Previous studies have shown that metallic coatings can be successfully cold sprayed (CS) onto several polymer substrates. However, the electrical performance of the cold-sprayed polymers is not generally enough to utilize them as an electronic device. In this study, an environment-friendly metallization technique has been proposed to achieve highly electrically conductive metal patterns onto polymer substrates using cold spray deposition and subsequent electroless copper plating (ECP). Copper feedstock powder was CS onto the surface of the acrylonitrile-butadiene-styrene (ABS) parts. The as-CS powders then served as the activating agent for the selective ECP to modify the surface of the polymers to be electrically conductive. A series of characterizations were conducted to investigate the morphology, analyze the surface chemistry, evaluate the electrical performance, mechanical adhesion, and mechanical strength performance of the fabricated coatings. Moreover, simple electrical circuits were presented for the ABS parts through the described method. Findings demonstrated that low-pressure cold spray copper deposition followed by the ECP processes could be used as an environmental-friendly manufacturing method of electrically conductive patterns on ABS polymer.

Graphene has attracted enormous research interest due to its extraordinary material properties. Process control to achieve high-quality graphene is indispensable for graphene-based applications. This research investigates the effects of process parameters on graphene quality in a low-pressure chemical vapor deposition (LPCVD) graphene growth process. A fractional factorial design of experiment is conducted to provide understanding on not only the main effect of process parameters, but also the interaction effect among them. Graphene quality including the number of layers and grain size is analyzed. To achieve monolayer graphene with large grain size, a condition with low CH 4 –H 2 ratio, short growth time, high growth pressure, high growth temperature, and slow cooling rate is recommended. This study considers a large set of process parameters with their interaction effects and provides guidelines to optimize graphene growth via LPCVD focusing on the number of graphene layers and the grain size.

In microsheet metal forming, the lengths of the contact zones between blank and die are important parameters to describe the contact behavior, but they can hardly be detected experimentally. Thus, a finite element simulation enables access to these zones and especially, their length. This length and its development during a metal forming process are analyzed in this work to establish its efficient measurement method. The part at the die called drawing edge is defined as a deformable body with material properties. Since every node of such a body can report pressure, the contact length is the product of the number of n – 1 nodes under contact pressure with the equidistant distance of l E = 1 μ m between each node. It is shown, that with this method the direct determination of the contact zones position and length is enabled. Additionally, the simulative results show that the contact length is influenced by the geometrical conditions of the punch and die.

Higher temperature assisted processing of silicon, such as heat-assisted diamond turning, is often being considered to improve surface integrity. At higher temperatures and under mechanical loading and unloading, caused by a moving tool, silicon deforms plastically often in association with occurrence of phase transformations. This paper investigates such phase transformations in rotational scratching of single crystal (100) p-type silicon with a conical diamond tool under various furnace-controlled temperatures ranging from room temperature (RT) to 500 °C and at scratching speeds comparable to that used in the diamond turning process (1 m/s). Phase transformation study, using Raman spectroscopy, at various crystal orientations, shows differences in phases formed at various temperatures when compared to that reported in indentation. The tendency to form phases is compared between scratched and diamond turned surfaces at RT, and also with that reported at low scratching speeds in the literature. Analytical indenting-based pressure calculations show that at higher temperatures, phase transformations can happen in silicon at significantly lower pressures. Analysis of depths of the scratched groove indicates that at temperatures beyond a certain threshold, plastic deformation and significant elastic recovery may be causing shallow grooves. Abrasive wear coefficients are thus seen to decrease with the increase in temperatures. This study is expected to help tune heat-assisted diamond turning conditions to improve surface formation.

The micro/nanotextured cemented carbide surface of different wettability was produced by laser scanning and fluorinated treatment. The tribological properties of the untextured, oleophobic and oleophilic micro/nanotextured surface were investigated experimentally including the effects of crank speed and contact pressure by a reciprocating friction and a wear tester. For all tested surfaces, the friction coefficient of the surface decreased as both the increasing crank speed and contact pressure increased. Compared to the untextured surface, the friction coefficient of the micro/nanotextured surface was significantly decreased, being sensitive to the wettability of the surface. Besides, the tribological properties of the oleophobic micro/nanotextured surface were superior to the oleophilic micro/nanotextured surface under the same experimental conditions. The improvement in tribological properties of the oleophobic micro/nanotextured surface could be attributed to the low wettability, which was beneficial to rapid accumulation of the lubricating oil on the surface.

A computational model to investigate the flushing of electric discharge machining (EDM) debris from the interelectrode gap during the spray-EDM process is developed. Spray-EDM differs from conventional EDM in that an atomized dielectric spray is used to generate a thin film that penetrates the interelectrode gap. The debris flushing in spray-EDM is investigated by developing models for three processes, viz., dielectric spray formation, film formation, and debris flushing. The range of spray system parameters including gas pressure and impingement angle that ensure formation of dielectric film on the surface is identified followed by the determination of dielectric film thickness and velocity. The debris flushing in conventional EDM with stationary dielectric and spray-EDM processes is then compared. It is observed that the dielectric film thickness and velocity play a significant role in removing the debris particles from the machining region. The model is used to determine the spray conditions that result in enhanced debris flushing with spray-EDM.

Vacuum venting is a method proposed to improve feature replication in microparts that are fabricated using micro-injection molding (MIM). A qualitative and quantitative study has been carried out to investigate the effect of vacuum venting on the nano/microfeature replication in MIM. Anodized aluminum oxide (AAO) containing nanofeatures and a bulk metallic glass (BMG) tool mold containing microfeatures were used as mold inserts. The effect of vacuum pressure at constant vacuum time, and of vacuum time at constant vacuum pressure on the replication of these features is investigated. It is found that vacuum venting qualitatively enhances the nanoscale feature definition as well as increases the area of feature replication. In the quantitative study, higher aspect ratio (AR) features can be replicated more effectively using vacuum venting. Increasing both vacuum pressure and vacuum time are found to improve the depth of replication, with the vacuum pressure having more influence. Feature orientation and final sample shape could affect the absolute depth of replication of a particular feature within the sample.

This paper reports on design, fabrication, and characterization of a microfilter to be used in biomedical applications. The microfilter, with mesh of 80 μ m, is fabricated by micro-injection molding process in polymeric material (polyoxymethylene (POM)) using a steel mold manufactured by micro-electrical discharge machining process. The characteristics of the filter are investigated by numerical simulation in order to define a suitable geometry for micro-injection molding. Then, different process configurations of parameters (melt temperature, injection velocity, mold temperature, holding pressure and time, cooling time, pressure limit) are tested in order to obtain the complete part filling via micro-injection molding process preventing any defects. Finally, the component is dimensionally characterized and the process parameters optimized to obtain the maximum filtration capacity.

In an effort to provide insights into the thermochemical composition of a microwave plasma chemical vapor deposition (MPCVD) reactor, the mole fraction of H 2 is measured at various positions in the plasma sheath, at pressures of 10 and 30 Torr, and at plasma powers ranging from 300 to 700 W. A technique is developed by comparing the Q(1) 01 transition of experimental and theoretical spectra aided by the Sandia CARSFT fitting routine. Results reveal that the mole fraction of H 2 does not vary significantly from its theoretical mixture at the parametric conditions examined. Furthermore, the ν ″ = 1 → ν ′ = 2 vibrational hot band was searched, but no transitions were found. An analytical explanation for the increase in the temperature of H 2 with the introduction of N 2 and CH 4 is also presented. Finally, because the mole fraction of H 2 does not appear to deviate from the theoretical composition, the rotational and translational modes of H 2 are shown to be approximately in equilibrium, and therefore, the rotational temperatures may be used to estimate the translational temperatures of H 2 .

One of the challenges in making layered metal composites reinforced at interfaces has been controlling the dispersion and microstructure of the reinforcement particles. The reinforcement elements are typically applied at the interface by manual spreading using brush or by immersing the substrate in a suspension. In this study, an ultrasonic spraying technique has been used to deposit silicon carbide (SiC) nanoparticles on aluminum 6061 (Al6061) substrate foils to fabricate a laminate metal composite to control the deposited structure. The suspension parameters and the spraying parameters were investigated, and their influence on the deposited microstructure was analyzed. The laminate composite was consolidated using hot compaction, and a three-point bend test was performed to evaluate the mechanical properties. The yield and ultimate flexural strengths of the laminate composite reinforced with SiC nanoparticles increased by 32% and 15%, respectively, compared with those of the unreinforced sample prepared at the same condition.

Mass-production of microfluidic devices is important for biomedical applications in which disposable devices are widely used. Injection molding is a well-known process for the production of devices on a mass scale at low-cost. In this study, the injection molding process is adapted for the fabrication of a microfluidic device with a single microchannel. To increase the product quality, high-precision mechanical machining is utilized for the manufacturing of the mold of the microfluidic device. A conventional injection molding machine is implemented in the process. Injection molding was performed at different mold temperatures. The warpage of the injected pieces was characterized by measuring the part deformation. The effect of the mold temperature on the quality of the final device was assessed in terms of the part deformation and bonding quality. From the experimental results, one-to-one correspondence between the warpage and the bonding quality of the molded pieces was observed. It was found that as the warpage of the pieces decreases, the bonding quality increases. A maximum point for the breaking pressure of the bonding and the minimum point for the warpage were found at the same mold temperature. This mold temperature was named as the optimum temperature for the designed microfluidic device. It was observed that the produced microfluidic devices at the mold temperature of 45 °C were able to withstand pressures up to 74 bar.

Pure titanium is an ideal material for biomedical implant applications for its superior biocompatibility, but it lacks of the mechanical strength required in these applications compared with titanium alloys. This research is concerned with an innovative laser peening-based material process to improve the mechanical strength and cell attachment property of pure titanium in biomedical applications. Evidence has shown that engineered surface with unsmooth topologies will contribute to the osteoblast differentiation in human mesenchymal pre-osteoblastic cells, which is helpful to avoid long-term peri-abutment inflammation issues for the dental implant therapy with transcutaneous devices. However, surface quality is difficult to control or mechanical strength is not enhanced using conventional approaches. In this paper, a novel high energy pulse laser peening (HEPLP) process is proposed to both improve the mechanical strength and introduce a micropattern into the biomedical implant material of a commercially pure Titanium (cpTi). The strong shock wave generated by HEPLP presses a stainless steel grid, used as a stamp, on cpTi foils to imprint a micropattern. To understand the basic science during the process, the HEPLP induced shock wave pressure profile and history are modeled by a multiphysics hydrodynamic numerical analysis. The micropatterns and strength enhancement are then simulated using a dislocation density-based finite element (FE) framework. Finally, cell culture tests are conducted to investigate the biomedical performance of the patterned surface.

The advancement of micro tube hydroforming (THF) technology has been hindered by, among others, the lack of robust microdie systems that could facilitate hydroforming of complex parts that require both expansion and feeding. This paper proposes a new micro-THF die assembly that is based on floating a microdie-assembly in a pressurized chamber. The fluid pressure inside the chamber which surrounds the dies and punches is the same as the pressure required to hydroform the tube. The fluid pressure intensity in the chamber varies in accordance with the predetermined pressure loading path required to successfully hydroform the part. The system was built, and hydroforming experiments were carried out for various micro- and meso-scale shapes, including bulge-shapes, Y-shapes, and T-shapes.

Rotational temperature profiles of H2 in a microwave plasma chemical vapor deposition (MPCVD) reactor were measured via coherent anti-Stokes Raman scattering (CARS) spectroscopy. The temperature was found to increase with reactor pressure, plasma generator power, and distance from the deposition surface. At 10 Torr, the measured temperature range was approximately 700–1200 K while at 30 Torr it was 1200–2000 K under the conditions studied. The introduction of CH4 and N2 to the plasma increased the rotational temperature consistently. These findings will aid in understanding the function of the chemical composition and reactions in the plasma environment of these reactors which, to date, remains obscure.

Micro-injection moulding is becoming increasingly important among the available processes for production of micro-electromechanical systems (MEMS) and microsystem technologies (MSTs), and higher number of polymer products is being manufactured by this process. Due to the sensitive nature of applications of this process, such as medical and aerospace applications, achieving high quality parts with high dimensional accuracy is crucial. In this work, a design of experiment (DoE) approach is used. The aim is to study the effects of three process parameters which are commonly used for research in this domain, on the dimensional accuracy of microchannels with different sizes; they are injection velocity, injection pressure, and melt temperature. The study focuses on two polymers, polyoxymethylene (POM) and liquid crystal polymer (LCP). Experimental results showed that higher melt temperature and injection pressure resulted in higher dimensional accuracy. Nevertheless, high settings for the three parameters resulted in higher percentage of flash in most cases. In conclusion, the most influential factors were shown to be melt temperature and injection pressure.

In order to improve the tribological properties of thermomechanically highly stressed surfaces such as cylinder liners, microdimples are produced by fly-cutting kinematics along the functional surface. The structures are used to hold back lubricant but also to increase the hydrodynamic pressure, which is built up between the sliding friction partners. For that, machining strategies for the pattern generation in cylindrical components are developed as well as a mathematical model of the microdimple arrangement and distribution. The tribological performance of the machined microdimples is analyzed by means of ring-on-disk experiments. At low sliding speeds the friction coefficient can be decreased clearly by microdimples. This indicates the potential for low-speed or reciprocating tribosystems like cylinder liners. This potential is quantified by motor driven experiments and the comparison between structured and nonstructured cylinder liners. A honed (fine) liner with additional microdimples along the interstice area shows friction losses up to 19% compared to standard honed nonstructured cylinder liner.