry environments and up to 17 body lengths/s (13.6 mm/s) in wet environments. Two different tumbling modes were observed and depend on the alignment of the magnetic particles. A technique was devised to measure the magnetic particle alignment angle relative to the robot’s geometry. Rotational frequency limits were observed experimentally, becoming more prohibitive as environment viscosity increases. The μ TUM’s performance was studied when traversing inclined planes (up to 60°), showing promising climbing capabilities in both dry and wet conditions. Maximum open loop straight-line trajectory errors of less than 4% and 2% of the traversal distance in the vertical and horizontal directions, respectively, for the μ TUM were observed. Full directional control of μ TUM was demonstrated through the traversal of a P-shaped trajectory. Additionally, successful locomotion of the optimized μ TUM design over complex terrains was also achieved. By implementing machine vision control and/or embedding of payloads in the middle section of the robot, it is possible in the future to upgrade the current design with computer-optimized mobility through multiple environments and the ability to perform drug delivery tasks for biomedical applications. Full article
(This article belongs to the Special Issue Micro/Nano Robotics, Volume II)
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Open AccessArticle High-Performance MIM Capacitors for a Secondary Power Supply Application
Micromachines 2018, 9(2), 69; doi:10.3390/mi9020069
Received: 20 October 2017 / Revised: 26 January 2018 / Accepted: 31 January 2018 / Published: 4 February 2018
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Abstract
Microstructure is important to the development of energy devices with high performance. In this work, a three-dimensional Si-based metal-insulator-metal (MIM) capacitor has been reported, which is fabricated by microelectromechanical systems (MEMS) technology. Area enlargement is achieved by forming deep trenches in a silicon
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Microstructure is important to the development of energy devices with high performance. In this work, a three-dimensional Si-based metal-insulator-metal (MIM) capacitor has been reported, which is fabricated by microelectromechanical systems (MEMS) technology. Area enlargement is achieved by forming deep trenches in a silicon substrate using the deep reactive ion etching method. The results indicate that an area of 2.45 × 103 mm2 can be realized in the deep trench structure with a high aspect ratio of 30:1. Subsequently, a dielectric Al2O3 layer and electrode W/TiN layers are deposited by atomic layer deposition. The obtained capacitor has superior performance, such as a high breakdown voltage (34.1 V), a moderate energy density (≥1.23 mJ/cm2) per unit planar area, a high breakdown electric field (6.1 ± 0.1 MV/cm), a low leakage current (10−7 A/cm2 at 22.5 V), and a low quadratic voltage coefficient of capacitance (VCC) (≤63.1 ppm/V2). In addition, the device’s performance has been theoretically examined. The results show that the high energy supply and small leakage current can be attributed to the Poole–Frenkel emission in the high-field region and the trap-assisted tunneling in the low-field region. The reported capacitor has potential application as a secondary power supply. Full article
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Open AccessArticle Optimization of Wavy-Channel Micromixer Geometry Using Taguchi Method
Micromachines 2018, 9(2), 70; doi:10.3390/mi9020070
Received: 17 January 2018 / Revised: 29 January 2018 / Accepted: 2 February 2018 / Published: 6 February 2018
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Abstract
The micro-mixer has been widely used in mixing processes for chemical and pharmaceutical industries. We introduced an improved and easy to manufacture micro-mixer design utilizing the wavy structure micro-channel T-junction which can be easily manufactured using a simple stamping method. Here, we aim
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The micro-mixer has been widely used in mixing processes for chemical and pharmaceutical industries. We introduced an improved and easy to manufacture micro-mixer design utilizing the wavy structure micro-channel T-junction which can be easily manufactured using a simple stamping method. Here, we aim to optimize the geometrical parameters, i.e., wavy frequency, wavy amplitude, and width and height of the micro channel by utilizing the robust Taguchi statistical method with regards to the mixing performance (mixing index), pumping power and figure of merit (FoM). The interaction of each design parameter is evaluated. The results indicate that high mixing performance is not always associated with high FoM due to higher pumping power. Higher wavy frequency and amplitude is required for good mixing performance; however, this is not the case for pumping power due to an increase in Darcy friction loss. Finally, the advantages and limitations of the designs and objective functions are discussed in the light of present numerical results. Full article
(This article belongs to the Special Issue Passive Micromixers)
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Open AccessArticle 3D Printing Solutions for Microfluidic Chip-To-World Connections
Micromachines 2018, 9(2), 71; doi:10.3390/mi9020071
Received: 2 January 2018 / Revised: 30 January 2018 / Accepted: 3 February 2018 / Published: 6 February 2018
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Abstract
The connection of microfluidic devices to the outer world by tubes and wires is an underestimated issue. We present methods based on 3D printing to realize microfluidic chip holders with reliable fluidic and electric connections. The chip holders are constructed by microstereolithography, an
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The connection of microfluidic devices to the outer world by tubes and wires is an underestimated issue. We present methods based on 3D printing to realize microfluidic chip holders with reliable fluidic and electric connections. The chip holders are constructed by microstereolithography, an additive manufacturing technique with sub-millimeter resolution. The fluidic sealing between the chip and holder is achieved by placing O-rings, partly integrated into the 3D-printed structure. The electric connection of bonding pads located on microfluidic chips is realized by spring-probes fitted within the printed holder. Because there is no gluing or wire bonding necessary, it is easy to change the chip in the measurement setup. The spring probes and O-rings are aligned automatically because of their fixed position within the holder. In the case of bioanalysis applications such as cells, a limitation of 3D-printed objects is the leakage of cytotoxic residues from the printing material, cured resin. This was solved by coating the 3D-printed structures with parylene-C. The combination of silicon/glass microfluidic chips fabricated with highly-reliable clean-room technology and 3D-printed chip holders for the chip-to-world connection is a promising solution for applications where biocompatibility, optical transparency and accurate sample handling must be assured. 3D printing technology for such applications will eventually arise, enabling the fabrication of complete microfluidic devices. Full article
(This article belongs to the Special Issue 3D Printed Microfluidic Devices)
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Open AccessArticle Controlling of Electrospray Deposition for Micropatterns
Micromachines 2018, 9(2), 72; doi:10.3390/mi9020072
Received: 31 December 2017 / Revised: 26 January 2018 / Accepted: 2 February 2018 / Published: 6 February 2018
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Abstract
Based on the electrohydrodynamic (EHD) theory, a novel method of near-field electrospray is proposed to fabricate micropatterns with micro/nano-scale particles. Compared with conventional electrospray technology, the deposition area can be decreased to print a regular pattern according to the moving trajectory of the
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Based on the electrohydrodynamic (EHD) theory, a novel method of near-field electrospray is proposed to fabricate micropatterns with micro/nano-scale particles. Compared with conventional electrospray technology, the deposition area can be decreased to print a regular pattern according to the moving trajectory of the substrate by shortening the distance between the nozzle and the collector to several millimeters in near-field electrospray. The controlling strategies in the near-field electrospray deposition process were investigated. The line width of printed pattern increased with the increase of applied voltage, deposition time, and flow rate of solution. However, it decreased with the increase of motion velocity of the substrate. By applying a suitable matching of electrospray parameters, the regular patterns with a line width under 500 μm were printed controllably on the substrate. Thereby, atomized particles from near-field electrospray were successfully deposited in specific patterns. Characters of ‘2’, ‘7’, and ‘9’ with uniform width and steady shape were patterned. This work provides an excellent way to promote the precision integrated manufacturing of electronic system. Full article
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Open AccessArticle Micro-Dosing of Fine Cohesive Powders Actuated by Pulse Inertia Force
Micromachines 2018, 9(2), 73; doi:10.3390/mi9020073
Received: 6 January 2018 / Revised: 2 February 2018 / Accepted: 3 February 2018 / Published: 7 February 2018
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Abstract
Micro-dosing of fine cohesive powders is the key technology in additive manufacturing and especially in high-potency active pharmaceutical ingredients (HPAPI). However, high accuracy micro-dosing (<5 mg) of fine cohesive powder is less trivial and still remains a challenge because it is difficult to
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Micro-dosing of fine cohesive powders is the key technology in additive manufacturing and especially in high-potency active pharmaceutical ingredients (HPAPI). However, high accuracy micro-dosing (<5 mg) of fine cohesive powder is less trivial and still remains a challenge because it is difficult to eliminate the aggregation phenomena caused by the strong interparticle cohesive forces (in small capillaries). This paper presents a novel micro-dose method of fine cohesive powders via a pulse inertia force system. A piezoelectric actuator is used to provide a high enough pulse inertia force for a tapered glass nozzle and drive powder particles in the nozzle to be discharged from the nozzle orifice with the help of particle self-gravity. The nozzles with outlet diameters in the range of 100–2000 µm were fabricated via a glass heating process. The α-lactose monohydrate powder is used as the micro-dosing powder. The influences of the tapered nozzle outlet diameter, amplitude of the applied pulse voltage, and angle of the nozzle axis on micro-dosing mass are researched. The minimum mean dose mass is 0.6 mg for a single pulse inertia force. The coefficient of variation of dose mass, which represents the micro-dosing stability, can be controlled below 5% when the dose mass is relatively small. Full article
(This article belongs to the Special Issue Additive Manufacturing for Medical Applications)
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Open AccessArticle Three-Dimensional Simulation of DRIE Process Based on the Narrow Band Level Set and Monte Carlo Method
Micromachines 2018, 9(2), 74; doi:10.3390/mi9020074
Received: 27 December 2017 / Revised: 31 January 2018 / Accepted: 7 February 2018 / Published: 9 February 2018
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Abstract
A three-dimensional topography simulation of deep reactive ion etching (DRIE) is developed based on the narrow band level set method for surface evolution and Monte Carlo method for flux distribution. The advanced level set method is implemented to simulate the time-related movements of
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A three-dimensional topography simulation of deep reactive ion etching (DRIE) is developed based on the narrow band level set method for surface evolution and Monte Carlo method for flux distribution. The advanced level set method is implemented to simulate the time-related movements of etched surface. In the meanwhile, accelerated by ray tracing algorithm, the Monte Carlo method incorporates all dominant physical and chemical mechanisms such as ion-enhanced etching, ballistic transport, ion scattering, and sidewall passivation. The modified models of charged particles and neutral particles are epitomized to determine the contributions of etching rate. The effects such as scalloping effect and lag effect are investigated in simulations and experiments. Besides, the quantitative analyses are conducted to measure the simulation error. Finally, this simulator will be served as an accurate prediction tool for some MEMS fabrications. Full article
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Open AccessArticle Development of a Triple-Coaxial Flow Device for Fabricating a Hydrogel Microtube and Its Application to Bioremediation
Micromachines 2018, 9(2), 76; doi:10.3390/mi9020076
Received: 10 January 2018 / Revised: 3 February 2018 / Accepted: 9 February 2018 / Published: 12 February 2018
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Abstract
This paper demonstrates a triple-coaxial flow device to continuously produce a hydrogel microtube using a microfluidic technique. The hydrogel microtube can encapsulate a microbial suspension, while allowing the diffusion of oxygen and nutrients into the microtube and preventing microbes from passing into or
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This paper demonstrates a triple-coaxial flow device to continuously produce a hydrogel microtube using a microfluidic technique. The hydrogel microtube can encapsulate a microbial suspension, while allowing the diffusion of oxygen and nutrients into the microtube and preventing microbes from passing into or out of the microtube. The microtubes also enable the collection of the microbes after task completion without contaminating the environment. In our previous study, we used a double-coaxial flow device to produce the microtubes, but continuous production was a challenge. In the present study, we developed a microfluidic device that fabricates a triple-coaxial flow to enable continuous production of the microtubes. Here, we characterize the production capacity of the microtubes along with their properties and demonstrate bioremediation using microtubes encapsulating a microbial suspension. Full article
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Open AccessArticle Ultrasonically Assisted Single Point Diamond Turning of Optical Mold of Tungsten Carbide
Micromachines 2018, 9(2), 77; doi:10.3390/mi9020077
Received: 10 January 2018 / Revised: 3 February 2018 / Accepted: 8 February 2018 / Published: 12 February 2018
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Abstract
To realize high efficiency, low/no damage and high precision machining of tungsten carbide used for lens mold, a high frequency ultrasonic vibration cutting system was developed at first. Then, tungsten carbide was precisely machined with a polycrystalline diamond (PCD) tool assisted by the
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To realize high efficiency, low/no damage and high precision machining of tungsten carbide used for lens mold, a high frequency ultrasonic vibration cutting system was developed at first. Then, tungsten carbide was precisely machined with a polycrystalline diamond (PCD) tool assisted by the self-developed high frequency ultrasonic vibration cutting system. Tool wear mechanism was investigated in ductile regime machining of tungsten carbide. The cutter back-off phenomenon in the process was analyzed. The subsequent experimental results of ultra-precision machining with a single crystal diamond tool showed that: under the condition of high frequency ultrasonic vibration cutting, nano-scale surface roughness can be obtained by the diamond tool with smaller tip radius and no defects like those of ground surface were found on the machined surface. Tool wear mechanisms of the single crystal diamond tool are mainly abrasive wear and micro-chipping. To solve the problem, a method of inclined ultrasonic vibration cutting with negative rake angle was put forward according to force analysis, which can further reduce tool wear and roughness of the machined surface. The investigation was important to high efficiency and quality ultra-precision machining of tungsten carbide. Full article
(This article belongs to the Special Issue Micro-Machining: Challenges and Opportunities)
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Open AccessArticle Perceptual Surgical Knife with Wavelet Denoising
Micromachines 2018, 9(2), 79; doi:10.3390/mi9020079
Received: 28 December 2017 / Revised: 22 January 2018 / Accepted: 11 February 2018 / Published: 13 February 2018
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Abstract
Robotic surgery is a new technology in medical applications and has been undergoing rapid development. The surgical knife, essential for robotic surgery, has the ability to determine the success of an operation. In this paper, on the basis of the principle of field-effect
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Robotic surgery is a new technology in medical applications and has been undergoing rapid development. The surgical knife, essential for robotic surgery, has the ability to determine the success of an operation. In this paper, on the basis of the principle of field-effect transistors (FETs), a perceptual surgical knife is proposed to detect the electrons or electric field of the human body with distinguishable signals. In addition, it is difficult to discriminate between the motions of surgical knives from the perceptual signals that are disturbed by high-frequency Gaussian white noise. Therefore, the wavelet denoising approach is chosen to reduce the high-frequency noise. The proposed perceptual surgical knife with the wavelet denoising method has the characteristics of high sensitivity, low cost, and good repeatability. Full article
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Open AccessArticle Active Control of a Small-Scale Wind Turbine Blade Containing Magnetorheological Fluid
Micromachines 2018, 9(2), 80; doi:10.3390/mi9020080
Received: 23 December 2017 / Revised: 29 January 2018 / Accepted: 12 February 2018 / Published: 14 February 2018
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Abstract
This research study proposes a new active control structure to suppress vibrations of a small-scale wind turbine blade filled with magnetorheological (MR) fluid and actuated by an electromagnet. The aluminum blade structure is manufactured using the SH3055 (Bergey Windpower Co. Inc., Norman, OK,
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This research study proposes a new active control structure to suppress vibrations of a small-scale wind turbine blade filled with magnetorheological (MR) fluid and actuated by an electromagnet. The aluminum blade structure is manufactured using the SH3055 (Bergey Windpower Co. Inc., Norman, OK, USA) code numbered airfoil which is designed for use on small wind turbines. A dynamic interaction model between the MR fluid and the electromagnetic actuator is constructed to obtain a force relation. A detailed characterization study is presented for the proposed actuator to understand the nonlinear behavior of the electromagnetic force. A norm based multi-objective H2/H controller is designed using the model of the elastic blade element. The H2/H controller is experimentally implemented under the impact and steady state aerodynamic load conditions. The results of experiments show that the MR fluid- electromagnetic actuator is effective for suppressing vibrations of the blade structure. Full article
(This article belongs to the Special Issue Selected Papers from ICMEAS 2017)
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Open AccessArticle Design and Simulation of A Novel Piezoelectric AlN-Si Cantilever Gyroscope
Micromachines 2018, 9(2), 81; doi:10.3390/mi9020081
Received: 28 December 2017 / Revised: 11 February 2018 / Accepted: 13 February 2018 / Published: 15 February 2018
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Abstract
A novel design of piezoelectric aluminum nitride (AlN)-Si composite cantilever gyroscope is proposed in this paper. The cantilever is stimulated to oscillate in plane by two inverse voltages which are applied on the two paralleled drive electrodes, respectively. The whole working principles are
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A novel design of piezoelectric aluminum nitride (AlN)-Si composite cantilever gyroscope is proposed in this paper. The cantilever is stimulated to oscillate in plane by two inverse voltages which are applied on the two paralleled drive electrodes, respectively. The whole working principles are deduced, which based on the piezoelectric equation and elastic vibration equation. In this work, a cantilever gyroscope has been simulated and optimized by COMSOL Multiphysics 5.2a. The drive mode frequency is 87.422 kHz, and the sense mode frequency is 87.414 kHz. The theoretical sensitivity of this gyroscope is 0.145 pm/◦/s. This gyroscope has a small size and simple structure. It will be a better choice for the consumer electronics. Full article
(This article belongs to the Special Issue Piezoelectric MEMS)
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Open AccessArticle On the Bipolar DC Flow Field-Effect-Transistor for Multifunctional Sample Handing in Microfluidics: A Theoretical Analysis under the Debye–Huckel Limit
Micromachines 2018, 9(2), 82; doi:10.3390/mi9020082
Received: 26 January 2018 / Revised: 11 February 2018 / Accepted: 13 February 2018 / Published: 16 February 2018
PDF Full-text (2287 KB) | Supplementary Files
Abstract
We present herein a novel method of bipolar field-effect control on DC electroosmosis (DCEO) from a physical point of view, in the context of an intelligent and robust operation tool for stratified laminar streams in microscale systems. In this unique design of the
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We present herein a novel method of bipolar field-effect control on DC electroosmosis (DCEO) from a physical point of view, in the context of an intelligent and robust operation tool for stratified laminar streams in microscale systems. In this unique design of the DC flow field-effect-transistor (DC-FFET), a pair of face-to-face external gate terminals are imposed with opposite gate-voltage polarities. Diffuse-charge dynamics induces heteropolar Debye screening charge within the diffuse double layer adjacent to the face-to-face oppositely-polarized gates, respectively. A background electric field is applied across the source-drain terminal and forces the face-to-face counterionic charge of reversed polarities into induced-charge electroosmotic (ICEO) vortex flow in the lateral direction. The chaotic turbulence of the transverse ICEO whirlpool interacts actively with the conventional plug flow of DCEO, giving rise to twisted streamlines for simultaneous DCEO pumping and ICEO mixing of fluid samples along the channel length direction. A mathematical model in thin-layer approximation and the low-voltage limit is subsequently established to test the feasibility of the bipolar DC-FFET configuration in electrokinetic manipulation of fluids at the micrometer dimension. According to our simulation analysis, an integrated device design with two sets of side-by-side, but upside-down gate electrode pair exhibits outstanding performance in electroconvective pumping and mixing even without any externally-applied pressure difference. Moreover, a paradigm of a microdevice for fully electrokinetics-driven analyte treatment is established with an array of reversed bipolar gate-terminal pairs arranged on top of the dielectric membrane along the channel length direction, from which we can obtain almost a perfect liquid mixture by using a smaller magnitude of gate voltages for causing less detrimental effects at a small Dukhin number. Sustained by theoretical analysis, our physical demonstration on bipolar field-effect flow control for the microfluidic device of dual functionalities in simultaneous electroconvective pumping and mixing holds great potential in the development of fully-automated liquid-phase actuators in modern microfluidic systems. Full article
(This article belongs to the Special Issue Micro/Nano-Chip Electrokinetics, Volume II)
Open AccessCommunication Mini-EmulsionFabricated Magnetic and Fluorescent Hybrid Janus Micro-Motors
Micromachines 2018, 9(2), 83; doi:10.3390/mi9020083
Received: 15 January 2018 / Revised: 9 February 2018 / Accepted: 11 February 2018 / Published: 15 February 2018
PDF Full-text (1365 KB) | Supplementary Files
Abstract
Self-propelling micro/nano-motors have attracted great attention due to their controllable active motion and various functional attributes. To date, a variety of technologies have been reported for the fabrication of micro/nano-motors. However, there are still several challenges that need to be addressed. One of
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Self-propelling micro/nano-motors have attracted great attention due to their controllable active motion and various functional attributes. To date, a variety of technologies have been reported for the fabrication of micro/nano-motors. However, there are still several challenges that need to be addressed. One of them is to endow micro/nano-motors with multi-functionalities by a facile fabrication process. Here, we present a universal approach, adopted from the emulsion templating method, for the fabrication of Janus micro-motors. With a one-step process, magnetic nanoparticles and fluorescent dyes are simultaneously embedded into the microparticles. The self-propelled motors can be used as an active label or fluorescent tracer through manipulation of their motion using magnetic guidance. Full article
Open AccessArticle Characterizing Sources of Small DC Motor Noise and Vibration
Micromachines 2018, 9(2), 84; doi:10.3390/mi9020084
Received: 22 December 2017 / Revised: 9 February 2018 / Accepted: 13 February 2018 / Published: 15 February 2018
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Abstract
Small direct current (DC) motors are widely used due to their low cost and compact structure. Small DC motors of various designs are available on the market in different sizes. The smaller the motor, the more closely it may be used by individuals.
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Small direct current (DC) motors are widely used due to their low cost and compact structure. Small DC motors of various designs are available on the market in different sizes. The smaller the motor, the more closely it may be used by individuals. Contrary to the size and simplicity of these motors in terms of structural design, sources of motor noise and vibration can be quite diverse and complicated. In this study, the source of motor noise and vibration was visualized over a very wide range of frequencies. The particle velocity of the motor was reconstructed from nearfield sound pressure measurements of motor noise. In addition to noncontact measurements conducted on a motor running at constant speed, the particle velocity of a stationary motor due to the impulse of an impact hammer was measured with an accelerometer. Furthermore, motor noise was measured under motor run-up conditions with different rotational speeds. As a result, by combination of these three methods, the sources of motor noise were accurately identified over a wide range of frequencies. Full article
(This article belongs to the Special Issue Micro/Nano Robotics, Volume II)
Open AccessArticle 3D Printing, Ink Casting and Micromachined Lamination (3D PICLμM): A Makerspace Approach to the Fabrication of Biological Microdevices
Micromachines 2018, 9(2), 85; doi:10.3390/mi9020085
Received: 29 December 2017 / Revised: 7 February 2018 / Accepted: 11 February 2018 / Published: 15 February 2018
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Abstract
We present a novel benchtop-based microfabrication technology: 3D printing, ink casting, micromachined lamination (3D PICLμM) for rapid prototyping of lab-on-a-chip (LOC) and biological devices. The technology uses cost-effective, makerspace-type microfabrication processes, all of which are ideally suited for low resource settings, and utilizing
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We present a novel benchtop-based microfabrication technology: 3D printing, ink casting, micromachined lamination (3D PICLμM) for rapid prototyping of lab-on-a-chip (LOC) and biological devices. The technology uses cost-effective, makerspace-type microfabrication processes, all of which are ideally suited for low resource settings, and utilizing a combination of these processes, we have demonstrated the following devices: (i) 2D microelectrode array (MEA) targeted at in vitro neural and cardiac electrophysiology, (ii) microneedle array targeted at drug delivery through a transdermal route and (iii) multi-layer microfluidic chip targeted at multiplexed assays for in vitro applications. The 3D printing process has been optimized for printing angle, temperature of the curing process and solvent polishing to address various biofunctional considerations of the three demonstrated devices. We have depicted that the 3D PICLμM process has the capability to fabricate 30 μm sized MEAs (average 1 kHz impedance of 140 kΩ with a double layer capacitance of 3 μF), robust and reliable microneedles having 30 μm radius of curvature and ~40 N mechanical fracture strength and microfluidic devices having 150 μm wide channels and 400 μm fluidic vias capable of fluid mixing and transmitted light microparticle visualization. We believe our 3D PICLμM is ideally suited for applications in areas such as electrophysiology, drug delivery, disease in a dish, organ on a chip, environmental monitoring, agricultural therapeutic delivery and genomic testing. Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)
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Open AccessArticle Microfluidics: A New Layer of Control for Extrusion-Based 3D Printing
Micromachines 2018, 9(2), 86; doi:10.3390/mi9020086
Received: 1 February 2018 / Revised: 14 February 2018 / Accepted: 15 February 2018 / Published: 16 February 2018
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Abstract
Advances in 3D printing have enabled the use of this technology in a growing number of fields, and have started to spark the interest of biologists. Having the particularity of being cell friendly and allowing multimaterial deposition, extrusion-based 3D printing has been shown
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Advances in 3D printing have enabled the use of this technology in a growing number of fields, and have started to spark the interest of biologists. Having the particularity of being cell friendly and allowing multimaterial deposition, extrusion-based 3D printing has been shown to be the method of choice for bioprinting. However as biologically relevant constructs often need to be of high resolution and high complexity, new methods are needed, to provide an improved level of control on the deposited biomaterials. In this paper, we demonstrate how microfluidics can be used to add functions to extrusion 3D printers, which widens their field of application. Micromixers can be added to print heads to perform the last-second mixing of multiple components just before resin dispensing, which can be used for the deposition of new polymeric or composite materials, as well as for bioprinting new materials with tailored properties. The integration of micro-concentrators in the print heads allows a significant increase in cell concentration in bioprinting. The addition of rapid microfluidic switching as well as resolution increase through flow focusing are also demonstrated. Those elementary implementations of microfluidic functions for 3D printing pave the way for more complex applications enabling new prospects in 3D printing. Full article
(This article belongs to the Special Issue 3D Printed Microfluidic Devices)
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Open AccessArticle Lattice Boltzmann Simulation of the Hydrodynamic Entrance Region of Rectangular Microchannels in the Slip Regime
Micromachines 2018, 9(2), 87; doi:10.3390/mi9020087
Received: 18 December 2017 / Revised: 31 January 2018 / Accepted: 13 February 2018 / Published: 16 February 2018
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Abstract
Abstract: Developing a three-dimensional laminar flow in the entrance region of rectangular microchannels has been investigated in this paper. When the hydrodynamic development length is the same magnitude as the microchannel length, entrance effects have to be taken into account, especially in relatively
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Abstract: Developing a three-dimensional laminar flow in the entrance region of rectangular microchannels has been investigated in this paper. When the hydrodynamic development length is the same magnitude as the microchannel length, entrance effects have to be taken into account, especially in relatively short ducts. Simultaneously, there are a variety of non-continuum or rarefaction effects, such as velocity slip and temperature jump. The available data in the literature appearing on this issue is quite limited, the available study is the semi-theoretical approximate model to predict pressure drop of developing slip flow in rectangular microchannels with different aspect ratios. In this paper, we apply the lattice Boltzmann equation method (LBE) to investigate the developing slip flow through a rectangular microchannel. The effects of the Reynolds number (1 < Re < 1000), channel aspect ratio (0 < ε < 1), and Knudsen number (0.001 < Kn < 0.1) on the dimensionless hydrodynamic entrance length, and the apparent friction factor, and Reynolds number product, are examined in detail. The numerical solution of LBM can recover excellent agreement with the available data in the literature, which proves its accuracy in capturing fundamental fluid characteristics in the slip-flow regime. Full article
(This article belongs to the Special Issue Microsystems for Power, Energy, and Actuation)

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Open AccessReview Light-Powered Micro/Nanomotors
Micromachines 2018, 9(2), 41; doi:10.3390/mi9020041
Received: 27 December 2017 / Revised: 17 January 2018 / Accepted: 18 January 2018 / Published: 23 January 2018
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Abstract
Designed micro/nanomotors are micro/nanoscale machines capable of autonomous motion in fluids, which have been emerging in recent decades owing to their great potential for biomedical and environmental applications. Among them, light-powered micro/nanomotors, in which motion is driven by light, exhibit various advantages in
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Designed micro/nanomotors are micro/nanoscale machines capable of autonomous motion in fluids, which have been emerging in recent decades owing to their great potential for biomedical and environmental applications. Among them, light-powered micro/nanomotors, in which motion is driven by light, exhibit various advantages in their precise motion manipulation and thereby a superior scope for application. This review summarizes recent advances in the design, manufacture and motion manipulation of different types of light-powered micro/nanomotors. Their structural features and motion performance are reviewed and compared. The challenges and opportunities of light-powered micro/nanomotors are also discussed. With rapidly increasing innovation, advanced, intelligent and multifunctional light-powered micro/nanomachines will certainly bring profound impacts and changes for human life in the future. Full article
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Open AccessReview The Fantastic Voyage of the Trypanosome: A Protean Micromachine Perfected during 500 Million Years of Engineering
Micromachines 2018, 9(2), 63; doi:10.3390/mi9020063
Received: 17 January 2018 / Revised: 30 January 2018 / Accepted: 1 February 2018 / Published: 2 February 2018
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Abstract
The human body is constantly attacked by pathogens. Various lines of defence have evolved, among which the immune system is principal. In contrast to most pathogens, the African trypanosomes thrive freely in the blood circulation, where they escape immune destruction by antigenic variation
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The human body is constantly attacked by pathogens. Various lines of defence have evolved, among which the immune system is principal. In contrast to most pathogens, the African trypanosomes thrive freely in the blood circulation, where they escape immune destruction by antigenic variation and incessant motility. These unicellular parasites are flagellate microswimmers that also withstand the harsh mechanical forces prevailing in the bloodstream. They undergo complex developmental cycles in the bloodstream and organs of the mammalian host, as well as the disease-transmitting tsetse fly. Each life cycle stage has been shaped by evolution for manoeuvring in distinct microenvironments. Here, we introduce trypanosomes as blueprints for nature-inspired design of trypanobots, micromachines that, in the future, could explore the human body without affecting its physiology. We review cell biological and biophysical aspects of trypanosome motion. While this could provide a basis for the engineering of microbots, their actuation and control still appear more like fiction than science. Here, we discuss potentials and challenges of trypanosome-inspired microswimmer robots. Full article
(This article belongs to the Special Issue Locomotion at Small Scales: From Biology to Artificial Systems)
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Open AccessReview Investigation on Single-Molecule Junctions Based on Current–Voltage Characteristics
Micromachines 2018, 9(2), 67; doi:10.3390/mi9020067
Received: 15 January 2018 / Revised: 30 January 2018 / Accepted: 31 January 2018 / Published: 2 February 2018
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Abstract
The relationship between the current through an electronic device and the voltage across its terminals is a current–voltage characteristic (IV) that determine basic device performance. Currently, IV measurement on a single-molecule scale can be performed using break
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The relationship between the current through an electronic device and the voltage across its terminals is a current–voltage characteristic (IV) that determine basic device performance. Currently, IV measurement on a single-molecule scale can be performed using break junction technique, where a single molecule junction can be prepared by trapping a single molecule into a nanogap between metal electrodes. The single-molecule IVs provide not only the device performance, but also reflect information on energy dispersion of the electronic state and the electron-molecular vibration coupling in the junction. This mini review focuses on recent representative studies on IVs of the single molecule junctions that cover investigation on the single-molecule diode property, the molecular vibration, and the electronic structure as a form of transmission probability, and electronic density of states, including the spin state of the single-molecule junctions. In addition, thermoelectronic measurements based on IVs and identification of the charged carriers (i.e., electrons or holes) are presented. The analysis in the single-molecule IVs provides fundamental and essential information for a better understanding of the single-molecule science, and puts the single molecule junction to more practical use in molecular devices. Full article
(This article belongs to the Special Issue Atomic and Molecular Junction for Molecular Electronic Devices)
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Open AccessReview Geometry Design, Principles and Assembly of Micromotors
Micromachines 2018, 9(2), 75; doi:10.3390/mi9020075
Received: 18 January 2018 / Revised: 6 February 2018 / Accepted: 7 February 2018 / Published: 11 February 2018
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Abstract
Discovery of bio-inspired, self-propelled and externally-powered nano-/micro-motors, rotors and engines (micromachines) is considered a potentially revolutionary paradigm in nanoscience. Nature knows how to combine different elements together in a fluidic state for intelligent design of nano-/micro-machines, which operate by pumping, stirring, and diffusion
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Discovery of bio-inspired, self-propelled and externally-powered nano-/micro-motors, rotors and engines (micromachines) is considered a potentially revolutionary paradigm in nanoscience. Nature knows how to combine different elements together in a fluidic state for intelligent design of nano-/micro-machines, which operate by pumping, stirring, and diffusion of their internal components. Taking inspirations from nature, scientists endeavor to develop the best materials, geometries, and conditions for self-propelled motion, and to better understand their mechanisms of motion and interactions. Today, microfluidic technology offers considerable advantages for the next generation of biomimetic particles, droplets and capsules. This review summarizes recent achievements in the field of nano-/micromotors, and methods of their external control and collective behaviors, which may stimulate new ideas for a broad range of applications. Full article
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Open AccessReview Tubular Micro/Nanomotors: Propulsion Mechanisms, Fabrication Techniques and Applications
Micromachines 2018, 9(2), 78; doi:10.3390/mi9020078
Received: 17 January 2018 / Revised: 9 February 2018 / Accepted: 11 February 2018 / Published: 13 February 2018
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Abstract
Micro/nanomotors are self-propelled machines that can convert various energy sources into autonomous movement. With the great advances of nanotechnology, Micro/Nanomotors of various geometries have been designed and fabricated over the past few decades. Among them, the tubular Micro/Nanomotors have a unique morphology of
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Micro/nanomotors are self-propelled machines that can convert various energy sources into autonomous movement. With the great advances of nanotechnology, Micro/Nanomotors of various geometries have been designed and fabricated over the past few decades. Among them, the tubular Micro/Nanomotors have a unique morphology of hollow structures, which enable them to possess a strong driving force and easy surface functionalization. They are promising for environmental and biomedical applications, ranging from water remediation, sensing to active drug delivery and precise surgery. This article gives a comprehensive and clear review of tubular Micro/Nanomotors, including propulsion mechanisms, fabrication techniques and applications. In the end, we also put forward some realistic problems and speculate about corresponding methods to improve existing tubular Micro/Nanomotors. Full article
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Open AccessReview Light-Controlled Swarming and Assembly of Colloidal Particles
Micromachines 2018, 9(2), 88; doi:10.3390/mi9020088
Received: 14 January 2018 / Revised: 4 February 2018 / Accepted: 11 February 2018 / Published: 19 February 2018
PDF Full-text (1648 KB)
Abstract
Swarms and assemblies are ubiquitous in nature and they can perform complex collective behaviors and cooperative functions that they cannot accomplish individually. In response to light, some colloidal particles (CPs), including light active and passive CPs, can mimic their counterparts in nature and
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Swarms and assemblies are ubiquitous in nature and they can perform complex collective behaviors and cooperative functions that they cannot accomplish individually. In response to light, some colloidal particles (CPs), including light active and passive CPs, can mimic their counterparts in nature and organize into complex structures that exhibit collective functions with remote controllability and high temporospatial precision. In this review, we firstly analyze the structural characteristics of swarms and assemblies of CPs and point out that light-controlled swarming and assembly of CPs are generally achieved by constructing light-responsive interactions between CPs. Then, we summarize in detail the recent advances in light-controlled swarming and assembly of CPs based on the interactions arisen from optical forces, photochemical reactions, photothermal effects, and photoisomerizations, as well as their potential applications. In the end, we also envision some challenges and future prospects of light-controlled swarming and assembly of CPs. With the increasing innovations in mechanisms and control strategies with easy operation, low cost, and arbitrary applicability, light-controlled swarming and assembly of CPs may be employed to manufacture programmable materials and reconfigurable robots for cooperative grasping, collective cargo transportation, and micro- and nanoengineering. Full article
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