Silver Ink Research Articles

A Manufacturing Method for High-Reliability Multilayer Flexible Electronics by Electrohydrodynamic Printing

To meet the demand for higher performance and wearability, integrated circuits are developing towards having multilayered structures and greater flexibility. However, traditional circuit fabrication methods using etching and lamination processes are not compatible with flexible substrates. As a non-contact printing method in additive manufacturing, electrohydrodynamic printing possesses advantages such as environmental friendliness, sub-micron manufacturing, and the capability for flexible substrates. However, the interconnection and insulation of different conductive layers become significant challenges. This study took composite silver ink as a conductive material to fabricate a circuit via electrohydrodynamic printing, applied polyimide spraying to achieve interlayer insulation, and drilled micro through-holes to achieve interlayer interconnection. A 200 × 200 mm2 ten-layer flexible circuit was thus prepared. Furthermore, we combined a finite element simulation with reliability experiments, and the prepared ten-layer circuit was found to have excellent bending resistance and thermal cycling stability. This study provides a new method for the manufacturing of low-cost, large-sized, multilayer flexible circuits, which can improve circuit performance and boost the development of printed electronics.

Frequency selective asymmetric coupled-fed (ACS) antenna using additive manufacturing

In this study, the development of diverse antenna designs using additive manufacturing processes, specifically spanning from L-band to K-band is proposed. All designs are implemented on a flexible FR4 substrate to make them suitable for wearable sensors and biomedical applications. The fabrication process involves the utilization of aerosol jet printing with nanoparticle silver ink, followed by curing in a vacuum chamber. Additionally, screen printing with copper paste is employed as another method, with subsequent curing in a laminator. The reflection coefficient (S11) and radiation patterns for the simulated design and fabricated samples were found to align closely. The achieved return loss consistently reaching −10 dB across fairly large operating frequency range underscores the efficacy of the proposed antennas and their associated additive manufacturing mechanisms. The design and simulation were performed using Ansys high frequency structural simulator (HFSS), and the parameters under test for the fabricated antennas were validated using a vector network analyzer (VNA) to assess overall performance.

An investigation of methods to enhance adhesion of conductive layer and dielectric substrate for additive manufacturing of electronics

Additive manufacturing of conductive layers on a dielectric substrate has garnered significant interest due to its promise to produce printed electronics efficiently and its capability to print on curved substrates. A considerable challenge encountered is the conductive layer’s potential peeling due to inadequate adhesion with the dielectric substrate, which compromises the durability and functionality of the electronics. This study strives to facilitate the binding force through dielectric substrate surface modification using concentrated sulfuric acid and ultraviolet (UV) laser treatment. First, polyetheretherketone (PEEK) and nanoparticle silver ink were employed as the studied material. Second, the surface treatment of PEEK substrates was conducted across six levels of sulfuric acid exposure time and eight levels of UV laser scanning velocity. Then, responses such as surface morphology, roughness, elemental composition, chemical bonding characteristics, water contact angle, and surface free energy (SFE) were assessed to understand the effects of these treatments. Finally, the nanoparticle silver ink layer was deposited on the PEEK surface, and the adhesion force measured using a pull-off adhesion tester. Results unveiled a binding force of 0.37 MPa on unmodified surface, which escalated to 1.99 MPa with sulfuric acid treatment and 2.21 MPa with UV laser treatment. Additionally, cross-approach treatment investigations revealed that application sequence significantly impacts results, increasing binding force to 2.77 MPa. The analysis further delves into the influence mechanism of the surface modification on the binding force, elucidating that UV laser and sulfuric acid surface treatment methods hold substantial promise for enhancing the binding force between heterogeneous materials in the additive manufacturing of electronics.

Rheological Properties and Inkjet Printability of a Green Silver-Based Conductive Ink for Wearable Flexible Textile Antennas.

The development of e-textiles necessitates the creation of highly conductive inks that are compatible with precise inkjet printing, which remains a key challenge. This work presents an innovative, syringe-based method to optimize a novel bio-sourced silver ink for inkjet printing on textiles. We investigate the relationships between inks' composition, rheological properties, and printing behavior, ultimately assessing the electrical performance of the fabricated circuits. Using Na-alginate and polyethylene glycol (PEG) as the suspension matrix, we demonstrate their viscosity depends on the component ratios. Rheological control of the silver nanoparticle-laden ink has become paramount for uniform printing on textiles. A specific formulation (3 wt.% AgNPs, 20 wt.% Na-alginate, 40 wt.% PEG, and 40 wt.% solvent) exhibits the optimal rheology, enabling the printing of 0.1 mm thick conductive lines with a low resistivity (8 × 10-3 Ω/cm). Our findings pave the way for designing eco-friendly ink formulations that are suitable for inkjet printing flexible antennas and other electronic circuits onto textiles, opening up exciting possibilities for the next generation of E-textiles.

High electrical conductivity and bending resistance of Ag NPs/Ag flakes composite silver paste are achieved by sintering Ag NPs

The investigation of conductive silver pastes and inks has witnessed extensive research within the domain of printed electronics in recent years, primarily owing to the exceptional electrical conductivity and steadfastness intrinsic to silver. This paper introduces an approach for the fabrication of stable, cost-effective, and low-resistance conductive silver paste tailored for flexible printed circuits. This method facilitates the solidification of the conductive silver paste into a highly conductive silver film at a curing temperature of 250 °C. In the process of preparing the conductive silver paste, Ag flakes is subject to modification through the incorporation of Ag NPs, which are subsequently sintered at a low temperature curing setting. The sintering of Ag NPs serves to establish connections between adjacent particles of Ag flakes within the paste, thereby enhancing the conductivity and flexibility of the resulting conductive printed silver film. When the ratio of Ag NPs to Ag flakes is maintained at 10:90, the volume resistivity of the Ag NPs-modified film registers at 2.7 × 10−5 Ω.cm. This demonstrates a substantial 53.45% reduction in the volume resistivity of the conductive printed silver film modified with Ag NPs, compared to its Ag NPs-absent counterpart. Post 200 cyclic bending tests, it becomes evident that the resistance change rate in the Ag NPs-modified conductive printed silver film is a mere 12.5%, whereas the Ag NPs-modified silver film lacking Ag NPs displays a resistance change rate of 21.5%. This discrepancy underscores the capacity of Ag NPs-modified Ag flakes to fortify the bending resistance of the conductive printed silver film. Comprehensive data analysis substantiates that the improvements in electrical conductivity and bending resistance can be attributed to the superior bridging facilitated by the sintering process on the surface of the Ag NPs-modified Ag flakes.

Enhancing interfacial bond strength between PEEK and inkjet-printed silver film through laser surface modification for additive manufacturing of electronics

Electronic 3D printing is a very promising technology, which is widely used in the manufacturing of conformal antennas, flexible electronics and sensors. Polyether ether ketone (PEEK) is one of the most popular substrate materials for electronic 3D printing due to its superior fatigue resistance, heat tolerance, chemical resistance, and mechanical properties. However, the deficient bond between the PEEK substrate and the conductive ink leads to the peeling and shedding of the conductive pattern. This paper investigated the enhancement of the bond strength between the PEEK substrate and the conductive layer through PEEK surface modification. A 355 nm ns solid-state laser was used to treat the PEEK surface with different values of laser scanning spacing (S) and spot overlap rate (R). The surface microstructure, surface roughness, wettability, and functional groups of the treated substrates have been measured. Then the nanoparticle silver ink was printed and cured on the treated substrate. After that, the bonding strength was measured using a pull-off adhesion tester. Results showed that regular grooves were generated and the content of active oxygen atoms was increased on the PEEK surface through laser modification. The mechanical interlocking between the grooves and silver particles and hydrogen bonds induced by the active oxygen atoms and the hydroxyl groups contribute to the enhancement of bond strength between PEEK and silver film. The bond strength for the laser treated PEEK reached the maximum of 1.9 MPa, which was 413.51% higher than that of the untreated PEEK. The laser modification can effectively enhance the interfacial bond strength for additive manufacturing of reliable electronics.

On-demand fabrication of piezoelectric sensors for in-space structural health monitoring

Inflatable structures, promising for future deep space exploration missions, are vulnerable to damage from micrometeoroid and orbital debris impacts. Polyvinylidene fluoride-trifluoroethylene (PVDF-trFE) is a flexible, biocompatible, and chemical-resistant material capable of detecting impact forces due to its piezoelectric properties. This study used a state-of-the-art material extrusion system that has been validated for in-space manufacturing, to facilitate fast-prototyping of consistent and uniform PVDF-trFE films. By systematically investigating ink synthesis, printer settings, and post-processing conditions, this research established a comprehensive understanding of the process-structure-property relationship of printed PVDF-trFE. Consequently, this study consistently achieved the printing of PVDF-trFE films with a thickness of around 40 µm, accompanied by an impressive piezoelectric coefficient of up to 25 pC N−1. Additionally, an all-printed dynamic force sensor, featuring a sensitivity of 1.18 V N−1, was produced by mix printing commercial electrically-conductive silver inks with the customized PVDF-trFE inks. This pioneering on-demand fabrication technique for PVDF-trFE films empowers future astronauts to design and manufacture piezoelectric sensors while in space, thereby significantly enhancing the affordability and sustainability of deep space exploration missions.

High-Performance, Easy-to-Fabricate, Nanocomposite Heater for Life Sciences and Biomedical Applications.

Microheaters are used in several applications, including medical diagnostics, synthesis, environmental monitoring, and actuation. Conventional microheaters rely on thin-film electrodes microfabricated in a clean-room environment. However, low-cost alternatives based on conductive paste electrodes fabricated using printing techniques have started to emerge over the years. Here, we report a surprising effect that leads to significant electrode performance improvement as confirmed by the thorough characterization of bulk, processed, and conditioned samples. Mixing silver ink and PVA results in the solubilization of performance-hindering organic compounds. These compounds evaporate during heating cycles. The new electrodes, which reach a temperature of 80 °C within 5 min using a current of 7.0 A, display an overall 42% and 35% improvement in the mechanical (hardness) and electrical (resistivity) properties compared to pristine silver ink electrodes. To validate our results, we use the composite heater to amplify and detect parasite DNA from Trypanosoma brucei, associated with African sleeping sickness. Our LAMP test compares well with commercially available systems, confirming the excellent performance of our nanocomposite heaters. Since their fabrication relies on well-established techniques, we anticipate they will find use in a range of applications.

Reconfigurable screen-printed terahertz frequency selective surface based on metallic checkerboard pattern

We employed the screen-printing method to fabricate terahertz (THz) frequency selective surfaces (FSSs) featuring an inductive metallic checkerboard (i-MCB) pattern based on conductive silver ink onto a flexible polyethylene terephthalate substrate, chosen for its excellent THz transmission properties below 1 THz [Jin et al 2006 J. Korean Phys. Soc. 49 513–17]. Analytical studies, along with simulations and experiments, were conducted to investigate the filtering characteristics of the printed FSSs, confirming their functionality as a band-pass filter. Subsequently, we demonstrated the reconfigurability of a two-layer system by vertically stacking two layers. This was achieved by systematically shifting the position of the second layer in the x or y-direction relative to the first layer. Experimental verification revealed a significant variation in normalized transmission, ranging from 94% to 6% at 0.15 THz for type-I:i-MCBs and 90% to 5% at 0.20 THz for type-II:i-MCBs, respectively. This study presents a simple scheme for a reconfigurable screen-printed i-MCB-FSS operating in the THz range. Consequently, our findings demonstrate that screen printing method can effectively be employed for the large-scale production of THz FSSs.

The Dagulf Psalter (Austrian National Library Cod. 1861): A Multi-Analytical Approach to Study Inks, Dyes, and Pigments of this Early Carolingian Manuscript

Abstract The Dagulf Psalter is a precious Carolingian manuscript on calf parchment, dated to 793–795. Its unique and high historical value required a non-invasive, multi-analytical approach to gain insights into the material composition of gold and silver inks, pigments, and dyes used for writing and illuminations. Elemental mapping based on X-ray fluorescence analysis (XRF), Fibre Optics Reflectance Spectroscopy (FORS) measurements, and hyperspectral imaging (HSI) gave complementary information on colour media and their brilliant shades. Knowledge of the material composition of inks, dyes, and pigments is of crucial importance not only for art historical research, but also for the preservation of the manuscript, as it is known that among other factors, silver inks and some pigments can lead to deterioration of parchment supports. The purple dye orchil and blue indigo were used for painted backgrounds on the initial folios. Lapis lazuli was found in decorative frames on these folios. Orchil, indigo, and lapis lazuli also appear in decorations of small initials throughout the manuscript. Red lead, ochre, cinnabar, orpiment, and lead white were also found in various painted details. Gold and silver inks of high purity were identified. The proof of chlorine in the silver ink indicates the presence of corrosion products.

Nanostructured Substrate-Mediated Bubble Degassing in Microfluidic Systems.

Microfluidic platforms have been widely used in a variety of fields owing to their numerous advantages. The prevention and prompt removal of air bubbles from microchannels are important to ensuring the optimal functioning of microfluidic devices. The entrapment of bubbles in the microchannels can result in flow instability and device performance disruption. Active and passive methods are the primary categories of degassing technologies. Active methods rely on external equipment, and passive methods operate autonomously without any external sources. This study proposed a passive degassing method that employs a nanoscale surface morphology integrated into the substrate of a microfluidic device. Nanostructures exhibit a microchannel geometry and are fabricated based on surface micromachining technology using silver ink and chemical etching. Consequently, the gas permeability is enhanced, resulting in effective degassing through the nanostructure. The performance of this degassing method was characterized under varying substrate permeabilities and input pressure conditions, and it was found that increased permeability facilitates the degassing performance. Furthermore, the applicability of our method was demonstrated by using a serpentine channel design prone to gas entrapment, particularly in the corner regions. The nanostructured substrate exhibited significantly improved degassing performance under the given pressure conditions in comparison to the glass substrate.

Membrane‐based mechanical characterization of screen‐printed inks: Deflection analysis of ink layers on polyimide membranes

AbstractMeasurements of Young's modulus and residual stresses of screen‐printed ink layers using a bulge test on coated polyimide‐based membranes are proposed in this work. The applied bulge test monitors the deflection of membranes under pressure with interferometry. The obtained Young's modulus ranges from 6 to 8 GPa for a carbon blend‐based ink and is around 12 GPa for a silver nanoparticle ink. These values are compared with standard nanoindentation and show good agreement. Besides, the residual stresses range from −4 to 8 MPa for the carbon blend‐based ink, while the silver ink is measured around −10 MPa. The use of the membrane‐based method underlines the influence of exact deposition and curing conditions on the ink film material properties. The impact of the substrate on the ink layer properties, such as the thickness and its uniformity, is discussed, especially with regard to the heat treatment of the membrane.

Flexible Embedded Metal Meshes by Sputter-Free Crack Lithography for Transparent Electrodes and Electromagnetic Interference Shielding.

A facile and novel fabrication method is demonstrated for creating flexible poly(ethylene terephthalate) (PET)-embedded silver meshes using crack lithography, reactive ion etching (RIE), and reactive silver ink. The crack width and spacing in a waterborne acrylic emulsion polymer are controlled by the thickness of the polymer and the applied stress due to heating and evaporation. Our innovative fabrication technique eliminates the need for sputtering and ensures stronger adhesion of the metal meshes to the PET substrate. Crack trench depths over 5 μm and line widths under 5 μm have been achieved. As a transparent electrode, our flexible embedded Ag meshes exhibit a visible transmission of 91.3% and sheet resistance of 0.54 Ω/sq as well as 93.7% and 1.4 Ω/sq. This performance corresponds to figures of merit (σDC/σOP) of 7500 and 4070, respectively. For transparent electromagnetic interference (EMI) shielding, the metal meshes achieve a shielding efficiency (SE) of 42 dB with 91.3% visible transmission and an EMI SE of 37.4 dB with 93.7% visible transmission. We demonstrate the highest transparent electrode performance of crack lithography approaches in the literature and the highest flexible transparent EMI shielding performance of all fabrication approaches in the literature. These metal meshes may have applications in transparent electrodes, EMI shielding, solar cells, and organic light-emitting diodes.

Determination of Δ9-Tetrahydrocannabinol and Cannabidiol by Voltammetry using Low-Cost Screen-Printed Electrodic Platforms: A Significant Potential for Application in Clinical and Forensic Fields

Cannabis sativa has been utilized for centuries due to its psychoactive and therapeutic effects resulting from the presence of cannabinoids, which are exclusively found in plants of the Cannabis genus. The methods currently used by law enforcement and pharmaceutical industries to detect and measure cannabinoids include colorimetric testing, as well as instrumental methods such as HPLC and GC-MS. The aim of this work is to create a new method that can overcome the limitations of existing methods. To achieve this goal, a voltammetric method was developed using CV and LSV techniques. The method used a 3D-printed electrodic platform that was chemically modified with carbon paste and silver ink. The developed electrode was successful in detecting and measuring the amounts of Δ9-THC and CBD. The analytical parameters and average concentrations obtained were similar to those of popular commercial electrodes such as the platinum disk electrode and SPPE. The values for the limits of detection (LOD) and quantification (LOQ) were in the range of µmol L-1. The developed method and electrode show promise for detecting and quantifying Δ9-THC and CBD. The method was compared to the GC-MS technique, yielding relative error values ranging from 2.27% to 18.66%. A miniaturized, portable, versatile, and cost-effective method was developed with significant potential for clinical and forensic applications.

A disposable homemade screen printed electrode for famotidine analysis using a computer-designed molecularly imprinted polymer based on the MWCNT-Fe3O4 nanocomposite in simulated real samples.

A home-made screen printed electrode (SPE) was designed with a magnetic multi-walled carbon nanotube composite (MWCNT-Fe3O4) and a molecularly imprinted polymer (MIP) for sensitive and selective electrochemical analysis of famotidine (FAM). The SPE was fabricated using non-commercial conductive inks such as carbon and silver inks. The electrodes were printed by a painting technique on polyvinyl chloride (PVC) sheets as a substrate. To optimize the composition of the carbon ink, a mixture design methodology was employed. A computational approach was used to select the functional monomer. The imprinted layer was synthesized by electropolymerization of FAM (template) and pyrrole (PY) (monomer) using cyclic voltammetry (CV) on the working electrode surface modified with the MWCNT-Fe3O4 nanocomposite. Differential pulse voltammetry (DPV) was applied to characterize the template removal and rebinding processes. The Plackett-Burman design (PBD) and central composite design (CCD) investigated the effect of parameters on the MIP/MWCNT-Fe3O4/SPE performance. The sensor exhibited a linear dynamic range of 1-1000 μM (R2 = 0.9919) with a limit of detection (LOD) of 0.027 μM (3sb, n = 3). It demonstrated good repeatability and reproducibility, with relative standard deviations (RSD) of 3.6 and 4.2, respectively. This disposable and cost-effective sensor successfully detected FAM in simulated real samples and correlated well with high-performance liquid chromatography (HPLC) results.

Reactive silver inks: a path to solar cells with 82% less silver

ITRPV silver consumption of standard low-temperature and high-temperature paste as compared to reactive silver ink. As little as 16.4 mg of silver is consumed when a busbarless cell is metallized with reactive silver ink.

Synthesis and Characterization of Ti3C2Tx Mxene for Flexible Current Collectors Fabricated through Inkjet Printing

Two-dimensional (2D) materials, as transition-metal carbides and/or nitrides (MXenes), have recently gained great attention due to their combination of electrochemical, electrical and mechanical properties, which can be tailored for the specific application by controlling the chemical composition. As a consequence, MXenes find applications in many fields as energy storage, sensing, photocatalysis and many more [1].MXenes are obtained by selective etching of a precursor layered material, known as MAX phase, and characterized by the general formula Mn+1XnTx, where M is a transition metal with n =1-4, X represents carbon and/or nitrogen atoms and Tx represents surface terminations of different nature (-O, -OH, -F and -Cl). The latter aspect is the one responsible for one important property related to the hydrophilicity of MXenes, which allows easy processing in water and/or solutions [2]. This aspect is particularly attractive for inkjet processing, as an easy water-based ink can be formulated. In addition, in aqueous solutions Ti3C2X flakes are negatively charged allowing the development of additive-free conductive inks.Ultimately, the MXenes extremely high conductivity is particularly attractive for final application as flexible current collector for lithium-ion batteries. The current collector can be considered as a bottleneck, especially when considering substrates selection, i.e. flexible/wearable substrates. Different silver or copper nanoparticles inks are commercially available, but they do require high curing temperatures, which are incompatible with plastic-based substrates, in order to reach the desired electrical conductivity. Another option is carbon-based inks, which despite being more cost-effective, they have limitations in terms of moderate electrical conductivity, which affects the Ohmic losses, and so the overall performance, of the battery device [3].Inkjet printing fabrication requires specific ink properties, in order to ensure a clogging-free condition, in terms of viscosity and surface tension of the ink. Generally, a clogging-free jetting is also forecast when particle size dimension is between 1/100 < d < 1/50 of the nozzle diameter [4]. This is a particularly meaningful aspect when considering MXene-based inks, as flake size should be finely controlled in order to avoid large or multilayered flakes, which can favor nozzle clogging. However, too small flakes can compromise the final electric conductivity.In this study, we provide an in-depth characterization of Ti3C2X MXene synthesis. The as-produced material will be characterized in terms of flake dimensions and electrical conductivity. IJP ink compatibility generally requires adjustments in terms of rheological and physical properties. Once chosen the optimal method, the Ti3C2X aqueous-based ink will be printed to obtain current collectors for lithium-ion batteries, which will be characterized from a morphological, electrical and electrochemical point of view. Preliminary study studies on inkjet printed full cell LTO/LFP were already obtained at the coin level. Flexible LTO/LFP full cell exploiting innovative Ti3C2X MXene current collector will be printed. Morphological and electrical analysis combined with an in-depth electrochemical characterization will be performed to demonstrate the battery device performances retention under different degrees of bending of the device.[1] M. Shekhirev, C. E. Shuck, A. Sarycheva, Y. Gogotsi, Progress in Materials Science 2021, 120, 100757.[2] K. Maleski, C. E. Ren, M.-Q. Zhao, B. Anasori, Y. Gogotsi, ACS Appl. Mater. Interfaces 2018, 10, 24491.[3] S. Uzun, M. Schelling, K. Hantanasirisakul, T. S. Mathis, R. Askeland, G. Dion, Y. Gogotsi, Small 2021, 17, 2006376.[4] Z. Tang, K. Fang, M. N. Bukhari, Y. Song, K. Zhang, Langmuir 2020, 36, 9481.

Fabrication of a Capacitive BaTiO3-PDMS Hand Sign Language Sensor and Its Signal Classification Aided by Machine Learning

The detection of sign language signals is an important aspect in the life of people with hearing and speaking impairment. It is one important application in the fabrication of capacitive strain sensors. In these kinds of sensors, the change in electrical properties such as capacitance depicts the change in a body’s movement. It is one of the variables along with sensitivity, repeatability, response time, fabrication cost, and ease of fabrication which are the important factors to consider in the fabrication of sensors. This paper presents the fabrication of multi-strain sensors that can be integrated into hand gloves to monitor hand sign language gestures. The designed sensor is composed of barium titanate oxide (BaTiO3) which served as the sensing material and polydimethylsiloxane (PDMS) as the stretchable substrate. The silver electrodes were inkjet printed on top of the prepared BaTiO3-PDMS composite after surface treatment to allow the adhesion of silver ink. The capacitance values of the sensors were continuously measured and recorded using an Inductance-Capacitance-Resistance (LCR) meter while bending the sensors at different bending angles for multiple cycles. The fabricated BaTiO3-PDMS capacitive sensors exhibited a high response of 42.85%, linearity of 0.941, fast response and recovery time of ~1s, and low hysteresis of less than 2%, and good stability over a thousand cyclic test. Its application as a hand sign language sensor was demonstrated to have a unique combination of sensing signals with respect to specific finger flexion angles that correspond to a specific hand sign language of the English alphabet. The interpretation of the sensing signals were aided by machine learning and depicted a classification accuracy of 92% signifying the ability of the sensor to detect a particular letter from the English alphabet.

A compact meander flexible UHF tag for industrial applications

The objective of this paper is to introduce a novel design for a flexible Ultra-High Frequency tag (UHF tag) through the utilization of the meander line technique (MLA) and loop antenna method. The primary goal is to achieve a compact UHF tag operating at 868 MHz. The physical dimensions of the UHF tag are 110×12×0.1mm3. The proposed UHF tag is manufactured using the inkjet printing method on a polyamide substrate featuring a relative dielectric constant of 3.5, a tangent loss of 0.0027, and a height of 0.0508 mm. Through electromagnetic simulation and validation, the functionality of the proposed UHF tag covers the UHF band ranging from 854.57 to 883.89 MHz, with a bandwidth of 29.32 MHz. The reflection coefficient at 868 MHz is approximately -22.46 dB. The simulated gain measures 1.79 dBi, while the theoretical read range is estimated at 5 m. The UHF tag is produced using silver ink with a thickness of 0.05 mm and assembled using an anisotropic conductive paste (ACP). Subsequent to electromagnetic simulation, the UHF tag’s performance is confirmed through a reading test conducted with a radio frequency identification (RFID) base station. The results are consistent with the theoretical expectations, showcasing a commendable read range of 5 m. To safeguard the UHF tag from challenging environmental conditions, it is enclosed within a polyethylene film (PE). Following encapsulation, the read range decreases to 3 m, making it suitable for RFID applications requiring mid-range capabilities.

Inkjet‐Printed Flexible Thin‐Film Thermal Sensors for Detecting Elevated Temperature Range

All inkjet‐printed thermal sensors are manufactured based on a metal–insulator–metal (MIM) interface or capacitor architecture, for the adapted device size ranging from 16 to 36 mm2 active area. Two different material inks, namely a nanoparticle conductive silver ink and an inorganic‐polymer‐based hybrid insulator ink, are applied layer by layer on a thin flexible polyimide substrate, for developing the printed MIM devices. To ensure the desired electronic conductivity and insulation from the layers, the manufacturing process steps and parameters are tuned, accordingly. The results show that the inkjet‐printed MIM devices could constitute up to 15 μm thickness and demonstrate average detection of a change in electrical capacitance ranging from 20 to 100 pF, when the temperature is varied between 100 and 300 °C. The investigations also summarize that the change in the electrical response is enough to detect an increment of 50 °C. The printed sensors also display high operational stability and repeatability, when subjected to thermal cycling.