Search Results (64)

Excessive osteoclast activity in bone remodeling can lead to an imbalance between bone resorption and formation, a common occurrence in abnormal bone metabolic diseases. This research investigates the effect of Coptidis rhizoma water extract (CRW) on osteoclastogenesis provoked by RANKL in vitro and bone destruction mediated by ovariectomy (OVX) in vivo. CRW, prepared from dried Coptidis rhizoma (CR), was analyzed for its active compounds—coptisine and berberine—using HPLC analysis. CRW markedly decreased the size and number of TRAP-positive multinucleated cells (TRAP⁺ MNCs), suppressed F-actin ring formation, and diminished bone resorption in RANKL-treated cultures. In the early phase of differentiation, CRW suppressed the phosphorylation of MAPKs p38, JNK, and ERK, as well as NF-κB p65, Iκ-Bα, and Akt. CRW also down-regulated RANKL-mediated induction of c-Fos and NFATc1 and attenuated the activation of NFATc1- dependent genes, such as OSCAR, ATP6V0D2, ACP5 (TRAP), OC-STAMP, DC-STAMP, CTSK (cathepsin K), CALCR (calcitonin receptor), and MMP-9. In ovariectomized rats, micro-CT and histological analyses showed that CRW alleviated femoral bone destruction. These findings indicate that CRW restrains osteoclast differentiation and function and may have therapeutic potential for disorders driven by excessive osteoclast activity. Full article

The stamp technique with bulk-fill composites aims to enhance occlusal surface replication in Class I restorations. Limited research exists on its void formation and volumetric changes. This study measures internal and external voids as well as volumetric changes in occlusal surfaces for both the stamp and conventional bulk-fill techniques. Materials and methods: Twenty-four permanent molars were divided into two groups (n = 12 each): Group 1 (conventional bulk fill) and Group 2 (stamp technique with bulk-fill composite). Standardized Class I cavities were prepared and restored using Tetric EvoCeram^® Bulk Fill composite. Micro-CT scanning was performed before and after restoration to quantify internal and external void percentages and volumetric changes. An independent samples t-test (α = 0.05) was used to compare void percentages and volumetric changes between groups. Results: The mean internal void percentage was similar between groups (Group 1: 0.38 ± 0.22%; Group 2: 0.39 ± 0.30%; p = 0.914), indicating comparable internal adaptation. Group 2 showed a significantly higher external void percentage (17.59 ± 1.76%) compared to Group 1 (9.05 ± 1.98%; p < 0.001), attributed to the stamp technique’s precise replication of occlusal micromorphology, misinterpreted as porosity by analysis software. Fractal dimension analysis revealed that the stamp technique resulted in the formation of a more complex structure. Restoration volumes (Group 1: 34.10 ± 8.09 mm³; Group 2: 35.52 ± 4.80 mm³; p = 0.639) and volumetric changes (Group 1: 5.91 ± 2.72 mm³; Group 2: 4.64 ± 1.31 mm³; p = 0.199) showed no significant differences. in conclusion, the stamp technique produced internal void percentages comparable to the conventional bulk-fill method in Class I restorations. The significantly higher external void percentage in the stamp technique group was due to the accurate replication of occlusal micromorphology, which was detected as porosity by analysis software. No significant differences were observed in volumetric changes of the occlusal surface before and after restoration between the two techniques, supporting the clinical viability of the stamp technique for precise occlusal restorations. Full article

Bistable microstructures are promising for implementation in many mictroelectromechanical system (MEMS)-based applications due to their ability to stay in several equilibrium states, high tunability and unprecedented sensitivity to external stimuli. As opposed to the extensively investigated one-dimensional curved beam-type devices of this kind, microfabrication of non-planar two-dimensional bistable structures, such as plates or shells, represents a remarkable challenge. Recently reported by us, a new moldless stamping procedure, based on pressing a soft stamp over a thin suspended metallic film, was demonstrated to be a feasible direction for the fabrication of initially curved micro plates. However, reliable implementation of this fabrication paradigm and its further development requires better understanding of the role of the process parameters, and of the effect of both the plate and the stamp material properties on the shape of the formed shell and on the postfabrication residual stresses, and therefore on the shell behavior. The need for an appropriate choice of these parameters requires the development of a systematic modeling approach to the stamping process. Here, we report on a finite element (FE)-based methodology for modeling the processing sequences of a successfully fabricated aluminum (Al) micro shell of realistic geometry. The model accounts for the elasto-plastic behavior of the plate material, the nonlinear material behavior of the foam and the contact between them. It was found that the stamping pressure and the plate material parameters are the key parameters affecting the residual shell curvature as well as its shape. Consistently with previously presented experimental results, we show that the fabrication procedure partially relieves the prestresses emerging during preceding fabrication steps, leaving a nontrivial distribution of residual stresses in the formed shell. The presented analysis approach and results provide tools for designers and manufacturers of systems including micro structural elements of shell type. Full article

This investigation aimed at evaluating the weldability of a 2.1 GPa-grade hot stamping steel (HSS) containing 0.40 wt.% carbon using laser butt welding. It is shown that the subject HSS can be properly joined by laser welding without welding defects, such as voids and micro-cracks. The mechanical properties of joints before and after hot stamping were examined using cross-weld uniaxial tension and Vickers hardness, while microstructure was systematically characterized using optical microscopy and electron backscatter diffraction. The experimental results demonstrate that fresh martensite was formed in the weld nugget after welding, leading to a hardness much higher than that of the base metal. Nevertheless, such cross-weld microstructural heterogeneity was erased after hot stamping and low-temperature baking heat treatments, resulting in a uniform microstructure of lath martensite across the weld. As a result, the joint after hot stamping and baking exhibited an ultimate tensile strength of 2140 MPa and a total elongation of 12.03%, with the fracture occurring in the base metal. Such excellent mechanical properties of the joint demonstrate the great weldability of the present 2.1 GPa-grade HSS during laser welding. Full article

The metal bipolar plate is a critical component of the hydrogen fuel cell stack used in proton exchange membrane fuel cells. Bipolar plates must have high accuracy micro-channels with a high aspect ratio (AR) between the channel depth and the half periodic width to achieve optimal cell performance. Conventional forming methods, such as micro-stamping, hydroforming, and rubber pad forming, cannot achieve these high ARs given that in these processes, material deformation is dominated by stretch deformation. In micro-roll forming the major deformation mode is bending, and this enables production of channels with higher ARs than is currently possible. However, micro-roll forming uses multiple sets of forming roll stands to form the part and this leads to technological challenges related to tool alignment and roll tool precision that must be overcome before widespread application can be achieved. This study presents a new methodology to achieve tight tool tolerances when producing micro-roll tooling by utilizing wire-EDM and micro-turning techniques. This is combined with a new micro-roll former design that enables high-precision tool alignment across multiple roll stations. Proof of concept is provided through micro-roll forming trials performed on ultra-thin titanium sheets that show that the proposed technology can achieve tight dimensional tolerances in the sub-millimeter scale that suits bipolar plate applications. Full article

The development of hydrophobicity on polymer surfaces in mass production is one of the most critical challenges in the plastic industry. This paper deals with a novel combined hot embossing process in which femtosecond laser ablation is utilized to texture the embossing stamps. By controlling the process temperature and axial forces, the laser textures were transferred to polymer surfaces, successfully resulting in hydrophobicity. Four different polymers, including ABS, PP, PA, and PC, along with two different laser textures, namely ball and pyramid, were tested. The laser and hot embossing parameters under which the textures were transferred to the polymers are introduced. The critical micro- and nano-features of the transferred textures that resulted in high hydrophobic contact angles are also discussed. The results indicate that PP and ABS have higher contact angles, respectively, while under the given parameters, PA and PC did not exhibit hydrophobic surfaces. Full article

Currently, the field of microgear manufacturing faces various processing challenges, particularly in terms of size reduction; these challenges increase the complexity and costs of manufacturing. In this study, a technique for microgear manufacturing is aimed at reducing subsequent processing steps and enhancing material utilization. This technique involves the use of trough dies with extrusion-cutting processing, which enables workpieces to undergo forming in a negative clearance state, thus reducing subsequent processing time for micro products. We conducted finite element simulations using microgear dies, measuring stress, velocity, and flow during the forming process of four types of dies-flat, internal-trough, external-trough, and double-trough dies. The results indicated that the buffering effect of the troughs reduced the rate of increase in the material’s internal stress. In the cavity, the material experiences a significant increase in hydrostatic pressure, leading to the formation of a “hydrostatic pressure wall”. This pressure barrier imposes substantial constraints on the flow of the material during dynamic processes, making it difficult for the material to move into the remaining areas. This effectively enhances the blockage of material flow, demonstrating the critical role of hydrostatic pressure in controlling material distribution and movement. In addition, combining the characteristics of both into a double-trough die enhances the overall stability of forming velocity, reduces forming load and energy consumption, and maximizes material utilization. Results further revealed that microgears manufactured using double-trough dies exhibited defect-free surfaces, with a dimensional error of less than 5 μm and tolerances ranging from IT5 to IT6. Overall, this study offers new insights into the traditional field of microgear manufacturing, highlighting potential solutions for the challenges encountered in current microstamping processes. Full article

Nanostructures with sufficiently large areas are necessary for the development of practical devices. Current efforts to fabricate large-area nanostructures using step-and-repeat nanoimprint lithography, however, result in either wide seams or low efficiency due to ultraviolet light leakage and the overflow of imprint resin. In this study, we propose an efficient method for large-area nanostructure fabrication using step-and-repeat nanoimprint lithography with a composite mold. The composite mold consists of a quartz support layer, a soft polydimethylsiloxane buffer layer, and multiple intermediate polymer stamps arranged in a cross pattern. The distance between the adjacent stamp pattern areas is equal to the width of the pattern area. This design combines the high imprinting precision of hard molds with the uniform large-area imprinting offered by soft molds. In this experiment, we utilized a composite mold consisting of three sub-molds combined with a cross-nanoimprint strategy to create large-area nanostructures measuring 5 mm × 30 mm on a silicon substrate, with the minimum linewidth of the structure being 100 nm. Compared with traditional step-and-flash nanoimprint lithography, the present method enhances manufacturing efficiency and generates large-area patterns with seam errors only at the micron level. This research could help advance micro–nano optics, flexible electronics, optical communication, and biomedicine studies. Full article

Scanning micrο X-ray fluorescence (μ-XRF) and multispectral imaging (MSI) were applied to study philately stamps, selected for their small size and intricate structures. The μ-XRF measurements were accomplished using the M6 Jetstream Bruker scanner under optimized conditions for spatial resolution, while the MSI measurements were performed employing the XpeCAM-X02 camera. The datasets were acquired asynchronously. Elemental distribution maps can be extracted from the μ-XRF dataset, while chemical distribution maps can be obtained from the analysis of the multispectral dataset. The objective of the present work is the fusion of the datasets from the two spectral imaging modalities. An algorithmic co-registration of the two datasets is applied as a first step, aiming to align the multispectral and μ-XRF images and to adapt to the pixel sizes, as small as a few tens of micrometers. The dataset fusion is accomplished by applying k-means clustering of the multispectral dataset, attributing a representative spectrum to each pixel, and defining the multispectral clusters. Subsequently, the μ-XRF dataset within a specific multispectral cluster is analyzed by evaluating the mean XRF spectrum and performing k-means sub-clustering of the μ-XRF dataset, allowing the differentiation of areas with variable elemental composition within the multispectral cluster. The data fusion approach proves its validity and strength in the context of philately stamps. We demonstrate that the fusion of two spectral imaging modalities enhances their analytical capabilities significantly. The spectral analysis of pixels within clusters can provide more information than analyzing the same pixels as part of the entire dataset. Full article

A review of studies on the electroplastic effect on the deformation process in various conductive materials and alloys for the last decade has been carried out. Aspects, such as the mode and regimes of electric current, the practical methods of its introduction into materials with different deformation schemes, features of deformation behavior accompanied by a pulsed current of different materials, structural changes caused by the combined action of deformation and current, the influence of structural features on the electroplastic effect, changes in the physical, mechanical, and technological properties of materials subjected to plastic deformation under current, possible mechanisms and methods of physical and computer modeling of the electroplastic effect, and potential and practical applications of the electroplastic effect are considered. The growing research interest in the manifestation of the electroplastic effect in such new modern materials as shape-memory alloys and ultrafine-grained and nanostructured alloys is shown. Various methods of modeling the mechanisms of electroplasticity, especially at the microlevel, are becoming the most realistic approach for the prediction of the deformation behavior and physical and mechanical properties of various materials. Original examples of the practical application of electropulse methods in the processes of drawing, microstamping, and others are given. Full article

Microscale elastomeric valves are an integral part of many lab-on-chip applications. Normally closed valves require lower actuation pressures to form tight seals, making them ideal for portable devices. However, fabrication of normally closed valves is typically more difficult because the valve structure must be selectively bonded to its substrate. In this work, an oligomer stamping technique for selective bonding of normally closed valves is optimized for bonding of PDMS devices on glass substrates. Contact angle and blister bursting testing measurements are used to quantitatively characterize the oligomer stamping process for the first time, and recommendations are made for plasma treatment conditions, microstamping technique, and valve construction. Glass–PDMS devices are ideal for lab-on-chip systems that integrate electrodes on the rigid glass substrate. Here, integrated electrodes are used to assess valve performance, demonstrating electrical isolation in excess of 8 M$\mathsf{\Omega }$ over the biologically relevant frequency range in the closed state. Further, electrical measurement is used to demonstrate that the valve design can operate under a pulsed actuation scheme, sealing to withstand fluid pressures in excess of 200 mbar. Full article

High-resolution nanotransfer printing (nTP) technologies have attracted a tremendous amount of attention due to their excellent patternability, high productivity, and cost-effectiveness. However, there is still a need to develop low-cost mold manufacturing methods, because most nTP techniques generally require the use of patterned molds fabricated by high-cost lithography technology. Here, we introduce a novel nTP strategy that uses imprinted metal molds to serve as an alternative to a Si stamp in the transfer printing process. We present a method by which to fabricate rigid surface-patterned metallic molds (Zn, Al, and Ni) based on the process of direct extreme-pressure imprint lithography (EPIL). We also demonstrate the nanoscale pattern formation of functional materials, in this case Au, TiO₂, and GST, onto diverse surfaces of SiO₂/Si, polished metal, and slippery glass by the versatile nTP method using the imprinted metallic molds with nanopatterns. Furthermore, we show the patterning results of nanoporous crossbar arrays on colorless polyimide (CPI) by a repeated nTP process. We expect that this combined nanopatterning method of EPIL and nTP processes will be extendable to the fabrication of various nanodevices with complex circuits based on micro/nanostructures. Full article

Metallic bipolar plates (BPPs) are key components in the proton-exchange membrane fuel cell (PEMFC), which can replace traditional fossil fuels as a kind of clean energy. However, these kinds of plates, characterized by micro-channels with a high ratio between depth and width, are difficult to fabricate with an ultra-thin metallic sheet. Then, ultrasonic-vibration-assisted stamping is performed considering the acoustic softening effect. Additionally, the influence of various vibration parameters on the forming quality is analyzed. The experimental results show that ultrasonic vibration can obviously increase the channel depth. Among the vibration parameters, the vibration power has the maximum influence on the depth, the vibration interval time is the second, and the vibration duration time is the last. In addition, the rolling direction will affect the channel depth. When the micro-channels are parallel to the rolling direction, the depth of a micro-channel is the largest. This means that the developed ultrasonic-vibration-assisted stamping process is helpful for improving the forming limitation of micro-channels used for the bipolar plates in PEMFC. Full article

Compared to traditional measurement devices, the micro-synchrophasor measurement unit (D-PMU or μPMU) in the distribution power system has great differences in data acquisition frequency, data format, data dimension, time-stamped information, etc. Hence, it is imperative to research the integration mechanism of heterogeneous data from multiple sources. Based on the analysis of the current technology of multi-source information fusion, this paper proposes a novel approach, which considers two aspects: the interoperability of multi-source data and the real-time processing of large-scale streaming data. To solve the problem of data interoperability, we have modified the model of D-PMU data and established a unified information model. Meanwhile, an advanced distributed processing technology has been deployed to solve the problem of real-time processing of streaming data. Based on this approach, a smart distribution power system wide-area measurement and control station can be established, and the correctness and practicality of the proposed method are verified by an on-field project. Full article

Spheroids are expected to aid the establishment of an in vitro-based cell culture system that can realistically reproduce cellular dynamics in vivo. We developed a fluoropolymer scaffold with an extracellular matrix (ECM) dot array and confirmed the possibility of mass-producing spheroids with uniform dimensions. Controlling the quality of ECM dots is important as it ensures spheroid uniformity, but issues such as pattern deviation and ECM drying persist in the conventional microstamping method. In this study, these problems were overcome via ECM dot printing using a resin mask with dot-patterned holes. For dot diameters of φ 300 μm, 400 μm, and 600 μm, the average spheroid diameters of human iPS cells (hiPSCs) were φ 260.8 μm, 292.4 μm, and 330.7 μm, respectively. The standard deviation when each average was normalized to 100 was 14.1%. A high throughput of 89.9% for colony formation rate to the number of dots and 89.3% for spheroid collection rate was achieved. The cells proliferated on ECM dots, and the colonies could be naturally detached from the scaffold without the use of enzymes, so there was almost no stimulation of the cells. Thus, the undifferentiated nature of hiPSCs was maintained until day 4. Therefore, this method is expected to be useful in drug discovery and regenerative medicine. Full article