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Micromachines, Volume 5, Issue 4 (December 2014) , Pages 797-1484

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Open AccessArticle
Performance Characterization of Micromachined Inductive Suspensions Based on 3D Wire-Bonded Microcoils
Micromachines 2014, 5(4), 1469-1484; https://doi.org/10.3390/mi5041469
Received: 30 September 2014 / Revised: 1 December 2014 / Accepted: 5 December 2014 / Published: 12 December 2014
Cited by 8 | Viewed by 2822 | PDF Full-text (8989 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We present a comprehensive experimental investigation of a micromachined inductive suspension (MIS) based on 3D wire-bonded microcoils. A theoretical model has been developed to predict the levitation height of the disc-shaped proof mass (PM), which has good agreement with the experimental results. The [...] Read more.
We present a comprehensive experimental investigation of a micromachined inductive suspension (MIS) based on 3D wire-bonded microcoils. A theoretical model has been developed to predict the levitation height of the disc-shaped proof mass (PM), which has good agreement with the experimental results. The 3D MIS consists of two coaxial wire-bonded coils, the inner coil being used for levitation, while the outer coil for the stabilization of the PM. The levitation behavior is mapped with respect to the input parameters of the excitation currents applied to the levitation and stabilization coil, respectively: amplitude and frequency. At the same time, the levitation is investigated with respect to various thickness values (12.5 to 50 μm) and two materials (Al and Cu) of the proof mass. An important characteristic of an MIS, which determines its suitability for various applications, such as, e.g., micro-motors, is the dynamics in the lateral direction. We experimentally study the lateral stabilization force acting on the PM as a function of the linear displacement. The analysis of this dependency allows us to define a transition between stable and unstable levitation behavior. From an energetic point of view, this transition corresponds to the local maximum of the MIS potential energy. 2D simulations of the potential energy help us predict the location of this maximum, which is proven to be in good agreement with the experiment. Additionally, we map the temperature distribution for the coils, as well as for the PM levitated at 120 μm, which confirms the significant reduction of the heat dissipation in the MIS based on 3D microcoils compared to the planar topology. Full article
(This article belongs to the Special Issue Microactuators)
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Open AccessArticle
Analysis of Thermal Performance in a Bidirectional Thermocycler by Including Thermal Contact Characteristics
Micromachines 2014, 5(4), 1445-1468; https://doi.org/10.3390/mi5041445
Received: 17 October 2014 / Revised: 21 November 2014 / Accepted: 4 December 2014 / Published: 12 December 2014
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Abstract
This paper illustrates an application of a technique for predicting the thermal characteristics of a bidirectional thermocycling device for polymerase chain reaction (PCR). The micromilling chamber is oscillated by a servo motor and contacted with different isothermal heating blocks to successfully amplify the [...] Read more.
This paper illustrates an application of a technique for predicting the thermal characteristics of a bidirectional thermocycling device for polymerase chain reaction (PCR). The micromilling chamber is oscillated by a servo motor and contacted with different isothermal heating blocks to successfully amplify the DNA templates. Because a comprehensive database of contact resistance factors does not exist, it causes researchers to not take thermal contact resistance into consideration at all. We are motivated to accurately determine the thermal characteristics of the reaction chamber with thermal contact effects existing between the heater surface and the chamber surface. Numerical results show that the thermal contact effects between the heating blocks and the reaction chamber dominate the temperature variations and the ramping rates inside the PCR chamber. However, the influences of various temperatures of the ambient conditions on the sample temperature during three PCR steps can be negligible. The experimental temperature profiles are compared well with the numerical simulations by considering the thermal contact conductance coefficient which is empirical by the experimental fitting. To take thermal contact conductance coefficients into consideration in the thermal simulation is recommended to predict a reasonable temperature profile of the reaction chamber during various thermal cycling processes. Finally, the PCR experiments present that Hygromycin B DNA templates are amplified successfully. Furthermore, our group is the first group to introduce the thermal contact effect into theoretical study that has been applied to the design of a PCR device, and to perform the PCR process in a bidirectional thermocycler. Full article
(This article belongs to the Special Issue Biomedical Microdevices)
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Open AccessArticle
Numerical Investigation of Pileup Process in Metal Microdroplet Deposition Manufacture
Micromachines 2014, 5(4), 1429-1444; https://doi.org/10.3390/mi5041429
Received: 22 August 2014 / Revised: 3 December 2014 / Accepted: 5 December 2014 / Published: 10 December 2014
Cited by 8 | Viewed by 2182 | PDF Full-text (6469 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a systematic numerical investigation of the transient transport phenomenon during the pileup of molten metal droplets on the substrate. The physical mechanisms of the pileup process, including the bulk liquid, capillarity effects at the liquid-solid interface, heat transfer, and solidification, [...] Read more.
This paper presents a systematic numerical investigation of the transient transport phenomenon during the pileup of molten metal droplets on the substrate. The physical mechanisms of the pileup process, including the bulk liquid, capillarity effects at the liquid-solid interface, heat transfer, and solidification, are identified and quantified numerically. The droplet diameter is 100 μm, and the impact velocities are 1–3 m/s. These conditions correspond to Re = O(100), We = O(1). The initial substrate temperature is 350 K. The initial droplet temperature of aluminum alloy molten droplets is 960 K. The numerical models are validated with experiments. The comparison between numerical simulations and experimental findings shows a good agreement. The effects of impacting velocity and relative distances between two successive molten droplets on the end-shapes of impact regime are examined. This investigation is essential to implement effective process control in metal microdroplet deposition manufacture. Full article
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Open AccessArticle
Miscible Organic Solvents Soak Bonding Method Use in a PMMA Multilayer Microfluidic Device
Micromachines 2014, 5(4), 1416-1428; https://doi.org/10.3390/mi5041416
Received: 23 September 2014 / Revised: 5 December 2014 / Accepted: 5 December 2014 / Published: 10 December 2014
Cited by 11 | Viewed by 2197 | PDF Full-text (2391 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we proposed a novel bonding technology to fabricate a microfluidic device based on Poly(methyl methacrylate) (PMMA). The method, which used chloroform and ethanol as miscible bonding solvent, can complete complex structures rapid assembly (10 min) at 40°C. A bonding strength [...] Read more.
In this paper, we proposed a novel bonding technology to fabricate a microfluidic device based on Poly(methyl methacrylate) (PMMA). The method, which used chloroform and ethanol as miscible bonding solvent, can complete complex structures rapid assembly (10 min) at 40°C. A bonding strength of 267.5 N/cm2 can be achieved, while the micro channel deformation was less than 7.26%. Then we utilized this method to produce a three layers micro mixer, which included a T-shaped inlet channel and six H-shaped mixing units. Numerical simulation indicated that, the well mixing length of the mixer was only about 6 mm when Re = 10. Finally, fluorescence microscopy was used to verify mixer performance. The method provided the potential for mass production of multilayer rigid polymer microfluidic devices. Full article
(This article belongs to the Special Issue Micro/Nano Fabrication)
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Open AccessReview
Advances in Silicon Based Millimeter-Wave Monolithic Integrated Circuits
Micromachines 2014, 5(4), 1373-1415; https://doi.org/10.3390/mi5041373
Received: 13 March 2014 / Revised: 15 September 2014 / Accepted: 5 November 2014 / Published: 10 December 2014
Cited by 2 | Viewed by 2839 | PDF Full-text (6178 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the advances of the silicon-based millimeter-wave (MMW) monolithic integrated circuits (MMICs) are reported. The silicon-based technologies for MMW MMICs are briefly introduced. In addition, the current status of the MMW MMICs is surveyed and novel circuit topologies are summarized. Some [...] Read more.
In this paper, the advances of the silicon-based millimeter-wave (MMW) monolithic integrated circuits (MMICs) are reported. The silicon-based technologies for MMW MMICs are briefly introduced. In addition, the current status of the MMW MMICs is surveyed and novel circuit topologies are summarized. Some representative MMW MMICs are illustrated as design examples in the categories of their functions in a MMW system. Finally, there is a conclusion and description of the future trend of the development of the MMW ICs. Full article
(This article belongs to the Special Issue Advances in MMICs)
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Open AccessArticle
Impacts of Ambient and Ablation Plasmas on Short- and Ultrashort-Pulse Laser Processing of Surfaces
Micromachines 2014, 5(4), 1344-1372; https://doi.org/10.3390/mi5041344
Received: 17 November 2014 / Accepted: 3 December 2014 / Published: 9 December 2014
Cited by 9 | Viewed by 4084 | PDF Full-text (3197 KB) | HTML Full-text | XML Full-text
Abstract
In spite of the fact that more than five decades have passed since the invention of laser, some topics of laser-matter interaction still remain incompletely studied. One of such topics is plasma impact on the overall phenomenon of the interaction and its particular [...] Read more.
In spite of the fact that more than five decades have passed since the invention of laser, some topics of laser-matter interaction still remain incompletely studied. One of such topics is plasma impact on the overall phenomenon of the interaction and its particular features, including influence of the laser-excited plasma re-radiation, back flux of energetic plasma species, and massive material redeposition, on the surface quality and processing efficiency. In this paper, we analyze different plasma aspects, which go beyond a simple consideration of the well-known effect of plasma shielding of laser radiation. The following effects are considered: ambient gas ionization above the target on material processing with formation of a “plasma pipe”; back heating of the target by both laser-driven ambient and ablation plasmas through conductive and radiative heat transfer; plasma chemical effects on surface processing including microstructure growth on liquid metals; complicated dynamics of the ablation plasma flow interacting with an ambient gas that can result in substantial redeposition of material around the ablation spot. Together with a review summarizing our main to-date achievements and outlining research directions, we present new results underlining importance of laser plasma dynamics and photoionization of the gas environment upon laser processing of materials. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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Open AccessEditorial
Special Issue on Microlenses
Micromachines 2014, 5(4), 1342-1343; https://doi.org/10.3390/mi5041342
Received: 4 December 2014 / Accepted: 5 December 2014 / Published: 8 December 2014
Viewed by 1681 | PDF Full-text (189 KB) | HTML Full-text | XML Full-text
Abstract
The study and application of microscale lenses and lens arrays have been actively researched in recent years; new approaches in the fabrication of microlenses and microlens arrays have emerged. Also, novel applications of these microlenses and microlens arrays have been demonstrated. In an [...] Read more.
The study and application of microscale lenses and lens arrays have been actively researched in recent years; new approaches in the fabrication of microlenses and microlens arrays have emerged. Also, novel applications of these microlenses and microlens arrays have been demonstrated. In an effort to disseminate the current advances in this specialized field of microlenses and microlens arrays, and to encourage discussion on the future research directions while stimulating research interests in this area, a Special Issue of Micromachines has been dedicated to “Microlenses”. [...] Full article
(This article belongs to the Special Issue Microlenses) Printed Edition available
Open AccessArticle
Design and Analysis of a High Force, Low Voltage and High Flow Rate Electro-Thermal Micropump
Micromachines 2014, 5(4), 1323-1341; https://doi.org/10.3390/mi5041323
Received: 11 August 2014 / Revised: 22 September 2014 / Accepted: 1 October 2014 / Published: 4 December 2014
Cited by 4 | Viewed by 3450 | PDF Full-text (5435 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the design and simulation of an improved electro-thermal micromachined pump for drug delivery applications. Thermal actuators, which are a type of Micro Electro Mechanical system (MEMS) device, are highly useful because of their ability to deliver with great force and [...] Read more.
This paper presents the design and simulation of an improved electro-thermal micromachined pump for drug delivery applications. Thermal actuators, which are a type of Micro Electro Mechanical system (MEMS) device, are highly useful because of their ability to deliver with great force and displacement. Thus, our structure is based on a thermal actuator that exploits the Joule heating effect and has been improved using the springy length properties of MEMS chevron beams. The Joule heating effect results in a difference in temperature and therefore displacement in the beams (actuators). Simulation results show that a maximum force of 4.4 mN and a maximum flow rate of 16 μL/min can be obtained by applying an AC voltage as low as 8 V at different frequencies ranging from 1 to 32 Hz. The maximum temperature was a problem at the chevron beams and the center shaft. Thus, to locally increase the temperature of the chevron beams alone and not that of the pumping diaphragm: (1) The air gaps 2 μm underneath and above the device layer were optimized for heat transfer. (2) Release holes and providing fins were created at the center shaft and actuator, respectively, to decrease the temperature by approximately 10 °C. (3) We inserted and used a polymer tube to serve as an insulator and eliminate leakage problems in the fluidic channel. Full article
(This article belongs to the Special Issue Micropumps: Design, Fabrication and Applications)
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Open AccessArticle
SU-8 Electrothermal Actuators: Optimization of Fabrication and Excitation for Long-Term Use
Micromachines 2014, 5(4), 1310-1322; https://doi.org/10.3390/mi5041310
Received: 2 October 2014 / Revised: 14 November 2014 / Accepted: 21 November 2014 / Published: 2 December 2014
Cited by 7 | Viewed by 2607 | PDF Full-text (4684 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we examine the suitability of SU-8 2000 as a construction material for electrothermal actuators and the actuator stability for long-term operation. The fabrication of SU-8 was optimized for mechanical and thermal stability. Samples with different softbake duration, exposure dose and [...] Read more.
In this paper we examine the suitability of SU-8 2000 as a construction material for electrothermal actuators and the actuator stability for long-term operation. The fabrication of SU-8 was optimized for mechanical and thermal stability. Samples with different softbake duration, exposure dose and postbake temperature were evaluated using Fourier-Transform IR-spectroscopy and dynamic-mechanical analysis. The exposure dose and postbake temperature proved to have a strong influence on the cross-linking and the glass transition temperature. A final hardbake levels the effects of the process history. A high degree of crosslinking, a low drop of the dynamic modulus over temperature (30%) up to the glass transition temperature 100–140 °C were achieved for SU-8 with an exposure dose of 1500 mJ/cm², a postbake temperature of 95 °C and hardbake of 240 °C. Electrothermal actuators proved to be stable until the end of the experiment after 2400 duty cycles. Actuator deflections up to 55 μm were measured (actuator length: 4 mm) for input powers up to 160 mW and a maximum operating temperature of 120 °C. Higher temperatures led to permanent deformations and failure. An offset drift of up to 20% occurs during actuation, but converges after a burn-in phase of about two hours. Full article
(This article belongs to the Special Issue Microactuators)
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Open AccessArticle
Laser Controlled Synthesis of Noble Metal Nanoparticle Arrays for Low Concentration Molecule Recognition
Micromachines 2014, 5(4), 1296-1309; https://doi.org/10.3390/mi5041296
Received: 9 October 2014 / Revised: 18 November 2014 / Accepted: 24 November 2014 / Published: 1 December 2014
Cited by 10 | Viewed by 2200 | PDF Full-text (1587 KB) | HTML Full-text | XML Full-text
Abstract
Nanostructured gold and silver thin films were grown by pulsed laser deposition.Performing the process in an ambient gas (Ar) leads to the nucleation and growth ofnanoparticles in the ablation plasma and their self-organization on the substrate. Thedependence of surface nanostructuring of the films [...] Read more.
Nanostructured gold and silver thin films were grown by pulsed laser deposition.Performing the process in an ambient gas (Ar) leads to the nucleation and growth ofnanoparticles in the ablation plasma and their self-organization on the substrate. Thedependence of surface nanostructuring of the films on the deposition parameters is discussedconsidering in particular the number of laser pulses and the ambient gas nature and pressure.The performance of the deposited thin films as substrates for surface-enhanced Ramanspectroscopy (SERS) was tested against the detection of molecules at a low concentration.Taking Raman maps on micrometer-sized areas, the spatial homogeneity of the substrateswith respect to the SERS signal was tested. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
Open AccessArticle
Motility Control of Bacteria-Actuated Biodegradable Polymeric Microstructures by Selective Adhesion Methods
Micromachines 2014, 5(4), 1287-1295; https://doi.org/10.3390/mi5041287
Received: 21 August 2014 / Revised: 14 November 2014 / Accepted: 21 November 2014 / Published: 28 November 2014
Cited by 3 | Viewed by 2401 | PDF Full-text (2693 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Certain bacteria have motility and can be made non-toxic, and using them for drug delivery has been proposed. For example, using bacteria with flagella motion in multiple spin actuators in drug delivery microrobots has been suggested. This paper investigates various adhesion enhancement methods [...] Read more.
Certain bacteria have motility and can be made non-toxic, and using them for drug delivery has been proposed. For example, using bacteria with flagella motion in multiple spin actuators in drug delivery microrobots has been suggested. This paper investigates various adhesion enhancement methods for attaching bacteria on preferred surfaces of cubic polymeric microstructures to achieve the directional control of motion. Serratia marcescens which has an excellent swimming behavior and 50-μm sized cubic structures made of biodegradable poly-capro-lactone (PCL) are used. Three treatment methods are investigated and compared to the untreated control case. The first method is retarding bacterial attachments by coating certain surfaces with bovine serum albumin (BSA) which makes those surfaces anti-adherent to bacteria. The second and third methods are roughening the surfaces with X-ray irradiation and plasma respectively to purposely increase bacterial attachments on the roughened surfaces. The measured motilities of bacteria-tethered PCL microactuators are 1.40 μm/s for the BSA coating method, 0.82 μm/s for the X-ray irradiation, and 3.89 μm/s for the plasma treatment method. Therefore, among the methods investigated in the paper the plasma treatment method achieves the highest directionality control of bacteria motility. Full article
(This article belongs to the Special Issue Microactuators)
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Open AccessArticle
The Effect of Inertia on the Flow and Mixing Characteristics of a Chaotic Serpentine Mixer
Micromachines 2014, 5(4), 1270-1286; https://doi.org/10.3390/mi5041270
Received: 9 October 2014 / Revised: 23 November 2014 / Accepted: 24 November 2014 / Published: 27 November 2014
Cited by 9 | Viewed by 2387 | PDF Full-text (4166 KB) | HTML Full-text | XML Full-text
Abstract
As an extension of our previous study, the flow and mixing characteristics of a serpentine mixer in non-creeping flow conditions are investigated numerically. A periodic velocity field is obtained for each spatially periodic channel with the Reynolds number (Re) ranging from 0.1 to [...] Read more.
As an extension of our previous study, the flow and mixing characteristics of a serpentine mixer in non-creeping flow conditions are investigated numerically. A periodic velocity field is obtained for each spatially periodic channel with the Reynolds number (Re) ranging from 0.1 to 70 and the channel aspect ratio from 0.25 to one. The flow kinematics is visualized by plotting the manifold of the deforming interface between two fluids. The progress of mixing affected by the Reynolds number and the channel geometry is characterized by a measure of mixing, the intensity of segregation, calculated using the concentration distribution. A mixer with a lower aspect ratio, which is a poor mixer in the creeping flow regime, turns out to be an efficient one above a threshold value of the Reynolds number, Re = 50. This is due to the combined effect of the enhanced rotational motion of fluid particles and back flows near the bends of the channel driven by inertia. As for a mixer with a higher aspect ratio, the intensity of segregation has its maximum around Re = 30, implying that inertia does not always have a positive influence on mixing in this mixer. Full article
(This article belongs to the Special Issue Micromixer & Micromixing)
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Open AccessArticle
Predictable Duty Cycle Modulation through Coupled Pairing of Syringes with Microfluidic Oscillators
Micromachines 2014, 5(4), 1254-1269; https://doi.org/10.3390/mi5041254
Received: 24 October 2014 / Revised: 19 November 2014 / Accepted: 19 November 2014 / Published: 27 November 2014
Cited by 4 | Viewed by 2700 | PDF Full-text (2622 KB) | HTML Full-text | XML Full-text
Abstract
The ability to elicit distinct duty cycles from the same self-regulating microfluidic oscillator device would greatly enhance the versatility of this micro-machine as a tool, capable of recapitulating in vitro the diverse oscillatory processes that occur within natural systems. We report a novel [...] Read more.
The ability to elicit distinct duty cycles from the same self-regulating microfluidic oscillator device would greatly enhance the versatility of this micro-machine as a tool, capable of recapitulating in vitro the diverse oscillatory processes that occur within natural systems. We report a novel approach to realize this using the coordinated modulation of input volumetric flow rate ratio and fluidic capacitance ratio. The demonstration uses a straightforward experimental system where fluid inflow to the oscillator is provided by two syringes (of symmetric or asymmetric cross-sectional area) mounted upon a single syringe pump applying pressure across both syringes at a constant linear velocity. This produces distinct volumetric outflow rates from each syringe that are proportional to the ratio between their cross-sectional areas. The difference in syringe cross-sectional area also leads to differences in fluidic capacitance; this underappreciated capacitive difference allows us to present a simplified expression to determine the microfluidic oscillators duty cycle as a function of cross-sectional area. Examination of multiple total volumetric inflows under asymmetric inflow rates yielded predictable and robust duty cycles ranging from 50% to 90%. A method for estimating the outflow duration for each inflow under applied flow rate ratios is provided to better facilitate the utilization of this system in experimental protocols requiring specific stimulation and rest intervals. Full article
(This article belongs to the collection Lab-on-a-Chip)
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Open AccessReview
Fabrication of Micro/Nano Structures on Metals by Femtosecond Laser Micromachining
Micromachines 2014, 5(4), 1219-1253; https://doi.org/10.3390/mi5041219
Received: 22 October 2014 / Revised: 13 November 2014 / Accepted: 13 November 2014 / Published: 20 November 2014
Cited by 102 | Viewed by 6534 | PDF Full-text (5211 KB) | HTML Full-text | XML Full-text
Abstract
Femtosecond laser micromachining has emerged in recent years as a new technique for micro/nano structure fabrication because of its applicability to virtually all kinds of materials in an easy one-step process that is scalable. In the past, much research on femtosecond laser micromachining [...] Read more.
Femtosecond laser micromachining has emerged in recent years as a new technique for micro/nano structure fabrication because of its applicability to virtually all kinds of materials in an easy one-step process that is scalable. In the past, much research on femtosecond laser micromachining was carried out to understand the complex ablation mechanism, whereas recent works are mostly concerned with the fabrication of surface structures because of their numerous possible applications. The state-of-the-art knowledge on the fabrication of these structures on metals with direct femtosecond laser micromachining is reviewed in this article. The effect of various parameters, such as fluence, number of pulses, laser beam polarization, wavelength, incident angle, scan velocity, number of scans, and environment, on the formation of different structures is discussed in detail wherever possible. Furthermore, a guideline for surface structures optimization is provided. The authors’ experimental work on laser-inscribed regular pattern fabrication is presented to give a complete picture of micromachining processes. Finally, possible applications of laser-machined surface structures in different fields are briefly reviewed. Full article
(This article belongs to the Special Issue Micro/Nano Fabrication)
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Open AccessArticle
Femtosecond Laser Irradiation of Plasmonic Nanoparticles in Polymer Matrix: Implications for Photothermal and Photochemical Material Alteration
Micromachines 2014, 5(4), 1202-1218; https://doi.org/10.3390/mi5041202
Received: 14 October 2014 / Revised: 11 November 2014 / Accepted: 11 November 2014 / Published: 19 November 2014
Cited by 7 | Viewed by 2430 | PDF Full-text (4603 KB) | HTML Full-text | XML Full-text
Abstract
We analyze the opportunities provided by the plasmonic nanoparticles inserted into the bulk of a transparent medium to modify the material by laser light irradiation. This study is provoked by the advent of photo-induced nano-composites consisting of a typical polymer matrix and metal [...] Read more.
We analyze the opportunities provided by the plasmonic nanoparticles inserted into the bulk of a transparent medium to modify the material by laser light irradiation. This study is provoked by the advent of photo-induced nano-composites consisting of a typical polymer matrix and metal nanoparticles located in the light-irradiated domains of the initially homogeneous material. The subsequent irradiation of these domains by femtosecond laser pulses promotes a further alteration of the material properties. We separately consider two different mechanisms of material alteration. First, we analyze a photochemical reaction initiated by the two-photon absorption of light near the plasmonic nanoparticle within the matrix. We show that the spatial distribution of the products of such a reaction changes the symmetry of the material, resulting in the appearance of anisotropy in the initially isotropic material or even in the loss of the center of symmetry. Second, we analyze the efficiency of a thermally-activated chemical reaction at the surface of a plasmonic particle and the distribution of the product of such a reaction just near the metal nanoparticle irradiated by an ultrashort laser pulse. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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Open AccessArticle
High Resolution Cell Positioning Based on a Flow Reduction Mechanism for Enhancing Deformability Mapping
Micromachines 2014, 5(4), 1188-1201; https://doi.org/10.3390/mi5041188
Received: 23 September 2014 / Revised: 30 October 2014 / Accepted: 11 November 2014 / Published: 18 November 2014
Cited by 10 | Viewed by 2665 | PDF Full-text (1505 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The dispersion of cell deformability mapping is affected not only by the resolution of the sensing system, but also by cell deformability itself. In order to extract the pure deformability characteristics of cells, it is necessary to improve the resolution of cell actuation [...] Read more.
The dispersion of cell deformability mapping is affected not only by the resolution of the sensing system, but also by cell deformability itself. In order to extract the pure deformability characteristics of cells, it is necessary to improve the resolution of cell actuation in the sensing system, particularly in the case of active sensing, where an actuator is essential. This paper proposes a novel concept, a “flow reduction mechanism”, where a flow is generated by a macroactuator placed outside of a microfluidic chip. The flow can be drastically reduced at the cell manipulation point in a microchannel due to the elasticity embedded into the fluid circuit of the microfluidic system. The great advantage of this approach is that we can easily construct a high resolution cell manipulation system by combining a macro-scale actuator and a macro-scale position sensor, even though the resolution of the actuator is larger than the desired resolution for cell manipulation. Focusing on this characteristic, we successfully achieved the cell positioning based on a visual feedback control with a resolution of 240 nm, corresponding to one pixel of the vision system. We show that the utilization of this positioning system contributes to reducing the dispersion coming from the positioning resolution in the cell deformability mapping. Full article
(This article belongs to the collection Lab-on-a-Chip)
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Open AccessArticle
Light-Addressable Electrodeposition of Magnetically-Guided Cells Encapsulated in Alginate Hydrogels for Three-Dimensional Cell Patterning
Micromachines 2014, 5(4), 1173-1187; https://doi.org/10.3390/mi5041173
Received: 3 September 2014 / Revised: 5 November 2014 / Accepted: 13 November 2014 / Published: 18 November 2014
Cited by 2 | Viewed by 3019 | PDF Full-text (6944 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes a light-addressable electrolytic system used to perform an electrodeposition of magnetically-guided cells encapsulated in alginate hydrogels using a digital micromirror device (DMD) for three-dimensional cell patterning. In this system, the magnetically-labeled cells were first manipulated into a specific arrangement by [...] Read more.
This paper describes a light-addressable electrolytic system used to perform an electrodeposition of magnetically-guided cells encapsulated in alginate hydrogels using a digital micromirror device (DMD) for three-dimensional cell patterning. In this system, the magnetically-labeled cells were first manipulated into a specific arrangement by changing the orientation of the magnetic field, and then a patterned light illumination was projected onto a photoconductive substrate serving as a photo-anode to cause gelation of calcium alginate through sol-gel transition. By controlling the illumination pattern on the DMD, we first successfully produced cell-encapsulated multilayer alginate hydrogels with different shapes and sizes in each layer via performing multiplexed micropatterning. By combining the magnetically-labeled cells, light-addressable electrodeposition, and orientation of the magnetic fields, we have successfully demonstrated to fabricate two layers of the cell-encapsulated alginate hydrogels, where cells in each layer can be manipulated into cross-directional arrangements that mimic natural tissue. Our proposed method provides a programmable method for the spatiotemporally controllable assembly of cell populations into three-dimensional cell patterning and could have a wide range of biological applications in tissue engineering, toxicology, and drug discovery. Full article
(This article belongs to the Special Issue Biomedical Microdevices)
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Open AccessArticle
Insulin Micropump with Embedded Pressure Sensors for Failure Detection and Delivery of Accurate Monitoring
Micromachines 2014, 5(4), 1161-1172; https://doi.org/10.3390/mi5041161
Received: 1 August 2014 / Revised: 4 November 2014 / Accepted: 13 November 2014 / Published: 18 November 2014
Cited by 8 | Viewed by 2894 | PDF Full-text (1709 KB) | HTML Full-text | XML Full-text
Abstract
Improved glycemic control with insulin pump therapy in patients with type 1 diabetes mellitus has shown gradual reductions in nephropathy and retinopathy. More recently, the emerging concept of the artificial pancreas, comprising an insulin pump coupled to a continuous glucose meter and a [...] Read more.
Improved glycemic control with insulin pump therapy in patients with type 1 diabetes mellitus has shown gradual reductions in nephropathy and retinopathy. More recently, the emerging concept of the artificial pancreas, comprising an insulin pump coupled to a continuous glucose meter and a control algorithm, would become the next major breakthrough in diabetes care. The patient safety and the efficiency of the therapy are directly derived from the delivery accuracy of rapid-acting insulin. For this purpose, a specific precision-oriented design of micropump has been built. The device, made of a stack of three silicon wafers, comprises two check valves and a pumping membrane that is actuated against stop limiters by a piezo actuator. Two membranes comprising piezoresistive strain gauges have been implemented to measure the pressure in the pumping chamber and at the outlet of the pump. Their high sensitivity makes possible the monitoring of the pumping accuracy with a tolerance of ±5% for each individual stroke of 200 nL. The capability of these sensors to monitor priming, reservoir overpressure, reservoir emptying, outlet occlusion and valve leakage has also been studied. Full article
(This article belongs to the Special Issue Micropumps: Design, Fabrication and Applications)
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Open AccessReview
Magnetic Shape Memory Microactuators
Micromachines 2014, 5(4), 1135-1160; https://doi.org/10.3390/mi5041135
Received: 29 September 2014 / Revised: 1 November 2014 / Accepted: 1 November 2014 / Published: 18 November 2014
Cited by 21 | Viewed by 3271 | PDF Full-text (5288 KB) | HTML Full-text | XML Full-text
Abstract
By introducing smart materials in micro systems technologies, novel smart microactuators and sensors are currently being developed, e.g., for mobile, wearable, and implantable MEMS (Micro-electro-mechanical-system) devices. Magnetic shape memory alloys (MSMAs) are a promising material system as they show multiple coupling effects as [...] Read more.
By introducing smart materials in micro systems technologies, novel smart microactuators and sensors are currently being developed, e.g., for mobile, wearable, and implantable MEMS (Micro-electro-mechanical-system) devices. Magnetic shape memory alloys (MSMAs) are a promising material system as they show multiple coupling effects as well as large, abrupt changes in their physical properties, e.g., of strain and magnetization, due to a first order phase transformation. For the development of MSMA microactuators, considerable efforts are undertaken to fabricate MSMA foils and films showing similar and just as strong effects compared to their bulk counterparts. Novel MEMS-compatible technologies are being developed to enable their micromachining and integration. This review gives an overview of material properties, engineering issues and fabrication technologies. Selected demonstrators are presented illustrating the wide application potential. Full article
(This article belongs to the Special Issue Microactuators)
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Open AccessReview
Femtosecond Laser 3D Fabrication in Porous Glass for Micro- and Nanofluidic Applications
Micromachines 2014, 5(4), 1106-1134; https://doi.org/10.3390/mi5041106
Received: 9 October 2014 / Revised: 22 October 2014 / Accepted: 22 October 2014 / Published: 17 November 2014
Cited by 8 | Viewed by 3641 | PDF Full-text (10770 KB) | HTML Full-text | XML Full-text
Abstract
The creation of complex three-dimensional (3D) fluidic systems composed of hollow micro- and nanostructures embedded in transparent substrates has attracted significant attention from both scientific and applied research communities. However, it is by now still a formidable challenge to build 3D micro- and [...] Read more.
The creation of complex three-dimensional (3D) fluidic systems composed of hollow micro- and nanostructures embedded in transparent substrates has attracted significant attention from both scientific and applied research communities. However, it is by now still a formidable challenge to build 3D micro- and nanofluidic structures with arbitrary configurations using conventional planar lithographic fabrication methods. As a direct and maskless fabrication technique, femtosecond laser micromachining provides a straightforward approach for high-precision, spatially-selective, modification inside transparent materials through nonlinear optical absorption. In this paper, we demonstrate rapid fabrication of high-aspect-ratio micro- and/or nanofluidic structures with various 3D configurations by femtosecond laser direct writing in porous glass substrates. Based on this approach, we demonstrate several functional micro- and nanofluidic devices including a 3D passive microfluidic mixer, a capillary electrophoresis (CE) analysis chip, and an integrated micro-nanofluidic system for single DNA analysis. The possible mechanisms behind the formation of high-aspect-ratio micro- and nanochannels are also discussed. This technology offers new opportunities to develop novel 3D micro-nanofluidic systems for a variety of lab-on-a-chip applications. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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Open AccessArticle
Executed Movement Using EEG Signals through a Naive Bayes Classifier
Micromachines 2014, 5(4), 1082-1105; https://doi.org/10.3390/mi5041082
Received: 15 May 2014 / Revised: 15 October 2014 / Accepted: 30 October 2014 / Published: 13 November 2014
Cited by 7 | Viewed by 2747 | PDF Full-text (1802 KB) | HTML Full-text | XML Full-text
Abstract
Recent years have witnessed a rapid development of brain-computer interface (BCI) technology. An independent BCI is a communication system for controlling a device by human intension, e.g., a computer, a wheelchair or a neuroprosthes is, not depending on the brain’s normal output pathways [...] Read more.
Recent years have witnessed a rapid development of brain-computer interface (BCI) technology. An independent BCI is a communication system for controlling a device by human intension, e.g., a computer, a wheelchair or a neuroprosthes is, not depending on the brain’s normal output pathways of peripheral nerves and muscles, but on detectable signals that represent responsive or intentional brain activities. This paper presents a comparative study of the usage of the linear discriminant analysis (LDA) and the naive Bayes (NB) classifiers on describing both right- and left-hand movement through electroencephalographic signal (EEG) acquisition. For the analysis, we considered the following input features: the energy of the segments of a band pass-filtered signal with the frequency band in sensorimotor rhythms and the components of the spectral energy obtained through the Welch method. We also used the common spatial pattern (CSP) filter, so as to increase the discriminatory activity among movement classes. By using the database generated by this experiment, we obtained hit rates up to 70%. The results are compatible with previous studies. Full article
(This article belongs to the Special Issue Mind-Controlled Robotics)
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Open AccessArticle
Growth of Ultra-Long ZnO Microtubes Using a Modified Vapor-Solid Setup
Micromachines 2014, 5(4), 1069-1081; https://doi.org/10.3390/mi5041069
Received: 27 August 2014 / Revised: 4 November 2014 / Accepted: 6 November 2014 / Published: 11 November 2014
Cited by 4 | Viewed by 2227 | PDF Full-text (3820 KB) | HTML Full-text | XML Full-text
Abstract
In this work, we have modified the experimental setup for a vapor-solid (VS) process to synthesize Zinc oxide (ZnO) microtubes (MTs) with lengths up to 3 mm during a 90-min growth period. The critical idea behind this modification is to control the distribution [...] Read more.
In this work, we have modified the experimental setup for a vapor-solid (VS) process to synthesize Zinc oxide (ZnO) microtubes (MTs) with lengths up to 3 mm during a 90-min growth period. The critical idea behind this modification is to control the distribution of Zn vapor along the Si substrates. The morphology evolution of ZnO structures with the increasing reaction time was particularly explored. We found that, within the 90-min growth period, four different types of ZnO microstructures appeared in this synthesis process: microrods (MRs), short MTs, two-tier structures, and long MTs. Growth mechanisms were proposed to interpret the formation of these structures. Full article
(This article belongs to the Special Issue Micro/Nano Fabrication)
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Open AccessArticle
Effect of Laser Power on the Quality of Drilled Micro Hole Using Cu50Zr50 Amorphous Alloys Foils
Micromachines 2014, 5(4), 1061-1068; https://doi.org/10.3390/mi5041061
Received: 31 July 2014 / Revised: 31 October 2014 / Accepted: 31 October 2014 / Published: 11 November 2014
Cited by 6 | Viewed by 2378 | PDF Full-text (2597 KB) | HTML Full-text | XML Full-text
Abstract
The rapid growth of the micro-electro-mechanical systems (MEMS) is being driven by the rapid development of the micro manufacturing processes. Laser beam machining is one of the micro manufacturing processes which can shape almost all ranges of engineering materials. In this study, the [...] Read more.
The rapid growth of the micro-electro-mechanical systems (MEMS) is being driven by the rapid development of the micro manufacturing processes. Laser beam machining is one of the micro manufacturing processes which can shape almost all ranges of engineering materials. In this study, the effect of laser power on the quality of drilled micro holes using Cu50Zr50 amorphous alloys foils is experimentally investigated. It indicates that both entrance and exit circularities diameters increase with laser power. The circularities of the holes at the entry and the exit are in the range of 0.893 to 0.997. The taper of drilled holes increases quickly to a stable value with the increase of laser power from 60 to 110 W, then decreases quickly when the laser power becomes larger than 170 W. The micro holes with a diameter of 400 to 1200 μm are manufactured successfully by laser drilling processes. The formation mechanism of the quality of the laser drilled hole is analyzed based on the laser beam and the properties of amorphous alloys foils. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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Open AccessArticle
Micromachining of AlN and Al2O3 Using Fiber Laser
Micromachines 2014, 5(4), 1051-1060; https://doi.org/10.3390/mi5041051
Received: 12 August 2014 / Revised: 23 October 2014 / Accepted: 3 November 2014 / Published: 10 November 2014
Cited by 14 | Viewed by 2588 | PDF Full-text (407 KB) | HTML Full-text | XML Full-text
Abstract
We report on high precision high speed micromachining of Al2O3 and AlN using pulsed near infrared fiber laser. Ablation thresholds are determined to be 30 J/cm2 for alumina and 18 J/cm2 for aluminum nitride. The factors influencing the [...] Read more.
We report on high precision high speed micromachining of Al2O3 and AlN using pulsed near infrared fiber laser. Ablation thresholds are determined to be 30 J/cm2 for alumina and 18 J/cm2 for aluminum nitride. The factors influencing the efficiency and quality of 3D micromachining, namely the surface roughness, the material removal rate and the ablation depth accuracy are determined as a function of laser repetition rate and pulse overlap. Using a fluence of 64 J/cm², we achieve a material removal rate of up to 94 mm³/h in Al2O3 and 135 mm³/h in AlN for high pulse overlaps (89% and 84%). A minimum roughness of 1.5 μm for alumina and 1.65 μm for aluminum nitride can be accomplished for medium pulse overlaps (42% to 56%). In addition, ablation depth deviation of the micromachining process of smaller than 8% for alumina and 2% for aluminum nitride are achieved. Based on these results, by structuring exemplarily 3D structures we demonstrate the potential of high quality and efficient 3D micromachining using pulsed fiber laser. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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Open AccessArticle
Analysis of Dynamic Performance of a Kalman Filter for Combining Multiple MEMS Gyroscopes
Micromachines 2014, 5(4), 1034-1050; https://doi.org/10.3390/mi5041034
Received: 25 August 2014 / Revised: 14 October 2014 / Accepted: 31 October 2014 / Published: 7 November 2014
Cited by 9 | Viewed by 2395 | PDF Full-text (1533 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the dynamic performance of a Kalman filter (KF) was analyzed, which is used to combine multiple measurements of a gyroscopes array to reduce the noise and improve the accuracy of the individual sensors. A principle for accuracy improvement by the [...] Read more.
In this paper, the dynamic performance of a Kalman filter (KF) was analyzed, which is used to combine multiple measurements of a gyroscopes array to reduce the noise and improve the accuracy of the individual sensors. A principle for accuracy improvement by the KF was briefly presented to obtain an optimal estimate of input rate signal. In particular, the influences of some crucial factors on the KF dynamic performance were analyzed by simulations such as the factors input signal frequency, signal sampling, and KF filtering rate. Finally, a system that was comprised of a six-gyroscope array was designed and implemented to test the dynamic performance. Experimental results indicated that the 1σ error for the combined rate signal was reduced to about 0.2°/s in the constant rate test, which was a reduction by a factor of more than eight compared to the single gyroscope. The 1σ error was also reduced from 1.6°/s to 0.48°/s in the swing test. It showed that the estimated angular rate signal could well reflect the dynamic characteristic of the input signal in dynamic conditions. Full article
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Open AccessArticle
A Particle Filter for Smartphone-Based Indoor Pedestrian Navigation
Micromachines 2014, 5(4), 1012-1033; https://doi.org/10.3390/mi5041012
Received: 4 September 2014 / Revised: 13 October 2014 / Accepted: 24 October 2014 / Published: 5 November 2014
Cited by 26 | Viewed by 2664 | PDF Full-text (1221 KB) | HTML Full-text | XML Full-text
Abstract
This paper considers the problem of indoor navigation by means of low-cost mobile devices. The required accuracy, the low reliability of low-cost sensor measurements and the typical unavailability of the GPS signal make indoor navigation a challenging problem. In this paper, a particle [...] Read more.
This paper considers the problem of indoor navigation by means of low-cost mobile devices. The required accuracy, the low reliability of low-cost sensor measurements and the typical unavailability of the GPS signal make indoor navigation a challenging problem. In this paper, a particle filtering approach is presented in order to obtain good navigation performance in an indoor environment: the proposed method is based on the integration of information provided by the inertial navigation system measurements, the radio signal strength of a standard wireless network and of the geometrical information of the building. In order to make the system as simple as possible from the user’s point of view, sensors are assumed to be uncalibrated at the beginning of the navigation, and an auto-calibration procedure of the magnetic sensor is performed to improve the system performance: the proposed calibration procedure is performed during regular user’s motion (no specific work is required). The navigation accuracy achievable with the proposed method and the results of the auto-calibration procedure are evaluated by means of a set of tests carried out in a university building. Full article
(This article belongs to the Special Issue Next Generation MEMS-Based Navigation—Systems and Applications)
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Open AccessArticle
Generation of Nanoliter Droplets on Demand at Hundred-Hz Frequencies
Micromachines 2014, 5(4), 1002-1011; https://doi.org/10.3390/mi5041002
Received: 25 August 2014 / Revised: 30 October 2014 / Accepted: 30 October 2014 / Published: 4 November 2014
Cited by 6 | Viewed by 2490 | PDF Full-text (1007 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We describe a precision micropump for generation of precisely metered micro-aliquots of liquid at high rates. The use of custom designed piezoelectric valves positioned externally to the microfluidic chip allows for on-demand formation of micro-droplets with online control of their individual volumes from [...] Read more.
We describe a precision micropump for generation of precisely metered micro-aliquots of liquid at high rates. The use of custom designed piezoelectric valves positioned externally to the microfluidic chip allows for on-demand formation of micro-droplets with online control of their individual volumes from nLs to μLs at frequencies up to 400 Hz. The system offers precision of administering volumes of 1% and of time of emission of <0.5 ms. The use of a piezoelectric actuator provides two distinct vistas for controlling the volume of the droplets—either by digital control of the “open” interval or by analogue tuning of the lumen of the valve. Fast and precise generation of droplets make this system a perfect constituent module for microfluidic high-speed combinatorial screening schemes. Full article
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Open AccessReview
Scanning Probe Microscope-Based Fluid Dispensing
Micromachines 2014, 5(4), 954-1001; https://doi.org/10.3390/mi5040954
Received: 26 July 2014 / Revised: 23 September 2014 / Accepted: 1 October 2014 / Published: 30 October 2014
Cited by 8 | Viewed by 3570 | PDF Full-text (9782 KB) | HTML Full-text | XML Full-text
Abstract
Advances in micro and nano fabrication technologies have enabled fabrication of smaller and more sensitive devices for applications not only in solid-state physics but also in medicine and biology. The demand for devices that can precisely transport material, specifically fluids are continuously increasing. [...] Read more.
Advances in micro and nano fabrication technologies have enabled fabrication of smaller and more sensitive devices for applications not only in solid-state physics but also in medicine and biology. The demand for devices that can precisely transport material, specifically fluids are continuously increasing. Therefore, integration of various technologies with numerous functionalities in one single device is important. Scanning probe microscope (SPM) is one such device that has evolved from atomic force microscope for imaging to a variety of microscopes by integrating different physical and chemical mechanisms. In this article, we review a particular class of SPM devices that are suited for fluid dispensing. We review their fabrication methods, fluid-pumping mechanisms, real-time monitoring of dispensing, physics of dispensing, and droplet characterization. Some of the examples where these probes have already been applied are also described. Finally, we conclude with an outlook and future scope for these devices where femtolitre or smaller volumes of liquid handling are needed. Full article
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Open AccessArticle
Characterization of Laser Beam Shaping Optics Based on Their Ablation Geometry of Thin Films
Micromachines 2014, 5(4), 943-953; https://doi.org/10.3390/mi5040943
Received: 9 September 2014 / Revised: 20 October 2014 / Accepted: 21 October 2014 / Published: 27 October 2014
Cited by 14 | Viewed by 4576 | PDF Full-text (3044 KB) | HTML Full-text | XML Full-text
Abstract
Thin film ablation with pulsed nanosecond lasers can benefit from the use of beam shaping optics to transform the Gaussian beam profile with a circular footprint into a Top-Hat beam profile with a rectangular footprint. In general, the quality of the transformed beam [...] Read more.
Thin film ablation with pulsed nanosecond lasers can benefit from the use of beam shaping optics to transform the Gaussian beam profile with a circular footprint into a Top-Hat beam profile with a rectangular footprint. In general, the quality of the transformed beam profile depends strongly on the beam alignment of the entire laser system. In particular, the adjustment of the beam shaping element is of upmost importance. For an appropriate alignment of the beam shaper, it is generally necessary to observe the intensity distribution near the focal position of the applied focusing optics. Systems with a low numerical aperture (NA) can commonly be qualified by means of laser beam profilers, such as a charge-coupled device (CCD) camera. However, laser systems for micromachining typically employ focus lenses with a high NA, which generate focal spot sizes of only several microns in diameter. This turns out to be a challenge for common beam profiling measurement systems and complicates the adjustment of the beam shaper strongly. In this contribution, we evaluate the quality of a Top-Hat beam profiling element and its alignment in the working area based on the ablated geometry of single pulse ablation of thin transparent conductive oxides. To determine the best achievable adjustment, we develop a quality index for rectangular laser ablation spots and investigate the influences of different alignment parameters, which can affect the intensity distribution of a Top-Hat laser beam profile. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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Open AccessReview
Electromagnetic Micromotors—Design, Fabrication and Applications
Micromachines 2014, 5(4), 929-942; https://doi.org/10.3390/mi5040929
Received: 24 September 2014 / Accepted: 20 October 2014 / Published: 24 October 2014
Cited by 6 | Viewed by 2616 | PDF Full-text (3664 KB) | HTML Full-text | XML Full-text
Abstract
Microactuators have become essential elements of microelectromechanical systems, for example, for positioning purposes and for fluid-handling tasks in microfluidic systems. UV depth lithography and other new micromachining technologies, which have been developed since the 1990s, have initiated extensive investigations of electromagnetic microactuators, which [...] Read more.
Microactuators have become essential elements of microelectromechanical systems, for example, for positioning purposes and for fluid-handling tasks in microfluidic systems. UV depth lithography and other new micromachining technologies, which have been developed since the 1990s, have initiated extensive investigations of electromagnetic microactuators, which are characterized by high forces, large deflections, low driving voltages resulting from low input impedances and robustness under harsh environments. This paper reviews the comprehensive research on the design, fabrication and application of electromagnetic micromotors performed in our laboratory over the past years. Full article
(This article belongs to the Special Issue Microactuators)
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