Micro and Nano Engineering最新文献

A thermally driven, micrometer-scale switch technology has been created that utilizes the ErH₃/Er₂O₃ materials system. The technology is comprised of novel thin film switches, interconnects, on-board micro-scale heaters for passive thermal environment sensing, and on-board micro-scale heaters for individualized switch actuation. Switches undergo a thermodynamically stable reduction/oxidation reaction leading to a multi-decade (>11 orders) change in resistance. The resistance contrast remains after cooling to room temperature, making them suitable as thermal fuses. An activation energy of 290 kJ/mol was calculated for the switch reaction, and a thermos-kinetic model was employed to determine switch times of 120 ms at 560 °C with the potential to scale to 1 ms at 680 °C.

A gold micro-electro-mechanical-systems (Au-MEMS) capacitive accelerometer having Ti/Au multi-layered structures is a promising device to detect very weak accelerations, such as muscle sounds, because of the high mass density of Au. However, Au is a soft metal, which raises concerns about the structural stability of the Au-MEMS capacitive accelerometers for practical use. In this work, we clarify the key geometric parameters to enhance their long-term structural stability by conducting a long-term vibration test for a total of 240 Ti/Au multi-layered micro-cantilevers with different geometric parameters, such as the length, width, and thickness of the micro-cantilevers, and the number of Ti/Au multi-layered structures. The long-term structural stability is evaluated from the change in the tip height of the micro-cantilevers before and after the vibration tests. These tests demonstrate that the micro-cantilevers with a shorter length, larger thickness, and more Ti/Au multi-layered structures are found to show better long-term structural stability.

This study shows the development and analysis of a novel capacity proximity sensor (CPS) based on a sensing layer made up of a mixture of silicon dioxide nanoparticles (SiO₂) and sodium chloride (NaCl), and an encapsulation layer based on a commercial acrylic-based varnish. The encapsulated and non-encapsulated proximity sensors were characterised using impedance spectroscopy (IS), revealing that the resulting impedimetric and capacitance responses exhibit different sensitivities and working sensing ranges. The non-encapsulated sensor presents impedimetric and maximum capacitive sensitivities of 0.0775 cm⁻¹ and -0.9831 cm⁻¹, respectively, within a 2–14 cm sensing range. In contrast, the encapsulated CPS shows maximum impedimetric and capacitive sensitivities of 0.3447 cm⁻¹ and −3.349 cm⁻¹, respectively, and an operation sensing range of 0–3 cm. The results show a 75% decrease in the total sensing range that could be attributed to: (i) a reduction of the effective sensing area due to a reduction of the roughness as demonstrated by SEM analysis, (ii) insulation effects limiting the impact of the material under test (MUT) on the charge carriers distribution, and (iii) decreased charge carrier density involved in the sensing process. Despite the reduced operational range, the encapsulation layer maintains the dual-parameter sensing capabilities, preserves the integrity of the sensing layer, and enables its dual functionality as a proximity and touch sensor. The reported comparison between the encapsulated and non-encapsulated CPSs highlights the effects of the encapsulation layer. The encapsulated version introduces a simple, fast, and cost-effective novel approach for developing CPSs that outperforms some reported CPSs in terms of reliability due to its dual-parameter sensing capability and sensitivity.

In this study we present a novel device for the direct transduction of optical radiation in the near-infrared region into mechanical actuation, which is based on a plasmonic optical nanoantenna integrated in a microcantilever. We propose and demonstrate the feasibility of a simple fabrication process consisting in the nano-tailoring of a commercially available Atomic Force Microscope (AFM) cantilever by means of the Focused Ion Beam (FIB) milling technique. Furthermore, the comprehensive analysis of the device performance characteristics included in this work reveals the different sensitivity values of these characteristics to the fabrication process tolerances of the most relevant geometric design parameters.

We present the large-scale synthesis of Manganese dioxide-graphitic carbon nitride (MnO₂-gCN) nanocomposite using a mechanochemical process. Hydrothermally synthesized rod-shaped MnO₂, combined with pyrolyzed gCN powder in appropriate proportions was mechanically ball-milled to form the MnO₂-gCN composite structure. The resulting nanocomposite characterized through X-ray diffraction, Fourier transformed infrared spectroscopy, scanning electron microscopy, UV–Vis spectroscopy, and photoluminesce study revealed the successful anchoring of gCN with MnO₂ nanostructure. Subsequently, the photocatalytic activity of MnO₂-gCN nanocomposite was assessed by studying the degradation of Rhodamine B, Eosin B, Congo red, Methylene Blue dyes and toxic phenol pollutants under UV light exposure. The MnO₂-gCN hybrid catalyst demonstrated impressive degradation efficiency, ca. 90% for Rhodamine B dye and 70% for phenol in 3 h and remarkable stability upto three cyclic runs. The superior performance of the composite, in comparison to its individual counterparts (MnO₂ or gCN), can be attributed to the effective separation of photogenerated electron-hole $(e^{-}-h^{+}$) pairs and the suppression of charge recombination at the interface. First principle based density functional theory calculations also support the experimental findings and the conclusion of this study.

Antibiotic resistance is a critical and expanding problem for public health, as well as a significant challenge for the pharmaceutical and medical industries. Pathogenic bacteria that are resistant to antibiotics are developing at a rate that is far faster than new drug development. Therefore, there is an urgent need for a novel class of antibiotics with a distinct mode of action with better effect. In this context, noble metal nanoparticles (NPs) (i.e. Ag, Au, Cu) and graphene oxide (GO) based nanocomposite materials have emerged as novel nanohybrid materials owing to their characteristics which combine to provide excellent antibacterial effects. These nanohybrids have been engineered and extensively investigated in recent years with a diverse range of applications including their antibacterial applications. This short review envisages the recent advances carried out in understanding the various antibacterial activities of noble metal NPs-GO nanohybrids with emphasis on the engineering of nanostructures and synergetic mechanisms of antibacterial actions. The synergetic antibacterial mechanism has been discussed, emphasizing the distinct role of GO and noble metal NPs towards combined antibacterial activities. Furthermore, the latest developments and antibacterial applications of such promising GO-noble metal NPs-based nanohybrids have been discussed followed by outlook and future prospects.

Experimental measurement for Short Range (SR) part of PSF in EBL is essential for at least three reasons: Proximity effect correction, the study of the resolution limit of electron lithography, and characterizing the beam size of an EBL instrument. In this work, we introduce a measurement technique that is adequate for the above tasks with the purpose of evaluating its performance. Our approach is based on the following principles. We use a derivate of PSF – Line Spread Function (LSF) - because the latter is an extended object whose size can be averaged along its length during size measurement. Second, the use of thin negative resists like HSQ and PMMA operating in a negative tone avoids distortion due to lateral development. Third, the experimental check of normalization requirement validates the obtained PSFs. SR parts of PSFs in the range of 8–26 nm (FWHM) are accurately measured.

Access to clean drinking water is a critical need for human societies. Intercepting atmospheric fog can help collect water from the atmosphere, even in situations of high-water scarcity in fog-prone areas. Metal meshes or screens are commonly used as fog collectors, where the mesh surfaces are often engineered to enhance water collection rates. Despite significant work over the past several decades, the ideal surface wettability desired in terms of surface roughness and functionalization for efficient fog harvesting is not well understood. The volume of water collected depends on the proportion of fog intercepted by the meshes and how effectively the deposited water droplets drain off into the collector. In this work, we employ scalable surface treatments such as chemical etching and atmospheric pressure vapor deposition on stainless steel meshes to alter the surface wettability. We evaluate the efficacy of fog harvesting on the wettability altered meshes, and compare their performance against untreated stainless steel meshes. We further investigate the effect of surface ageing on the wettability and fog collection performance. Our work not only offers valuable design guidelines for the development of effective fog collectors but also highlights the significant influence of the atmosphere in controlling wetting behaviour.

Investigations on microplastic (MPs) particles in soils are extremely rare, and the published results often lack comparability due to different sampling, extracting, and analytical approaches used. The current techniques for examining tiny MPs in soil samples are not particularly effective, but minor adjustments and method combinations should be explored. The complexity of the soil matrix presents challenges in developing a standardized approach for characterizing MPs and removing them effectively, due to the heterogeneity of soil composition, variability in their size/shape, interactions with soil particles, background contamination, and methodological variations. This review focuses on evaluating various methods for sampling, extraction, purification, identification, measurement and removal of tiny MPs in complex soil systems. A recommended methodology for extracting MPs from complex soil samples is proposed, aiming to provide a systematic approach for their recovery and identification. Furthermore, the article discusses sampling plans, drying and sieving techniques, density separation methods, and removal the MPs with special emphasis on photocatalytic removal. The review also addresses the challenges encountered in such analyses and suggests possible solutions, followed by future prospects. Additionally, the importance of removing MPs from the environment is highlighted, underscoring the need for effective methodologies in tackling this pressing issue.

With the rapid development of microelectronics and the telecommunication industry, a variety of high performance, portable and slim electronic devices have become available. Miniaturization of devices and increased packing density of electronics can generate “hot spots” i.e. a high heat flux on a small area. Thus, in such devices the heat management requirements go beyond the limits of typical approaches and the development of miniaturized, high-performance thermal management concepts to cool high-performance, compact electronic devices is urgently required. To this direction, micro and nanofabrication methods can provide solutions in both miniaturizing existing concepts of passive cooling as well as in improving their performance. In this review, we start by introducing the most commonly used metrics used to evaluate the performance of passive cooling devices (i.e. vapor chambers and flattened heat pipes) together with the most prominent performance limitations. Then, in the main part, we present state of the art examples of microfabricated, thin vapor chambers and flattened heat pipes on rigid substrates (i.e. using metals and silicon), but also vapor chambers on thin and flexible polymeric or composite materials. Finally, the main conclusions and the steps which should be followed to further enhance the performance of such devices are summarized in the conclusions and future perspectives section.