Micro and Nano Engineering最新文献

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.

In this study, we present the performance of an extreme ultraviolet interference lithography (EUV-IL) setup that was reconstructed at Taiwan Light Source 21B2 EUV beamline in the National Synchrotron Radiation Research Center (NSRRC), Taiwan. An easy-to-perform fabrication method to produce a high-quality transmission grating mask and a simple design of experimental setup for EUV-IL were developed. The current EUV-IL setup is capable of fabricating line/space patterns down to 25 nm half-pitch in hydrogen silsesquioxane (HSQ) resist. Preliminary exposure results revealed that optimized slit width and exposure time significantly improved line/space pattern quality. The current EUV-IL tool at NSRRC can be used for nano-patterning and resist screening to advance the next generation of semiconductor devices.

The synthesis of MoS₂ with chemical vapor deposition (CVD) using sodium molybdate (Na₂MoO₄) as the Mo precursor produces a big number of large flakes (∼100-300 μm) compared to other CVD methods that use different precursors. In this work, humidity sensors based on MoS₂ are developed, whereby MoS₂ is grown using this Mo precursor in an aqueous solution form. The final devices exhibit a response-switching during operation under high (>50%) relative humidity conditions, due to the presence of Na₂MoO₄ residues on their surface. By decreasing the concentration of the aqueous Mo precursor during the CVD process we partially diminish the switching effect, as the Na₂MoO₄ residue is reduced To completely overcome this issue, we present a post-fabrication surface treatment using hydrochloric acid that removes the Na₂MoO₄ residue from the devices' surface. Rinsing the devices with an HCl solution results in the elimination of the response-switching effect and the sensors demonstrate a constant positive response from the initial operation steps.

This work describes the integration of a Resistance Thermal Detector (RTD) microcalorimeter integrated into a 324 nL microfluidic channel. The sensor is fabricated in a clean room using photolithography and evaporation techniques, and it has a platinum serpentine with 60 windings. The RTDs undergo testing in the 30 to 45 °C temperature range, exhibiting great linearity and a sensitivity of 8.42 Ω/°C. Additionally, to perform the thermic measurement, we also provide a circuit architecture that ensures stability against external thermal fluctuations and the self-heating Joule effect. We showed that this measurement method allow us to achieve a precision of ±6.7·10⁻³ °C, compared to ±0.178 °C total fluctuations found by using the traditional 2-wire method.

Hydrogel based carriers have been predominantly investigated to combat the prominent challenges faced by oral biomacromolecule delivery. Several micromolding, microfluidic and photolithographic techniques have been described for the fabrication of non-spherical hydrogel based microcarriers. However, these techniques are unsuitable for loading biomacromolecules as integral part of the fabrication process due to the use of high temperatures, solvents and multiple processing steps. Here, we introduce UV-assisted punching as a novel two-step fabrication technique for the development of biocompatible microgel shapes for oral drug administration. Poly-ethylene glycol (PEG) microgel shapes with lateral dimensions of 25–100 μm and a height of 25 μm were fabricated on a flexible poly vinyl alcohol (PVA) substrate with a robust cycloolefin polymer (COP) stamp. The proposed process uses UV-initiated crosslinking of aqueous solutions at ambient temperatures, thereby providing a highly attractive method for the fabrication of biomacromolecule loaded hydrogel based carriers. For the proof-of-concept, the microgel shapes were loaded with the fluorescently labelled model biomacromolecule bovine serum albumin without any additional steps. The successful loading is demonstrated by fluorescence microscopy. In vitro studies are performed to quantify the macromolecular content and the release profile associated with the fabricated microgel shapes.

Wastewater containing synthetic dyes has caused a significant risk to the environment and human health. Among the various methods to treat wastewater, photocatalysis recommends itself as a particularly efficient tool for the removal of dyes from industrial effluents. In this work, Au@Cu₂O core@shell nanocrystals with controllable shell thicknesses from 38.1 ± 2.8 (Au@Cu₂O-2), 48.1 ± 3.7 (Au@Cu₂O-3) to 59.1 ± 4.1 nm (Au@Cu₂O-4) have been prepared and immobilized on polyethylene terephthalate (PET) fabrics for applications in photocatalytic degradation of methylene orange (MO). The influence of the shell thickness of Au@Cu₂O on the photocatalytic performance of the functionalized PET fabrics has been examined. Among all the samples tested, immobilization of Au@Cu₂O-3 rendered PET fabrics the largest photocatalytic activity for MO degradation, achieving an apparent rate constant of MO degradation of 7.43 × 10⁻³ min⁻¹. A plausible mechanism accounting for the degradation process of MO over the functionalized PET has been proposed based on the results of scavenger experiments. This work has provided a delicate yet practical functional textile paradigm by combining the photocatalytic capability of Au@Cu₂O and the adaptable feature of PET fabrics. The findings from this study can deliver a viable idea for the design of versatile textiles with competent photocatalytic capacity for environmental purifications and energy conversion.

High strength Ni matrix TiO₂ composites are prepared by co-electrodeposition with an electrolyte composed of Ni Watts bath, surfactants, CO₂ in the supercritical fluid state and various sizes of TiO₂ particles. The surfactants and supercritical CO₂ (SC-CO₂) are used to emulsify the aqueous Ni Watts bath to promote the incorporation of TiO₂ particles into the Ni matrix. TiO₂ particles with three different average sizes are used in the co-electrodeposition to evaluate the effect on properties of the Ni-TiO₂ composites. The grain sizes of the Ni matrix in the composites are compared from the X-ray diffraction results and the Scherrer eq. A refined average grain size in the Ni matrix is observed when using TiO₂ particles with a larger size. The TiO₂ is evaluated by energy-dispersive X-ray spectroscopy (EDX), and the TiO₂ distribution is quantified by the coefficient of variation (cov) of the local density of Ti from the EDX result. The TiO₂ content attained 4.5 wt% with the lowest cov value (which suggests the most uniform distribution) in the composite when the smallest (21 nm) TiO₂ particles are used. The TiO₂ content achieves 22.3 wt% with the highest cov value (which suggests the least uniform distribution) when the largest (5 μm) TiO₂ particles are used. Microhardness of the Ni-TiO₂ composites is found to be highly depended on the cov value. Hence, the Ni-TiO₂ composite prepared with the smallest TiO₂ particles shows the highest microhardness at 1274 HV.