Screen Printing Technique Research Articles

Characteristic of graphene-based thick film gas sensor for ethanol and acetone vapor detection at room temperature

<p>Ethanol and acetone are volatile organic compound gases widely used in food processing. Health problems such as irritation of the eyes, nose, and throat can affect human health if exposed to these gases. Two graphene gas sensors were fabricated using a screen-printing technique onto a glass substrate to compare their performance to the acetone and ethanol vapors at room temperature. The graphene paste was prepared by mixing 95 wt.% of the binder with 5 wt.% of graphene nanoflakes. A silver paste was used asthe interdigitated electrode of the gas sensor and becamethe first layer of the gas sensor. The silver paste was deposited on the glass substrate using a screen-printing technique and fired at 150°C for 15 minutes. Next, the graphene paste was depositedonto the interdigitated electrode using a screen-printing technique and becamethe second layer of the gas sensor. The graphene was annealed at 200°C for 30 minutes. Both graphene gas sensors responded well to ethanol and acetone vapor with an n-typed gas sensor at room temperature. As a comparison, the graphene gas sensor showed better characteristics in terms of response and recovery characteristicsto ethanol vapor than acetone vapor at room temperature. The response and response time of the graphene-based thick film gas sensor to ethanol were approximately 21.89 and 24.08, respectively.</p>

Screen printable PANI/carbide-derived carbon supercapacitor electrode ink with chitosan binder

Polyaniline (PANI)/carbide-derived carbon (CDC) was synthesized by using in-situ chemical oxidative polymerization of PANI in presence of CDC. Conductive electrode ink materials were prepared by using eco-friendly chitosan binder in water media. In the following, symmetrical supercapacitors (SCs) were fabricated by both doctor blade coating and screen printing technique. The electrical conductivity, morphology, specific capacitance, and energy density of these composites were evaluated for their applicability as SC electrodes. Pure PANI with chitosan binder was not printable because of its brittleness, however, the presence of CDC allows the preparation of smooth films which are suitable for electrode preparation. The fabricated composite electrode has a higher specific capacitance (up to 419 F g−1) and higher energy density (up to 6.7 W h kg−1) compared to the pristine CDC electrode. The capacitance of screen-printed SCs was 440–470 mF with an equivalent series resistance of about 27 Ω.

Preparation and effect of additives n-ZnO doped p-NiO Screen printed thick films on Structural and Electrical Properties

Abstract: Zinc oxide (ZnO) doped Nickel oxide (NiO) thick films prepared using glass substrate by screen printing technique successfully. Synthesis of nanoparticles was confirmed using characterisation techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and static gas sensing system. The structural properties of the prepared thick films were studied by XRD analysis. The observed prepared thick film shows polycrystalline nature of the films with a cubic structure and crystallite size found to be in the range of 18.21 to 35.44 nm. SEM analysis of prepared films enabled the conclusion that the prepared films are uniform, large crystals and heavily agglomerated particles were observed spherical in shape. Also, with increase in concentration specific surface area increases. The quantitative chemical compositions were analysed by SEM-EDS and it shows nonstoichiometric in nature. The correlation between structural and morphological properties are reported. The prepared thick films of ZnO doped NiO nanoparticles were analysed for electrical parameters namely TCR, activation energy and sheet resistivity, specific surface area were evaluated at different concentration of zinc oxide that assured the prepared material has a semiconducting nature. Electrical characterization results resistivity decreases from 6283.377 to 1972.727 with increase in wt.% concentration of ZnO. Such a prepared film can be used in fabrication of optoelectronic devices.

Pore-existing phosphor-in-glass film realizing ultra-efficient and uniform laser lighting

The development of phosphor-converted laser lighting has encountered a significant problem: the difficulty of homogeneously mixing the laser light with the luminescent light. Previous studies reveal that enhancing the scattering of the phosphor can improve color mixing but often sacrifices luminous efficacy and limits the peak luminance. To address this, a pore-existing YAG:Ce-based phosphor-in-glass film is prepared using the screen-printing technique. Interestingly, it is found that the pore size is highly correlated with the thickness, with thicker samples having larger pores. When excited by blue laser, a typical sample with a thickness of 60 μm exhibits an ultra-high luminous efficacy of 261 lm/W and a high saturation threshold of 20.5 W (9.1 W/mm2), resulting in a peak luminous exitance of 1244 lm/mm2@3839 lm. Furthermore, the color mixing was evaluated via angular color temperature distribution, showing uniform light emission with a maximum correlated color temperature (CCT) variation of only ∼800 K.

Halogen-Free Waterborne Polymeric Hybrid Coatings for Improved Fire Retardancy of Textiles.

Wildfires are becoming more intense and more frequent, ravaging the habitations and ecosystems in their path. One solution to reducing the risk of damage to buildings and other structures during a fire event is the use of fire-retardant coatings that can stop or slow down the spread of flames, especially for textile materials. The present study focuses on the preparation and application of halogen-free boron/bentonite-based polymeric fire-retardant (FR) hybrid coating formulations for fabrics such as cotton (CO) and polyester (PE) fibers. For the preparation of FR composites, two types of boron derivatives, disodium octaborate and zinc borate, were used in combination with sodium bentonite. A styrene-acrylic copolymer was specifically synthesized and used as a coating binder for FR components to apply on fabrics. The properties of the synthesized copolymer and FR composites were characterized with a particle size analysis, FTIR spectroscopy, a dynamic mechanical thermal analysis (DMTA), and rheological measurements. The obtained hybrid composites based on styrene-acrylic copolymers and two different inorganic fillers were applied on cotton (CO) and polyester (PE) fabrics with a screen-printing technique, and the flame retardancy performance of the finished textile samples was investigated by means of flame spread and limit oxygen index (LOI) tests. The findings showed that the FR-composite-coated fabrics had higher LOI values and much decreased flame spread rates in comparison with uncoated ones. Among the boron derivatives, the composites prepared with disodium octaborate (FR-A) had much more pronounced LOI values and decreased flame spread behavior in comparison with the composite with zinc borate (FR-B). When compared to a commercial product, the FR-A composite, in conjunction with the specially synthesized polymer, demonstrated commendable fire retardancy performance and emerged as a promising candidate for a halogen-free waterborne fire-retardant coating for fabrics.

Thermally matched multilayer ceramic composite insulating layers for high-temperature thick/thin-film sensors on nickel-based superalloy

Thick/thin-film sensors are used for health monitoring of components such as aero-engines, which are mainly cast from electrically conductive nickel-based superalloys. It is necessary to prepare an insulating layer between the nickel-based superalloys and the thick/thin film sensor. For this purpose, a thermally matched multilayer ceramic composite insulating layers for thick/thin-film sensors have been designed. Three dielectric pastes with coefficients of thermal expansion similar to those of the metal substrate and Pt/Rh–Pt thick-film thermocouples were prepared on nickel-based superalloys by screen printing technique. Problems regarding the bonding strength of the insulating layers were solved, which improved the insulating properties. The microstructural characteristics of the insulating layers were characterized by scanning electron microscopy, and their insulation resistance at high temperatures was tested. The results show that the insulation resistance of insulating layers is increased by a factor of about 10 in this paper compared to the insulation resistance of insulating layers prepared by sputtering and other techniques in previous articles. When the temperature is 800 °C, the resistance value of the samples reaches 30.47 MΩ. It is noteworthy that the insulation resistance is still higher than 21 MΩ after annealing at 800 °C for 10 h. Moreover, the insulating coating survived thermal shock tests without cracking or delaminating. A S-type thermocouple is prepared on the insulating layers to verify its high-temperature electrical insulation performance. Test results show that the output voltage of the S-type thermocouple had a high linearity with an average Seebeck coefficient of 10.5 μV/°C during the temperature range of 200–1000 °C. Experiments show that the S-type thermocouple works stably at high temperatures and thermally matched multilayer composite insulation layers have good insulating properties.

Integral screen printed solar cells panel

This paper summarizes our activities in the field of process technologies for the fabrication of photovoltaic devices. The study is strongly focused on the integral screen printing technique for the fabrication of single crystal solar cells, using standard equipments available in our laboratory. The challenging aim of this survey is to attain encouraging results with very modest means. Knowing that any problem coming unexpectedly with the cell structure may influence more than one electrical parameter and as the process consists on several steps; we will stop at each stage and discuss the factors, which affect it. In pursuit of this goal a doping phosphorus1, a back contact silver-aluminium2, a front side silver3 and an anti reflective coating4 commercial pastes are printed and fired. The 36 fully screen printed solar cells connected in series offer a module with power output of 31 Watts5 and 11 % as efficiency.

Sustainable plant-wearable sensors for on-site, rapid decentralized detection of pesticides toward precision agriculture and food safety

The synergy between eco-friendly biopolymeric films and printed devices leads to the production of plant-wearable sensors for decentralized analysis of pesticides in precision agriculture and food safety. Herein, a simple method for fabrication of flexible, and sustainable sensors printed on cellulose acetate (CA) substrates has been demonstrated to detect carbendazim and paraquat in agricultural, water and food samples. The biodegradable CA substrates were made by casting method while the full electrochemical system of three electrodes was deposited by screen-printing technique (SPE) to produce plant-wearable sensors. Analytical performance was assessed by differential pulse (DPV) and square wave voltammetry (SWV) in a linear concentration range between 0.1 and 1.0 μM with detection limits of 54.9 and 19.8 nM for carbendazim and paraquat, respectively. The flexible and sustainable non-enzymatic plant-wearable sensor can detect carbendazim and paraquat on lettuce and tomato skins, and also water samples with no interference from other pesticides. The plant-wearable sensors had reproducible response being robust and stable against multiple flexions. Due to high sensitivity and selectivity, easy operation and rapid agrochemical detection, the plant-wearable sensors can be used to detect biomarkers in human biofluids and be used in on-site analysis of other hazardous chemical substances.

Functionalized GD2 Electrochemical Immunosensor to Diagnose Minimum Residual Disease of Bone Marrow in Neuroblastoma Effectively.

Neuroblastoma (NB) is known as the "king of childhood tumors" due to its highly metastatic, recurrence-prone, and difficult-to-treat characteristics. International Neuroblastoma Risk Grading Group (INRG) has recommended GD2, a disialoganglioside expressed on neuroectodermal tumor cells, as the target for detecting minimal residual disease in bone marrow metastases of high-risk neuroblastoma in children. Therefore, accurately identifying GD2-positive cells is crucial for diagnosing children with high-risk NB. Here, we designed a graphene/AuNP/GD2 Ab-functionalized electrochemical biosensor for GD2 detection. A three-electrode system was processed using a screen-printed technique with a working electrode of indium tin oxide, a counter electrode of carbon, and a reference electrode of silver/silver chloride. Graphene/AuNPs were modified on the indium tin oxide electrode using chronoamperometric scans, and then, the GD2 antibody was modified on the biosensor by electrostatic adsorption to achieve sensitive and specific detection of GD2-positive cells in bone marrow fluid. The results showed that a graphene/AuNP/GD2 Ab-functionalized electrochemical biosensor achieved GD2-positive cell detection in the range of 102 cells/mL~105 cells/mL by differential pulse voltammetry. Bone marrow fluid samples from 12 children with high-risk NB were retained for testing on our biosensor and showed 100% compliance with the clinical application of the gold-standard immunocytochemical staining technique for detecting GD2-positive cells qualitatively. The GD2-based electrochemical assay can accurately detect children with high-risk NB, providing a rapidly quantitative basis for clinical diagnosis and treatment.

Encounter with the Father of Op Art, Victor Vasarely: Research in Conservation and Art History, and Conservation Work on the Barson Collage

ABSTRACT The father of Op Art, Victor Vasarely, is the author of a paper collage called Barson, owned by the Museum of Contemporary Art, in Zagreb, which is the only such example in Croatian public cultural institutions. The collage was created in 1967 using the screen printing technique on paper glued to a paper support and then onto large-sized hardboard, and its creation was influenced by the leading objectivist artistic and philosophical trends and knowledge of the time, under the influence of which Vasarely created his art. The collage was found very dusty and with many damages on the entire surface of the paper support, such as cracks, dried and detached parts and traces of activities of insects. Works of Op Art imply an undisturbed perception of the artwork, which in the case of the Barson collage, due to caused damage, was impossible. Therefore, conservation and restoration work was carried out that included extensive research and numerous tests, followed by dry cleaning, gluing both layers of the paper carrier, removing traces of insects and the necessary, minimal retouching. The corresponding wooden frame was cleaned of a layer of dust, and the smaller, missing part was reconstructed with the same type of wood and finally retouched.

Design- and optimizing zinc gallate blue phosphor toward versatile applications in photo- and electroluminescence

The development of the blue light-emitting device is receiving much attention due to its wide application in display and optoelectronics matter. Herein, the cost-effective self-activated ZnGa2O4 blue phosphors have been demonstrated in photoluminescence as well as the alternating-current powder-based electroluminescence device. The phosphors are prepared in a facile method solid-state reaction with optimum annealing temperature and mixed with an organic binder before being coated in the ITO glass substrate through the screen-printing technique. In a low threshold voltage (0.4 × 104 V/cm in an electric field), it emits a broad spectrum from violet to the green region with an emission center at 440 nm originating from the defect vacancies in the ZnGa2O4 lattice. It has excellent stability and afterglow effect under ultraviolet exposure and a superior lifetime maintaining an intensity of more than 80% for 3000 min without any encapsulation under AC-driven voltage. In addition, due to the high radiation energy from the blue color emission, it can be used as a color-down conversion for red-yellow-green phosphors and photocatalysis in a dilute solution of TiO2 and methylene blue.

Synthesis, analysis and characterization of nitrogen/sulfur co-doped activated carbon for high-performance all-printed flexible supercapacitor

Achieving more effective nitrogen/sulfur (N/S) co-doping activated carbon (AC) with superior specific surface area and pseudocapacitive properties remains challenging. Herein, a simple hydrogen peroxide preprocessing of commercial AC has been demonstrated to dramatically promote the co-doping of N/S into AC. The N/S co-doped AC with hydrogen peroxide preprocessing (N/S-HAC) exhibits >2-fold increase in specific capacitance and exceptional rate capability (70 % capacitance retention from 0.5 A g−1 to 100 A g−1) relative to the pristine commercial AC. Systematic experiments and characterizations reveal the significantly enhanced capacitive performances of N/S-HAC can be attributed to the etching-induced pore expansion and high-concentration N/S co-doping incorporated pseudocapacitance. Furthermore, an all-printed N/S-HAC based flexible supercapacitor is fabricated by a facile screen-printing technique and shows an outstanding areal capacitance of 100 mF cm−2, energy and power density of 0.027 mWh cm−2 and 28 mW cm−2, respectively, as well as ultrahigh stability (90 % capacitance retention after 20,000 cycles at 10 mA cm−2). These results are superior to most of carbon-based flexible supercapacitors and even better than some pseudocapacitive materials. In addition, the printed flexible supercapacitor maintains stable capacitance after 1000 bending cycles, even when bent to different angles (45°, 90°, 135°, and 180°), indicating the excellent flexibility. Additionally, the packaged flexible supercapacitor arrays integrating multiple supercapacitors solidly light up LEDs, even during dynamic bending. This work opens a promising prospect for the development of carbon-based flexible supercapacitors with both outstanding power and energy density, remarkable stability, and excellent flexibility.

Printed flexible supercapacitor from conductive ink of graphite nanocomposite blended with Co3O4 to facilitate the fabrication of energy storage device

An easy-to-make and potential technique for designing of supercapacitor has been proposed by printing conductive ink from porous Co3O4 and graphite nanocomposite. This method simplifies the process of fabrication of energy storage devices. The ink used in this fabrication was prepared after blending the porous Co3O4 nanoparticle composite with graphite, porous Co3O4 nanosphere was synthesized in situ through a single-step calcination process of the zeolitic imidazolate framework precursor (ZIF-67). To ensure homogenous fabrication, the supercapacitor was prepared by screen-printing technology, which allowed for the even distribution of ink using a standard squeeze spreader. The performance was evaluated by designing two types of supercapacitors: an ultra-flexible symmetric supercapacitor (CG-1) and an asymmetric supercapacitor (ASSC), both of which utilized the solid polymeric electrolyte with a resistance of 4.92 Ω. Our research showed an enhanced specific capacitance of 85 Fg−1 for CG-1 and 137 Fg−1 for ASSC, indicating the high efficiency of these lab-created screen-printed supercapacitor devices. The ASSC supercapacitor exhibited remarkable capacitance retention (%). After 2500 cycles, it retained 96.3 %, and even after 5000 cycles, it retained 85.9 %. The results highlight its exceptional flexibility and durability, with a retention rate ranging from 97.8 % to 99.3 % when subjected to various bending angles. Finally, the current works present the fabrication of supercapacitors using a user-friendly screen-printing technique, where ink was prepared by the optimal recipe of ZIFs and graphite nanocomposite. Our approach involved preparing an ink with an optimized recipe of zeolitic imidazolate frameworks (ZIFs) and graphite nanocomposites. It emphasizes the promising prospects of employing metal-organic frameworks, specifically ZIFs, as effective templates for producing porous electrode materials. This breakthrough paves the way for the production of innovative devices and their application in the future of state-of-the-art flexible energy storage.

Luminescent Mechanism and Anti-Counterfeiting Application of Hydrophilic, Undoped Room-Temperature Phosphorescent Silicon Nanocrystals.

Silicon nanocrystals (SiNCs) have attracted extensive attention in many advanced applications due to silicon's high natural abundance, low toxicity, and impressive optical properties. However, these applications are mainly focused on fluorescent SiNCs, little attention is paid to SiNCs with room-temperature phosphorescence (RTP) and their relative applications, especially water-dispersed ones. Herein, this work presents water-dispersible RTP SiNCs (UA-SiNCs) and their optical applications. The UA-SiNCs with a uniform particle size of 2.8nm are prepared by thermal hydrosilylation between hydrogen-terminated SiNCs (H-SiNCs) and 10-undecenoic acid (UA). Interestingly, the resultant UA-SiNCs can exhibit tunable long-lived RTP with an average lifetime of 0.85 s. The RTP feature of the UA-SiNCs is confirmed to the n-π* transitions of their surface C═O groups. Subsequently, new dual-modal emissive UA-SiNCs-based ink is fabricated by blending with sodium alginate (SA) as the binder. The customized anticounterfeiting labels are also prepared on cellulosic substrates by screen-printing technique. As expected, UA-SiNCs/SA ink exhibits excellent practicability in anticounterfeiting applications. These findings will trigger the rapid development of RTP SiNCs, envisioning enormous potential in future advanced applications such as high-level anti-counterfeiting, information encryption, and so forth.

Printed Devices for Wearable Biosensors: Laboratory to Emerging Markets

Advances in flexible electrochemical sensors have opened up opportunities for various applications, such as biomedical and fitness monitoring. This brief review explores the key advancements in printed wearable electrochemical sensing systems, including an analysis of literature trends, printing strategies (flexographic, screen, and inkjet printing techniques), recent applications of printed wearable biosensors (epidermal sensing films and patches, textile platforms, and biofuel cell energy devices), their relative merits, and perspectives on this emerging technology. This article also provides an overview of sensing systems and concludes with a synopsis of the market drivers for printed and flexible sensors.

Flexo and screen printing of graphene/ multiwall carbon nanotube hybrid

In this work, we present the development of conductive graphene waterbased inks suitable for printing of several themes on different kinds of papers based on flexography and screen printing techniques. The inks were prepared by a hydrophilic graphene/carbon nanotube hybrid and suitable mixtures of resins. The as-prepared conductive inks were stable, highly conductive and their printing quality was comparable with that of conventional commercial inks. Especially, for flexography, the relationship between printing quality and the ink-carrying volume of the cells of the anilox roll and the pre-inking was investigated.

Solid Oxide Electrolysis Cells Fabrication: From Single Cells to Batch Production

Energy transition towards a net-zero emission scenario requires, primarily, a significant increase on the renewable energy production capabilities. However, the inherent intermittency of most common renewable sources, added to the limitations of full electrification in some important hard-to-abate sectors (heavy-duty transport, aviation, steel industry...), implies also the need of developing reliable solutions for energy conversion and storage. Here, hydrogen is gaining more and more popularity in the recent years as an effective solution as energy carrier, mostly for the decarbonization of the key industries and transport. Among the different technologies under development for power-to-hydrogen conversion, solid oxide electrolysis (SOE) outstands due to its high conversion efficiency, fuel flexibility (e.g. CO2 electrolysis) and possibility of working in reversible mode (the same device both as electrolyser and fuel cell).Currently behind competing low temperature electrolysis technologies (AEL, PEMEL) in terms of technology readiness, main challenges of SOE today relate to long-term degradation, heat management and design and reliable fabrication of large stacks and systems. Although many projects are lately flourishing in this line, the number of players able to demonstrate an upscaled fabrication of SOE stacks and systems is still limited. The work presented here represents the first step carried out at CENER for the future demonstration of a pilot fabrication line of SOE stacks, from the optimization of functional materials and inks to the fabrication of single cells and building of 2-10 kW stacks.In this study, a fabrication route for SOE planar cells (5x5 cm2) is proposed, including the optimization of every single step of the process: raw material pre-treatment, ink/slurry development, functional printing and sintering. Particular emphasis is placed on ensuring a reliable upscaling for batch production of cells and thus materials are processed in large quantities (~1 L/batch). In terms of functional materials, standard electrode and electrolytes are chosen in a first approach, viz. Ni-YSZ as hydrogen electrode, YSZ as electrolyte and LSM-YSZ as air electrode. For film deposition, tape casting and screen printing techniques are combined. The electrochemical characterization of the fabricated cells will be presented and compared with commercial ones, including degradation analysis.

Environmentally-Friendly Electroplating Process Using Solid Electrolyte Membranes

The automobile is a very broad industry, and consists of tens of thousands of parts. Many parts of automobile employ surface treatment to provide several functions such as electronic and anti-corrosion properties. Among several surface treatment process, plating is an important elemental technology for automobile industry. For the industrial perspective, interest in SDGs significantly increases, and efforts to reduce environmental impact are highly urgent. Recently, we have developed novel electroplating process, solid electrodeposition (SED), which is based on ion transfer through solid electrolyte membrane1). This process has unique deposition characteristics that the metal film can be deposited only on the contact area between cathode and the membrane, in a fashion similar to stamping deposition. The SED process has an advantage for reducing amounts of waste effluent and CO2 gas. Moreover, this process has a potential of high deposition rate due to utilization of thin electrolyte membrane, providing lower electrical resistance between electrodes1), 2). Therefore, in the environmental and economical perspective, we believe that SED is promising process to metallize the substrate surface as an alternative to the conventional electroplating, especially in the field of electronics manufacturing. In this study, we report on SED system in details and characterization of deposited copper and nickel films. We also introduce copper fine patterning technique combined with SED using hard mask. Figure 1 shows schematic of the present SED system. The head part composed of anode plate, electrolyte solution and membrane are placed on substrate under controlled temperature and pressure. The membrane mainly plays a role of selective cation transfer from electrolyte solution to the substrate, although a small amounts of electrolyte solution can also be transferred due to pressure difference between internal head part and atmosphere. This solution uniformly spread to the interface between membrane and substrate so that uniform metal deposition is continuously proceeded without adhering the membrane with the substrate. Additionally, the SED system allows one to shorten the distance between electrodes because membrane can act as a diaphragm. Therefore, the power consumption is smaller than that of conventional electroplating, owing to decrease in an internal electrical resistance, providing the decrease of exhaust CO2 gas. The deposited film has relatively uniform thickness as shown in Figure 2, the result of which is due to the short distance between electrodes as well as uniform current feeding to deposit metal films through the back side of the cathode. The deposited copper and nickel films are crystalline and highly conductive, the quality of which are being enough for application of the SED process in the current electronics device manufacturing. By combining the SED process with the conventional screen printing technique, copper circuit patterns with line width of below 50 μm could also be successfully fabricated.1) Akamatsu, S. Nakano, K. Kimura, Y Takashima, T. Tsuruoka, H. Nawafune, Y. Sato, J. Murai, H. Yanagimoto, ACS Appl. Mater. Interfaces, 13, 13896-13906 (2021)2) Narui, Y. Hoshi, I. Shitanda, M. Itagaki, H. Yanagimoto, M. Hiraoka and H. Iisaka, E01-920, 232nd ECS Meeting. Figure 1

Electrohydrodynamic Printed Ultra-Micro AgNPs Thin Film Temperature Sensors Array for High-Resolution Sensing.

Current methods for thin film sensors preparation include screen printing, inkjet printing, and MEMS (microelectromechanical systems) techniques. However, their limitations in achieving sub-10 μm line widths hinder high-density sensors array fabrication. Electrohydrodynamic (EHD) printing is a promising alternative due to its ability to print multiple materials and multilayer structures with patterned films less than 10 μm width. In this paper, we innovatively proposed a method using only EHD printing to prepare ultra-micro thin film temperature sensors array. The sensitive layer of the four sensors was compactly integrated within an area measuring 450 μm × 450 μm, featuring a line width of less than 10 μm, and a film thickness ranging from 150 nm to 230 nm. The conductive network of silver nanoparticles exhibited a porosity of 0.86%. After a 17 h temperature-resistance test, significant differences in the performance of the four sensors were observed. Sensor 3 showcased relatively superior performance, boasting a fitted linearity of 0.99994 and a TCR of 937.8 ppm/°C within the temperature range of 20 °C to 120 °C. Moreover, after the 17 h test, a resistance change rate of 0.17% was recorded at 20 °C.

Flexible Sensor Film Based on Rod-Shaped SWCNT-Polypyrrole Nanocomposite for Acetone Gas Detection.

A nanocomposite rod-shaped structure with a single-walled carbon nanotube (SWCNT) embedded in polypyrrole (PPy) doped with nonafluorobutanesulfonic acid (C4F), SWCNT/C4F-PPy, was synthesized using emulsion polymerization. The hybrid ink was then directly coated on a polyimide film interdigitated with the Cu/Ni/Au electrodes via a screen-printing technique to create a flexible film sensor. The sensor film showed a response of 1.72% at 25 °C/atmospheric pressure when acetone gas of 5 ppm was injected, which corresponds to almost 95% compared to the Si wafer-based array interdigitated with the Au electrode. Additionally, C4F was used as a hydrophobic dopant of PPy to improve the stability of humidity and to produce a highly sensitive film-type gas sensor that provides stable detection even in humid conditions.