Search

Paper-based vanadium membraneless co-laminar flow fuel cells with graphene paste electrodes are developed to enhance the power density. The developed fuel cells are precisely microfabricated utilizing photolithography and screen printing methods for flow channel patterning and electrode forming, respectively. The measured fuel cell performances change with varying concentrations of fuel/oxidant (0.5–2.0 M V2+/VO 2 +) and a support electrolyte (0.5–4.0 M H 2 SO 4). The maximum power density (15.09 ± 1.05 mW cm−2) and maximum current density (30 ± 0.62 mA cm−2) are the highest for concentrations of 2.0 M vanadium redox couple and 2.0 M sulfuric acid. The performance of the proposed fuel cell is also affected by contact with air. Regardless of air contact, the prototype paper-based vanadium fuel cell shows higher performance than those of previously reported paper-based co-laminar flow fuel cells. This novel proof-of-concept fuel cell is important for achieving the required power density for practical use of paper-based microfluidic fuel cells. • Vanadium redox couple is proposed for both fuel and oxidant in the paper-based fuel cell. • Micromachining is used to make precise and reproducible paper-based fuel cells. • Vanadium-based fuel cell shows better performance than other fuel-based fuel cells. • Contact with air adversely affects paper-based vanadium co-laminar flow fuel cells. • The performance depends on the concentration of fuel, oxidant, and electrolyte. [ABSTRACT FROM AUTHOR]

This paper reports the performance of different tool electrode structures in micropatterning of vertically aligned carbon nanotube (CNT) forests through dry micro-electro-discharge machining (μEDM). Micro cylindrical electrodes of tungsten with flat and hemispherically rounded tips were employed in this study. The rounded-tip electrode was shaped using a custom wet μEDM process. Both types of electrodes were used to pattern arrays of micro test slots at different depths and discharge voltages on a multi-walled CNT forest from which the resultant discharge gaps were experimentally characterized. The rounded-tip electrode showed a 2.1–2.4× reduction in the discharge gap with applied voltages of 15–20 V, suggesting its potential to improve the lateral resolution of the patterning process when compared with the flat-tip case. Finite element analysis of the process configuration with these two electrodes was conducted and showed good agreement with the improvement factors of the discharge gap experimentally observed. However, the process using the rounded-tip electrode resulted in larger variations on the bottom surfaces of the created patterns, while the use of the flat-tip electrode provided higher uniformity on these surfaces, revealing an apparent trade-off relationship between the discharge gap and the patterning uniformity for the two electrode types under the tested conditions. Elemental analysis of the processed CNT forest surfaces showed no detectable contamination from the electrodes onto the forest structures patterned using either electrode. [Display omitted] • Tool geometry affects precision in microplasma machining of carbon nanotube forest. • Flat- and rounded-tip electrodes contrast in their electrostatic behavior. • Discharge gap found to be 2.1–2.4 × smaller for round tip with 15–20 V of voltage. • Round tip yields tighter tolerance while flat tip offers higher surface uniformity. • Simulation reproduces the discharge gap ratio observed between two electrodes well. [ABSTRACT FROM AUTHOR]

The lift-off process is a microfabrication technique that has the capability of forming thin film structures. However, several issues, such as structural shape and burr formation, arise when applying this method to the formation of thick film structures. Thick film structures formed through the lift-off process exhibit a mountainous cross-sectional shape and non-uniform film thickness due to variations in the width of the structure. These challenges make it difficult to apply the method to MEMS. While the reverse lift-off process addresses some of the structural shape problems, its initial development using metal molds makes it challenging to directly apply to MEMS without modification. Therefore, this paper proposes an adaptation to the Si process and presents a method to reduce burrs. The microfabrication characteristics are evaluated by comparing the cross-sectional shapes of thick metallic glass structures formed through both the lift-off and reverse lift-off processes. The structures formed through the reverse lift-off process exhibit a rectangular cross-sectional shape, and the film thickness remains consistent regardless of the structure's width. However, burrs persist on the backside edge of the structure, which hinders its application to MEMS. This paper confirms that pre-etching the underlying Si substrate into an inverse tapered shape effectively reduces burrs. As an illustration of the improved reverse lift-off process applied to MEMS, MEMS mirror structures are fabricated, and their resonance frequency closely aligns with the design value. [Display omitted] • The reverse lift-off process fabricates thick film structures, addressing shape issues in the lift-off process. • Pre-etching Si wafers into reverse tapered projection shapes solves the burr formation issue. • MEMS mirror structures with thick film metallic glass are successfully fabricated using enhanced reverse lift-off process. [ABSTRACT FROM AUTHOR]

As an established tool-based micro-machining technique, micro electrical discharge machining (μ EDM) has received widespread attention from academia and industry for its capability of producing intricate micro-scale structures and features on various difficult-to-cut materials. However, assurance of the as-built surface quality and consistency has been a challenge due to the complex interactions among machining parameters and the unpredictable variability of material properties and the discharge process. In this paper, an efficient closed-loop control methodology based on an innovative application of on-machine metrology (OMM) and in-process roughness prediction (IPRP) is proposed for automatically ensuring the μ EDM surface quality. The work takes into consideration process fundamentals related to size and distribution of craters by means of single crater experiments and pulse discrimination studies in order to analyze the influence of actual energy parameter on the evolving surface roughness. The OMM enables accurate in situ surface characterization while the IPRP, which is built on an online Bayesian regression model, allows for the prediction of surface quality according to the monitored process features. This IPRP model presents an increased predictive performance and confidence when more OMM data become available. Depending on the acquired quality outputs, a two-step quality control strategy involving energy adaptation and discharge stability regulation is implemented. This novel control strategy has proven to achieve a consistent areal surface roughness with variations smaller than 0.1 μ m for a specific material and dielectric combination in μ EDM milling. [Display omitted] [ABSTRACT FROM AUTHOR]

Despite numerous benefits, the additively manufactured (AM) parts present poor surface quality and dimensional errors, requiring semi-finishing or finishing operations. Machining of AM metals presents multiple challenges due to porosity, anisotropy, microcracks, and uneven layer thickness. This paper studies the role of porosity in the machinability of AM porous Titanium alloy (Ti6Al4V). Microendmilling experiments are conducted using the AM Ti6Al4V with four porosity levels. The machining response is analyzed in terms of machining force, chip morphology, tool wear, and machined surface finish; and compared with that of solid/continuous Ti6Al4V. A new metric has been proposed to quantify and statistically correlate the random variations in the machining force with AM part porosity. At higher porosities, tool chipping increases due to thermo-mechanical shocks as the tool encounters random pore-material boundaries. This results in microburrs and an increase in surface roughness (R a). The chip and surface morphology show pore closure phenomenon at lower porosity levels, while chip segmentation is observed at higher porosities. Overall, the findings of this research provide valuable insights into the cutting mechanism of AM porous metals. Moreover, the correlation between the machining response and the porosity-driven part quality could be instrumental in in-situ process monitoring/control of hybrid additive-subtractive processes. • Micromachining of additively manufactured (AM) porous material exhibits both interrupted cutting and deformation cutting phenomena. • The machinability of AM Ti-6Al-4V decreases with an increase in the part porosity. • The machining response of AM material is strongly correlated with the porosity-driven part quality, and could be used for in-situ process monitoring/control of hybrid additive-subtractive manufacturing processes. [ABSTRACT FROM AUTHOR]

On-machine surface measurement of micro-scale components after micromachining becomes crucial to satisfy the increasing quality requirements. It implements a seamless measurement activity without interrupting manufacturing actions and hence facilitates the closed-loop quality control inline. Chromatic confocal probe sensing is a promising technique for on-machine integration thanks to its capability of assessing the surface with high accuracy and high speed. This paper presents the development of an on-machine measuring system using a chromatic confocal sensor, integrated in a micro-electrical discharge machining (micro-EDM) machine. The effects of scanning speed are qualitatively investigated in relation to outliers and quantitatively reflected through surface height parameters. In addition, the effects of surface gradient and surface contamination upon the measurement quality are studied. Two study cases, i.e. an array of micro-dimples and a micro-gear which are drilled and milled by micro-EDM, respectively, have been implemented to evaluate the developed system and to compare with off-line commercial confocal microscope. This comparative study demonstrates the system capability for on-machine areal measurement with sub-μm accuracy and reduced inspection time of 64 %. • An on-machine chromatic confocal probe measurement (OM-CCPM) system is integrated into a micro-EDM machine tool. • The developed OM-CCPM system has a proven sub-μm accuracy for areal surface measurement and reduced inspection time of 64 %. • The on-machine measurement quality is critically evaluated under extreme conditions. [ABSTRACT FROM AUTHOR]

Control of the cross-sectional shape of micro-channels may be of interest in micro-heat-sinks, microfluidic particle sorting, and micro-machine lubrication applications. It has been previously shown that inverse methods can be used to determine the abrasive jet micromachining (AJM) traverse speed and path required to sculpt desired micro-channel topographies, as long as the aspect ratios (AR, ratio of depth to width) are low (<0.06), such that the channel sidewall slopes are negligible. However, for many applications, higher AR channels with steep sidewalls are required. This paper introduces an iterative inverse method which allows prediction of the machining procedure required to sculpt higher (AR up to 1) micro-channels of prescribed cross-sectional shape using mask-less AJM. The method is developed for AJM in both ductile and brittle erosive systems, its robustness and limitations are discussed, and the iterative methodology is compared to the General Reduced Gradient optimization technique. Part II of the paper will experimentally verify the procedure for a wide variety of desired topographies machined in borosilicate glass and Poly(methyl methacrylate) (PMMA). • Inverse algorithm predicts the machining requirements for high AR cross-sections. • Most challenging topographies are semicircles in glass and ramps in PMMA. • Machining requirements are unique, a minimum radius of curvature is required. • Inverse algorithm converges faster than GRG-nonlinear optimization. [ABSTRACT FROM AUTHOR]

To improve the sensitivity of humidity sensors, the interdigital electrode size should be paid more attention, apart from the development of high performance sensing materials. This paper investigated the interaction between testing electrode and the performance of capacitive humidity sensor. To our best knowledge, no other reported papers have investigated it before. We found that the gap size of interdigital electrode had crucial influence on the response of SnO 2 /MoS 2 based capacitive humidity sensors due to the different surface electrical conduction mechanisms. For the sensor with small gap interdigital electrode structure, the capacitance decreases exponentially as relative humidity (RH) rises so that high sensitivity is obtained at low humidity range (0%–45% RH). While the gap is wide enough, the capacitance increases exponentially as RH grows to get ultrahigh sensitivity at high humidity range (45%–90% RH). The experimental results show that the sensor with 5 μm gap have the largest sensitivity (161 μF/% RH) at low humidity range while the best sensitivity of 3170 pF/% RH is obtained at high humidity range for the sensor with gap of 100 μm. The as-prepared SnO 2 /MoS 2 hybrid sensing nanocomposite was synthesized through a two-step hydrothermal route and its morphology and structure were further characterized using field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). Moreover, the SnO 2 /MoS 2 based capacitive humidity sensors have fast response, short recovery time, little hysteresis and good repeatability. [ABSTRACT FROM AUTHOR]

Traditionally, photolithography and soft-lithography methods have been used to fabricate micro-molds for casting polymeric microfluidic chips. Because of the time and cost involved, there has been motivation to fabricate microfluidic micro-molds using other techniques. A previous study utilized stainless steel masks cut using abrasive waterjet micro-machining (AWJM) together with abrasive slurry jet micro-machining (ASJM) to mill micro-molds in Al6061 which would allow casting of polymeric microfluidic chips with intersecting micro-channels. However, the deflected slurry jet from the mask edge struck the substrate at oblique incidence and led to two undesirable effects: a trench along the edges of the raised structures representing the channels, and an undercut of the mask. Both effects were linked to the propensity for ductile materials to erode more rapidly at oblique incidence than perpendicular. The present paper demonstrates that these effects can be greatly reduced by using AWJM to create molds in more brittle materials which erode in the opposite fashion, i.e., more rapidly at perpendicular than oblique incidence. To demonstrate this, AWJM was used to machine masks from aluminum oxide and subsequently mill micro-molds with raised intersecting free-standing structures into aluminum oxide substrates. It was found that for molds of identical depth, the undercut and the undesirable erosion in aluminum oxide molds could be reduced by five and four times, respectively, when compared to molds machined in Al6061 using the previous AWJM/ASJM hybrid technique. It was also found that much deeper molds containing intersecting raised free-standing structures of up to 435 μm in height could be made in aluminum oxide, while still maintaining an acceptable surface quality (1.51 μm Ra and 2.47 μm Wa), undercut (25 μm), and undesirable erosion (3%). Finally, since the technique involved only AWJM, it was much more convenient than the previously utilized hybrid AWJM/ASJM. • AWJM used to fabricate novel micro-molds with free-standing structures in alumina. • Effect of process parameters on the surface quality and shape of the structures was studied. • Mold quality was improved compared to previous AWJM/ASJM method for metals. • Using the optimum parameters, molds were fabricated and microfluidic chips cast. [ABSTRACT FROM AUTHOR]

A method of two-step laser etching for bulk micromachining of 4H–SiC membranes through a femtosecond (fs) laser with a wavelength of 532 nm, a pulse width of 290 fs and a repetition rate of 100 kHz is present in this paper. Using a control variable method, the first step of fs-laser etching for rapid material removal and the second step of fs-laser etching mainly for improving surface morphology are studied by changing the laser fluence, scanning spacing, number of scans and scanning speed. The average surface roughness of the membrane bottom after the first step of laser etching is 691 nm, which is reduced to 237 nm after the second step. Compared with one-step laser etching, two-step laser etching obtains a better surface morphology, and it only takes 38% of the processing time of one-step laser etching. The finite element analysis shows that the sensitivity of the SiC pressure sensor drops with the decrease of the membrane roughness. The sensor sensitivity of the membrane fabricated by two-step laser etching is only 3.0% lower than that of the ideal smooth model. Furthermore, a 4H–SiC laser-prepared membrane with a diameter of 1.2 mm and a thickness of 75 μm applied in pressure sensor is tested, showing good linearity and repeatability at a load of up to 10 MPa. [ABSTRACT FROM AUTHOR]

Zerodur glass-ceramic has potential uses in many fields from aerospace to electro-optical industries due to its extremely low thermal expansion coefficient. However, being extremely hard and brittle makes it difficult to process using traditional machining methods. This paper deals with a novel hybrid technology for machining 3-D microstructures using Zerodur glass-ceramic. Based on a Semi-ductile cutting depth, experiments are conducted using different cutting modes: regular cutting, current-feedback cutting, and a current-feedback control strategy with high-frequency vibration-assistance. High-frequency vibration-assisted cutting creates extremely shallow microcracks on the surface of the glass-ceramic that facilitate the removal of material. It was also found that the designed diamond tool with a −70° rake angle and negative rake angle of abrasive-grains can produce an exceptional negative rake-angle press-cut effect helping to suppress brittle-fracturing from occurring. Experimental results show that the proposed 'high-frequency vibration-assisted cutting' mode with a 'self-controlling cutting force' can automatically adjust the tool feed-rate on-line, increasing the material removal rate and protecting the glass-ceramic against brittle-fracturing. A 3-D microstructure made of Zerodur glass-ceramic is successfully machined under semi-ductile regime cutting, confirming the feasibility of the proposed technology, and opening-up the potential for micromachining hard-brittle materials such as Zerodur glass-ceramics for commercial applications. • Semi-ductile cutting regime for efficiently machining glass-ceramic is proposed in this study. • The purposefully created nano-scale microcracked subsurface layer facilitates glass-ceramic material removal. • The 'crack blocking instinct' of Zerodur glass-ceramic prevents larger cracks from occurring. • The cutting-edge of the novel PCD end-mill tool can produce an excellent dual-press-cut effect. • A 3-D microstructure made of Zerodur glass-ceramic has been successfully machined. [ABSTRACT FROM AUTHOR]

Abrasive jet machining (AJM) is a manufacturing technology based on erosion localization and intensification. AJM has a progressively important influence on the machining technology market. Over the past 20 years, there has been an exponential growth in the number of papers that discuss AJM. Various innovations and process developments such as intermittent, submerged, thermally assisted and other jet conditions were proposed. This paper examines AJM’s technological advantages and the variety of machining operations in different industries where AJM is utilized. Particular attention is devoted to the micro-texturing capabilities of powder blasting and its application in tribology. New evidence of ductile and brittle material removal mechanisms are reviewed together with recently discovered elastic removal mode. The effects of hydraulic, abrasive and machining parameters on particles kinetic energy, machined surface roughness and footprint size are described in detail. Nozzle wear has a strong dependence on nozzle materials, its geometry, particles size, hardness, and flow rate. The trend of AJM development is a shift from macro to micro scale. Improvements in micro-machining resolution, process controlling and erosion prediction are current challenges facing AJM. [ABSTRACT FROM AUTHOR]

This paper investigates the use of air-driven abrasive jets as a lathe and as a means of machining helical patterns into rotating rods. The first part of the paper presents a model for the prediction of material removal during the machining of rotating and translating ductile (PMMA) and brittle (glass) rods using abrasive jet micromachining (AJM). The model predictions were in good agreement with the experimental measurements, showing that, for a given particle speed, the volumetric removal was only a function of the abrasive dose received by the surface, and was unaffected by the rod diameter, its rotational speed, and the axial feed speed. The second part of the paper presents a new experimental procedure for machining helical channels in glass and PMMA rods using a cylindrical steel spring as a mask. Such helical channels may have applications in microfluidic devices where they can be used to aid liquid mixing and the separation of particles from a flow. The use of spring masks at various pitches and the control of the exposure time of the jet to the workpiece made it possible to fabricate helical channels with a wide range of aspect ratios, from 0.09 to 1.2. High curvature, which is favorable in the microfluidic separation of particles, was achieved by machining rods of small diameter. In addition to microfluidic applications, the models and techniques can potentially be used to machine threads in glass and other difficult to machine materials. [ABSTRACT FROM AUTHOR]

In computer-aided manufacturing systems, generation strategies are classified into two main types according to the generation domain of the tool path: real space and the parametric domain. Although generation methods in the parametric domain defined using a parametric surface, such as a non-uniform rational B-spline surface, have the advantage of rapid calculation, tool path variations are limited because few methods using this type of tool path generation recognize features of the surface in the parametric domain. This study proposes a new algorithm for tool path generation that can generate machining points in the parametric domain without losing information about the distances among the corresponding points in real space. Using this proposed method, a tool path with a constant pitch in real space and an efficient tool path, such as a spiral path, can be rapidly calculated. This paper explains the theory behind this method and describes its implementation using free-form surfaces composed of a single patch. The proposed method was then expanded to surfaces composed of multiple patches. In this case, because correspondence between each surface patch is required, parametric boundary representation using a half-edge structure is also proposed in this paper. Parametric boundary representation can be used to represent connections among the outer and inner trimming boundaries of each surface patch on the parametric domain. Finally, the proposed method was implemented for two surfaces composed of multiple patches, and its effectiveness was confirmed by simulating and machining these surfaces. [ABSTRACT FROM AUTHOR]

The widespread use of hard turning processes in industry has been facilitated by efficient work holding methods. In this paper, a novel application of the shoe-centerless work holding method is proposed for hard turning. Since changes in cutting forces during hard turning affect force balance, rotational instability can occur with shoe-centerless work holding. This paper describes the effect of changes in cutting forces due to tool wear on work rotational stability during shoe-centerless hard turning. It also presents guidelines to determine the optimum shoe setup angles for various hard turning process conditions to ensure work rotational stability and geometrical rounding stability. [ABSTRACT FROM AUTHOR]

Gyroscopes are sensors that measure the angular rate of an rotating object along one or more coordinate axis. For measuring angular rate along all three axes, usually three different single axis gyroscopes are used. Three sensor systems imply more space and power requirements which are precious commodities in microelectronics. Single-drive tri axis gyroscopes overcome this issue. Owing to their design complications, they have not been explored to the scale of the single axis gyroscopes. In this paper we present a novel design of single drive tri-axis MEMS gyroscope with detail explanation of its working principle. Since gyroscopes are resonant sensors, the natural frequencies of drive and sense modes are expected to be as close to each other as possible to ensure maximum sensitivity. These frequencies depend on the structural dimensions of the design. A design optimization procedure using Finite Element Method (FEM) based parametric modal analysis has been suggested in order to achieve mode matching. An equivalent analytical model is also presented for drive mode and all three sense modes. The optimized design is fabricated using modified silicon on glass bulk micromachining technique. The natural frequencies in drive and sense modes of as fabricated devices were measured and compared with the numerical and analytical values, The experimental values of frequencies are well within 16% of the numerical values. A design upgrade has been suggested to further reduce this error value. • Novel design of single drive tri axis MEMS gyroscope. • Finite Element method based parametric eigenfrequency analysis to achieve mode matching. • Analytical model of novel single drive tri axis MEMS gyroscope. • Fabrication of MEMS gyroscope using silicon on glass bulk micromachining technique. [ABSTRACT FROM AUTHOR]

In this paper, a 100 GHz rectangular waveguide band-pass filter with two transmission zeros symmetrically located at both ends of pass-band is presented. The four-pole filter with two transmission zeros is composed of two dual-mode resonators with unequal width, two WR-10 standard waveguide interfaces, and three groups of round corner inductive irises in series. The filter is designed and analyzed based on the Synthesis and Simplification Theory of coupling matrix, simulated by using commercial full-wave simulation software HFSS, and fabricated using UV Lithography Technology with SU-8 photo-resist. The specifications of the filter are as follows: 100 GHz center frequency with 3.7% fractional bandwidth, the transmission zeros at frequency of 97.75 GHz and 102.75 GHz respectively to improve the out of band rejection, and return loss which is better than −18 dB across the whole pass-band. Results from measurement are in good agreement with simulations considering the inaccuracy of fabrication and measurement. Therefore, the availability of design, analysis, and fabrication methods mentioned in this paper is confirmed. [ABSTRACT FROM AUTHOR]

The natural characteristics of sintered ceramics limit the micromachining of functional surface textures in terms of tool wear, processing quality and economic effectiveness. So, the micro-machining of green ceramics before completely sintering is introduced. In this paper, micro-channels are fabricated on the surfaces of green ceramics pretreated by different annealing temperatures. The effect of parametric combination of annealing temperature and laser parameters on the response of processing quality, channel dimension and material removal rate (MRR) are studied by single fact experiments and multi-objective optimization by the response surface method (RSM). The mathematical models of the interaction between different factor combinations are developed based on RSM. Results show that the annealing temperature has significant influence on the aspect ratio under different laser parameters. Continuous channels with few recast layers are always formed at the annealing temperatures of 500–800 °C and a higher annealing temperature always contributes to a larger aspect ratio. Based on the responses of RSM, the optimal parameters of laser ablation and annealing temperature are chosen as laser power of 6 W, scanning speed of 350 mm/s, laser frequency of 40 KHz, and the pretreatment annealing temperature of 750 °C. The experiments validate good agreement of proposed model. [ABSTRACT FROM AUTHOR]

This paper reports the experimental studies and time-resolved observations of the ultrasound-assisted water-confined laser micromachining (UWLM) process on metal workpieces using 532-nm nanosecond laser pulses. UWLM is a new machining process proposed by the corresponding author (Wu, 2014). During UWLM, a laser beam interacts with a workpiece’s front surface location immersed in water to ablate the workpiece, and in-situ ultrasonic waves in water are also applied (for example, from above the front surface using an ultrasonic horn) to the laser ablation site (which energize the water and generate cavitations) to improve the machining process. This paper reports the experimental study of the UWLM process on multiple types of metal workpieces and time-resolved in-situ observations of the process. This kind of study on UWLM has been rarely reported in the literature. Under the studied conditions, it has been found that the ablation depths produced by UWLM at 200 laser pulses are about 2.3–3.8 times the depths by laser ablation in water without ultrasound. Through in-situ time-resolved shadowgraph imaging observations, it has been found that one important likely underlying mechanism for the enhanced material removal rate in the studied UWLM process is that the in-situ ultrasound in UWLM can reduce the material cloud resulted from the previous laser pulse ablation that lingers around laser ablation site, which can enhance the coupling of the subsequent laser pulse(s)’ energy to the workpiece. [ABSTRACT FROM AUTHOR]

This paper reviews recent progress and applications of nanofluids in machining processes. In addition to reviewing the various conventional and advanced cooling techniques during machining, the paper also discusses the preparation methods, factors for enhancing thermal conductivity and properties of nanofluids. In line with fast development of nanofluid in machining process, the purpose of this paper is to review recent progress on the application of nanoparticles in lubricants especially for MQL technique. The conclusions and important summaries were also presented according to the data collected. [ABSTRACT FROM AUTHOR]

This paper discusses the fabrication, assembly, and testing of a single-stage and a two-stage micro gas compressor cascaded in series to demonstrate the effectiveness of a multistage serial configuration with the utilization of piezoelectric unimorph diaphragms and passive microvalves. Gas compression is enabled with the large stroke volume from the diaphragm resonance frequency of ∼4.5–5.8 kHz, generating pressure rise for the single and multistage microcompressors. The microcompressors consist of passive micro check valves fabricated with SU-8 using MEMS microfabrication method and a piezo disc integrated to the CNC micromachined housings. The microcompressor pressure-flow performance curves and its performance based on the dependent parameters such as the voltage and the drive frequency are presented in this paper. The single-stage and the two-stage microcompressors operate at a low max voltage of 60 Vpp and at the resonance of the piezo diaphragm to achieve maximum pressure rise. From experimental result, maximum pressure rise of 10 kPa and a maximum flow rate of 32 standard cubic cm per min (sccm) were achieved from the single-stage device. The two-stage microcompressor showed improvement over the single-stage by generating a maximum pressure rise of 18 kPa and maintained the same maximum flow rate of 32 sccm. This was achieved with each stage operating independently at the diaphragm resonance. Additionally, we provided test results of the microvalve pressure-flow curve and test characterization of the unimorph piezo disc. [ABSTRACT FROM AUTHOR]

The accurate, high-throughput fabrication of light weight optical systems for applications like next-generation space telescopes and semiconductor wafers is both crucial and challenging. A potential solution is to first fabricate thin substrates with traditional methods, then apply surface stress to bend them into desired shapes to correct residual height errors. We have developed a stress-based figure correction method for thin silicon mirrors using a femtosecond laser micromachining technique to generate patterned stress fields, through the removal of selective stressed film regions and adjacent substrate regions. In this paper, we present an in-depth analysis for the laser-induced stresses and resulting shape changes of thin mirrors due to the periodic patterning of a stressed film (silicon oxide) on silicon substrates using femtosecond laser surface ablation. Experimental results are presented, and a 3D finite element model (FEM) is developed to study the substrate curvature in directions parallel and perpendicular to the patterned troughs in the substrates. We simulate the stress relief process in the thin-film/substrate system, and the numerical predictions compare reasonably well with curvature measurements for several different geometrical combinations of depth, width and spacing of the patterned troughs, achieving > 82 % quantitative agreement with the experiments. It is also shown in the simulations that certain geometries of patterned troughs induce more dramatic shape changes and counter-intuitive reversals of curvature in the direction perpendicular to the troughs, and a qualitative explanation involving the Poisson effect is presented. The 3D finite element methods and findings of this paper can be used to determine the optimal parameters of the stressed film patterns for figure correction of thin telescope mirrors and other types of thin substrates used in the semiconductor industry. • Micromachined stressed film for thin optic figure correction using femtosecond laser. • Selectively removed stressed film regions and adjacent silicon substrate regions. • Periodic hole patterns create equibiaxial stress. • Periodic trough patterns lead to non-equibiaxial stress. • 3D FEM Abaqus model predicts deformation from patterned troughs more accurately. • Micromachining into substrate releases additional stress due to edge effects. [ABSTRACT FROM AUTHOR]

In recent years there has been increasing interest in the use of structured surfaces to provide specific functional performance. Such surfaces often consist of localised micro-scale surface features with predetermined geometries. The performance of the feature manufacturing process affects the functional performance of the surface, and can be assessed by measurement of the resulting surface features. Measurement of the resulting micro-manufactured surface features necessitates use of areal optical surface topography instruments. However, conventional characterisation methods, based on areal surface texture parameters, often prove inadequate, and may fail to capture the relevant geometric properties needed for an effective dimensional verification. This paper investigates an alternative route to verification, based on the determination of geometric attributes of the micro-fabricated features. This approach allows for direct assessment of manufacturing process performance, by comparison of the geometric attributes with their nominal values. An example application is shown in which a micromachining process (laser texturing) is used to fabricate a periodic pattern of dimples, which provide a low friction bearing surface. In this paper, manufacturing process performance is assessed by characterisation of the diameter and out-of-roundness. Sources of uncertainty associated with these geometric parameters are also considered. [ABSTRACT FROM AUTHOR]

[Display omitted] Laser induced plasma micro-machining (LIPMM) has proved its superiority in micro-machining of hard and brittle materials due to less thermal defects, smaller heat affected zone and larger aspect ratio compared to conventional laser ablation. In order to improve characteristics and stability of induced plasma, this paper proposed magnetically controlled LIPMM (MC-LIPMM) to achieve a good performance of processing single-crystal silicon which is widely used in solid state electronics and infrared optical applications. A comprehensive study on surface integrity and geometrical shape was conducted based on the experimental method. Firstly, the mechanism of MC-LIPMM including laser-plasma, laser-materials interactions and transport effects was theoretically analyzed. Then a series of experiments was conducted to completely investigate the effect of magnetic field intensity, pulse repetition frequency, and bubble behavior on surface integrity and geometrical shape of micro channels. It revealed that magnetic field contributed to maximum reduction of 12.64% for heat affected zone and 62.57% for width while maximum increase of 26.23% for depth and 90.26% for aspect ratio. This research confirms that MC-LIPMM can improve the machining characteristics of silicon materials and cavitation bubbles shows an apparently negative impact on the surface morphology. [ABSTRACT FROM AUTHOR]

• - A new accelerometer is designed for highest possible sensitivity using a novel surface micromachining approach. • - A modified topology optimization methodology is developed and implemented to maximize sensitivity of the desired MEMS accelerometer for landslide monitoring. • - Despite of traditional topology optimization approaches, a range of variable inertial forces considered in designing this new MEMS accelerometer. • - In addition, as another novel modification in topology optimization algorithm, the performance and manufacturing constraints are inherently applied into the optimization process. • - In order to control cross-sensitivity, as another unique approach the sensitive vibration mode was recognized and was kept in the sensing direction by preventing the mode switch. • - The design of this novel MEMS accelerometer is fully fabricated and tested for performance to confirm the efficiency of the design. MEMS accelerometers capable of detecting weak motions are required in measuring landslide movements. The sensor's sensitivity and its independent readings of various acceleration modes are crucial factors in the design of these sensors. In addition, it is highly desired to fabricate these sensors with low-cost and flexible manufacturing technologies such as surface micromachining. This paper presents an advanced topology optimization approach to design the suspended structure for the maximum level of sensitivity and for a low cross-sensitivity in the reading of principal and lateral modes, while it is manufacturable with a low-cost surface micromachining process. The effect of inertial forces as a variable loading condition and mode switch prevention is applied using a meta -heuristic topology optimization method with simulated annealing. Considering the unique results of this topology optimization, PolyMUMPs surface micromachining is employed to manufacture the developed sensor. The fabricated sensor is subjected to measurement and subsequent comparison with analogous designs from the literature. The outcomes reveal a sensitivity of 0. 3 pF/g and cross-axis sensitivity of 0. 048%, signifying a noteworthy advancement for surface micromachined accelerometers. Notably, this design, coupled with the devised topology optimization methodology, holds the potential for adoption by sensor manufacturers for diverse commercial applications. [ABSTRACT FROM AUTHOR]

• A bulk-micromachined MEMS resonant differential pressures sensor is developed. • The sensor output was theoretically modeled to instruct the design of the sensitive element. • A novel silicon-based stress isolation structure was designed and fabricated to improve the stability of sensor. • The process based on Au-Au bonding and Au/Sn welding were employed to package the sensor. • The developed sensor demonstrated high accuracy and stability. This paper presents the design method and manufacture of a new resonant differential pressure sensor where the sensitive element is assembled with packaging components through an embedded boss type stress isolation structure. The responses of differential pressure, temperature and static pressure are theoretically modeled, which provide guidance on sensor design. And a method based on finite-element is used to conduct dimensional optimization of sensitive elements and embedded boss type stress isolation structures based on device sensitivities and isolation effect. Fabrication based on bulk micromachining and packaging based on Au-Au bonding and Au/Sn welding are employed to manufacture the sensor. Experimental results indicate that the fabricated sensor yields a high differential pressure sensitivity of − 87.06 Hz/kPa, a low temperature sensitivity of 5.24 Hz/°C and a low static pressure sensitivity of − 0.48 Hz/kPa. Additionally, a high accuracy of 0.05 %FS is reported under full scale. Furthermore, the sensor demonstrates an excellent long-term stability with no decrease on accuracy within a 15-day experiment. [ABSTRACT FROM AUTHOR]

[Display omitted] • We introduce an innovative approach to electrochemical micromachining using a Two-tone sinusoidal signal and investigate the mechanism behind the reduced machining gap with this signal. • Using the Taguchi optimization method, we study the impact of the control variables on the micromachining process during micro-hole drilling, and results show that using the optimized parameters greatly enhanced processing accuracy. • We use this technology to machine the microstructures on 5-μm pure nickel sheet and hard-to-cut super alloy plates, and improve the machining accuracy to the nanometer level. Electrochemical micromachining is an emerging technology in the machining field. This method offers several advantages such as exceptional surface quality, minimal cathode depletion, and a high elimination rate. Often, an ultrashort pulse power supply is employed in electrochemical micromachining to address over-machining in non-processing areas. While reducing the pulse duration can enhance processing accuracy, its high cost and impracticality for regular production limit its development. This paper presents the use of a Two-tone sinusoidal signal as an alternative to ultrashort pulse in electrochemical micromachining. We investigated the mechanism behind the reduced machining gap with this signal. By drilling micro-holes in the nickel sheet to optimize parameters such as voltage, fundamental frequency, and harmonic order. Using the Taguchi optimization method, we studied the impact of these control variables on the micromachining process during micro-hole drilling. The study also focused on fabricating micro-structures using the best processing parameters. Our results showed that using the optimized parameters greatly enhanced processing accuracy. Moreover, we found that high machining accuracy could be achieved when working on hard-to-cut super alloy plates. [ABSTRACT FROM AUTHOR]

Cross sectional shape and centerline waviness along the length of a micro-channel can affect different characteristics of microfluidic flow, including heat transfer, pressure distribution and dissipation, and separation of flow. Current existing technologies that allow such micro-machining have many limitations. The accompanying paper presented inverse techniques that can be used to predict the required non-uniform velocity to gradient etch, using abrasive jet micro-machining (AJM), micro-channels and pockets with a wide variety of prescribed textures and cross-sectional shapes. Methods to predict the final three-dimensional (3D) profiles of such features were also presented. In this paper, the velocity functions predicted using the inverse methods were used to machine micro-channels with prescribed centerline depths that varied linearly, parabolically and sinusoidally, pockets with prescribed textures in two directions, and micro-channels with prescribed W-shaped cross sections. Two different erosive efficacy sources were used, one resulting from an adjustable shadow mask and one using a maskless technique. The inverse and 3D shape prediction techniques were verified by comparing the measured feature topographies with those that were initially prescribed. The effect of process parameters such as source shape and the machined feature size on the accuracy of machined features and predictions of the models were also discussed. Overall, the inverse techniques were found to be very effective for predicting the process parameters required to machine a wide variety of desired micro-channel and pocket topographies. [ABSTRACT FROM AUTHOR]

Ultrasonic vibration cutting is an efficient cutting process for mechanical micro-machining. This process can generate intricate surface textures with different geometric characteristics. Micro-grooves/micro-channels are among the most frequently encountered micro-structures and, as such, are the focus of this paper. The effectiveness of both the linear and ultrasonic elliptical vibration-assisted machining technique in micro-groove turning is analyzed and discussed in the paper. The paper first investigates the mechanisms of micro-groove generation induced by the linear and elliptical vibration modes. A simplified cutting force analysis method is given to compare the effectiveness of the two modes in micro-groove turning. The surface roughness of the generated micro-grooves is analyzed next and theoretical expressions are given for the two cases. Finally, micro-groove turning experiments are conducted to compare the influences of the two vibration modes on the cutting forces and the surface roughness. The experimental results show that linear vibration-assisted micro-groove turning leads to better surface roughness as compared to the elliptical vibration-assisted case, while elliptical vibration-assisted micro-groove turning shows advantages in terms of decreasing the cutting forces. [ABSTRACT FROM AUTHOR]

This paper presents a multi-orientation error separation technique to remove the artifact form error from the radial measurements to obtain the radial spindle error motions of miniature ultra-high-speed (UHS) spindles. Unlike the existing approaches, the present technique neither relies on high-accuracy fixtures, nor necessitates measurements from specific orientations of the artifact. Rather, the spindle error motions are measured from a set of arbitrary artifact orientations using laser Doppler vibrometry (LDV). The angle of each artifact-setup orientation with respect to the spindle is determined with high precision through reflectivity measurement of the marks made on both the artifact and the spindle using another LDV. Although the presented approach can be applied by using different sensors (e.g., capacitance probes), we demonstrate the approach using LDVs. With the displacement measurement direction fixed, measurements are conducted from both LDVs for multiple orientations of the artifact. Using the unique implementation scheme developed in this paper, data from these orientations are post-processed to compute the artifact form error and further remove it from the radial motion measurements to obtain the synchronous radial spindle error motions. A thorough experimental evaluation is presented to quantify both the repeatability of the measured artifact form errors as well as the bandwidth of error separation for various number of artifact orientations. The spindle error motions measured from both the sphere and stem portions of a custom fabricated sphere-on-stem artifact mounted on a typical miniature UHS spindle, are seen to be similar in shape and within 5 nm in magnitude across the revolution, thus demonstrating the effectiveness of the technique. Using this technique, spindle error motions at ultra-high speeds up to 150 krpm were successfully quantified. Although the implementation scheme is demonstrated for miniature UHS spindles, it is readily applicable for error separation on macro-scale spindles without the need for any high-precision fixtures and precise setting of angles. [ABSTRACT FROM AUTHOR]

Cutting tool wear is inevitable and becomes even more critical in micromachining processes, due to the small size of the microtools, which makes it impossible to detect any damage or break in the microtool without the use of high magnification microscopy. Therefore, monitoring the wear conditions of microtools is essential to guarantee the quality of the surfaces generated by micromachining processes. Even with the use of sensors, because of the complexity and similarity of the signals, identifying changes related to variation in wear is not a simple task. To overcome these problems, this paper presents a new approach to monitor the wear of cutting tools used in the micromilling process using SVM (Support Vector Machine) artificial intelligence model, vibration and sound signals. The signals were acquired for microchannels manufactured using carbide microtools coated with (Al, Ti) N, with a cutting diameter of 400 μm. The input features for the model were selected using the RFE method (Recursive Feature Elimination). In addition to the main objective, the behavior of the wear curve of the microtool in relation to the wear curve of the conventional machining process was studied. The results showed that the behavior of the curves were similar and the microtool with shorter cutting length had a longer life. The proposed classification methodology obtained a classification accuracy of up to 97.54%, showing that it is possible to use it to monitor the cutting tool wear. • A new approach has been developed to monitor the wear of microtools based on SVM, vibration, and sound signals. • Signal analyzes in the time and frequency domain showed no differences in the wear conditions of the microtools. • The wear of the microtools is similar to the wear of the macrotools. • The new approach used in the methodology obtained a classification accuracy of up to 97.54%. [ABSTRACT FROM AUTHOR]

Turbine blade cores are made of porous alumina ceramic and determine the molding accuracy of the cavity of turbine blades, which strongly affect thermal diffusion performance and service life of turbine engines. To get a high quality ceramic core, accurate trimming for a preliminarily processed core is needed and therefore, micromachining porous alumina ceramic, which differs from general alumina substrates, is crucial. This paper dealt with a processing technology for the special material via double femtosecond laser scanning. The materials ablation threshold was firstly determined through parameter fitting and then this material was machined at a combination of different laser processing parameters. Considering the produced debris blocks the lasers further propagation into the material, double femtosecond laser scanning was newly proposed and experimentally verified with the comparison of gas jet assist and underwater laser processing ways. The removal profiles of the machined material were characterized in terms of cutting width, cutting depth, deviation of linearity and surface morphology, which exhibited high dependence on the femtosecond laser processing parameters. The optimal laser operating window was identified and high quality laser cutting of the porous alumina ceramic was demonstrated. The developed processing technology has potential application in trimming for ceramic casting cores. In addition, it might also give a novel view for high quality laser micromachining another materials. [ABSTRACT FROM AUTHOR]

Electrochemical discharge machining (ECDM) is an emerging method suitable for the micromachining of nonconductive materials such as glass. ECDM is a hybrid process in which material removal involves both chemical and thermal mechanisms. Various process parameters affect the performance of ECDM. Improper ECDM working conditions may lead to undesirable surface damages in glass machining. This paper investigates the methods to mitigate surface wrinkle formation caused by the chemical mechanism and surface cracks caused by the thermal mechanism in the ECDM machining of borosilicate glass. ECDM in an acidic environment was found to avoid surface wrinkling caused by chemical etching in glass machining. Moreover, both thermal and chemical damages are mitigated when ECDM was performed with a mixed electrolyte. [ABSTRACT FROM AUTHOR]

High-quality pure-nickel microstructures, which are characterized with multiple superior machining indicators, including machining homogeneity, machining surface roughness, and machining round edge, are now highly anticipated in the field of micromachines and microsystems. However, according to the published studies, a gap remains in achieving high-quality machining. In this paper, wire electrochemical micromachining (WECMM) is proposed for machining high-quality pure-nickel microstructures focusing on different machining indicators. The appropriate electrolyte is selected by combining analysis of the electrochemical characteristics and machining experiments involving microslits of pure nickel. In contrast with previous studies that usually focused on the machining homogeneity or machining surface roughness of the machining results, the effects of several critical machining parameters on the machining homogeneity, machining surface roughness, and machining rounded edge are studied comprehensively, and the relative results for different machining indicators are also revealed. Finally, the combinations of process parameters for manufacturing high-quality pure-nickel microstructures focusing on different machining indicators are identified, and corresponding high-quality pure-nickel microstructures are fabricated. • The appropriate electrolyte is selected by combining analysis of electrochemical characteristics and machining experiments. • The influence with several critical parameters on different machining indicators are discussed. • High-quality pure-nickel microstructures focusing on different machining indicators can be fabricated using WECMM. [ABSTRACT FROM AUTHOR]

Several hybrid laser machining processes have been proposed in recent years to eliminate and/or prevent the deposition of material debris, formation of recast layer and thermal damage in the laser-ablated region. Laser micromachining process performing in an ice layer is a novel technique which is of potential to limit these negative effects in work materials. In this paper, the thermal modeling of the laser ablation in ice is presented to advance the understanding of heat transfer and cut formation induced by the process. A nanosecond-pulse laser was used in this study for grooving a single-crystalline silicon wafer shielded by an ice layer. A 3D numerical simulation associated with the finite element method was performed and then verified by a set of experiments. Phase changes, plasma shielding effect and energy losses caused by thermal conduction and convection were also included in the model. The simulation results obtained under the different levels of laser power were found to have a good agreement with the experiments. The evolution of temperature field and cut formation in the workpiece can be realized at the different heating and cooling cycles of the pulsed laser irradiation. The model developed in this study could facilitate the design and optimization of the ice-assisted laser micromachining process to further advance the ablation of thermally sensitive materials in manufacturing. [ABSTRACT FROM AUTHOR]

This paper discusses the design of a micromachined regenerator in an Active Magnetic Regenerative Refrigeration (AMRR) system for space applications. The AMRR system is designed to provide continuous remote/distributed cooling at about 2K and reject heat at temperatures of about 15K. This paper first discusses the general thermal and fluid performance requirements for an AMRR regenerator, a unique structured bed configuration that enables the regenerator to meet these requirements, and its thermal and fluid performance based on numerical analyses. The paper then discusses the general design consideration for the magnetic field driving the regenerator for optimal thermal performance, and the analysis processes to optimize the variation rate of the magnetic field in an actual superconducting magnet during the isothermal processes of the AMRR cycle to enhance the performance of an actual regenerator. The paper finally presents the thermal performance of the regenerator from such iterative design optimization processes. [ABSTRACT FROM AUTHOR]

Abstract: High performance ceramic-reinforced metal matrix composites (MMCs) are becoming widely popular in industry and the mechanical machining method is one of the most suitable manufacturing techniques for near net shape MMC components. This paper provides a comprehensive literature review to enhance the fundamental understanding of the tool–workpiece interactions in micro-scale during cutting process on engineered-heterogeneous materials. The paper focuses on mechanical properties, fracture mechanism and machinability of ceramic-reinforced MMCs, with significant emphasis on the chip formation mechanism considering different dominant effects, such as materials strengthening mechanisms, micro-structural effect, size effect and minimum chip thickness effect. It also includes some work that, while not directly focused on micro-scale cutting ceramic-reinforced MMCs, but provided important insight to the field of cutting engineered-heterogeneous materials (non-eutectic). Furthermore, process modeling studies for micro-scale cutting are also surveyed, including the cutting force modeling, dynamics modeling and surface generation modeling. The comments on future needs and directions are provided at the end. [Copyright &y& Elsevier]

Abstract: End Milling operations have been developed in response to productivity, quality and economical cost concerns. Significant advancements in controls and machining technologies have recently come together to enable the wide spread use of this operation. The main objective of this work is to develop a new procedure for predicting the metal cutting forces and coefficients during machining. The new technique proposed in this paper was found to be more flexible and easier to use than other available techniques. Experimental validation of the proposed procedure was carried out with the help of regression analysis using MINITAB-16 software. The present paper discusses a response surface methodological approach for prediction of metal cutting coefficients in an end-milling operation of an Aluminum alloy. In this work, an approach was used to develop mathematical model based on RSM design for predicting the metal cutting forces and coefficients in an end milling operation. Different machining conditions like cutting speed, feed rate, and axial depth of cut are considered. The first order cutting force equations are developed using the response surface methodology (RSM) to study the effect of input metal cutting parameters such as spindle speed, feed rate and axial depth of cut at 50% radial immersion on metal cutting forces and It has been observed the decrease of cutting speed along with the increase in the feed rate, axial depths of cut results in higher metal cutting forces. The differences between experimental and metal cutting forces obtained from the mathematical modeling using regression analysis at different feed rate, spindle speed, depth of cuts are presented. From the experimental results, metal cutting coefficients were determined with and without the influence of magneto rheological damping to the end milling tool. It has been observed from the experimental data that the metal cutting forces are less when compared to the forces obtained without the application of the magneto-rheological damper. The cutting parameter which affects the cutting force and their interaction are investigated in this study with and without the effect of Magneto-rheological damping. The regression models in this study are believed to produce values for metal cutting coefficients close to readings recorded experimentally with a 95% confident level. [Copyright &y& Elsevier]

• Need of hybrid micromachining. • Laser-based hybrid micromachining process classifications. • Hybrid micromachining principles and setup. • Current scenario of hybrid machining setup development. • Future scope to develop hybrid micromachining processes. Laser beam micromachining is a prominent method for micromachining applications. But it has some drawbacks like thermal stresses, uncontrolled dimensions, burrs, and spatter. Similarly, non-conventional processes like ECM, EDM, and conventional machining processes, namely turning, drilling and milling, also have limitations due to slow process and tooling costs. Researchers are continuously seeking hybrid machining, like laser-based hybrid machining methods, to improve the product's quality characteristics. Researchers have thoroughly investigated the laser-based hybrid process mechanism in the last decade and have identified different issues and control strategies to improve its performance. This paper reviews laser-based hybrid micromachining processes (LHMMP) in which LBM is combined with conventional processes and non-conventional processes in an assisted or sequential manner. Also, other energy sources assisting the laser beam machining process, viz. vibration, magnetic field, electric field, fluids, and gases, are reviewed in the current work. This paper summarizes the work performed on metals, non-metals and ceramics in the area of the LHMMP to create 3D micro features. Theoretical and experimental studies, mechanisms of machining, machining setups, and the impact of process parameters on laser-based hybrid micromachining techniques are reviewed in detail. The hybrid processes elevate the process efficiency, surface quality, tooling cost and precision of fabricated parts. In the last section of this paper, future development efforts needed in this area of laser-based hybrid machining are suggested to multiply the process utility. [ABSTRACT FROM AUTHOR]

• A low-pass filter has been designed using periodic self-similar coplanar waveguide. • The filter is used in large integrated or hybrid circuits without require wire bonding. • The paper gives the MEMS surface fabrication processing of the filter. • The MEMS switch has relatively lower driven voltag with 26 V. This paper presents a low-pass filter based on microelectromechanical system using periodic self-similar coplanar waveguide. The device is fabricated on 525-μm high-resistivity silicon substrate using surface micromachining process which partial compatible process with IC. The tunable resonant frequency is achieved using micro-electromechanical contact capacitive switches. The total area of the filter is about 6 mm2 including bias lines and pads. The parameters of the filter has been analyzed by applying the Ansoft-HFSS. When switch is on original state, the measured results of the filter show that the 3-dB cutoff frequency is 16.15 GHz with the average insertion loss of 0.95 dB. The 3 dB cut-off frequency of the reconfigurable filters is 22.85 GHz with the average insertion loss of 2.33 dB. A relatively lower driven voltage is around 26 V. [ABSTRACT FROM AUTHOR]

Abstract: The introduction of microvia and surface mount technologies into the manufacturing process for printed circuit boards (PCBs) has significantly improved the interconnection density. However, as the speed of signals for data communication on the board approaches and begins to exceed 10Gb/s, the loss and crosstalk of copper interconnections increase. To resolve these problems, optical interconnections (OI) have been suggested as a viable solution. Literature reports have proved the photochemical nature of excimer laser ablation with its minimal thermal effect, and other ultra-violet lasers are also being investigated for the fabrication of polymer waveguides by laser ablation. In this paper, the authors demonstrate the fabrication of multimode optical polymer waveguides by using infra-red 10.6μm CO2 laser micromachining to etch acrylate-based photopolymer (Truemode™). CO2 lasers offer a low cost and high speed fabrication route as CO2 lasers can be used to cut through various engineering materials including polymers and metals. The paper characterises the relationship between the laser ablation power, the fabrication speed and the resulting effect on the waveguide optical insertion loss for the first time. [Copyright &y& Elsevier]

Abstract: This paper presents the static characterization of the bulk micromachined quad beam accelerometer structure using a nanoindenter as a loading tool. The paper reveals how a nanoindenter, an instrument designed to measure mechanical properties of the films or objects, can be used in a non-traditional fashion to characterize MEMS accelerometer structure. The stiffness and breaking load of the mechanical structures of this device were experimentally measured and compared with the predictions based on FEM simulations. [Copyright &y& Elsevier]

Abstract: In this paper, a novel electrochemical micro-machining method is proposed to fabricate a tungsten micro-rod with a high aspect ratio. In this method, the periphery of the iron needle is surrounded by an insulator so that only its end face with the diameter of 50μm is exposed on the electrolyte as the cathode of the tool electrode. A tungsten rod with a diameter of 200μm is taken as the workpiece and the anode. These two electrodes are immersed to a depth of 3mm in the electrolyte of 2wt% sodium hydroxide. This small end face of the tool electrode is against the workpiece in vertically reciprocating motion with a certain stroke to conduct the electrochemical micro-machining under DC electric field. During the machining, since the diameter of the workpiece is gradually reduced, the tool electrode is adjusted so that the gap between its end face and the anode remains 30μm. The effects of supply voltage or current, rotational speed and stroke of workpiece, and relative position between the end faces of electrodes on the geometry of one end of the workpiece are investigated. This relative position can be used to control the workpiece geometry at one end and its amount of the length reduction. When this relative position is adjusted to a preset position at each stroke, the ratio of the length to the diameter can be increased, but the average decreasing rate in diameter remains invariable. The novel method developed in this paper can fabricate an extremely thin straight rod in diameter of 2μm with an aspect ratio of 120 from a tungsten rod with a diameter of 200μm using a tool electrode with an end diameter of 50μm under two-stage procedure. [Copyright &y& Elsevier]

Abstract: This paper reports the design, fabrication, and performance of miniature micromachined high frequency PMN-PT/epoxy 1–3 composite ultrasonic annular arrays. The PMN-PT single crystal 1–3 composites were made with micromachining techniques. The area of a single crystal pillar was 9×9μm. The width of the kerf among pillars was ∼5μm and the kerfs were filled with a polymer. The composite thickness was 25μm. A six-element annular transducer of equal element area of 0.2mm2 with 16μm kerf widths between annuli was produced. The aperture size the array transducer is about 1.5mm in diameter. A novel electrical interconnection strategy for high density array elements was implemented. After the transducer was attached to the electric connection board and packaged, the array transducer was tested in a pulse/echo arrangement, whereby the center frequency, bandwidth, two-way insertion loss (IL), and cross talk between adjacent elements were measured for each annulus. The center frequency was 50MHz and −6dB bandwidth was 90%. The average insertion loss was 19.5dB at 50MHz and the crosstalk between adjacent elements was about −35dB. The micromachining techniques described in this paper are promising for the fabrication of other types of high frequency transducers, e.g. 1D and 2D arrays. [Copyright &y& Elsevier]

Abstract Recently, ultrafast laser-material interaction has become a research focus. This paper experimentally investigated multiple-pulse drilling on titanium alloy in picosecond laser processing. Ablation morphology, quality and feature sizes of drilled craters were investigated under different laser fluences and pulse numbers. Laser parameter experiments, SEM characterization and 3D profile measurement were performed to obtain the characteristics of drilled craters. Then, the relationship between laser fluence, pulse number and feature sizes was determined. Besides, the ablation mechanism, material removal rate for single pulse and ablation threshold of picosecond pulse laser on titanium alloy were analyzed. This research contributes to the theory and practice of titanium alloy micromachining with picosecond laser, which suggests that the craters with specific size and high material removal rate can be obtained. [ABSTRACT FROM AUTHOR]

Abstract This paper presents an experimental analysis on micromachining of green-state silicon carbide (SiC) and aluminum nitride (AlN) using uncoated tungsten carbide (WC) micro-endmills. Although the unique properties of ceramics make them ideal materials for many applications involving micro-scale features, the industrial adaptation of ceramics at the micro-scale has been hindered due to the lack of viable ceramic micro-manufacturing techniques. Green micromachining (GMM), where micro-scale features are created by micromachining green-state ceramics that contain ceramic particles and a polymer binder, offers a potential solution for this problem by affording tremendous improvements in micromachinability with respect to sintered ceramics. After the completion of GMM, the green parts are debound and sintered to obtain the final component with the desired micro-scale features. In this work, we evaluated GMM characteristics of powder-injection molded green-state SiC and AlN to correlate process conditions and green-material compositions with the micromachining forces, quality, and tool wear. An experimental study that involves full immersion micromilling tests with 254 μm diameter micro-endmills at different cutting speeds and feed rates is conducted. For each of the two materials, two binder states (with and without wax) and two powder states (with micro particles only, or with both micro- and nano-particles) are investigated. Green micromachining forces, specific energies and the resulting surface roughness are analyzed quantitatively. A qualitative analysis of burr formation and channel quality, as well as a preliminary study on micro-tool wear are also performed. Both the machining conditions and the material compositions are seen to have a strong effect on micromachinability of green-state ceramics. Overall, we conclude that GMM can be a viable ceramic micro-manufacturing strategy if favorable (or optimal) micromachining and material parameters are identified through the presented (or a similar) micromachinability study. [ABSTRACT FROM AUTHOR]

Abstract A silicon-compatible laser source is of utmost importance for a successful photonic integrated circuit. The conventional solution using direct band gap III-V materials adds significant complexity into the fabrication process because the active materials have to be bonded or grown on a largely mismatched silicon substrate. Recently, germanium has been considered a promising material for silicon photonic applications due to its interesting electronic band structure. Several concepts to realise a direct band gap Ge-based material will be reviewed in this paper, such as: tensile strain combined with high n-type doping, high tensile strain created by micromachining, synthesis of Ge-Sn alloys by chemical vapour deposition and, in particular, synthesis of Ge-Sn alloys by ion implantation followed by pulsed laser melting (PLM). Besides providing a very high level of reproducibility and purity in conventional device fabrication, ion implantation followed by PLM is shown to have potential for realising an intrinsically direct band gap material of high quality. Producing a 10 at. % Sn alloy is now possible and a highly strain-relaxed layer can also be realised by this technique. [ABSTRACT FROM AUTHOR]

Abstract Single-layered gold nano-hole arrays lead to extraordinary optical transmission (EOT)-modulated surface plasmonic resonance (SPR) and have seen much progress in biochemical sensing. To further improve the sensing performance, the single-layered structure need to be changed. In this paper, a micromachined Fabry-Perot interferometer (µFPI), featuring two parallel and flat gold-coated mirrors, one of which has sub-wavelength nano-hole arrays, was designed, fabricated, and tested experimentally. Its transmission spectrum was confirmed to have EOT-modulated SPR patterns, and its characteristic peak wavelength was found to have a refractive index sensitivity of 593 nm / RIU and a Q factor up to 128.4, which is 10.2 times its EOT counterparts. By applying AC electric signals across the two gold layers, dielectrophoresis (DEP) induced near the nano-holes was proven to enrich particles significantly. To remove the thermal effects on the transmission spectrum, heat was dissipated by flowing sample during measurement. Biochemical sensing experiments were conducted using BSA protein medium of different low concentrations, demonstrating the detection sensitivity enhancement of ~ 6-fold for 1 pM compared to 100 pM. This novel µFPI presents a new paradigm in EOT-based SPR sensing technology by combining the benefits of µFPI interference, EOT near-field measurement and DEP enrichment of molecules. Highlights • Micro-Fabry-Perot interferometer featuring sub-wavelength nano-holes in one mirror. • High refractive index sensitivity (593 nm/RIU). • Q factor (128.4), 10.2 times its extraordinary optical transmission counterparts. • Dielectrophoresis-enhanced detection sensitivity and assay time by ~ 6-fold. • Thermal effects were removed simply by flowing sample continually in interferometer. [ABSTRACT FROM AUTHOR]

Highlights • A novel single-edge tool micro-cutting process is proposed. • A hybrid machine-tool has been developed for the new process. • The interaction between the micro-cutting process and the structure is analysed. • A machining strategy is developed to obtain the feasibility of the process. • A new micro-cutting model is developed and tested. Abstract This paper presents a novel micro machining process as an alternative to other micro machining processes like micro milling. Its main advantage is the simplicity of the cutting tool geometry compared to other complex micro tools. The basis of this process consists of keeping the cutting tool always tangent to its trajectory. To achieve this goal, an innovative 6 degree-of-freedom parallel machine tool with high stiffness and with the tool tip precisely positioned, has been designed and built. The new machine is based on a hybrid device composed of three PRS (prismatic-revolution-spherical) parallel mechanisms with a linear XY stage and a C rotational axis. In order to determine the cutting load on the machine and consequently, its deformation, a resultant cutting tool force model has been developed which considers all the angles of the cutting process. A machining strategy has also been developed which takes into account the tool geometry and the kinematic restrictions of the machine tool. As a result of the kinematic and dynamic modelling of the machine, it has been possible to establish the level of precision for a given machining strategy. From the tests carried out, it is shown that the proposed machining process combined with the parallel machine tool, is an alternative to micro milling technology. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract With the recent rise of laser additive manufacturing (AM), it has become critical to streamline the process from concept to the finished component. In this paper we demonstrate novel capabilities achieved through post-processing of the laser AM part by femtosecond laser micromachining. For the first time, we show surface roughness values can be reduced by a factor of five in an efficient single pass process, nanogratings can be written into the surface for encoding numerical information, and finally, the surface as printed (SAP) can be altered to produce micro-cone structures which can change surface wetting properties. [ABSTRACT FROM AUTHOR]