A simple method for producing freestanding 3D microstructures by integrated photomask micromolding

In a deep-learning-based algorithm, generative adversarial networks can generate images similar to an input. Using this algorithm, an artificial three-dimensional (3D) microstructure can be reproduced from two-dimensional images. Although the generated 3D microstructure has a similar appearance, its reproducibility should be examined for practical applications. This study used an automated serial sectioning technique to compare the 3D microstructures of two dual-phase steels generated from three orthogonal surface images with their corresponding observed 3D microstructures. The mechanical behaviors were examined using the finite element analysis method for the representative volume element, in which finite element models of microstructures were directly constructed from the 3D voxel data using a voxel coarsening approach. The macroscopic material responses of the generated microstructures captured the anisotropy caused by the microscopic morphology. However, these responses did not quantitatively align with those of the observed microstructures owing to inaccuracies in reproducing the volume fraction of the ferrite/martensite phase. Additionally, the generation algorithm struggled to replicate the microscopic morphology, particularly in cases with a low volume fraction of the martensite phase where the martensite connectivity was not discernible from the input images. The results demonstrate the limitations of the generation algorithm and the necessity for 3D observations.

A scanning tunneling microscope-based multi-axis measuring system is specially developed for the on-machine measurement of three-dimensional (3D) microstructures, to address the quality control difficulty with the traditional off-line measurement process. A typical 3D microstructure of the curved compound eye was diamond-machined by the slow slide servo technique, and then the whole surface was on-machine scanned three-dimensionally based on the tip-tracking strategy by utilizing a spindle, two linear motion stages, and an additional rotary stage. The machined surface profile and its shape deviation were accurately measured on-machine. The distortion of imaged ommatidia on the curved substrate was distinctively evaluated based on the characterized points extracted from the measured surface. Furthermore, the machining errors were investigated in connection with the on-machine measured surface and its characteristic parameters. Through experiments, the proposed measurement system is demonstrated to feature versatile on-machine measurement of 3D microstructures with a curved substrate, which is highly meaningful for quality control in the fabrication field.

Three-dimensional (3D) microstructures are fabricated in negative photoresist SU-8 through two-photon polymerization by direct laser writing using a femtosecond pulse laser. The influence of beam power and baking conditions on the obtained structures is investigated. X-ray photoelectron spectroscopy is used to characterize the crosslinking of SU-8 photoresist after two-photon polymerization. The baking time for prebaking at 65 °C and that for soft baking at 95 °C before laser irradiation are investigated. These conditions are significantly related to the migration of photoacid produced upon laser irradiation. 3D woodpiles, helixes, cylinders, jungle gyms, and double cubic structures are fabricated by controlling the micron scale movement in the X, Y, and Z-axis direction. With a small elevation angle, the overlap of helical lines induces the cylindrical wall structure. Double cubic structures are fabricated: small cubic structure inside the outer large cubic structure.

Reconstruction of three-dimensional heterogeneous media from a single two-dimensional section via co-occurrence correlation function

ABSTRACTThe scalable storage of renewable energy by means of converting water to hydrogen fuels electrochemically hinges on fundamental improvements in catalytic materials. However, many applications exist where an extended lifetime is virtually crucial for their functionality and success, e.g. in case of limited accessibility such as tire pressure sensors or biomedical implants. For these kinds of applications, the ultimate power supply should be a self-renewing energy source. This strategy is pursued by the concept of Micro Energy Harvesting (MEH). Within a MEH system a micro generator converts ambient energy to electrical energy for driving an application. Unfortunately, it is not ensured that the ambient energy level will maintain always high enough to provide sufficient power to the system as harvested energy usually manifests itself in rather irregular, random and low-energy bursts. One appealing form of integrated energy storage is the use of H2/air, a so called fuel cell type (FC) battery. Such devices promise very high volumetric energy densities of more than 2000 Wh/l. Consequently, this type of battery has recently attracted more and more attention and primary as well as secondary cells have been realized. Alkaline polymer electrolyte fuel cells have been recognized as the most promising solution in order to overcome the dependency on noble metal catalysts. Nevertheless, further improvements for these kinds of fuel cells have to be reached with respect to high power. Therefore, one promising approach is to increase the skin surface of porous chromium decorated nickel electrodes for enhancement of exchange current density by forming three-dimensional (3D) microstructures directly into the electrode. Therefore, a novel laser structuring process was applied using ultrashort laser pulses. Ultrashort laser processing of complex multimaterial systems for energy storage allow for precise material removal without changing the material properties. By applying this novel laser-based structuring technique, 3D microstructures could be formed permitting shortened diffusion lengths between the electrolyte and the electrode surface being necessary for increased exchange current densities.

The effect of compound fields of ultrasonic vibration and applied pressure (UV+AP) on three-dimensional (3D) microstructure and tensile properties of recycled Al-Cu-Mn-Fe-Si alloys was systematically studied using conventional two-dimensional (2D) microscopy, synchrotron X-ray tomography, and tensile test. The properties of UV+AP treated alloys with the pouring temperature of 740, 710 and 680 °C were compared when those alloys achieved after gravity casting. After UV+AP treatment, the alloy with pouring temperature of 710 °C show the smallest grain size. Also, the sizes of Fe-rich phases and Al2Cu are greatly reduced and their 3D morphologies are compacted. The mechanical properties of UV+AP treated alloys are relatively higher than those measured for gravity cast equivalents. This improvement can be explained by the synergistic effect of acoustic cavitation, acoustic streaming, and force-feeding, which resulted in the dendrite fragmentation, uniform solute distribution, and microstructural refinement. The Orowan strengthening and solution strengthening were identified as the main strengthening mechanisms.

The generation of three-dimensional (3D) microstructures with multiple constituents is an important part of multiscale computational simulation and design for a wide range of materials including heterogeneous polycrystalline metals, ceramics, composites, and energetics. Realistic 3D microstructures for multiphase materials are difficult to obtain experimentally or computationally. Challenges include generation and representation of complex constituent morphologies, topological arrangement and distribution, defect description, and statistical conformity. Here, we present a novel technique for systematically composing complex 3D statistically equivalent microstructure sample sets (SEMSS) with prescribed statistical constituents and morphological attributes. Based on large libraries of varying representations of individual constituents, the technique can be used with experimental micro computerized tomography (CT) scans to establish SEMSS that track the attributes of existing materials as well as to design SEMSS for new materials not yet in existence for computational exploration. Heterogeneous systems involving different combinations of molecular crystallites, metallic particles, oxidizer granules, and a polymeric matrix are designed and generated to track the properties of an existing material. The corresponding SEMSS are used in multiphysics simulations accounting for coupled thermal–mechanical processes or thermal–mechanical-chemically reactive processes. The results are used to quantify microstructure-induced response variations and point out the limitations of two-dimensional (2D) microstructures that are direct sections of the full 3D microstructures. The use of the SEMSS has also enabled uncertainty quantification (UQ) and the development of probabilistic characterizations for variations in macroscopic responses due to intrinsic material microstructural heterogeneities.

Three-dimensional (3D) microstructures have various applications in many fields due to their unique physical properties. Manufacturing 3D microstructures with precise micron-scale features is difficult. Although the assembly of two-dimensional (2D) structures is a smart way to construct complex 3D microstructures, the way to assemble those 2D structures precisely is still immature. One key issue is that alignment errors often occur during the assembly process, affecting the architecture accuracy of the assembled 3D structures. In this paper, we propose a method to eliminate the alignment error during the self-assembly process only by lateral fluid force. Theoretical analysis has been conducted to demonstrate how alignment errors in the assembly channel are automatically corrected, during which a force perpendicular to the flow direction is generated by the channel’s local spatial asymmetry to automatically correct those alignment errors. Besides, the movement of microstructures in the channel has been numerically simulated, whose results were consistent with the theoretical analysis, and there was indeed a lateral force that causes the self-aligning of the microstructure in the channel. The effect of the microstructure’s dimensions and the channel’s size for self-alignment procedure has also been analyzed. It shows that the self-alignment of the microstructure can complete when the ratio of the diameter of microstructures to the width of the channel is greater than 85%. Besides, experiments of the self-alignment between adjacent layers of microstructures were successful, which show the presented idea using lateral fluid force is a promising way to build 3D structures with less assembly errors.

Although the image quality from modern distal chip endoscopes is superior, limited mobility of the endoscopic tower prevents this technology from being used in inpatient and emergency departments. In these settings, otolaryngologists commonly use older flexible laryngoscopes with portable light sources. However, these light sources could malfunction. Smartphones are ubiquitous nowadays, and the smartphone's flashlight may be used alternatively to provide illumination when primary light malfunctions. This study compares the ability of flashlights from various smartphone models in providing adequate illumination for flexible laryngoscopy when compared to a commercially available portable light source. White wall and mucosal images were captured using Olympus P4 flexible scope and lights from the Stryker X8000 endoscopy tower light source, Storz 11301D3 portable light source (control), iPhone 4, iPhone 6, iPhone 8, iPhone X, Galaxy S6, and Galaxy S7. ImageJ was used to quantify pixel intensities with white and black standardized as 250 and 0, respectively. Student 2-tailed t test was used for analysis. The endoscopic tower outperformed all other light sources in all categories. The iPhone 4 and iPhone 6 consistently underperformed in comparison to the Storz 11301D3 portable light source (P < .05). Galaxy S6, Galaxy S7, and newer generation iPhone 8 and iPhone X provide comparable pixel intensities to Storz 11301D3 portable light. Smartphones incorporate different types of light-emitting diodes. Newer Galaxy and iPhone provide adequate illumination for the endoscopic assessment of the airway when compared to commercially available portable light source. However, one should always utilize the best commercially available light source in nonemergent cases.

To evaluate a cost-effective modified rigid laryngoscopy setup with a portable light source and high-resolution commercially available digital camera for use in smaller otolaryngology and family practice clinics. The modified setup was used to obtain images of the larynx using both a traditional light source and a portable light source. Varying shutter speeds and ISOs were evaluated, and the optimal settings were determined for the modified setup. Picture quality was adequate, and the portable light source was bright enough. ISO from 640 to 1600 with shutter speeds ranging from 1/60 to 1/160 are ideal under the normal light source, while it is better to set the ISO between 4000 and 10 000 with shutter speeds from 1/60 to 1/100 under the portable light source. Picture quality was adequate with a resolution of 2768 pixels × 1848 pixels with 350 dpi × 350 dpi. Results show that the modified setup obtains images of adequate quality for use in the clinic. Additionally, since the larynx requires the most illumination for endoscopic imaging, a similar setup would work for imaging the ear and nose. This setup may make laryngoscopic exams more accessible to patients at smaller laryngoscopy clinics or family practice providers.

Visualization of three-dimensional microstructures

A direct programming control approach for fabrication of three-dimensional (3D) microstructures by use of focused ion beam (FIB) milling is put forth in this article. The previously reported Vasile mathematical model was simplified by our model of constant dwell time and sputter yield during the milling process. Milling of the 3D microstructures can be transferred to the milling of many discrete two-dimensional (2D) slices with thin and constant thickness. The 3D milling can be completed by the direct FIB 2D milling slice by slice with the same layer thickness. The number of the slices can be determined according to maximum depth of the 3D microstructures. The milling depth for each slice depends on the slice thickness. The simplified model and process parameters can be written in a program code running in the FIB equipped computer. The whole process can be performed automatically after adjusting the focusing status of the ion beam on the sample. It was shown by the experimental results that the method has the advantages of simple mathematical model, less memory space used, and fast milling speed.

Background: The fabrication of micro-groove and microstructures in non-conductive hard and brittle materials is always difficult. The electrochemical discharge milling process is a good selection for the fabrication of micro-grooves and microstructures. Objective: In this paper, an electrochemical discharge milling process for fabricating micro-grooves is introduced. In order to investigate the influences of pulse voltage, pulse frequency, duty cycle and feed rate on machining accuracy and localization, the experiment of the microgrooves and microstructures was carried out. Methods: Firstly, the electrochemical discharge milling set-up has been built based on the machining principle. Secondly, a discharge energy control model was established. Then, a series of experiments has been carried out to investigate the effect of applied voltage, frequency, duty factor, and feed rate on the groove width. An array of micro-grooves was obtained by the optimized parameters. Finally, some complex microstructures like micro-channels and 3D microstructures on glass were fabricated successfully. Results: The groove width increases with the increase of machining voltage and duty cycle, the groove width decreases with the increase of pulse frequency and feed rate. Better machining localization can be obtained with the smaller voltage and duty cycle, the larger pulse frequency and feed rate. Conclusion: Two-dimensional microchannel and three-dimensional microstructures have been successfully machined on the glass workpiece. It has some guiding significance for the fabrication of nonconductive hard brittle materials.

MEMS (microelectromechanical systems) or nanotechnology is expected as one of the most promising R&D fields for the future business success, as MEMS or nanotechnology has a variety of applications from electronics to bio-technology. However R&D investment to MEMS facility is too heavy even for the large scale companies. Although MEMS foundry services by private companies have been introduced in these five years in Japan, their targets are not small batch production or R&D but mainly large or middle batch production. The number of products of the most MEMS applications is now limited and not enough to be called as "mass production" level except for automobile sensors and ink-jet heads. The above mentioned is the reason why AIST has started R&D activities and services for MEMS commercialization. The activities include foundry service to promote MEMS industry, R&D on Desktop MEMS or Nano Factory. MEMS foundry activities in AIST are described in "MN-One" strategy with special emphasis laid on cost effective micro/nano fabrication and new materials integration to MEMS with rapid realization of new ideas by collaboration. Desktop MEMS and nano factory concept is proposed and the desktop prototypes of EB writing machine and nanoimprint machine are presented. This is mainly targeted for reduction of R&D cost and time, and eventually the speedy realization of ideas to be a winner in high technology based business.

We report the synthesis of three-dimensional (3D) urchin-like Nb2O5 microstructures by a facile hydrothermal approach with subsequent annealing treatment. As anode materials for lithium-ion batteries, the 3D urchin-like Nb2O5 microstructures exhibit superior electrochemical performance with excellent rate capability as well as long-term cycling stability. The electrode delivers high capacity of 131 mA h g−1 after 1000 cycles at a high current density of 1 A g−1. The excellent electrochemical performance suggests the 3D urchin-like Nb2O5 microstructures may be a promising anode candidate for high-power lithium ion batteries.