Editorial

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Open AccessEditorial

Micro/Nano Manufacturing

by Guido Tosello

Micromachines 2017, 8(10), 297; https://doi.org/10.3390/mi8100297 - 02 Oct 2017

Cited by 1 | Viewed by 3265

Micro- and nano-scale manufacturing has been the subject of an increasing amount of interest and research effort worldwide in both academia and industry over the past 10 years.[...] Full article

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

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8606 KiB

Open AccessArticle

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

by Emanuele Cannella, Emil Krabbe Nielsen and Alessandro Stolfi

Micromachines 2017, 8(7), 214; https://doi.org/10.3390/mi8070214 - 06 Jul 2017

Cited by 9 | Viewed by 5742

Abstract

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

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

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

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6021 KiB

Open AccessArticle

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

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

Micromachines 2017, 8(6), 195; https://doi.org/10.3390/mi8060195 - 21 Jun 2017

Cited by 15 | Viewed by 4611

Abstract

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

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

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

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

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

Micromachines 2017, 8(6), 187; https://doi.org/10.3390/mi8060187 - 16 Jun 2017

Cited by 45 | Viewed by 8240

Abstract

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

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

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Fabrication of Functional Plastic Parts Using Nanostructured Steel Mold Inserts

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

Micromachines 2017, 8(6), 179; https://doi.org/10.3390/mi8060179 - 06 Jun 2017

Cited by 6 | Viewed by 6059

Abstract

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

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

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1987 KiB

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Slurry Injection Schemes on the Extent of Slurry Mixing and Availability during Chemical Mechanical Planarization

by Matthew Bahr, Yasa Sampurno, Ruochen Han and Ara Philipossian

Micromachines 2017, 8(6), 170; https://doi.org/10.3390/mi8060170 - 29 May 2017

Cited by 7 | Viewed by 5581

Abstract

In this study, slurry availability and the extent of the slurry mixing (i.e., among fresh slurry, spent slurry, and residual rinse-water) were varied via three different injection schemes. An ultraviolet enhanced fluorescence technique was employed to qualitatively indicate slurry availability and its flow [...] Read more.

In this study, slurry availability and the extent of the slurry mixing (i.e., among fresh slurry, spent slurry, and residual rinse-water) were varied via three different injection schemes. An ultraviolet enhanced fluorescence technique was employed to qualitatively indicate slurry availability and its flow on the pad during polishing. This study investigated standard pad center area slurry application and a slurry injection system (SIS) that covered only the outer half of the wafer track. Results indicated that the radial position of slurry injection and the alteration of fluid mechanics by the SIS played important roles in slurry mixing characteristics and availability atop the pad. Removal rates were found to decrease with slurry availability, while a higher degree of slurry mixing decreased the fraction of fresh slurry and consequently lowered the removal rate. By using a hybrid system (i.e., a combination of slurry injection via SIS and standard pad center slurry application), the polishing process benefited from higher slurry availability and higher fraction of fresh slurry than the conventional pad center slurry application and the shorter SIS, individually. This work underscores the importance of optimum slurry injection geometry and flow for obtaining a more cost-effective and environmentally benign chemical mechanical planarization process. Full article

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

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12694 KiB

Open AccessArticle

Handling in the Production of Wire-Based Linked Micro Parts

by Philipp Wilhelmi, Christian Schenck and Bernd Kuhfuss

Micromachines 2017, 8(6), 169; https://doi.org/10.3390/mi8060169 - 25 May 2017

Cited by 3 | Viewed by 4358

Abstract

For simplified processing and the enhancement of output rate in multi-stage production, micro parts are handled as linked parts. This contribution discusses handling specific challenges in production based on an exemplary process chain. The examined linked parts consist of spherical elements linked by [...] Read more.

For simplified processing and the enhancement of output rate in multi-stage production, micro parts are handled as linked parts. This contribution discusses handling specific challenges in production based on an exemplary process chain. The examined linked parts consist of spherical elements linked by wire material. Hence, the diameter varies between the wire and part. Nevertheless, the linked parts must be handled accurately. The feed system is an important component too, but special focus is given to the guides in this present study. They must adapt to the diameters of both the parts and the linking wires. Two alternative variants of adaptive guides are presented and investigated under the aspects of precise radial guiding, vibration isolation, damping behavior and friction force. Full article

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

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4213 KiB

Open AccessArticle

Low Temperature Plasma Nitriding of Inner Surfaces in Stainless Steel Mini-/Micro-Pipes and Nozzles

by Tatsuhiko Aizawa and Kenji Wasa

Micromachines 2017, 8(5), 157; https://doi.org/10.3390/mi8050157 - 13 May 2017

Cited by 11 | Viewed by 4222

Abstract

Metallic miniature products have been highlighted as mini-/micro-structural components working as a precise mechanism, in dispensing systems, and in medical operations. In particular, the essential mechanical parts such as pipes and nozzles have strength and hardness sufficient for ejecting viscous liquids, solders, and [...] Read more.

Metallic miniature products have been highlighted as mini-/micro-structural components working as a precise mechanism, in dispensing systems, and in medical operations. In particular, the essential mechanical parts such as pipes and nozzles have strength and hardness sufficient for ejecting viscous liquids, solders, and particles. A low-temperature plasma nitriding process was proposed as a surface treatment to improve the engineering durability of stainless steel mini-/micro-pipes and nozzles. Various analyses were performed to describe the inner nitriding process only, from the inner surface of pipes and nozzles to their depth in thickness. AISI316 pipes and AISI316/AISI304 nozzle specimens were used to demonstrate by plasma nitriding for 14.4 ks at 693 K that their inner surfaces had a hardness higher than 800 HV. Full article

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

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14338 KiB

Open AccessArticle

Development of Novel Platform to Predict the Mechanical Damage of a Miniature Mobile Haptic Actuator

by Byungjoo Choi, Jiwoon Kwon, Yongho Jeon and Moon Gu Lee

Micromachines 2017, 8(5), 156; https://doi.org/10.3390/mi8050156 - 13 May 2017

Cited by 4 | Viewed by 4326

Abstract

Impact characterization of a linear resonant actuator (LRA) is studied experimentally by a newly-developed drop tester, which can control various experimental uncertainties, such as rotational moment, air resistance, secondary impact, and so on. The feasibility of this test apparatus was verified by a [...] Read more.

Impact characterization of a linear resonant actuator (LRA) is studied experimentally by a newly-developed drop tester, which can control various experimental uncertainties, such as rotational moment, air resistance, secondary impact, and so on. The feasibility of this test apparatus was verified by a comparison with a free fall test. By utilizing a high-speed camera and measuring the vibrational displacement of the spring material, the impact behavior was captured and the damping ratio of the system was defined. Based on the above processes, a finite element model was established and the experimental and analytical results were successfully correlated. Finally, the damage of the system from impact loading can be expected by the developed model and, as a result, this research can improve the impact reliability of the LRA. Full article

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

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1858 KiB

Open AccessArticle

Rapid Fabrication of Disposable Micromixing Arrays Using Xurography and Laser Ablation

by J. Israel Martínez-López, H.A. Betancourt, Erika García-López, Ciro A. Rodriguez and Hector R. Siller

Micromachines 2017, 8(5), 144; https://doi.org/10.3390/mi8050144 - 04 May 2017

Cited by 14 | Viewed by 4939

Abstract

We assessed xurography and laser ablation for the manufacture of passive micromixers arrays to explore the scalability of unconventional manufacture technologies that could be implemented under the restrictions of the Point of Care for developing countries. In this work, we present a novel [...] Read more.

We assessed xurography and laser ablation for the manufacture of passive micromixers arrays to explore the scalability of unconventional manufacture technologies that could be implemented under the restrictions of the Point of Care for developing countries. In this work, we present a novel split-and-recombine (SAR) array design adapted for interfacing standardized dispensing (handheld micropipette) and sampling (microplate reader) equipment. The design was patterned and sealed from A4 sized vinyl sheets (polyvinyl chloride), employing low-cost disposable materials. Manufacture was evaluated measuring the dimensional error with stereoscopic and confocal microscopy. The micromixing efficiency was estimated using a machine vision system for passive driven infusion provided by micropippetting samples of dye and water. It was possible to employ rapid fabrication based on xurography to develop a four channel asymmetric split-and-recombine (ASAR) micromixer with mixing efficiencies ranging from 43% to 65%. Full article

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

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20731 KiB

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Fabrication of Mesoscale Channel by Scanning Micro Electrochemical Flow Cell (SMEFC)

by Cheng Guo, Jun Qian and Dominiek Reynaerts

Micromachines 2017, 8(5), 143; https://doi.org/10.3390/mi8050143 - 04 May 2017

Cited by 18 | Viewed by 5677

Abstract

A unique micro electrochemical machining (ECM) method based on a scanning micro electrochemical flow cell (SMEFC), in which the electrolyte is confined beneath the tool electrode instead of spreading on the workpiece surface, has been developed and its feasibility for fabricating mesoscale channels [...] Read more.

A unique micro electrochemical machining (ECM) method based on a scanning micro electrochemical flow cell (SMEFC), in which the electrolyte is confined beneath the tool electrode instead of spreading on the workpiece surface, has been developed and its feasibility for fabricating mesoscale channels has been investigated. The effects of the surface conditions, the applied current, the feed rate, the concentration of the electrolyte and several geometrical parameters on the machining performance have been investigated through a series of experiments. The cross-sectional profile of the channels, the roughness of the channel bottom, the width and depth of the channel, the microstructures on the machined surface and the morphologies of the moving droplet have been analyzed and compared under different machining conditions. Furthermore, experiments with different overlaps of the electrolyte droplet traces have also been conducted, in which the SMEFC acts as a “milling tool”. The influences of the electrode offset distance (EOD), the current and the feed rate on the machining performance have also been examined through the comparison of the corresponding cross-sectional profiles and microstructures. The results indicate that, in addition to machining individual channels, the SMEFC system is also capable of generating shallow cavities with a suitable superimposed motion of the tool electrode. Full article

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

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9374 KiB

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Ultrasonic-Assisted Incremental Microforming of Thin Shell Pyramids of Metallic Foil

by Toshiyuki Obikawa and Mamoru Hayashi

Micromachines 2017, 8(5), 142; https://doi.org/10.3390/mi8050142 - 03 May 2017

Cited by 17 | Viewed by 5139

Abstract

Single point incremental forming is used for rapid prototyping of sheet metal parts. This forming technology was applied to the fabrication of thin shell micropyramids of aluminum, stainless steel, and titanium foils. A single point tool used had a tip radius of 0.1 [...] Read more.

Single point incremental forming is used for rapid prototyping of sheet metal parts. This forming technology was applied to the fabrication of thin shell micropyramids of aluminum, stainless steel, and titanium foils. A single point tool used had a tip radius of 0.1 mm or 0.01 mm. An ultrasonic spindle with axial vibration was implemented for improving the shape accuracy of micropyramids formed on 5–12 micrometers-thick aluminum, stainless steel, and titanium foils. The formability was also investigated by comparing the forming limits of micropyramids of aluminum foil formed with and without ultrasonic vibration. The shapes of pyramids incrementally formed were truncated pyramids, twisted pyramids, stepwise pyramids, and star pyramids about 1 mm in size. A much smaller truncated pyramid was formed only for titanium foil for qualitative investigation of the size reduction on forming accuracy. It was found that the ultrasonic vibration improved the shape accuracy of the formed pyramids. In addition, laser heating increased the forming limit of aluminum foil and it is more effective when both the ultrasonic vibration and laser heating are applied. Full article

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

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5330 KiB

Open AccessArticle

Modeling of the Effect of Process Variations on a Micromachined Doubly-Clamped Beam

by Lili Gao, Zai-Fa Zhou and Qing-An Huang

Micromachines 2017, 8(3), 81; https://doi.org/10.3390/mi8030081 - 05 Mar 2017

Cited by 5 | Viewed by 4850

Abstract

In the fabrication of micro-electro-mechanical systems (MEMS) devices, manufacturing process variations are usually involved. For these devices sensitive to process variations such as doubly-clamped beams, mismatches between designs and final products will exist. As a result, it underlies yield problems and will be [...] Read more.

In the fabrication of micro-electro-mechanical systems (MEMS) devices, manufacturing process variations are usually involved. For these devices sensitive to process variations such as doubly-clamped beams, mismatches between designs and final products will exist. As a result, it underlies yield problems and will be determined by design parameter ranges and distribution functions. Topographical changes constitute process variations, such as inclination, over-etching, and undulating sidewalls in the Bosch process. In this paper, analytical models are first developed for MEMS doubly-clamped beams, concerning the mentioned geometrical variations. Then, finite-element (FE) analysis is performed to provide a guidance for model verifications. It is found that results predicted by the models agree with those of FE analysis. Assigning process variations, predictions for performance as well as yield can be made directly from the analytical models, by means of probabilistic analysis. In this paper, the footing effect is found to have a more profound effect on the resonant frequency of doubly-clamped beams during the Bosch process. As the confining process has a variation of 10.0%, the yield will have a reduction of 77.3% consequently. Under these circumstances, the prediction approaches can be utilized to guide the further MEMS device designs. Full article

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

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Open AccessFeature PaperArticle

The Effects of Profile Errors of Microlens Surfaces on Laser Beam Homogenization

by Axiu Cao, Hui Pang, Jiazhou Wang, Man Zhang, Jian Chen, Lifang Shi, Qiling Deng and Song Hu

Micromachines 2017, 8(2), 50; https://doi.org/10.3390/mi8020050 - 13 Feb 2017

Cited by 10 | Viewed by 4403

Abstract

Microlens arrays (MLAs) are key optical components in laser beam homogenization. However, due to imperfect surface profiles resulting from microfabrication, the functionalities of MLAs in beam modulation could be compromised to some extent. In order to address this issue, the effects of surface [...] Read more.

Microlens arrays (MLAs) are key optical components in laser beam homogenization. However, due to imperfect surface profiles resulting from microfabrication, the functionalities of MLAs in beam modulation could be compromised to some extent. In order to address this issue, the effects of surface profile mismatches between ideal and fabricated MLAs on beam homogenization were analyzed. Four types of surface profile errors of MLAs were modeled theoretically and numerical simulations were conducted to quantitatively estimate the effects of these profile errors on beam homogenization. In addition, experiments were conducted to validate the simulation results, revealing that profile errors leading to optical deviations located on the apex of microlenses affected beam homogenization less than deviations located further away from it. This study can provide references for the further applications of MLAs in beam homogenization. Full article

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

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