Fabrication Steps Research Articles

On-Chip Annealing Using Embedded Micro-Heater for Highly Sensitive and Selective Gas Detection.

The demand for gas sensing systems that enable fast and precise gas recognition is growing rapidly. However, substantial challenges arise from the complex fabrication process of sensor arrays, time-consuming data transmission to an external processor, and high energy consumption in multi-stage data processing. In this study, a gas sensing system using on-chip annealing for fast and power-efficient gas detection is proposed. By utilizing a micro-heater embedded in the gas sensor, the sensing material of adjacent sensors in the same substrate can be easily varied without further fabrication steps. The response to oxidizing gas is constrained in metal oxide (MOX) sensing material with small grain sizes, as the depletion width of grain cannot extend beyond the grain size during the gas reaction. On the other hand, the response to reducing gases and humidity, which decrease the depletion width, is less affected by grain sizes. A readout circuit integrating a differential amplifier and dual FET-type gas sensors effectively emphasizes the response to oxidizing gases by canceling the response to reducing gases and humidity. The selective on-chip annealing method is applicable to various MOX sensing materials, demonstrating its potential for application in commercial fields due to its simplicity and expandability.

Sensitivity, linearity, and noise evaluation of L‐shaped dielectrically modulated label free tunnel field‐effect transistor biosensor

AbstractThis research article examines a L‐shaped dielectrically modulated label free TFET (L‐DM‐TFET) biosensor for the purpose of detecting different biomolecules using a label‐free biosensing detection technique. The proposed structure allows for the recognition of biomolecules by modulating various electrical properties, such as the drain current, transconductance, and linearity parameters. The source region of the proposed TFET incorporates a SiGe (source)/Si (channel) heterojunction, utilizing a low bandgap material of SiGe. This heterojunction is employed to enhance the ON‐state current of the devices. The materials used and the fabrication steps involved in our proposed device are compatible with complementary metal‐oxide‐semiconductor (CMOS) technology. This analysis is conducted using a calibrated Silvaco technology computer‐aided design (TCAD) simulator. Additionally, by considering a dielectric constant range of 1–12, we calculate various figure of merits (FOMs) parameters for the device. These include evaluation of linearity, sensitivity, and noise characteristics. Furthermore, we have conducted an analysis of linearity FOMs, such as VIP2, VIP3, IIP3, and IMD3 for the proposed device under study. Additionally, the linearity analysis of the presented tunneling FET (TFET) indicates the device's excellent performance in distortionless switching operations. Consequently, the L‐shaped dielectrically modulated biosensor holds potential suitability for high‐speed circuit designs.

Self-Assembled Block Copolymers as a Facile Pathway to Create Functional Nanobiosensor and Nanobiomaterial Surfaces.

Block copolymer (BCP) surfaces permit an exquisite level of nanoscale control in biomolecular assemblies solely based on self-assembly. Owing to this, BCP-based biomolecular assembly represents a much-needed, new paradigm for creating nanobiosensors and nanobiomaterials without the need for costly and time-consuming fabrication steps. Research endeavors in the BCP nanobiotechnology field have led to stimulating results that can promote our current understanding of biomolecular interactions at a solid interface to the never-explored size regimes comparable to individual biomolecules. Encouraging research outcomes have also been reported for the stability and activity of biomolecules bound on BCP thin film surfaces. A wide range of single and multicomponent biomolecules and BCP systems has been assessed to substantiate the potential utility in practical applications as next-generation nanobiosensors, nanobiodevices, and biomaterials. To this end, this Review highlights pioneering research efforts made in the BCP nanobiotechnology area. The discussions will be focused on those works particularly pertaining to nanoscale surface assembly of functional biomolecules, biomolecular interaction properties unique to nanoscale polymer interfaces, functionality of nanoscale surface-bound biomolecules, and specific examples in biosensing. Systems involving the incorporation of biomolecules as one of the blocks in BCPs, i.e., DNA-BCP hybrids, protein-BCP conjugates, and isolated BCP micelles of bioligand carriers used in drug delivery, are outside of the scope of this Review. Looking ahead, there awaits plenty of exciting research opportunities to advance the research field of BCP nanobiotechnology by capitalizing on the fundamental groundwork laid so far for the biomolecular interactions on BCP surfaces. In order to better guide the path forward, key fundamental questions yet to be addressed by the field are identified. In addition, future research directions of BCP nanobiotechnology are contemplated in the concluding section of this Review.

Ultrathin and Deformable Graphene Etch Mask for Fabrication of 3D Microstructures.

Three-dimensional (3D) microfabrication techniques play a crucial role across various research fields. These techniques enable the creation of functional 3D structures on the microscale, unlocking possibilities for diverse applications. However, conventional fabrication methods have limits in producing complex 3D structures, which require numerous fabrication steps that increase the costs. Graphene is an atomically thin material known for its deformability and impermeability to small gases and molecules, including reactive gases like XeF2. These features make graphene a potential candidate as an etch mask for 3D microfabrication. Here, we report the fabrication of various 3D microstructures using graphene etch masks directly grown and patterned on a Si substrate. The patterned graphene deforms and wraps the etched structures, allowing for the fabrication of complicated 3D microstructures, such as mushroom-like and step-like microstructures. As a practical demonstration of the graphene etch mask, we fabricate an omniphobic surface of reentrant 3D structures on a Si substrate. Our work provides a method for fabricating complex 3D microstructures using a graphene etch mask, contributing to advancements in etching and fabrication processes.

Direct Laser Writing: From Materials Synthesis and Conversion to Electronic Device Processing.

Direct Laser Writing (DLW) has been increasingly selected as a microfabrication route for efficient, cost-effective, high-resolution material synthesis and conversion. Concurrently, lasers participate in the patterning and assembly of functional geometries in several fields of application, of which electronics stand out. In this review, recent advances and strategies based on DLW for electronics microfabrication are surveyed and outlined, based on laser material growth strategies. First, the main DLW parameters influencing material synthesis and transformation mechanisms are summarized, aimed at selective, tailored writing of conductive and semiconducting materials. Additive and transformative DLW processing mechanisms are discussed, to open space to explore several categories of materials directly synthesized or transformed for electronics microfabrication. These include metallic conductors, metal oxides, transition metal chalcogenides and carbides, laser-induced graphene, and their mixtures. By accessing a wide range of material types, DLW-based electronic applications are explored, including processing components, energy harvesting and storage, sensing, and bioelectronics. The expanded capability of lasers to participate in multiple fabrication steps at different implementation levels, from material engineering to device processing, indicates their future applicability to next-generation electronics, where more accessible, green microfabrication approaches integrate lasers as comprehensive tools.

The Role of Interdigitated Electrodes in Printed and Flexible Electronics.

Flexible electronics, also referred to as printable electronics, represent an interesting technology for implementing electronic circuits via depositing electronic devices onto flexible substrates, boosting their possible applications. Among all flexible electronics, interdigitated electrodes (IDEs) are currently being used for different sensor applications since they offer significant benefits beyond their functionality as capacitors, like the generation of high output voltage, fewer fabrication steps, convenience of application of sensitive coatings, material imaging capability and a potential of spectroscopy measurements via electrical excitation frequency variation. This review examines the role of IDEs in printed and flexible electronics since they are progressively being incorporated into a myriad of applications, envisaging that the growth pattern will continue in the next generations of flexible circuits to come.

Multi-scale corrosion behavior of Al/Ti/Fe multi-interfaces composites

In this study, we are presented a thermodynamics and kinetics model to reveal the corrosion sensitivities of Al/Ti/Fe multi-interface composites. The model demonstrates that impurity elements (Mn) and interface intermetallics alter the electrochemical polarization behavior of the Al and Fe layers, leading to a shift to cathodic control. Additionally, intermetallic compounds, which are formed at the interface enhance wear resistance and modify its electrochemical corrosion behavior. This study provides new insights into the interface corrosion mechanism of multi-interface composites and offers directions to improve the multi-interfaces composites corrosion resistance, which is an important step for future fabrication and applications of multi-interface composites.

Enabling low-power analog and RFIC design through advanced semiconductor FDSOI MOSFETs

This study investigates the electrical performance of advanced semiconductor Ge-pocket-doped fully depleted silicon-on-insulator MOSFETs in comparison to conventional fully depleted silicon-on-insulator (FDSOI) MOSFETs. In this study vital electrical parameters such as the drain current, band diagram, lateral electric field, surface potential, and work function of the gate material were investigated. The advanced Ge pocket-doped FDSOI MOSFET structure demonstrates superior characteristics, such as a higher Ion/Ioff ratio, smaller subthreshold slope, lower capacitance, and higher cut-off frequency, when compared to conventional FDSOI MOSFETs. The structure of the Ge pocket-doped FDSOI MOSFET in the source and drain regions is designed to overcome the scaling effects of the transistor. In addition, this paper delves into the fabrication of the proposed device structure, outlining the key steps and intricacies involved. This study shows that the proposed device can be used for both digital and analog applications because it has good switching performance and a low cut-off frequency. In addition, the fabrication steps of the proposed structure were compatible with the existing fabrication process steps for conventional FDSOI MOSFETs. The simulation and analysis of the advanced semiconductor structure were performed using the Sentaurus TCAD simulator.

Low-cost ternary composite photocatalysts consisting of TiO2, kaolinite and cement for an efficient organic waste decontamination in water

The present study demonstrates the fabrication of heterogeneous ternary composite photocatalyst consisting of TiO2, kaolinite and cement (TKCe), which is essential to overcome the practical barriers that are inherent to currently available photocatalysts. TKCe is prepared via a cost-effective method, which involved the mechanical compression and thermal activation as a major fabrication steps. Clay-cement ratio primarily determines TKCe mechanical strength and photocatalytic efficiency where TKCe with the optimum clay-cement ratio, which is 1:1 results in uniform matrix with fewer surface defects. The composites that have clay-cement ratio below or above the optimum ratio account for comparatively low mechanical strength and photocatalytic activity due to inhomogeneous surface with more defects, including particle agglomeration and cracks. The TKCe mechanical strength is mainly from clay-TiO2 interactions and TiO2-cement interactions. TiO2-cement interactions result in CaTiO3 formation, which significantly increases matrix interactions; however, the maximum composite performance is observed at the optimum titanate level; anything above or below this level deteriorates composite performance. Over 90% degradation rates are characteristic to all TKCe, which follow pseudo first order kinetics in methylene blue decontamination. The highest rate constant is observed with TKCe 1-1, which is 1.57 h−1 and being the highest among all the binary composite photocatalyst that were fabricated previously. The TKCe 1-1 accounts for the highest mechanical strength, which is 6.97 MPa, while the lowest is observed with TKCe 3-1, indicating that clay-cement ratio has direct relation to composite strength. TKCe is a potential photocatalyst, which can be obtained in variable sizes and shapes, complying with real industrial wastewater treatment requirements.

On the reproducibility of electron-beam lithographic fabrication of photonic nanostructures.

Photonic nanostructures such as gratings and ring resonators have become ubiquitous building blocks in Photonics. For example, they are used in filters, they resonantly enhance signals and act as grating couplers. Much research effort is invested in using such structures to create novel functionalities, which often employs electron-beam lithography. An intrinsic issue in this field is the ability to accurately achieve a specific operating wavelength, especially for resonant systems, because nanometer-scale variations in feature size may easily detune the device. Here, we examine some of the key fabrication steps and show how to improve the reproducibility of fabricating wavelength scale photonic nanostructures. We use guided mode resonance grating sensors as our exemplar and find that the exposure condition and the development process significantly affect the consistency of the resonance wavelength, amplitude, and sensitivity of the sensor. By having careful control over these factors, we can achieve consistent performance for all the sensors studied, with less than 10% variation in their resonance behaviors. These investigations provide useful guidelines for fabricating nanostructures more reliably and to achieve a higher success rate in exploratory experiments.

Reduced graphene oxide/gold nanoparticles based ultrasensitive resistive sensor for PCA3

Early prostate cancer detection can be improved by detecting more specific markers like PCA3 RNA. This study reports a novel and simple method for detecting PCA3 RNA using a sensor based on reduced graphene oxide (RGO), gold nanoparticles (AuNP), and a single-stranded DNA (ssDNA). The device was characterized at each fabrication step using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The RGO/AuNP/ssDNA sensor exhibited a significant change in resistance (6.51–15.01%) when exposed to varying concentrations of PCA3 (0.1–100 ng/mL). The developed device showed selective response towards PCA3 (14.5% for 50 ng/mL) when compared with negative controls like phosphate buffer saline solution (0.28%), PCA3-negative control sample (1.03%), RNA extracted from lung cancer (0.88%), and breast cancer (1.17%) cell lines. The RGO/AuNP/ssDNA sensor could also be employed to quantify the PCA3 RNA present in the RNA mixture extracted from a prostate cancer cell line and the observed findings were in excellent agreement with semi-quantitative real-time polymerase chain reaction (RT-PCR) results.

Two-photon polymerized wetting morphologies for tunable external and internal electrode micropatterning

Numerous existing and emerging microsize technologies operate by utilizing electrical circuits on surfaces and within solid objects, i.e., external and internal electrodes, respectively. While current micropatterning techniques have achieved extensive progress on current systems via pattern resolution and discretization on simple surfaces, the introduction of new applications relies on the complexity of the parts on which these patterns are fabricated. Additionally, many state-of-the-art applications utilize novel materials for functional systems, which further complicates their fabrication. This paper introduces innovative electrode micropatterning and microchannel filling approaches that support complex 3D designs and reduce the number of fabrication steps. The approaches leverage microsize hydrophobic and hydrophilic morphologies fabricated using the two-photon polymerization (2PP) additive manufacturing (AM) process, in conjunction with the target part. Once fabricated, the part is dipped into a conductive solution or other functional liquids, forming patterns on the surfaces and filling the channels based on the pre-designed wetting morphologies. These morphologies incorporate additional structures beyond the conventional hydrophilic and reentrant hydrophobic structures to facilitate the dipping process. This paper demonstrates the efficacy of the tunable electrode micropatterning approach to fabricate various microsystems utilizing 2PP, wetting morphologies, and the developed dipping process.

Development of Anti-TNT@Cu-BTC MOF thin film using drop caste method for trinitrotoluene (TNT) sensing

Antibody functionalised Cu-BTC MOF thin film was prepared using drop-casting method on indium tin oxide (ITO) coated glass substrate for trinitrotoluene (TNT) sensing under certain experimental conditions. Initially, APTES functionalization on ITO substrate using EDC-NHS chemistry was carried out, after which biofunctionalization of Anti-TNT on Cu-BTC MOF (1,3,5-tricarboxylic acid as an organic linker and copper ions as metal) thin film was carried out. Each step of sensor fabrication was characterised by the X-ray diffraction, microscopic and spectroscopic techniques. The interaction of one layer with another is confirmed with the help of FTIR and EDX. ITO substrate modification increases resistance at each stage from 1.29 to 3.3 KΩ. This modified substrate used as a working electrode during the sensing experiment. Afterward, response cum detection of 2,4,6-trinitrotoluene (TNT) in the 0.1 ppm to 0.6 ppm range has been noted by impedance method using three electrode systems of an electrochemical workstation. Host-guest interaction cum mechanism between TNT antibody functionalised APTES@Cu-BTC and TNT analyte has been observed which origins change in their resistance/impedance. The variation in resistance is directly proportional to the concentrations, exhibiting a strong linear relationship with 0.9702 value for R2. We find out that the presence of TNT antibody increases the specificity of TNT sensing and minimizes cross-reactivity with unknown/other interfering compounds. The concentration–response graph shows a 0.04 ppm limit of detection at room temperature.

All Solution Processable OTFT-Based on Direct-Written Printing Method Towards Flexible Electronics Applications

Development of organic electronics, particularly organic thin film transistors (OTFTs), have been centred of discussion among researchers due to their potential uses in flexible electronics applications. Conventionally, an inkjet printing method has been deployed to fabricate the OTFTs due to its simplicity in fabrication steps and applicability to diverse substrates and solution-processable materials. Nonetheless, this technique has a major drawback which requires low viscosity materials to prevent clogging issue at the printer’s nozzle. This in return limits the material selections and requires additional steps i.e. modification of the selected materials to fit the printer’s requirement or in other words, to avoid clogging at the nozzle. Therefore, this paper proposes a method to fabricate a bottom gate bottom contact (BGBC) OTFT by using a direct-write printing technique which is compatible with a commercial conductive ink that can be directly used without any further modification. This technique does not compromise the fabricated devices overall performance and can fabricate the devices up to micrometre scale. The proposed OTFT achieved a saturation mobility of 4.28x10-5 cm2/Vs, a threshold voltage of -0.4 V, an on/off current ratio of 102, and a subthreshold swing of 10 V/dec with overall fabrication temperature is less than 150 ℃, hence, makes it suitable for flexible electronics applications.

Current-Dependent Resistance in TES Wiring Superimposed Nb Striplines

During the characterization of the demonstration model of the Cryogenic AntiCoincidence (CryoAC) Detector (ACS-10), a current-dependent parasitic resistance was found in series with the TES network on board the detector. Analysis was possible because the resistance rises for currents above 11 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu$$\\end{document}A, and is therefore not observed at low bias excitation. A comparison of measurements of the TES across its Nb wiring at different temperatures suggested that the source of resistance was in the wiring and not in the TES network. After several analysis of the wiring fabrication steps, FIB-FE-SEM studies of film sections and tests of niobium film quality, we understood that the parasitic resistance was due to point contact in the Nb step coverage caused by film cracks. The fracture was due to the wall steepness and thickness of the films, since rapid step coverage is less mechanically stable and the stress on the films is proportional to the fourth power of the thickness. Therefore, all thicknesses in the wiring were reduced to the minimum optimum step coverage values and the first negative lithography parameters were optimized to reduce the wall film angle. The samples after this optimization showed no current-dependent series resistance to TES.

Nontoxic Initiator Alternatives to TEMED for Redox Hydrogel Polymerization.

Polymeric hydrogels are versatile biomaterials, offering unique advantages in tunability and biocompatibility that make them well-suited to a range of applications. Cross-linking, a fundamental step in hydrogel fabrication, is often initiated using a toxic redox system, ammonium persulfate (APS), and tetramethylethylenediamine (TEMED), which hinders hydrogel utility in direct contact with cells (e.g., wound dressings). To overcome this limitation, we developed alternative redox gelation systems that serve as nontoxic replacements for TEMED. The alternate initiators were either synthetic or bioinspired amine-containing polymers, Glycofect and polyethylenimine (PEI). Used with APS, these initiator candidates produced hydrogels with short gelation time and comparable moduli to TEMED-based gels and underwent further mechanical testing and biocompatibility characterization. While achieving mechanical properties similar to those of the control, the gels based on Glycofect and PEI outperformed TEMED-based gels in two cell viability studies, with Glycofect-initiated gels displaying significantly higher cytocompatibility. Taken together, these results indicate that Glycofect may serve as a drop-in replacement for TEMED to fabricate hydrogels with improved biocompatibility.

A Fully Integrated Microfluidic Device with Immobilized Dyes for Simultaneous Detection of Cell-Free DNA and Histones from Plasma Using Dehydrated Agarose Gates.

Sepsis, a life-threatening condition resulting from a failing host response to infection, causes millions of deaths annually, necessitating rapid and simple prognostic assessments. A variety of genomic and proteomic biomarkers have been developed for sepsis. For example, it has been shown that the level of plasma cell-free DNA (cfDNA) and circulating histones increases considerably during sepsis, and they are linked with sepsis severity and mortality. Developing a diagnostic tool that is capable of assessing such diverse biomarkers is challenging as the detection methodology is quite different for each. Here, a fully integrated microfluidic device capable of detecting a genomic biomarker (cfDNA) and a proteomic biomarker (total circulating histones) using a common detection platform has been demonstrated. The microfluidic device utilizes dehydrated agarose gates loaded with pH-specific agarose to electrophoretically trap cfDNA and histones at their respective isoelectric points. It also incorporates fluorescent dyes within the device, eliminating the need for off-chip sample preparation and allowing the direct testing of plasma samples without the need for labeling DNA and histones with fluorescent dyes beforehand. Xurography, which is a low-cost and rapid method for fabrication of microfluidics, is used in all the fabrication steps. Experimental results demonstrate the effective accumulation and separation of cfDNA and histones in the agarose gates in a total processing time of 20 min, employing 10 and 30 Volts for cfDNA and histone accumulation and detection, respectively. The device can potentially be used to distinguish between the survivors and non-survivors of sepsis. The integration of the detection of both biomarkers into a single device and dye immobilization enhances its clinical utility for rapid point-of-care assessment of sepsis prognosis.

Nanofabrication Process Scale-Up via Displacement Talbot Lithography of a Plasmonic Metasurface for Sensing Applications

The selection of an affordable method to fabricate plasmonic metasurfaces needs to guarantee complex control over both tunability and reproducibility of their spectral and morphological properties, making plasmonic metasurfaces suitable for integration into different sensing devices. Displacement Talbot lithography could be a valid solution thanks to the limited fabrication steps required, also providing the highly desired industrial scalability. Fabricated plasmonic metasurfaces are represented by a gold nanohole array on a glass substrate based on a triangular pattern. Scanning electron microscopy measurements have been recorded, showing the consistency of the surface features with the optimized design parameters. Reflectance and transmittance measurements have also been carried out to test the reliability and standardization of the metasurface’s optical response. Furthermore, these plasmonic metasurfaces have also been successfully tested for probing refractive index variations in a microfluidic system, paving the way for their use in sensitive, real-time, label-free, and multiplexing detection of bio-molecular events.

Investigation of Aluminum and Gold Flip-Chip Bonding for Quantum Device Integration

The majority of qubit chip integration is realized in a two-dimensional (2D) architecture. Whereas 3D architecture enables more advantages like efficient interconnect routing, allowing for more compact qubit coupling geometries, reducing form factor, and increased connectivity beyond nearest-neighbor interactions. Flipchip (FC) assembly has been demonstrated to enable 3D architecture connecting qubit chip, interposer, and readout in a sandwich-like structure. Moreover, 3D integration allows the fabrication of hosting chip circuitry without degrading the qubit performance [1–4]. Different material considerations have to be taken into account since qubit operational frequency is in the gigahertz range and operating temperature is in the mK range to avoid thermal excitation. Materials that possess superconducting characteristics like Indium (In), Titanium Nitride (TiN), Tantalum Nitride (TaN), and Niobium (Nb) have been discussed as potential interconnect between building blocks [3, 5]. The In bumping on Aluminum (Al) redistribution layers require under-bump metallization (UBM) layers thus introducing multiple fabrication steps before the bonding process. An alternative approach would be to use the existing Al surface to electrochemically grow Al bumps and bond the chip using thermosonic bonding (TSB) at below 150°C to form a homogeneous metal-metal interface [6, 7].

Fabrication of an electrochemical impedance sensor for ketamine hydrochloride and its application in the detection of doping substances in sports

This work reports an ultrasensitive impedimetric immunosensor for ketamine detection using self-assembled monolayers of 3-mercaptopropionic acid on gold electrodes. Monoclonal ketamine antibodies were covalently tethered via EDC/NHS crosslinking chemistry. Each fabrication step was validated by electrochemical and microscopic characterization. The optimized immunoelectrode demonstrated a broad dynamic range from 1 to 1000 ng/mL ketamine and record low detection limit of 0.5 ng/mL attributed to excellent antibody affinity. Analytical recovery of spiked serum and urine samples ranged 92–103% proving reliability despite biosample complexity. The simple, rapid and portable sensor surpasses existing chromatography and electrochemical techniques in terms of detection sensitivity as well as cost, instrumentation and training needs. The capabilities are attributed to rational antibody immobilization strategies enabling efficient binding events. The attractive detection limits coupled with label-free operation and microscale construct provide optimism regarding translation to viable clinical and on-site testing devices for toxicology, anti-doping and therapeutic applications.