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This study explores the intricate interaction between the properties of textile substrates and screen-printing parameters in shaping fabric circuits using silver conductive ink. Via analyzing key variables such as fabric type, mesh density, and the number of overprinted layers, the research revealed how the porous structure, large surface area, and fiber morphology of textile substrates influence ink absorption, ultimately enhancing the electrical connectivity of the printed circuits. Notably, the hydrophilic cotton staple fibers fabric effectively absorbed the conductive ink into the fabric substrate, demonstrating superior electrical performance compared with the hydrophobic polyester filament fabric after three overprinting, unlike the results observed after a single print. As mesh density decreased and the number of prints increased, the electrical resistance of the circuit gradually reduced, but ink bleeding on the fabric surface became more pronounced. Cotton fabric, via absorbing the ink deeply, exhibited less surface bleeding, while polyester fabric showed more noticeable ink spreading. These findings provide valuable insights for improving screen printing technology for textile circuits and contribute to the development of advanced fabric circuits that enhance the functionality of smart wearable technology. [ABSTRACT FROM AUTHOR]

Vibration sensors are widely applied in the detection of faults and analysis of operational states in engineering machinery and equipment. However, commercial vibration sensors with a feature of high hardness hinder their usage in some practical applications where the measured objects have irregular surfaces that are difficult to install. Moreover, as the operating environments of machinery become increasingly complex, there is a growing demand for sensors capable of working in wet and humid conditions. Here, we present a flexible, superhydrophobic vibration sensor with parallel microcracks. The sensor is fabricated using a femtosecond laser direct writing ablation strategy to create the parallel cracks on a PDMS film, followed by spray-coating with a conductive ink composed of MWCNTs, CB, and PDMS. The results demonstrate that the developed flexible sensor exhibits a high-frequency response of up to 2000 Hz, a high acceleration response of up to 100 m/s2, a water contact angle as high as 159.61°, and a linearity of 0.9812 between the voltage signal and acceleration. The results indicate that the sensor can be employed for underwater vibration, sound recognition, and vibration monitoring in fields such as shield cutters, holding significant potential for mechanical equipment vibration monitoring and speech-based human–machine interaction. [ABSTRACT FROM AUTHOR]

Simple and scalable production of micro-supercapacitors (MSCs) is crucial to address the energy requirements of miniature electronics. Although significant advancements have been achieved in fabricating MSCs through solution-based printing techniques, the realization of high-performance MSCs remains a challenge. In this paper, graphene-based MSCs with a high power density were prepared through screen printing of aqueous conductive inks with appropriate rheological properties. High electrical conductivity (2.04 × 104 S∙m−1) and low equivalent series resistance (46.7 Ω) benefiting from the dense conductive network consisting of the mesoporous structure formed by graphene with carbon black dispersed as linkers, as well as the narrow finger width and interspace (200 µm) originating from the excellent printability, prompted the fully printed MSCs to deliver high capacitance (9.15 mF∙cm−2), energy density (1.30 µWh∙cm−2) and ultrahigh power density (89.9 mW∙cm−2). Notably, the resulting MSCs can effectively operate at scan rates up to 200 V∙s−1, which surpasses conventional supercapacitors by two orders of magnitude. In addition, the MSCs demonstrate excellent cycling stability (91.6% capacity retention and ~100% Coulombic efficiency after 10,000 cycles) and extraordinary mechanical properties (92.2% capacity retention after 5000 bending cycles), indicating their broad application prospects in flexible wearable/portable electronic systems. [ABSTRACT FROM AUTHOR]

Flexible electronics have revolutionized the field by overcoming the rigid limitations of traditional devices, offering superior flexibility and adaptability. Conductive ink performance is crucial, directly impacting the stability of flexible electronics. While metal filler-based inks exhibit excellent conductivity, they often lack mechanical stability. To address this challenge, we present a novel conductive ink utilizing a ternary composite filler system: liquid metal and two micron-sized silver morphologies (particles and flakes). We systematically investigated the influence of filler type, mass ratio, and sintering process parameters on the composite ink's conductivity and mechanical stability. Our results demonstrate that flexible wires fabricated with the liquid metal/micron silver particle/micron silver flake composite filler exhibit remarkable conductivity and exceptional bending stability. Interestingly, increasing the liquid metal content results in a trade-off, compromising conductivity while enhancing mechanical performance. After enduring 5000 bending cycles, the resistance change in wires formulated with a 4:1 mass ratio of micron silver particles to flakes is only half that of wires with a 1:1 ratio. This study further investigates the mechanism governing resistance variations during flexible wire bending. Additionally, we observed a positive correlation between sintering temperature and pressure with the conductivity of flexible wires. The significance of the sintering parameters on conductivity follows a descending order: sintering temperature, sintering pressure, and sintering time. Finally, we demonstrate the practical application of this technology by integrating the composite ink-based flexible wires with conductive polymer-based strain sensors. This combination successfully achieved the detection of human movements, including finger and wrist bending. [ABSTRACT FROM AUTHOR]

In this research, a novel electrochemical biosensor is proposed based on inducing graphene formation on polyimide substrate via laser engraving. Graphene polyaniline (G-PANI) conductive ink was synthesized by planetary mixing and applied to the working zone of the developed sensor to effectively enhance the electrical signals. The laser-induced graphene (LIG) sensor was used to detect alpha-fetoprotein (AFP) and 17β-Estradiol (E2) in the phosphate buffer saline (PBS) buffer and human serum. The electrochemical performance of the biosensor in determining these biomarkers was investigated by differential pulse voltammetry (DPV) and chronoamperometry (CA). In a buffer environment, alpha-fetoprotein (AFP) and 17β-Estradiol detection range were 4–400 ng/mL and 20–400 pg/mL respectively. The experimental results showed a limit of detection (LOD) of 1.15 ng/mL and 0.96 pg/mL for AFP and estrogen, respectively, with an excellent linear range (R2 = 0.98 and 0.99). In addition, the designed sensor was able to detect these two types of biomarkers in human serum successfully. The proposed sensor exhibited excellent reproducibility, repeatability, and good stability (relative standard deviation, RSD = 0.96%, 1.12%, 2.92%, respectively). The electrochemical biosensor proposed herein is easy to prepare and can be successfully used for low-cost, rapid detection of AFP and E2. This approach provides a promising platform for clinical detection and is advantageous to healthcare applications. [ABSTRACT FROM AUTHOR]

This paper presents an innovative method for fabricating reflectarray antennas using inkjet printing technology on flexible substrates, markedly enhancing integration and manufacturability compared to traditional PCB methods. The technique employs inkjet printing to deposit conductive inks directly onto a flexible polyethylene naphthalate (PEN) substrate, seamlessly integrating feed and reflectarray components without complex assembly processes. This streamlined approach not only reduces manufacturing complexity and costs but also improves mechanical flexibility, making it ideal for applications requiring deployable antennas. The design process includes an origami-inspired folding of the substrate to achieve the desired three-dimensional antenna structures, optimizing the focal length to dimension ratio (F/D) to ensure maximum efficiency and performance. The feed and the reflectarray geometry are optimized for an F/D of 0.6, which achieves high gain and aperture efficiency, demonstrated through detailed simulations and measurements. For normal incidence, the configuration achieves a peak gain of 9.3 dBi and 48% radiation efficiency at 10 GHz; for oblique incidence, it achieves 7.3 dBi and 40% efficiency. The study underscores the significant potential of inkjet-printed antennas in terms of cost-efficiency, precision, and versatility, paving the way for new advancements in antenna technology with a substantial impact on future communication systems. [ABSTRACT FROM AUTHOR]

Silver-based metal–organic decomposition inks composed of silver salts, complexing agents and volatile solvents are now the subject of much research due to the simplicity and variability of their preparation, their high stability and their relatively low sintering temperature. The use of this type of ink in inkjet printing allows for improved cost-effective and environmentally friendly technology for the production of electrical devices, including flexible electronics. An approach to producing a silver salt-based reactive ink for jet printing has been developed. The test images were printed with an inkjet printer onto polyimide substrates, and two-stage thermal sintering was carried out at temperatures of 60 °C and 100–180 °C. The structure and electrical properties of the obtained conductive lines were investigated. As a result, under optimal conditions an electrically conductive film with low surface resistance of approximately 3 Ω/square can be formed. [ABSTRACT FROM AUTHOR]

In this work, a chemical grafting polymerization method was employed to synthesize EHPMC-g-PANI self-supporting films. Polyaniline (PANI) was grafted onto hydroxypropyl methylcellulose (HPMC) modified with epichlorohydrin (EPHMC) to obtain an EHPMC-g-PANI aqueous dispersion, which was subsequently dried to form the self-supporting films. The introduction of HPMC, with its excellent film-forming ability and mechanical strength, successfully addressed the poor film-forming ability and mechanical properties intrinsic to PANI. Compared to in situ polymerized HPMC/PANI, the EHPMC-g-PANI exhibited significantly improved storage stability. Moreover, the fabricated EHPMC-g-PANI films displayed a more uniform and smoother morphology. The conductivity of all the films ranged from 10−2 to 10−1 S/cm, and their tensile strength reached up to 36.1 MPa. These results demonstrate that the prepared EHPMC-g-PANI holds promising potential for applications in various fields, including conductive paper, sensors, and conductive inks. [ABSTRACT FROM AUTHOR]

Catechol (CT) is a phenolic compound widely used in various industrial sectors, but it is toxic; thus, there is a need for methods that aim to identify and quantify the existence of residues of this material in the environment. In this study a disposable printed electrochemical sensor was developed as an effective alternative for determining CT in water samples. The electrode, called SPEC, was manufactured using the screen-printing method using polyethylene terephthalate (PET) as a support, in which a conductive ink based on carbonaceous materials was used to print the working and auxiliary electrodes and a silver/silver chloride of ink on the reference electrode. The optimal ratio for the conductive ink was 6.25% carbon black, 35.42% graphite, and 58.33% nail polish. The ink obtained was characterized by scanning electron microscopy (SEM). The assessment of the effect of pH on the redox process showed Nernstian behavior (0.057 V pH−1), indicating that the process involves the same number of protons and electrons. Under optimized conditions, with 0.2 mol L−1 acetate buffer at pH 5.0, and by square wave voltammetry, the sensor presented sensitivity values of 0.31 μA L μmol−1, a detection limit of 5.96 μmol L−1, and a quantification limit of 19.87 μmol L−1. The sensor was applied to determine CT in tap water samples, and the results showed recoveries between 97.95 and 100.17%. [ABSTRACT FROM AUTHOR]

The functionalization of conductive inks has been carried out through the decomposition of hydrogen peroxide (H2O2) onto the surface of silver nanoparticles (AgNPs). The ink prepared using this eco-friendly chemical reagent has been characterized structurally, chemically, and morphologically, showing the presence of stable AgNPs with suitable properties as well as the absence of residual contamination. The electrical conductivity of such a solution-processable ink is evidenced for patterns designed on flexible photographic paper substrates, using a refillable fountain pen that is implemented as a printing mechanism for the fabrication of simple printed circuit boards (PCBs). The functionality and durability of the tested systems are demonstrated under various mechanical constraints, aiming to basically reproduce the normal operation conditions of flexible electronic devices. The obtained results indicate that the implementation of these AgNP-based inks is relevant for direct applications in inkjet printing technology, thus paving the way for the use of greener chemicals in ink preparation. [ABSTRACT FROM AUTHOR]

This work provides a method for the development of conductive water-based printing inks for gravure, flexography and screen-printing incorporating commercial resins that are already used in the printing industry. The development of the respective conductive materials/pigments is based on the simultaneous (in one step) reduction of silver salts and graphene oxide in the presence of 2,5-diaminobenzenesulfonic acid that is used for the first time as the common in-situ reducing agent for these two reactions. The presence of aminophenylsulfonic derivatives is essential for the reduction procedure and in parallel leads to the enrichment of the graphene surface with aminophenylsulfonic groups that provide a high hydrophilicity to the final materials/pigments. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study presents the functionalization of silk fabric with SWCNT ink. The first step was the formation of a polydopamine (PDA) thin coating on the silk fabric to allow for effective bonding of SWCNTs. PDA formation was carried out directly on the fabric by means of polymerization of dopamine in alkali conditions. The Silk/PDA fabric was functionalized with SWCNT ink of different SWCNT concentrations by using the dip-coating method. IR and Raman analyses show that the dominant β-sheet structure of silk fibroin after the functionalization process remains unchanged. The heat resistance is even slightly improved. The hydrophobic silk fabric becomes hydrophilic after functionalization due to the influence of PDA and the surfactant in SWCNT ink. The ink significantly changes the electrical properties of the silk fabric, from insulating to conductive. The volume resistance changes by nine orders of magnitude, from 2.4 × 1012 Ω to 2.3 × 103 Ω for 0.12 wt.% of SWCNTs. The surface resistance changes by seven orders of magnitude, from 2.1 × 1012 Ω to 2.4 × 105 Ω for 0.17 wt.% of SWCNTs. The volume and surface resistance thresholds are determined to be about 0.05 wt.% and 0.06 wt.%, respectively. The low value of the percolation threshold indicates efficient functionalization, with high-quality ink facilitating the formation of percolation paths through SWCNTs and the influence of the PDA linker. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A disposable voltammetric immunosensor was developed to measure breast cancer biomarker 15-3 (CA 15-3) in human saliva and serum samples. Screen-printed paper-based electrodes (f-SPE) previously fabricated by our research group using homemade conductive inks were used as transducers, which were later modified only with gold nanoparticles to immobilize anti-CA 15-3 antibodies. The sensor was operated using antigen–antibody interactions in conjunction with a redox species (ferrocyanide potassium) for the indirect determination of the CA 15-3 antigen. The device characterization involved atomic force microscopy (AFM) and electrochemical analysis. Optimization of the construction and response of the immunosensor was achieved at incubation times of 6 h for anti-CA 15-3, 1 h for bovine serum albumin, and 1 h for interaction with CA 15-3. The sensor displays a linear range between 2 and 16 U/mL, with a sensitivity of 0.012 μA/U mL−1, a limit of detection (LOD) of 0.56 U/mL, and a limit of quantification (LOQ) of 1.88 U/mL. The interfering substances minimally affected the signal, with 4.94% response variation, and the reproducibility of the immunosensor demonstrated a relative standard deviation (RSD) of 5.65%. The sensor successfully determined the CA 15-3 concentration in human serum and saliva, demonstrating its potential for clinical analysis. [ABSTRACT FROM AUTHOR]

In recent years, inkjet printing has emerged as a promising advanced fabrication technology in the field of electronics, offering remarkable advantages in terms of cost-effectiveness, design flexibility, and rapid prototyping. For these reasons, inkjet printing technology has been widely adopted in various applications, including printed circuit board fabrication, sensor development (e.g., temperature, humidity, and pressure sensing), and antenna and filter production, up to the microwave frequency range. The present paper is focused on the investigation of a methodology based on Monte Carlo simulations for quantitatively assessing the influence of fabrication tolerances on the performance of inkjet-printed microwave devices. In particular, the proposed methodology is applied to an inkjet-printed hairpin band pass filter specifically tailored for operation in the L band (i.e., from 1 GHz to 2 GHz). The initial design phase involved the use of computer aided design (CAD) software to optimize the geometric dimensions of the designed filter to closely match the desired performance specifications in terms of bandwidth, insertion loss, and return loss. Later, a Monte Carlo analysis was conducted to evaluate the propagation of tolerances in the fabrication process throughout the design and to estimate their effects on device performance. The fabrication process exploited the advanced capabilities of the Voltera inkjet printer, which was used to deposit a silver-based conductive ink on a commercial Rogers substrate. The device's performance was evaluated by comparing the simulated scattering parameters with those measured on the developed filter using a vector network analyzer (VNA), thus ensuring accurate validation of real-world performance. [ABSTRACT FROM AUTHOR]

We report the design, fabrication, and experimental characterization of an optically transparent printed planar inverted-F antenna (PIFA) operating at 2.45 GHz using the aerosol jet (AJ) printing method. The proposed antenna was fabricated using a clear conductive ink on glass and Delrin. The antenna exhibits a wide fractional bandwidth (FBW) of 20% centered at 2.45 GHz, with a peak realized gain of −3.6 dBi and transparency of ~80%. The proposed fabrication method provides a cost-effective and scalable solution for manufacturing transparent antennas with potential applications in wireless communication, sensing, and wearable devices operating at mmWave frequencies higher than 30 GHz. [ABSTRACT FROM AUTHOR]

In the background of 6G communication requiring a high data rate and energy efficiency, global coverage and connectivity, as well as high reliability and low latency, most existing reconfigurable metasurfaces face limitations in flexibility, integrability, energy consumption, and cost. This paper proposes a dual-polarized intelligent reflection surface (IRS) based on a paper-based flexible substrate as a solution. The proposed design uniquely enables the independent control of two orthogonally polarized electromagnetic waves to achieve customized scattering effects. Compared to conventional reconfigurable intelligent surfaces using PCB technology and active components, this design utilizes paper as the substrate material combined with conductive ink and silver ink, significantly reducing production costs and process complexity. The manufacturing cost is only about one-tenth of the traditional PCB solutions. This approach is not only cost-effective but also excels in both flexibility and portability. These attributes signify its suitability for a broader range of potential applications, encompassing areas where traditional RIS may be impractical due to cost, rigidity, or complexity constraints. By drawing rotationally symmetric small metal block structures on paper using silver ink, four structures are designed that achieve a phase difference of 90 degrees for both x-polarized and y-polarized wave incidences at the resonant frequency of 4.5754 GHz, realizing independent phase modulation. The dual-polarized flexible 2-bit intelligent reflection surface consists of 20 × 20 unit cells, and six different coding patterns are designed for single-beam and dual-beam design based on different scattering angles. The experimental results show that this polarization-independent flexible 2-bit intelligent reflection surface structure successfully allows independent control of two orthogonally polarized electromagnetic waves, enabling customized scattering effects. The experimental results are highly consistent with the simulation results. The independent control of two orthogonal polarized electromagnetic waves is a key feature of our design, enabling more flexible and effective signal coverage in complex urban environments. This precise control over polarization not only enhances the adaptability of the system but also offers practical solutions for real-world applications, particularly in meeting the growing demands of urban communication. The proposed metasurface based on paper-based flexible substrate is low-cost and highly portable, and the polarization independence provides more degrees of freedom for the metasurface, which is beneficial for more precise and efficient beam control and can be applied in the field of communication, especially 6G communication and IRS wireless communication. In addition, it also has broad application prospects in radar systems and remote sensing applications. [ABSTRACT FROM AUTHOR]

This work developed a conductive ink composed of carbonaceous material for printing electrochemical sensors. The optimized ink comprises graphite, carbon black, and nail polish, respectively (35.3:11.7:53%), as well as acetone as a solvent. The proportion was optimized with consideration of the binder's solubilization, the ink's suitability for the screen-printing process, and lower electrical resistance. The materials used, and the resulting ink, were analyzed by way of Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), Raman spectroscopy, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The charge transfer resistance (Rct) obtained was 0.348 kΩ. The conductive ink was used to print an electrode on a PET substrate, and a flexible and disposable electrode was obtained. The electroactive area obtained was 13.7 cm2, which was calculated by the Randles-Sevcik equation. The applicability of the device was demonstrated with a redox probe, providing a sensitivity of 0.02 µ A L mmol−1. The conductive ink has adequate homogeneity for producing electrodes using the screen-printing technique, with a low estimated production cost of $ 0.09 mL−1. [ABSTRACT FROM AUTHOR]

Real-time monitoring of human joint motion holds paramount importance in assessing joint health status, preventing and treating joint diseases, and evaluating physical flexibility and coordination. However, traditional strain sensors face limitations in meeting the substantial strain requirements associated with human joint motion. Recently, there has been considerable attention directed towards flexible strain sensors prepared using pliable substrates combined with silk and cotton fabrics. Nonetheless, these sensors exhibit insufficient linearity across the entire measurement range, thereby compromising the predictability of real joint motion based on the output signal. This paper introduced a flexible strain sensor designed to address this issue by offering an enhanced range and high linearity. Specifically, the core wire of the strain sensor was produced by coating a polybutylene terephthalate thread with conductive carbon ink integrated with carbon nanotubes, encapsulated in a thin layer of polydimethylsiloxane in an "S" configuration. The proposed strain sensor maintained excellent linearity within its strain range of 60%, along with advantages such as rapid response speed and robust durability. On-trial tests further affirmed the sensor's capability to effectively monitor the motion of human joints. [ABSTRACT FROM AUTHOR]

Three new methods for accurate electronic component positioning for thermoformed electronics are presented in this paper. To maintain the mechanical and electrical properties of printed-ink tracks, prevent deformation and stretching during thermoforming, and ensure reproducibility, the component positioning principle for all three proposed methods is based on keeping the temperature of some regions in the thermoplastic substrate less than the glass transition temperature of the thermoplastic carrier, to keep those regions resistant to plastic deformation. We have verified the accuracy of the different approaches by implementing these methods in a semi-sphere mold for positioning seven LEDs and one printed capacitive touch sensor. We compared the result of our fabrication processes with the typical fabrication process of in-mold electronics (direct printing on a thermoplastic foil and followed by a thermoforming step) and noticed that the sample produced by the typical process had tracks that were randomly stretched, tracks were not in a straight path after thermoforming and they were not electrically conductive. Furthermore, the final 3D position of the components was not reproducible sample by sample. However, with our proposed fabrication methods, the tracks and pads do not deform or expand during thermoforming and are electrically conductive after. Moreover, the round shape of the touch sensor remains the same as in the 2D design. Based on the results of the experiments, it appears that the proposed methods are capable of positioning electronic components with high precision in thermoformed electronics. [ABSTRACT FROM AUTHOR]

The use of AgNO3-polyvinyl alcohol (PVA) ink and oxygen plasma to form conductive coatings on plastic substrates was studied. It was found that oxygen plasma can decompose silver complexes to form metallic silver without high-temperature heating. The AgNO3-PVA ratio and plasma parameters (time, power) were optimized to obtain uniform conductive coatings. The morphology and electrical characteristics of the coatings were evaluated. Composite coatings with high reflectivity and good adhesion were prepared with a resistivity of 1.66 × 10−6 Ω·m using MOD inks with a silver ion mass fraction of 5%, after 300 W plasma treatment of the PET substrate for 2 min (the chamber temperature was 37.3 °C). These results demonstrate the potential feasibility of silver MOD inks and oxygen plasma treatment for the production of silver connectors, electromagnetic shielding films, and antimicrobial coatings on low-cost plastic substrates. [ABSTRACT FROM AUTHOR]

Aerosol jet printing (AJP) is a technique that allows for high-resolution printing of complex circuits on flexible substrates. This method has the potential to be used in various applications, such as electronic sensors, antennas, and micro-coils. The selection of ink is crucial for achieving excellent performance, and different studies have explored the use of silver nanoparticle ink and aqueous silver ink for improved conductivity and printability. Additionally, optimizing process parameters and conducting post-treatments and testing can enhance the quality and reliability of printed circuits. Overall, these investigations highlight the importance of ink selection, parameter optimization, and post-processing in achieving high-performance printed electronics. [Extracted from the article]

Reliable measurements in structural health monitoring mean for the instrumentation to be set in perfect reproducible conditions. The solution described in this study consists of printing the sensors directly on the parts to be controlled. This method solves the reproducibility issue, limits human error, and can be used in confined or hazardous environments. This work was limited to eddy current testing, but the settings and conclusions are transposable to any non-destructive testing methods (ultrasounds, etc.). The first salve of tests was run to establish the best dielectric and conductive ink combination. The Dupont ink combination gave the best performances. Then, the dispenser- and the screen-printing methods were carried out to print flat spiral coils on flexible substrates. The resulting sensors were compared to flex-printed circuit boards (PCB-flex) using copper for the electrical circuit. The conductive ink methods were revealed to be just as efficient. The last stage of this work consisted of printing sensors on solid parts. For this, 20-turn spiral coils were printed on 3 mm thick stainless-steel plates. The permanent sensors showed good sensibility in the same range as the portative ones, demonstrating the method's feasibility. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel tactile sensor with a "fingerprint" design, named due to its spiral shape and dimensions of 3.80 mm × 3.80 mm. The sensor is duplicated in a four-by-four array containing 16 tactile sensors to form a "SkinCell" pad of approximately 45 mm by 29 mm. The SkinCell was fabricated using a custom-built microfabrication platform called the NeXus which contains additive deposition tools and several robotic systems. We used the NeXus' six-degrees-of-freedom robotic platform with two different inkjet printers to deposit a conductive silver ink sensor electrode as well as the organic piezoresistive polymer PEDOT:PSS-Poly (3,4-ethylene dioxythiophene)-poly(styrene sulfonate) of our tactile sensor. Printing deposition profiles of 100-micron- and 250-micron-thick layers were measured using microscopy. The resulting structure was sintered in an oven and laminated. The lamination consisted of two different sensor sheets placed back-to-back to create a half-Wheatstone-bridge configuration, doubling the sensitivity and accomplishing temperature compensation. The resulting sensor array was then sandwiched between two layers of silicone elastomer that had protrusions and inner cavities to concentrate stresses and strains and increase the detection resolution. Furthermore, the tactile sensor was characterized under static and dynamic force loading. Over 180,000 cycles of indentation were conducted to establish its durability and repeatability. The results demonstrate that the SkinCell has an average spatial resolution of 0.827 mm, an average sensitivity of 0.328 m Ω / Ω / N , expressed as the change in resistance per force in Newtons, an average sensitivity of 1.795 µV/N at a loading pressure of 2.365 PSI, and a dynamic response time constant of 63 ms which make it suitable for both large area skins and fingertip human–robot interaction applications. [ABSTRACT FROM AUTHOR]

The monitoring of potassium ion (K+) levels in human sweat can provide valuable insights into electrolyte balance and muscle fatigue non-invasively. However, existing laboratory techniques for sweat testing are complex, while wearable sensors face limitations like drift, fouling and interference from ions such as Na+. This work develops printed electrodes using β-cyclodextrin functionalized reduced graphene oxide (β-CD-RGO) for selective K+ quantification in sweat. The β-CD prevents the aggregation of RGO sheets while also providing selective binding sites for K+ capture. Electrodes were fabricated by screen printing the β-CD-RGO ink onto conductive carbon substrates. Material characterization confirmed the successful functionalization of RGO with β-CD. Cyclic voltammetry (CV) showed enhanced electrochemical behavior for β-CD-RGO-printed electrodes compared with bare carbon and RGO. Sensor optimization resulted in a formulation with 30% β-CD-RGO loading. The printed electrodes were drop-casted with an ion-selective polyvinyl chloride (PVC) membrane. A linear range from 10 μM to 100 mM was obtained along with a sensitivity of 54.7 mV/decade. The sensor showed good reproducibility over 10 cycles in 10 mM KCl. Minimal interference from 100 mM Na+ and other common sweat constituents validated the sensor's selectivity. On-body trials were performed by mounting the printed electrodes on human subjects during exercise. The K+ levels measured in sweat were found to correlate well with serum analysis, demonstrating the sensor's ability for non-invasive electrolyte monitoring. Overall, the facile synthesis of stable β-CD-RGO inks enables the scalable fabrication of wearable sensors for sweat potassium detection. [ABSTRACT FROM AUTHOR]

In recent years, researchers prepared composite conductive inks with high conductivity, high thermal conductivity, strong stability, and excellent comprehensive mechanical properties by combining carbon-based materials such as graphene and carbon nanotubes with metal-based materials. Through new electronic printing technologies, conductive inks can be used not only to promote the development of integrated circuits but also in various new electronic products. The conductive mechanism and the main types of conductive inks are introduced in this review. The advantages of electronic printing technology for preparing integrated circuits are analyzed. The research progress of fabricating integrated circuits with different electronic printing processes, such as screen printing, gravure printing, flexographic printing, and inkjet printing, are summarized. The development trend of carbon-based composite conductive ink for integrated circuits is prospected. [ABSTRACT FROM AUTHOR]

In recent years, there has been a huge surge in interest in improving the efficiency of smart electronic and optoelectronic devices via the development of novel materials and printing technologies. Inkjet printing, known to deposit 'ink on demand', helps to reduce the consumption of materials. Printing inks on various substrates like paper, glass, and fabric is possible, generating flexible devices that include supercapacitors, sensors, and electrochromic devices. Newer inks being tested and used include formulations of carbon nanoparticles, photochromic dyes, conducting polymers, etc. Among the conducting polymers, PANI has been well researched. It can be synthesized and doped easily and allows for the easy formation of composite conductive inks. Doping and the addition of additives like metal salts, oxidants, and halide ions tune its electrical properties. PANI has a large specific capacitance and has been researched for its applications in supercapacitors. It has been used as a sensor for pH and humidity as well as a biosensor for sweat, blood, etc. The response is generated by a change in its electrical conductivity. This review paper presents an overview of the investigations on the formulation of the inks based on conductive polymers, mainly centered around PANI, and inkjet printing of its formulations for a variety of devices, including supercapacitors, sensors, electrochromic devices, and patterning on flexible substrates. It covers their performance characteristics and also presents a future perspective on inkjet printing technology for advanced electronic, optoelectronic, and other conductive-polymer-based devices. We believe this review provides a new direction for next-generation conductive-polymer-based devices for various applications. [ABSTRACT FROM AUTHOR]

Electrocardiogram (ECG) electrodes are important sensors for detecting heart disease whose performance determines the validity and accuracy of the collected original ECG signals. Due to the large drawbacks (e.g., allergy, shelf life) of traditional commercial gel electrodes, textile electrodes receive widespread attention for their excellent comfortability and breathability. This work demonstrated a dry electrode for ECG monitoring fabricated by screen printing silver/silver chloride (Ag/AgCl) conductive ink on ordinary polyester fabric. The results show that the screen-printed textile electrodes have good and stable electrical and electrochemical properties and excellent ECG signal acquisition performance. Furthermore, the resistance of the screen-printed textile electrode is maintained within 0.5 Ω/cm after 5000 bending cycles or 20 washing and drying cycles, exhibiting excellent flexibility and durability. This research provides favorable support for the design and preparation of flexible and wearable electrophysiological sensing platforms. [ABSTRACT FROM AUTHOR]

The development of three-dimensional printed electronics has garnered significant interest due to the ease of integration of electronic circuitry on 3D surfaces. However, it is still very challenging to achieve the desired conformability, stretchability, and adhesion of conductive pastes used for printing on thermoformable substrates. In this study, we propose the use of novel thermoformable ink composed of copper flakes coated with silver, which enables us to prevent the oxidation of copper, instead of the commonly used silver inks. Various polymer/solvent/flake systems were investigated, resulting in thermoformable conductive printing compositions that can be sintered under air. The best inks were screen printed on PC substrates and were thermoformed using molds with different degrees of strain. The effects of the various components on the thermoforming ability and the electrical properties and morphology of the resulting 3D structures were studied. The best inks resulted in a low sheet resistivity, 100 mΩ/□/mil and 500 mΩ/□/mil before and after thermoforming at 20%, respectively. The feasibility of using the best ink was demonstrated for the fabrication of a thermoformable 3D RFID antenna on PC substrates. [ABSTRACT FROM AUTHOR]

This study presents graphene inks produced through the liquid-phase exfoliation of graphene flakes in water using optimized concentrations of dispersants (gelatin, triton X-100, and tween-20). The study explores and compares the effectiveness of the three different dispersants in creating stable and conductive inks. These inks can be printed onto polyethylene terephthalate (PET) substrates using an aerosol jet printer. The investigation aims to identify the most suitable dispersant to formulate a high-quality graphene ink for potential applications in printed electronics, particularly in developing chemiresistive sensors for IoT applications. Our findings indicate that triton X-100 is the most effective dispersant for formulating graphene ink (GTr), which demonstrated electrical conductivity (4.5 S·cm−1), a high nanofiller concentration of graphene flakes (12.2%) with a size smaller than 200 nm (<200 nm), a low dispersant-to-graphene ratio (5%), good quality as measured by Raman spectroscopy (ID/IG ≈ 0.27), and good wettability (θ ≈ 42°) over PET. The GTr's ecological benefits, combined with its excellent printability and good conductivity, make it an ideal candidate for manufacturing chemiresistive sensors that can be used for Internet of Things (IoT) healthcare and environmental applications. [ABSTRACT FROM AUTHOR]

Graphene and its derivatives have been widely used to develop novel materials with applications in energy storage. Among them, reduced graphene oxide has shown great potential for more efficient storage of Na ions and is a current target in the design of electrodes for environmentally friendly Na ion batteries. The search for more sustainable and versatile manufacturing processes also motivates research into additive manufacturing electrodes. Here, the electrochemical responses of porous 3D-printed free-standing log-type structures fabricated using direct ink writing (DIW) with a graphene oxide (GO) gel ink are investigated after thermal reduction in a three-electrode cell configuration. The structures delivered capacities in the range of 50–80 mAh g−1 and showed high stability for more than 100 cycles. The reaction with the electrolyte/solvent system, which caused an initial capacity drop, was evidenced by the nucleation of various Na carbonates and Na2O. The incorporation of Na into the filaments of the structure was verified with transmission electron microscopy and Raman spectroscopy. This work is a proof of concept that structured reduced GO electrodes for Na ion batteries can be achieved from a simple, aqueous GO ink through DIW and that there is scope for improving their performance and capacity. [ABSTRACT FROM AUTHOR]

This article presents a novel approach to designing and validating a fully electronic braking pedal, addressing the growing integration of electronics in vehicles. With the imminent rise of brake-by-wire (BBW) technology, the brake pedal requires electronification to keep pace with industry advancements. This research explores technologies and features for the next-generation pedal, including low-power consumption electronics, cost-effective sensors, active adjustable pedals, and a retractable pedal for autonomous vehicles. Furthermore, this research brings the benefits of the water injection technique (WIT) as the base for manufacturing plastic pedal brakes towards reducing cost and weight while enhancing torsional stiffness. Communication with original equipment manufacturers (OEMs) has provided valuable insights and feedback, facilitating a productive exchange of ideas. The findings include two sensor prototypes utilizing inductive technology and printed-ink gauges. Significantly, reduced power consumption was achieved in a Hall-effect sensor already in production. Additionally, a functional BBW prototype was developed and validated. This research presents an innovative approach to pedal design that aligns with current electrification trends and autonomous vehicles. It positions the braking pedal as an advanced component that has the potential to redefine industry standards. In summary, this research significantly contributes to the electronic braking pedal technology presenting the critical industry needs that have driven technical studies and progress in the field of sensors, electronics, and materials, highlighting the challenges that component manufacturers will inevitably face in the forthcoming years. [ABSTRACT FROM AUTHOR]

Cracks have a primary effect on the failure of a structure. Therefore, the development of crack sensors with high accuracy and resolution and cracks detection method are important. In this study, the crack sensors were fabricated, and the crack locations were detected with the electrical signal of the crack sensor. First, a metal grid-type micro-crack sensor based on silver was fabricated. The sensor is made with electrohydrodynamics (EHD) inkjet printing technology, which is well known as the next generation of printed electronics technology. Optimal printing conditions were established through experiments, and a grid sensor was obtained. After that, single cracks and multiple cracks were simulated on the sensor, and electrical signals generated from the sensor were measured. The measured electrical signal tracked the location of the cracks in three steps: simple cross-calculation, interpolation, and modified P-SPICE. It was confirmed that cracks could be effectively found and displayed using the method presented in this paper. [ABSTRACT FROM AUTHOR]

Soft sensors are attracting much attention from researchers worldwide due to their versatility in practical projects. There are already many applications of soft sensors in aspects of life, consisting of human-robot interfaces, flexible electronics, medical monitoring, and healthcare. However, most of these studies have focused on a specific area, such as fabrication, data analysis, or experimentation. This approach can lead to challenges regarding the reliability, accuracy, or connectivity of the components. Therefore, there is a pressing need to consider the sensor's placement in an overall system and find ways to maximize the efficiency of such flexible sensors. This paper proposes a fabrication method for soft capacitive pressure sensors with spacer fabric, conductive inks, and encapsulation glue. The sensor exhibits a good sensitivity of 0.04 kPa−1, a fast recovery time of 7 milliseconds, and stability of 10,000 cycles. We also evaluate how to connect the sensor to other traditional sensors or hardware components. Some machine learning models are applied to these built-in soft sensors. As expected, the embedded wearables achieve a high accuracy of 96% when recognizing human walking phases. [ABSTRACT FROM AUTHOR]

Copper-based nanoinks are emerging as promising low-cost alternatives to widely used silver nanoinks in electronic printing. However, the spontaneous oxidation of copper under ambient conditions poses significant challenges to its broader application. To address this issue, this paper presents an economical, large-scale, and environmentally friendly method for fabricating Cu@Ag nanoparticles (Cu@Ag NPs). The as-prepared nanoparticles exhibit a narrow size distribution of approximately 100 nm and can withstand ambient exposure for at least 60 days without significant oxidation. The Cu@Ag-based ink, with a 60 wt% loading, was screen-printed onto a flexible polyimide substrate and subsequently heat-treated at 290 °C for 15 minutes under a nitrogen atmosphere. The sintered pattern displayed a low electrical resistivity of 25.5 μΩ·cm (approximately 15 times the resistivity of bulk copper) along with excellent reliability and mechanical fatigue strength. The innovative Cu@Ag NPs fabrication method holds considerable potential for advancing large-scale applications of copper-based inks in flexible electronics. [ABSTRACT FROM AUTHOR]

In this article, a facile way for the doping of graphene and graphene derivatives with silver nanoparticles at different Ag ratios is described. Ag nanoparticles were formed directly on the surface of two different graphene substrates dispersed in dimethylformamide by the reduction of Ag cations with NaBH4. A few layered graphene nanosheets (FLG) produced from graphite and reduced graphene oxide functionalized with amino arylsulfonates (f-rGO) were used as substrates. The final graphene/Ag nanoparticle hybrid in the form of solid, dense spots showed enhanced electrical conductivity, which can be attributed to the formation of conductive interconnections between the 2D nanosheets. Importantly, electrical conductivities of 20 and 167 103 S m−1 were measured for the hybrids of f-rGO and FLG, respectively, with the higher Ag percentage without an annealing process. A representative hybrid f-rGO with Ag nanoparticles was used for the development of a highly conductive water-based gravure ink with excellent printing properties. [ABSTRACT FROM AUTHOR]

In the last decades, the demand for electronics and, therefore, electronic waste, has increased. To reduce this electronic waste and the impact of this sector on the environment, it is necessary to develop biodegradable systems using naturally produced materials with low impact on the environment or systems that can degrade in a certain period. One way to manufacture these types of systems is by using printed electronics because the inks and the substrates used are sustainable. Printed electronics involve different methods of deposition, such as screen printing or inkjet printing. Depending on the method of deposition selected, the developed inks should have different properties, such as viscosity or solid content. To produce sustainable inks, it is necessary to ensure that most of the materials used in the formulation are biobased, biodegradable, or not considered critical raw materials. In this review, different inks for inkjet printing or screen printing that are considered sustainable, and the materials that can be used to formulate them, are collected. Printed electronics need inks with different functionalities, which can be mainly classified into three groups: conductive, dielectric, or piezoelectric inks. Materials need to be selected depending on the ink's final purpose. For example, functional materials such as carbon or biobased silver should be used to secure the conductivity of an ink, a material with dielectric properties could be used to develop a dielectric ink, or materials that present piezoelectric properties could be mixed with different binders to develop a piezoelectric ink. A good combination of all the components selected must be achieved to ensure the proper features of each ink. [ABSTRACT FROM AUTHOR]

Acetylcholine (ACh) is involved in memory and learning and has implications in neurodegenerative diseases; it is therefore important to study the dynamics of ACh in the brain. This work creates a flexible solid-contact potentiometric sensor for in vitro and in vivo recording of ACh in the brain and tissue homogenate. We fabricate this sensor using a 250 μm diameter cotton yarn coated with a flexible conductive ink and an ACh sensing membrane that contains a calix[4]arene ionophore. The exposed ion-to-electron transducer was sealed with a 2.5 μm thick Parylene C coating to maintain the flexibility of the sensor. The resulting diameter of the flexible ACh sensing thread (FAST) was 400 μm. The FAST showed a linear response range from 1.0 μM to 10.0 mM in deionized water, with a near-Nernstian slope of 56.11 mV/decade and a limit of detection of 2.6 μM. In artificial cerebrospinal fluid, the limit of detection increased to 20 μM due to the background signal of ionic content of the cerebrospinal fluid. The FAST showed a signal stability of 226 μV/h over 24 h. We show that FAST can measure ACh dynamics in sheep brain tissue and sheep brain homogenate after ACh spiking. FAST is the first flexible electrochemical sensor for monitoring ACh dynamics in the brain. [ABSTRACT FROM AUTHOR]

Metal nanoparticles are increasingly used as key elements in the fabrication and processing of advanced electronic systems and devices. For future device integration, their charge transport properties are essential. This has been exploited, e.g., in the development of gold-nanoparticle-based conductive inks and chemiresistive sensors. Colloidal wires and metal nanoparticle lines can also be used as interconnection structures to build directional electrical circuits, e.g., for signal transduction. Our scalable bottom-up, template-assisted self-assembly creates gold-nanorod (AuNR) lines that feature comparably small widths, as well as good conductivity. However, the bottom-up approach poses the question about the consistency of charge transport properties between individual lines, as this approach leads to heterogeneities among those lines with regard to AuNR orientation, as well as line defects. Therefore, we test the conductance of the AuNR lines and identify requirements for a reliable performance. We reveal that multiple parallel AuNR lines (>11) are necessary to achieve predictable conductivity properties, defining the level of miniaturization possible in such a setup. With this system, even an active area of only 16 µm2 shows a higher conductance (~10−5 S) than a monolayer of gold nanospheres with dithiolated-conjugated ligands and additionally features the advantage of anisotropic conductance. [ABSTRACT FROM AUTHOR]

In recent research, 3D printing has become a powerful technique and has been applied in the last few years to carbon-based materials. A new generation of 3D-printed electrodes, more affordable and easier to obtain due to rapid prototyping techniques, has emerged. We propose a customizable fabrication process for flexible (and rigid) carbon-based biosensors, from biosensor design to printable conductive inks. The electrochemical biosensors were obtained on a 50 µm Kapton® (polyimide) substrate and transferred to a 500 µm PDMS substrate, using a 3D-extrusion-based printing method. The main features of our fabrication process consist of short-time customization implementation, fast small-to-medium batch production, ease of electrochemical spectroscopy measurements, and very good resolution for an extrusion-based printing method (100 µm). The sensors were designed for future integration into a smart wound dressing for wound monitoring and other biomedical applications. We increased their sensibility with electro-deposited gold nanoparticles. To assess the biosensors' functionality, we performed surface functionalization with specific anti-N-protein antibodies for SARS-CoV 2 virus, with promising preliminary results. [ABSTRACT FROM AUTHOR]

Herein, we report results of the studies relating to the development of an impedimetric, magnetic bead-assisted supersandwich DNA hybridization assay for ultrasensitive detection of Neisseria gonorrhoeae, the causative agent of a sexually transmitted infection (STI), gonorrhea. First, a conductive ink was formulated by homogenously dispersing carboxylated multiwalled carbon nanotubes (cMWCNTs) in a stable emulsion of terpineol and an aqueous suspension of carboxymethyl cellulose (CMC). The ink, labeled C5, was coated onto paper substrates to fabricate C5@paper conductive electrodes. Thereafter, a magnetic bead (MB)-assisted supersandwich DNA hybridization assay was optimized against the porA pseudogene of N. gonorrhoeae. For this purpose, a pair of specific 5′ aminated capture probes (SCP) and supersandwich detector probes (SDP) was designed, which allowed the enrichment of target gonorrheal DNA sequence from a milieu of substances. The SD probe was designed such that instead of 1:1 binding, it allowed the binding of more than one T strand, leading to a 'ladder-like' DNA supersandwich structure. The MB-assisted supersandwich assay was integrated into the C5@paper electrodes for electrochemical analysis. The C5@paper electrodes were found to be highly conductive by a four-probe conductivity method (maximum conductivity of 10.1 S·cm−1). Further, the biosensing assay displayed a wide linear range of 100 aM-100 nM (109 orders of magnitude) with an excellent sensitivity of 22.6 kΩ·(log[concentration])−1. The clinical applicability of the biosensing assay was assessed by detecting genomic DNA extracted from N. gonorrhoeae in the presence of DNA from different non-gonorrheal bacterial species. In conclusion, this study demonstrates a highly sensitive, cost-effective, and label-free paper-based device for STI diagnostics. The ink formulation prepared for the study was found to be highly thixotropic, which indicates that the paper electrodes can be screen-printed in a reproducible and scalable manner. [ABSTRACT FROM AUTHOR]

Electrochemical sensors consisting of screen-printed electrodes (SPEs) are recurrent devices in the recent literature for applications in different fields of interest and contribute to the expanding electroanalytical chemistry field. This is due to inherent characteristics that can be better (or only) achieved with the use of SPEs, including miniaturization, cost reduction, lower sample consumption, compatibility with portable equipment, and disposability. SPEs are also quite versatile; they can be manufactured using different formulations of conductive inks and substrates, and are of varied designs. Naturally, the analytical performance of SPEs is directly affected by the quality of the material used for printing and modifying the electrodes. In this sense, the most varied carbon nanomaterials have been explored for the preparation and modification of SPEs, providing devices with an enhanced electrochemical response and greater sensitivity, in addition to functionalized surfaces that can immobilize biological agents for the manufacture of biosensors. Considering the relevance and timeliness of the topic, this review aimed to provide an overview of the current scenario of the use of carbonaceous nanomaterials in the context of making electrochemical SPE sensors, from which different approaches will be presented, exploring materials traditionally investigated in electrochemistry, such as graphene, carbon nanotubes, carbon black, and those more recently investigated for this (carbon quantum dots, graphitic carbon nitride, and biochar). Perspectives on the use and expansion of these devices are also considered. [ABSTRACT FROM AUTHOR]

In the field of flexible electronics manufacturing, inkjet printing technology is a research hotspot, and it is key to developing low-temperature curing conductive inks that meet printing requirements and have suitable functions. Herein, methylphenylamino silicon oil (N75) and epoxy-modified silicon oil (SE35) were successfully synthesized through functional silicon monomers, and they were used to prepare silicone resin 1030H with nano SiO2. 1030H silicone resin was used as the resin binder for silver conductive ink. The silver conductive ink we prepared with 1030H has good dispersion performance with a particle size of 50–100 nm, as well as good storage stability and excellent adhesion. Additionally, the printing performance and conductivity of the silver conductive ink prepared with n,n-dimethylformamide (DMF): proprylene glycol monomethyl ether (PM) (1:1) as solvent are better than those of the silver conductive ink prepared by DMF and PM solvent. Cured at a low temperature of 160 °C, the resistivity of 1030H-Ag-82%-3 conductive ink is 6.87 × 10−6 Ω·m, and that of 1030H-Ag-92%-3 conductive ink is 0.564 × 10−6 Ω·m, so the low-temperature curing silver conductive ink has high conductivity. The low-temperature curing silver conductive ink we prepared meets the printing requirements and has potential for practical applications. [ABSTRACT FROM AUTHOR]

Featured Application: Wearable Antenna Technology. Screen-printed and inkjet-printed conductive fabric antennas have been investigated in this manuscript. The former showed optimal radiation performance after fabrication and measurement, which was the basis for developing a new fabric antenna feeding technique. The aperture-fed technique is achieved with a single coaxial cable overlayed on a cut-out slot on the ground layer of the patch antenna. The cable is connected with conductive silver-based epoxy paste with high resilience to mechanical stress. Two antenna models for Bluetooth low energy (BLE) and long-range (LoRa) wireless applications were designed, fabricated, and measured at 2.44 GHz and 868 MHz, respectively, with good impedance and radiation performance. The measured antennas operated from 2.4 to 2.48 GHz (BLE) and 853 to 886 MHz (LoRa) at −10 dB S11. Measured results also showed a 56% radiation efficiency at BLE and 44.9% at LoRa. The screen-printing procedure and feeding technique have been presented in this manuscript. [ABSTRACT FROM AUTHOR]

Metamaterial absorbers (MMAs) that absorb electromagnetic waves among an ultra-broad frequency band have attracted great attention in military and civilian applications. In this paper, an ultra-broadband and highly-efficient MMA is presented. The unit cell of the proposed MMA was constructed with two cross-placed stand-up gradient impedance graphene films, which play a key role in improving impedance matching. Considering the trade-off between absorbing performance and processing complexity, in our design, we adopted the stand-up graphene films that have a gradient with three orders of magnitude in total. The simulated results of the proposed absorber show an ultra-broadband absorption (absorptivity > 90%) from 1.8 GHz to 66.7 GHz and a highly-efficient absorption (absorptivity > 97%) in the range of 2–21.7 GHz and 39.6–57 GHz. The field analysis was adopted to explain the mechanism of the proposed absorber. To validate this design, a prototype of 20 × 20 units was processed and assembled. The graphene films were processed with graphene conductive ink using screen print technology. The measured results are in good agreement with the simulated ones. The proposed absorber may find potential applications in the field of stealth technologies and electromagnetic interference. [ABSTRACT FROM AUTHOR]

Graphene conductive inks have attracted significant attention in recent years due to their high conductivity, corrosion resistance, and environmentally friendly nature. However, the dispersion of graphene in aqueous solution is still challenging. In this work, we synthesized an amphiphilic graft copolymer, polyvinyl alcohol-g-polyaniline (PVA-g-PANI), and studied the graphene dispersion prepared with the graft copolymer by high-speed shear dispersion. The amphiphilic graft copolymer can be used as a stabilizer and adhesive agent in graphene dispersion. Given the steric hindrance of the graft copolymer, the stability of graphene dispersion is improved by decreasing the probability of π–π stacking. PVA-g-PANI has a better stability on graphene dispersion than carboxymethylcellulose sodium (CMC-Na) and a mixture of PVA and PANI. The graft copolymer has only a slight effect on the conductivity of graphene dispersion due to the existence of conductive PANI, which is beneficial for preparing the graphene dispersion with good conductivity and adhesion. Graphene dispersion is well-adapted to screen printing and is very stable with regard to the sheet resistance bending cycle. [ABSTRACT FROM AUTHOR]

We present, for the very first time, the fabrication and electrochemical characterization of a paper-based experimental platform for dengue virus analysis. The paper-based device incorporates a screen-printing technology with the help of black carbon conductive ink. The paper-based device utilizes two styles of electrode setups, i.e., the two-electrode system and three-electrode system, and both setups effectively detected the dengue virus with an LOD of 0.1 µg/mL; however, these paper electrodes exhibit various current ranges, and the created sensor was encompassed and compared in this research based on current response. It is observed that the three-electrode system has a substantially higher current range, ranging from 55.53 µA to 322.21 µA, as compared to the two-electrode system, which has a current range of 0.85 µA to 4.54 µA. According to this study, the three-electrode system displayed a good range of current amplification that is roughly 50 times higher than the two-electrode system, which had a weak current response. As a result, the three-electrode method has emerged as a viable option for the very sensitive detection of the dengue virus, as well as for the diagnosis of other diseases. [ABSTRACT FROM AUTHOR]

The large-scale manufacturing of flexible electronics is nowadays based on inkjet printing technology using specially formulated conductive inks, but achieving adequate wetting of different surfaces remains a challenge. In this work, the development of a silver nanoparticle-based functional ink for printing on flexible paper and plastic substrates is demonstrated. Amphiphilic silver nanoparticles with narrow particle size distribution and good dispersibility were prepared via a two-step wet chemical synthesis procedure. First, silver nanoparticles capped with poly(acrylic acid) were prepared, followed by an amidation reaction with 3-morpholynopropylamine (MPA) to increase their lipophilicity. Density functional theory (DFT) calculations were performed to study the interactions between the particles and the dispersion medium in detail. The amphiphilic nanoparticles were dispersed in solvents of different polarity and their physicochemical and rheological properties were determined. A stable ink containing 10 wt% amphiphilic silver nanoparticles was formulated and inkjet-printed on different surfaces, followed by intense pulsed light (IPL) sintering. Low sheet resistances of 3.85 Ω sq–1, 0.57 Ω sq–1 and 19.7 Ω sq–1 were obtained for the paper, coated poly(ethylene terephthalate) (PET) and uncoated polyimide (PI) flexible substrates, respectively. Application of the nanoparticle ink for printed electronics was demonstrated via a simple flexible LED circuit. [ABSTRACT FROM AUTHOR]