Search Results (28)

This work presents a low-cost and scalable method for fabricating thin-film transistors (TFTs) using a single-step, 3D-printed shadow mask approach. Room temperature growth of both aluminum-doped zinc oxide (AZO) thin film was used as the semiconductor channel, and zirconium oxide (ZrO₂) as the high-k dielectric, and the films were never exposed to any post-annealing treatment. Structural and morphological characterization confirmed smooth, compact films with stable dielectric behavior. Electrical measurements revealed a field-effect mobility of 13.1 cm²/V·s, a threshold voltage of ~4.1 V, and an on/off ratio of ~10⁴, validating effective gate modulation and drain current saturation. The off-state current, estimated from AZO conductivity measurements, was ~10⁻¹⁰ A, while the on-state current reached ~10⁻⁶ A. Benchmarking against state-of-the-art devices shows that these transistors rival ALD-processed IGZO TFTs and significantly outperform reported indium-free ZnO/AZO devices, while avoiding scarce indium and costly high-temperature or photolithographic processing. These findings establish 3D-printed shadow masks as a practical alternative to conventional lithography for oxide TFT fabrication. The method offers high device performance with simplified, indium-free, and room-temperature processing, underscoring its potential for scalable, transparent, and flexible electronics. Full article

Continuous monitoring of glucose (CGM) level is of utmost importance to diabetic patients, especially with no or minimal pain. Microneedle arrays with desired electrode patterns have been fabricated by soft lithographic molding, and the patterned electrodes were formed via shadow evaporation through a shadow mask that was made from a modified molding technique. With immobilization of glucose oxidase (GOx), the microneedle electrode arrays (MEAs) have been successfully employed for the in vitro CGM using impedance spectroscopy. The fabricated MEAs could monitor the varying glucose level continuously for up to ~10 days. Similar processes have been applied for the fabrication of stretchable MEAs, which can conform to complex curvilinear surfaces. The simple and low-cost fabrication of MEAs, either in flexible or stretchable forms, may find various applications in wearable health monitoring techniques. Full article

Quartz crystal out-of-plane vibration units are critical components of QMEMS devices. However, the fabrication of their 3D sidewall electrode structures presents significant challenges, particularly within ultrafine etched grooves. These challenges seriously limit further miniaturization, which is critical for portable and wearable electronic applications. In this paper, we propose a novel 3D self-masking fabrication strategy that enables the precise formation of sidewall electrodes by using the etched beam structure as a self-aligned pattern transfer medium. Based solely on photolithography and wet etching processes, this approach overcomes the limitations of the conventional shadow mask technique by improving alignment accuracy, process efficiency, and fabrication yields. In addition, a predictive mathematical model was developed to guide process optimization, enabling adaptive and reliable fabrication. Sidewall electrodes were successfully achieved in etched grooves as narrow as 45 μm, closely matching the theoretical predictions. To validate the approach, an ultra-miniaturized out-of-plane vibration unit with a beam spacing of just 150 μm—the narrowest reported to date—was fabricated, representing an 80% reduction compared to previously documented structures. The unit exhibited a repeatability error below 1.13%, confirming the precision and reliability of the proposed fabrication strategy. Full article

This study introduces a novel deposition technique capable of depositing thin films with any arbitrary thickness profile. The apparatus consists of a fixed shadow mask and a rotating sample carrier plate. The shadow mask features a specifically designed opening curve that corresponds to the particular thickness profile of the deposited film. We successfully designed two shadow masks and used them to deposit films with linear thickness gradients of 49.3 and 86.8 Å/mm and films with sinusoidal thickness profiles with a period of 40 mm. Furthermore, a linear variable filter was designed on the basis of a quarter-wavelength stack of Si₃N₄ and SiO₂, combined with a TiO₂ cavity layer with a linearly varying thickness. By coaxially rotating the sample carrier plate relative to the shadow mask, films with the desired thickness profiles could be fabricated in a single deposition step without the need for additional rotational or translational devices inside the deposition chamber. By rotating the carrier plate, the chips attached at different circumferential positions can achieve consistent thickness profiles, making this method well-suited for mass production. Full article

Due to advances in additive manufacturing and prototyping, affordable and rapid microfluidic sensor-integrated assays can be fabricated using additive manufacturing, xurography and electrode shadow masking to create versatile platform technologies aimed toward qualitative assessment of acute cytotoxic or cytolytic events using stand-alone biochip platforms in the context of environmental risk assessment. In the current study, we established a nasal mucosa biosensing platform using RPMI2650 mucosa cells inside a membrane-integrated impedance-sensing biochip using exclusively rapid prototyping technologies. In a final proof-of-concept, we applied this biosensing platform to create human cell models of nasal mucosa for monitoring the acute cytotoxic effect of zinc oxide reference nanoparticles. Our data generated with the biochip platform successfully monitored the acute toxicity and cytolytic activity of 6 mM zinc oxide nanoparticles, which was non-invasively monitored as a negative impedance slope on nasal epithelial models, demonstrating the feasibility of rapid prototyping technologies such as additive manufacturing and xurography for cell-based platform development. Full article

We present two approaches for fabricating shadow masks for the evaporation of electrodes onto nanomaterials. In the first one, we combine the use of a commercial fiber laser engraving system with readily available aluminum foil. This method is suitable for fabricating shadow masks with line widths of 50 µm and minimum feature separation of 20 µm, and using it to create masks with complex patterns is very straightforward. In the second approach, we use a commercially available vinyl cutting machine to pattern a vinyl stencil mask, and we use a glass fiber to define the separation between the electrodes. With this approach, we achieve well-defined electrodes separated by 15 µm, but this technique is less versatile in creating complex masks as compared with the laser-based one. We demonstrate the potential of these techniques by fabricating field-effect transistor devices based on MoS₂. Our approach is a cost-effective and easily accessible method for fabricating shadow masks with high resolution and accuracy, making it accessible to a wider range of laboratories. Full article

This study proposes a low-cost, portable paper-fluidic vertical flow assay bacterium counter with high accuracy. We designed sensors with low fabrication costs based on e-beam evaporation and three-dimensional printing based on the impedance measurement principle. Interdigitated (IDT) electrodes were coated on the filter membrane by e-beam evaporation with a shadow mask. We could print wafer-scale frames with low melting temperature three-dimensional-printing materials for confining liquid bacterial samples within the IDT sensing region. This novel fabrication technique significantly reduced the chip’s cost to less than 1% of that of silicon-based chips. Two equivalent circuit models were proposed for different concentration ranges to analyze the principle of paper-based impedance bacterial sensors. We proposed an improved model based on the Randles model for low concentrations by considering the leaky double-layer capacitor effect and spherical diffusion from the nano-structural electrodes of the gold-coated filter membrane. The phenomenon in which charge transfer resistance, R_ct, declines at high concentration ranges was found and explained by the pearl chain effect. The pearl effect could cause a false-negative at high concentrations. We modeled the pearl chain effect as an R and C, connected parallel to the low-concentration model. When users properly applied both models for analyses, this sensor could quantitatively measure cell concentrations from 400 to 400 M per milliliter with superior linearity. Full article

The Mo/Si multilayer mirror has been widely used in EUV astronomy, lithography, microscopy and other fields because of its high reflectivity at the wavelength around 13.5 nm. During the fabrication of Mo/Si multilayers on large, curved mirrors, shadow mask was a common method to precisely control the period thickness distribution. To investigate the effect of shadow mask on the microstructure of Mo/Si multilayers, we deposited a set of Mo/Si multilayers with and without the shadow mask on a curved substrate with aperture of 200 mm by direct current (DC) magnetron sputtering in this work. Grazing incidence X-ray reflectivity (GIXR), diffuse scattering, atomic force microscope (AFM) and X-ray diffraction (XRD) were used to characterize the multilayer structure and the EUV reflectivity were measured at the National Synchrotron Radiation Laboratory (NSRL) in China. By comparing the results, we found that the layer microstructure including interface width, surface roughness, layer crystallization and the reflectivity were barely affected by the mask and a high accuracy of the layer thickness gradient can be achieved. Full article

A millimeter-wave substrate-integrated waveguide (SIW) was firstly demonstrated using the micromachining of photoetchable glass (PEG) for 5G applications. A PEG substrate was used as a dielectric material of the SIW, and its photoetchable properties were used to fabricate through glass via (TGV) holes. Instead of the conventional metallic through glass via (TGV) array structures that are typically used for the SIW, two continuous empty TGV holes with metallized sidewalls connecting the top metal layer to the bottom ground plane were used as waveguide walls. The proposed TGV walls were fabricated by using optical exposure, heat development and anisotropic HF (hydrofluoric acid) etching of the PEG substrate, followed by a metal sputtering technique. The SIW was fed by microstrip lines connected to the waveguide through tapered microstrip-to-waveguide transitions. The top metal layer, including these feedlines and transitions, was fabricated by selective metal sputtering through a silicon shadow mask, which was prefabricated by a silicon deep-reactive ion-etching (DRIE) technique. The developed PEG-based process provides a relatively simple, wafer-level manufacturing method to fabricate the SIW in a low-cost glass dielectric substrate, without the formation of individual of TGV holes, complex time-consuming TGV filling processes and repeated photolithographic steps. The fabricated SIW had a dimension of 6 × 10 × 0.42 mm³ and showed an average insertion loss of 2.53 ± 0.55 dB in the Ka-band frequency range from 26.5 GHz to 40 GHz, with a return loss better than 13.86 dB. The proposed process could be used not only for SIW-based devices, but also for various millimeter-wave applications where a glass substrate with TGV structures is required. Full article

In this article, we present a systematic investigation on a multistep nanosphere lithography technique to uncover its potential in fabricating a wide range of two- and three-dimensional nanostructures. A tilted (polar angle) electron beam shower on a nanosphere mask results in an angled shadow mask deposition. The shape of the shadow also depends on the azimuthal angle of the mask sitting on top of the substrate. We performed angled shadow mask depositions with systematic variation of these two angular parameters, giving rise to complex nanostructures (down to 50 nm), repeated over a large area without defect. In this article, nanosphere lithography with two- and four-fold azimuthal symmetry was studied at constant tilt angles followed by variations in tilt without azimuthal rotation of the substrate. Finally, both angular parameters were simultaneously varied. The structure of shadow crystals was explained using Matlab simulation. This work stretches the horizons of nanosphere lithography, opening up new scopes in plasmonic and magnonic research. Full article

The investigation of the preparation of polystyrene (PS) nanosphere monolayers for the fabrication of carbon nanotube (CNT) forest fishnet metamaterial structures is studied in this paper, as a cheap alternative for top-down patterning methods. The precise control of dry etching conditions resulted in a highly controlled diameter of PS nanobeads, which were then used as a shadow mask for CNT fishnet preparation. The change of the size of the holes from 370 nm to 665 nm resulted in a gradual change of the CNT morphology from multi-walled to single-walled CNTs. The ultraviolet-visible (UV-Vis) reflectance spectra showed that the variation of the hole diameter resulted in the nonlinear light absorption in CNT fishnets that caused the change of the resonance frequency. The change of the fishnet wire width (inductance) and the hole size (capacitance) resulted in the blueshift of the broadband resonance frequency peak. The presented work has a significant potential to allow for the large-scale fabrication of CNT-based fishnet metamaterial structures for applications in energy harvesting, energy storage, solar cells, or optoelectronic devices, such as neuromorphic networks. Full article

The fast and precise fabrication of micro-devices based on single flakes of novel 2D materials and stacked heterostructures is vital for exploration of novel functionalities. In this paper, we demonstrate a fast high-resolution contact mask lithography through a simple upgrade of metallographic optical microscope. Suggested kit for the micromask lithography is compact and easily compatible with a glove box, thus being suitable for a wide range of air-unstable materials. The shadow masks could be either ordered commercially or fabricated in a laboratory using a beam lithography. The processes of the mask alignment and the resist exposure take a few minutes and provide a micrometer resolution. With the total price of the kit components around USD 200, our approach would be convenient for laboratories with the limited access to commercial lithographic systems. Full article

Detection of light dark matter, such as axion-like particles, puts stringent requirements on the efficiency and dark-count rates of microwave-photon detectors. The possibility of operating a current-biased Josephson junction as a single-microwave photon-detector was investigated through numerical simulations, and through an initial characterization of two Al junctions fabricated by shadow mask evaporation, done in a dilution refrigerator by measuring escape currents at different temperatures, from 40 mK up to the Al transition temperature. The escape dynamics of the junctions were reproduced in the simulation, including the dissipative effects. Inhibition of thermal activation was observed, leaving the macroscopic quantum tunneling as the dominant effect well beyond the crossover temperature. Full article

Electrochemical analysis is an efficient way to study various materials. However, nanoparticles are challenging due to the difficulty in fabricating a uniform electrode containing nanoparticles. We developed novel approaches to incorporate nanoparticles as a working electrode (WE) in a three-electrode microfluidic electrochemical cell. Specifically, conductive epoxy was used as a medium for direct application of nanoparticles onto the electrode surface. Three approaches in this work were illustrated, including sequence stamping, mix stamping, and droplet stamping. Shadow masking was used to form the conductive structure in the WE surface on a thin silicon nitride (SiN) membrane. Two types of nanomaterials, namely cerium oxide (CeO₂) and graphite, were chosen as representative nanoparticles. The as-fabricated electrodes with attached particles were characterized using atomic force microscopy (AFM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Electrochemical analysis was performed to verify the feasibility of these nanoparticles as electrodes. Nanomaterials can be quickly assessed for their electrochemical properties using these new electrode fabrication methods in a microfluidic cell, offering a passport for rapid nanomaterial electrochemical analysis in the future. Full article

This article presents an ablative method of cutting masks from ultra-thin metal foils using nanosecond laser pulses. As a source of laser radiation, a pulsed fiber laser with a wavelength of 1062 nm with the duration of pulses from 15 to 220 nanoseconds (ns), was used in the research. The masks were made of stainless-steel foil with thicknesses of 30 µm, 35 µm, and 120 µm. Channels of different lengths from 50 to 300 µm were tested. The possibilities and limitations of the presented method are described. The optimization of the cutting process parameters was performed using the experiment planning techniques. A static, determined complete two-level plan (SP/DC 2⁴) was used. On the basis of the analysis of the test structures, we designed and produced precise shading masks used in the process of organic field effect transistor (OFET) electrode evaporation. The ablative method proved suitable to produce masks with canals of minimum lengths of 70 µm. It offers facile, fast, and economically viable shadow mask fabrication for organic electronics applications, which moreover might enable fast prototyping and circuit design. Full article