Search Results (201)

This study evaluated the influence of drying time, application mode, and agitation on the micro-tensile bond strength (μTBS) of a novel mesoporous bioactive glass-containing universal adhesive (Hi-Bond Universal). Twelve experimental groups were established according to drying time (blot-dry, 10 s dry, or 20 s dry), application mode (total-etch or self-etch), and agitation (with or without). The μTBS test and failure mode analysis were performed for each experimental group (n = 20), and an adhesive interface was observed using field-emission scanning electron microscopy. The μTBS of all experimental groups was analyzed using a three-way ANOVA and Tukey’s honestly significant difference (HSD) post hoc test (α = 0.05). The total-etch mode yielded higher μTBS than the self-etch mode in the blot-dry and 10 s dry groups (p < 0.05). Agitation also significantly increased the μTBS in the blot-dry and 10 s dry groups for both application modes (p < 0.05). However, application mode and agitation had no effect on the μTBS in the 20 s dry group (p > 0.05). FE-SEM revealed longer and more uniform resin tags after agitation in the blot-dry and 10 s dry groups for both application modes. In conclusion, total-etch mode and agitation effectively increased the bond strength of mesoporous bioactive glass-containing universal adhesives. Full article

A novel empirical method for fabricating Van der Pauw Hall test samples on GaN epitaxy is proposed and tested, which enables rapid preparation of Van der Pauw Hall test samples on both conductive and non-conductive substrates. Compared to traditional Van der Pauw Hall sample preparation, this approach eliminates the need for annealing to form Ohmic contacts, thereby facilitating more accurate measurement of the resistivity, Hall coefficient, majority carrier concentration, and mobility in semiconductor wafers, which may be subject to change after high-temperature annealing. This method is based on the use of specialized plasma dry-etched patterns to form the Ohmic electrodes, which reduces the metal–semiconductor contact barrier, allowing the tunneling current to dominate and thus forming Ohmic contacts. In the validation experiments, three different substrate materials for GaN-epi—silicon, sapphire, and silicon carbide—were selected for the preparation of the Van der Pauw Hall test samples, followed by testing and analysis to confirm the accuracy of the new test method. The measurement results for the electron mobility and carrier concentration on the sapphire and silicon carbide substrate samples were verified via the contactless RF reflectance mapping method, with an average difference only 4.0% and 7.0%, respectively, and a minimum of only 0.53% and 1.8%. The proposed fabrication method features a relatively simple structure, enabling rapid preparation and avoiding the damage and errors caused by high-temperature annealing processes. It shows great potential for industrial application on precise carrier property measurements, especially for GaN-epi on a conductive substrate. Full article

This study evaluates the effects of gliding arc discharge low-temperature plasma (GAD-LTP) pretreatment on the drying performance and quality attributes of blueberries. Fresh blueberries were pretreated under varying conditions—treatment durations of 6 s, 12 s, and 18 s and power levels of 300 W, 600 W, and 900 W—prior to convective hot air drying at 65 °C. Results demonstrate that plasma pretreatment significantly reduced drying time, with an 18 s treatment at 900 W reducing drying time by 31.25%. Moisture diffusion coefficients increased with both treatment duration and power. Under optimal conditions, total phenolic content improved by up to 33.47%, while anthocyanin retention initially declined then recovered, reaching a 7.9% increase over the control. However, plasma-treated samples exhibited darker color due to surface etching and oxidation. Rehydration capacity improved, with a maximum enhancement of 27.94%. Texture analysis indicated increased hardness and decreased adhesiveness and chewiness in treated samples. Overall, GAD-LTP pretreatment enhances drying efficiency and preserves bioactive compounds in dried blueberries, offering a scalable approach for industrial application. Full article

A high-activity, low-cost, and easy-to-prepare monolithic catalyst is crucial for the industrial catalytic combustion of volatile organic compounds (VOCs) in a cost-effective manner. In this study, a highly efficient monolithic catalyst, designated as 4GM/COR, was developed by loading 4% graphene-doped α-MnO₂ (4GM) catalyst onto pre-etched cordierite (COR) blocks using a straightforward “ball-milling-assisted impregnation” method. The anchoring force of the cordierite pores, generated through oxalic acid etching, enables the uniform and robust loading of powdered 4GM onto COR, preventing detachment under high temperatures or high gas flow rates. The loading rate, specific surface area, and concentrations of Mn³⁺ and surface-lattice and absorbed oxygen species in the monolithic catalyst increase with impregnation times from 2 to 4, indicating that catalytic activity is optimized through repeated impregnation. Catalytic performance tests demonstrated that the 4-4GM/COR exhibited the highest activity, achieving 90% degradation of toluene at 200 °C under both dry and humid (relative humidity is 85%) conditions. Furthermore, the 4-4GM/COR maintains high catalytic stability and activity even at a large GHSV of 6000 h⁻¹. To conclude, the 4-4GM/COR monolithic catalyst developed in this study not only represents a promising option for industrial applications but also serves as an important reference for the synthesis of monolithic catalysts. Full article

WO₃-based electrochemical transistors (ECTs) are recognized as candidates for three-terminal memristors due to their high on–off ratio, long retention time, and rapid switching speed. However, their patterned fabrication often relies on complex vacuum systems or extreme processing conditions, hindering cost-effective scalability. Here, we developed a novel wet etching technique integrated with sol–gel-derived WO₃ channels, enabling ambient-air fabrication of Nafion-WO₃ ECTs. The wet-etched devices achieve an on–off ratio of ~10⁵, surpassing unetched and dry-etched counterparts by orders of magnitude. Furthermore, they exhibit exceptional paired-pulse facilitation and long-term stability, maintaining 12 distinct conductance states for 10³ s, and an on–off ratio of ~10² over 25 read–write cycles. XPS result shows higher W⁵⁺ content and M-O-H bond proportion for wet-etched devices, revealing an optimized interface, with enhanced H⁺ injection efficiency. The simulated artificial neural network using this wet-etched ECT shows ~97% recognition accuracy for handwritten numerals. This approach offers a novel patterning strategy for developing cost-effective, high-performance neuromorphic devices. Full article

The heterogeneous integration of ferroelectric thin films on silicon- or silicon nitride-based platforms for photonic integrated circuits plays a crucial role in the development of nanophotonic thin film modulators. For this purpose, an ultrathin seed film was recently introduced as an integration method for ferroelectric thin films such as BaTiO₃ and Pb(Zr,Ti)O₃. One issue with this self-orienting seed film is that for non-planarized circuits, it fails to act as a template film for the thin films. To circumvent this problem, we propose a method of planarization without the need for wafer-scale chemical mechanical polishing by using hydrogen silsesquioxane as a precursor to forming amorphous silica, in order to create an oxide cladding similar to the thermal oxide often present on silicon-based platforms. Additionally, this oxide cladding is compatible with the high annealing temperatures usually required for the deposition of these novel ferroelectric thin films (600–800 °C). The thickness of this silica film can be controlled through a dry etch process, giving rise to a versatile platform for integrating nanophotonic thin film modulators on a wider variety of substrates. Using this method, we successfully demonstrate a hybrid BaTiO₃-Si ring modulator with a high Pockels coefficient of $r_{wg}=155.57\pm 10.91$ pm V⁻¹ and a half-wave voltage-length product of $V_{\pi }L=2.638\pm 0.084$ V cm, confirming the integration of ferroelectric thin films on an initially non-planar substrate. Full article

Water testing is becoming increasingly important due to dangerous phenomena such as Harmful Algal Blooms (HABs). Commonly, the content of a water sample is measured for the detection, monitoring and control of these events. Raman spectroscopy is a technique for the molecular characterization of materials in solid, liquid or gaseous form, which makes it an attractive method for analysing materials’ components. However, Raman scattering is a weak optical process and requires an accurate system for detection. In our work, we present, from design to fabrication, a microfluidic device on fused silica adapted to optimise the Raman spectrum of liquid samples when using a Raman probe. The device features a portable design for rapid on-site continuous flow measurements avoiding the use of large, costly and complex laboratory equipment. The main manufacturing technique used was ultrafast laser-assisted etching (ULAE). Finally, the effectiveness of the microfluidic device was demonstrated by comparing the Raman spectra of a known species of cyanobacteria with those obtained using other conventional substrates in laboratory analysis. The results demonstrate that the microfluidic device, under continuous flow conditions, exhibited a lower standard deviation of the Raman signal, reduced background noise and avoided signal variations caused by sample drying in static measurements. Full article

Cavity silicon on insulator (Cavity-SOI) offers significant design flexibility for microelectromechanical systems (MEMS). Notably, the shape and depth of the cavity can be tailored to specific requirements, facilitating the realization of intricate multi-layer structural designs. The novelty of the proposed fabrication methodology is manifested in its employment of a micromachining process flow, which integrates dry etching, wafer level Au–Si eutectic bonding, and chemical mechanical polishing (CMP) to create Cavity-SOI. This innovative approach substantially mitigates the complexity of fabrication, and the implementation of wafer-level gold–silicon eutectic bonding and vacuum packaging can be achieved, representing a distinct advantage over conventional methods. To evaluate the technical viability, a MEMS resonant pressure sensor (RPS) was designed. Experimental findings demonstrate that during the formation of Cavity-SOI, dry etching can accurately fabricate cavities of predefined dimensions, wafer-level Au–Si eutectic bonding can achieve efficient sealing, and CMP can precisely regulate the depth of cavities, thus validating the feasibility of the Cavity-SOI formation process. Additionally, when implementing Cavity-SOI in the fabrication of MEMS RPS, it enables the spontaneous release of resonators, effectively circumventing the undercut and adhesion issues commonly encountered with hydrofluoric acid (HF) release. The sensors fabricated using Cavity-SOI exhibit a sensitivity of 100.695 Hz/kPa, a working temperature range spanning from −10–60 °C, a pressure range of 1–120 kPa, and a maximum error of less than 0.012% full scale (FS). The developed micromachining process for Cavity-SOI not only streamlines the fabrication process but also addresses several challenges inherent in traditional MEMS fabrication. The successful fabrication and performance validation of the MEMS RPS confirm the effectiveness and practicality of the proposed method. This breakthrough paves the way for the development of high-performance MEMS devices, opening up new possibilities for various applications in different industries. Full article

Effective high-aspect-ratio molds that minimize vacuum processes are becoming increasingly important for producing metalenses and other devices. To fabricate a high-aspect-ratio structure, a metal film must be used as a mask for dry etching, typically achieved via vacuum deposition. To avoid this vacuum process, we devised a method to develop an etching mask in the air using silver ink. The manufacturing method involved filling the mold with silver ink, baking it, removing silver from the convex parts of the mold with a polyethylene terephthalate film, and placing silver from the concave parts of the mold on top of the ultraviolet (UV)-cured resin using ultraviolet-nanoimprint lithography. The transferred pattern had silver on the convex parts, which was used as a mask for the oxygen dry etching of the UV-curable resin. Consequently, high-aspect-ratio resin shapes were obtained from three types of nano- and micromolds. Additionally, a high-aspect-ratio resin with silver was used as a replica mold to form a silver pattern. This process is effective and allows high-aspect-ratio patterns to be obtained from master molds. Full article

Inductively coupled plasma–reactive etching (ICP-RIE) of InGaZnO (IGZO) thin films was studied with variations in gas mixtures of hydrochloride (HCl) and argon (Ar). The dry etching characteristics of the IGZO films were investigated according to radiofrequency bias power, gas mixing ratio, and chamber pressure. The IGZO film showed an excellent etch rate of 83.2 nm/min from an optimized etching condition such as a plasma power of 100 W, process pressure of 3 mTorr, and HCl ratio of 75% (HCl:Ar at 30 sccm:10 sccm). In addition, this ICP-RIE etching condition with a high HCl composition ratio at a moderate RIE power of 100 W showed a low etched pattern skew and low photoresist damage on the IGZO patterns. It also provided excellent surface morphology of the SiO₂ film underneath after the entire dry etching of the IGZO layer. The IGZO thin film as an active layer was successfully patterned under the ICP-RIE dry etching under the HCl-Ar gas mixture, affording an excellent electrical characteristic in the resultant top-gate IGZO thin-film transistor. Full article

In this paper, we report the growth of high-quality ${\mathrm{In}}_{0.59}{\mathrm{Ga}}_{0.41}\mathrm{As}/{\mathrm{In}}_{0.37}{\mathrm{Al}}_{0.63}\mathrm{As}$ strain-balanced quantum cascade lasers (QCLs) in the low-pressure MOCVD production type multi-wafer planetary reactor addressing, in particular, quality and scaled manufacturing issues. Special attention was given to achieving the sharp interfaces (IFs), by optimizing the growth interruptions time and time of exposure of InAlAs layer to oxygen contamination in the reactor, which all result in extremely narrow IFs width, below 0.5 nm. The lasers were designed for emission at $7.7\mu$m. The active region was based on diagonal two-phonon resonance design with 40 cascade stages. For epitaxial process control, the High Resolution X-Ray Diffraction (HR XRD) and Transmission Electron Microscopy (TEM) were used to characterize the structural quality of the QCL samples. The grown structures were processed into mesa Fabry-Perot lasers using dry etching RIE ICP processing technology. The basic electro-optical characterization of the lasers is provided. We also present results of Green’s function modeling of QCLs and demonstrate the capability of non-equilibrium Green’s function (NEGF) approach for sophisticated, but still computationally effective simulation of laser’s characteristics. The sharpness of the grown IFs was confirmed by direct measurements of their chemical profiles and as well as the agreement between experimental and calculated wavelength obtained for the bandstructure with ideally abrupt (non-graded) IFs. Full article

Polymers with micro- and mesoporous structure are promising as materials for gas storage and separation, encapsulating agents for controlled drug release, carriers for catalysts and sensors, precursors of nanostructured carbon materials, carriers for biomolecular immobilization and cellular scaffolds, as materials with a low dielectric constant, filtering/separating membranes, proton exchange membranes, templates for replicating structures, and as electrode materials for energy storage. Sol–gel technologies, track etching, and template synthesis are used for their production, including in micelles of surfactants and microemulsions and sublimation drying. The listed methods make it possible to obtain pores with variable shapes and sizes of 5–50 nm and achieve a narrow pore size distribution. However, all these methods are technologically multi-stage and require the use of consumables. This paper presents a review of the use of macromolecular architecture in the synthesis of micro- and mesoporous polymers with extremely high surface area and hierarchical porous polymers. The synthesis of porous polymer frameworks with individual functional capabilities, the required chemical structure, and pore surface sizes is based on the unique possibilities of developing the architecture of the polymer matrix. Full article

In recent years, the emission of greenhouse gases (GHGs) has increased significantly, contributing to global warming. Among these GHGs, CH₄, CO₂, and CO are particularly potent contributors. Remediation techniques primarily rely on materials capable of capturing, storing, and converting these gases. Catalytic processes, particularly heterogeneous catalysis, are essential to chemical and petrochemical industries as well as environmental remediation. Due to the growing demand for catalysts, efforts are being made to reduce energy consumption and make technologies more environmentally friendly. Green chemistry emphasizes minimizing the use of hazardous reactants and harmful solvents in chemical processes. Achieving these principles should be paired with processes that reduce time and costs in catalyst preparation while improving their efficiency. Non-thermal plasma (NTP) has been widely used for the preparation of supported metal catalysts. NTP has attracted significant attention for its ability to improve the physicochemical properties of catalysts, enhancing process efficiency through low-temperature operation and shorter processing times. NTP has been applied to various catalyst synthesis techniques, including reduction, oxidation, metal oxide doping, surface etching, coating, alloy formation, surface treatment, and surface cleaning. Plasma-prepared transition-metal catalysts offer advantages over conventionally prepared catalysts due to their unique material properties. These properties enhance catalytic activity by lowering the activation energy barrier, improving stability, and increasing conversion and selectivity compared to untreated samples. This review demonstrates how plasma activation modifies material properties and, based on extensive literature, illustrates its potential to combat climate change by converting CO₂, CH₄, CO, and other gases, showcasing the benefits of plasma-treated materials and catalysts. A succinct introduction to this review outlines the advantages of plasma-based synthesis and modification over traditional synthesis techniques. The introduction also highlights the various types of plasma and their physical characteristics across different factors. Additionally, this review addresses methods by which materials are synthesized and modified using plasma. The latter section of this review discusses the use of non-thermal plasma for greenhouse gas mitigation, covering applications such as the dry reforming of CH₄, CO and CH₄ oxidation, CO₂ reduction, and other uses of plasma-modified catalysts. Full article

Silicon nanowires (SiNWs) have garnered considerable attention in the last few decades owing to their versatile applications. One extremely desirable aspect of fabricating SiNWs is controlling their dimensions and alignment. In addition, strict control of surface roughness or diameter modulation is another key parameter for enhanced performance in applications such as photovoltaics, thermoelectric devices, etc. This study investigates a method of fabricating silicon nanowires using electron beam lithography (EBL) and the deep reactive ion etching (DRIE) Bosch process to achieve precisely controlled fabrication. The fabricated nanowires had a pitch error within 2% of the pitch of the direct writing mask. The maximum error in the average diameter was close to 25%. The simplified two-step method with tight control of the dimensions and surface tunability presents a reliable technique to fabricate vertically aligned SiNWs for some targeted applications. Full article

Traditional mechanical processing of zirconium leads to an unfavorable transformation, from a metastable tetragonal phase to a monoclinic phase (t→m), which weakens the structure of the material and subsequently leads to damage to the prosthetic restoration. The aim of this research is to compare commonly used surface treatments to determine which has the least effect on t→m. Thirty cylindrical samples made of sintered zirconium were divided into six groups based on the following treatments: polishing, grinding, sandblasting, chemical etching, laser structuring or dry plasma etching. After surface treatment, the samples were subjected to the following tests: X-Ray Diffraction, microscopic examination, surface wettability and surface roughness measurements. Chemical etching, laser structuring and plasma etching significantly reduce the content of the monoclinic phase. All surface treatments significantly reduced the final amount of the monoclinic phase. However, chemical etching did not provide sufficient surface roughness. Both laser and plasma processing offer the advantage of creating structural patterns on the surface of elements. However, as plasma etching requires a mask to obtain the appropriate pattern on the surface, it seems that laser processing offers more and varied structuring possibilities. Laser structuring is easier to control and more economical than the other methods. Full article