Micro and Nano Engineering最新文献

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.

Traditional nanolithography methods, such as electron beam or ion beam lithography, can be expensive and slow, limiting their applications. Edge lithography offers a promising alternative for efficiently and effectively creating nanoscale patterns using lower-cost lithography equipment with higher throughput. Our paper presents a new edge lithography technique to pattern fine structures with coarse patterns utilizing aluminum plasma dry etching without thin film deposition. The aluminum oxide layer generated on the sidewall of the Al structure during the etching process defines the final nanostructures. Our experiments show that this layer is formed through the oxidation of the aluminum layer itself, providing a simple and practical approach to creating complex nanostructures without additional steps or materials. In addition, using the non-switching pseudo-Bosch etching process, we transferred the nano-edge pattern formed in aluminum oxide into the silicon substrate. Our technique allows for cost-effective and efficient nanoscale patterning for various applications.

This paper presents the fabrication of widely-spaced high aspect ratio ring-shape pillars (i.e. hollow pillars). Lateral etching of the pillars during deep reactive ion etching is challenging. To reduce this problem, we proposed adding sacrificial structures surrounding the pillars such that the lateral etching mainly occurs on the sacrificial structures. We designed two different kinds of sacrificial structures, one is circular ring structures surrounding the pillars, the other one is two half circle structures with two small gaps. Both sacrificial structures could help to fabricate pillars with vertical sidewalls. When the width of the sacrificial structures was well designed for a given etching condition, the sacrificial structures could be removed by ultrasonic agitation after the process with clean surface because they had been weakened by the lateral etching. Using this method, 2D widely-spaced ring-shape pillar array with 470 μm high pillars (diameter 200 μm, aspect ratio 2.35) and 370 μm deep holes (diameter 80 μm, aspect ratio 4.63) was fabricated simultaneously.

In this study, we present a label-free non-faradaic impedimetric biosensor to detect bacterial cells using microfabricated gold interdigitated electrode (IDE). Silver nanoparticles (AgNP) are green synthesized using aqueous neem extract and characterized using Attenuated Total Reflectance- Fourier Transform Infrared spectra (ATR-FTIR), Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), and UV–Visible spectroscopy techniques. The synthesized AgNPs are well dispersed with an average size of 84 nm and showed an extensive antibacterial property indicated by a standard bioassay against Escherichia coli (E. coli). Gold IDEs are microfabricated by lithography on borosilicate glass wafers. The biofunctionalization of gold IDE is carried out using thiol‑gold covalent chemistry with mercaptohexanol (MCH). The self-assembled monolayer (SAM) of MCH facilitates drop-cast deposition of AgNP on the surface forming an MCH-AgNP. The functionalized IDE is electrochemically stable for further experiments and was validated by open circuit potential measurements. The objective of developing a label-free approach is confirmed by cyclic voltammetry analysis. Non-faradaic electrochemical impedance spectroscopy (nf-EIS) is carried out to detect E.coli cells suspended in water. The antibacterial property of AgNP is exploited to detect the decrease in cell concentration using nf-EIS. The impedance signatures corresponding to the trapping of cells are recorded with respect to time. Bacterial growth is a major challenge in maintaining water quality. The results demonstrated in this work would help to mitigate this problem effectively in a quick time without the need for skilled labor and sophisticated instruments required in traditional antibacterial testing.

Operating nanofluidic biosensors requires threading single molecules to be analyzed from microfluidic networks into nanostructures, mostly nanochannels or nanopores. Different inlet structures have been employed as a means of enhancing the number of the capture events into nanostructures. Here, we systematically investigated the effects of various engineered inlet structures formed at the micro/nanochannel interface on the capture of single λ-DNA molecules into the nanochannels. Different inlet geometries were evaluated and ranked in order of their effectiveness. Adding an inlet structure prior to a nanochannel effectively improved the DNA capture rate by 190–700% relative to that for the abrupt micro/nanochannel interface. The capture of DNA from the microchannel to various inlets was determined mainly by the capture volumes of the inlet structures and the geometrically modified electric field in the inlet structure. However, as the width of the inlet structure increased, the hydrodynamic flow existing in the microchannel negatively influenced the DNA capture by dragging some DNA molecules deep into the inlet structure back to the microchannel. Our results indicate that engineering inlet structures is an effective means of controlling the capture of DNA molecules into nanostructures, which is important for operation of nanofluidic biosensors.