Micro and Nano Engineering最新文献

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.

Energy harvesting and conservation are essential for all kinds of power sources, particularly renewable energy sources, given their global distribution. Usually, batteries are employed to mitigate the imbalance between abundant renewable energy generation and inefficient energy transmission. However, batteries suffer from a drawback in terms of low power density. In recent years, supercapacitor devices have gained significant traction in energy systems due to their enormous power density, competing favorably with conventional energy storage solutions. This research paper comprehensively overviews various supercapacitor modalities, encompassing electrode materials, electrolytes, structures, and working principles. Furthermore, it explores the diverse applications of supercapacitors in the consumption of renewable energy, showcasing their potential in various domains, thereby reflecting the thriving prospects of these devices in modern society. Finally, the paper addresses the challenge of energy management in conjunction with supercapacitors.

As proven early on in the pandemic, SARS-CoV-2 is mainly transmitted by aerosols. This urged us to develop a silicon impactor that collects the virus particles directly from breath. Performing PCR on these breath samples proved equally sensitive as nasopharyngeal swabs during the first week of an infection [Stakenborg et al., 2022], yet it remained a mostly manual process and PCR turn-around-time was still long. To overcome these drawbacks, we developed a fast and sensitive, fully integrated point-of-need breath test, comprising a novel breath sampler device and PCR instrument. The breath sampler combines virus collection and in-situ RNA amplification. The PCR instrument performs very fast amplification of the released viral RNA. Sample-to-result time was reduced to <20 min with an equal performance as the original manual procedure.

The wafer-scale fabrication of deep channel microfluidics for lab-on-a-chip applications by reactive ion etching and wafer bonding is reported. The microfluidic channels are etched in B-stage bisbenzocyclobutene (BCB) and Cytop with the latter used as a bonding agent. The channels are hermetically sealed between Borofloat glass and Si wafers by wafer bonding. Fluidic coupling is achieved in the plane of the channels via inlets and outlets that are revealed on the end facets of chips after dicing. Process techniques and details are reported for uniform coating and curing of BCB and Cytop, defining the channels with high accuracy using photolithography, dry etching the polymers using a hard mask, and sealing the channels by wafer bonding. Fluidic measurements are carried out at various flow rates and compared with modeling. The low Reynold's numbers of the channels ensure laminar flow conditions. Deep fluidic channels are less difficult to align to fluidic interfaces, they support higher flow rates and are less susceptible to clogging. In-plane fluidic coupling precludes the need to etch holes through the substrate. Our wafer-scale process was applied to 4 in. diameter wafers yielding 195 precision-aligned and hermetically sealed microfluidic chips, but is readily scalable to larger diameter wafers for volume production.

Au-based micro-electro-mechanical-system (Au-MEMS) capacitance accelerometers show high sensitivity by suppressing the mechanical noise because of the high mass density of gold (ρ = 19.3 g/cm³). On the other hand, their long-term reliability suffers from drift phenomena induced by the impurities incorporated in the key component during their fabrication process, such as the gold electroplating step. Herein, impurities in electroplated Au-based components for MEMS capacitive accelerometers are evaluated by thermal desorption spectrometry (TDS) measurements. The TDS measurement reveals that dominant desorption gases from the Au-based component are molecular hydrogen (H₂) and water (H₂O). These desorption gases are derived from impurities in the electroplated Au-based component, and the amount of these gases is significantly suppressed by a thermal treatment step. In conclusion, this study demonstrates that the electroplated Au-based component contains impurities originated from the fabrication process, and these impurities could be removed by a thermal treatment step.

Low temperature detectors (LTDs) used for decay energy spectrometry (DES) can provide accurate and reliable decay data thanks to their high-energy resolution and a near 100% detection efficiency for the radiations of interest. However, it is essential to consider the source quality to mitigate spectral distortion due to the self-absorption of particle energy in the source deposited.

This work aimed to produce a replaceable 4π 3-layer gold absorber for DES in reusable metallic magnetic calorimeters, a class of LTDs. We present a novel 3-layer microfabrication process for a 1 mm diameter absorber with a total gold thickness ranging from 20 μm to 120 μm depending on the measured radionuclide (⁵⁵Fe or ²⁴¹Am). The absorber integrates a gold nanofoam in which the radionuclide is deposited by nanodrop deposition of a few tenths of μL of a radioactive solution. We fabricated a high quality gold nanofoam layer with controllable porosity through a dealloying process using wet etching and integrating it on a thick electrodeposited gold layer. The fine study of the nanofoam microfabrication is performed using high-resolution scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX).

Electronic waste has become a pressing issue, necessitating sustainable solutions for the disposal of electronic devices. While the development of environmentally degradable electronics has gained attention, the fabrication of stable and performant sensors from biodegradable materials remains challenging. We present printed degradable resistance temperature detectors (RTDs) based on the photonic sintering of a zinc microparticles ink on a cellulosic substrate. Efficient sintering is attained via a two-step process involving electrochemical oxide removal and pulsed light exposure using a xenon lamp. By optimizing the pulse energy and pulse count, we obtain highly linear zinc-based RTDs with a high temperature coefficient of resistance (TCR). The printed zinc reaches a TCR value of 3160 ppm/K, which represents about 80% of the value of the bulk material. The dynamic response of the sensors in a range from −20 to 40 °C closely matches the temperature signal recorded by a commercial sensor. The encapsulation of the screen-printed sensors on paper substrate with a biodegradable beeswax coating ensures protection against the interference of moisture. These printed RTDs, fully made of degradable materials, pave the way to the cost-effective manufacturing of eco-friendly yet performant sensors for environmental monitoring.