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Carbon-based conductive inks, with their low cost, ease of fabrication, and environmental friendliness, have a wide range of applications. In this study, we present the development of a candle-soot-based conductive ink through a simple and cost-effective synthesis process. The composite was formulated by incorporating candle-soot with PVDF-HFP polymer using DMF as a solvent. The study evaluates the performance of different amounts of carbon present in a candle-soot-polymer composite. The conductive ink was also filled in a ballpoint refill, circuits were drawn, and I–V responses were studied. The conductive films were thoroughly characterized using SEM, EDX, TGA, and IV characteristics. XRD and FTIR analyses were performed to assess the properties of the conductive film (CPC4) and candle-soot. Four distinct conductive ink formulations were synthesized by varying the percentage of candle-soot. I-V studies revealed that the electrical resistance of the composite films decreased with increasing candle-soot content. The results demonstrated excellent conductivity, enabling the fabrication of simple and functional conductive circuits on paper using the developed CPC4 ink. Candle-soot, as filler, exhibited promising results comparable to expensive conductive fillers such as graphene and multi-walled carbon nanotubes. The developed conductive ink shows promising performance in flexible electronic devices, offering a cost-effective and environmentally friendly alternative. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs), owing to their superior electrical and mechanical properties, are a promising alternative to nonmetallic electrically conducting materials. In practice, cellulose as a low‐cost sustainable matrix has been used to prepare the aqueous dispersion of cellulose‐CNT (C‐CNT) nanocomposites. However, the compatibility with conventional solution‐processing and structural rearrangement for improving conductivity has yet to be determined. Herein, a straightforward route to prepare a conductive composite material from single‐walled CNTs (SWCNTs) and natural pulp is reported. High‐power shaking realizes the self‐alignment of individual SWCNTs in a cellulose matrix, resulting from the structural change in molecular orientations owing to countless collisions of zirconia beads in the aqueous mixture. The structural analysis of the dried C‐CNT films confirms that the entanglement and dispersion of C‐CNT nanowires determine the mechanical and electrical properties. Moreover, the rheological behavior of C‐CNT inks explains their coating and printing characteristics. By controlling shaking time, the electrical conductivity of the C‐CNT films with only 9 wt.% of SWCNTs from 0.9 to 102.4 S cm−1 are adjusted. the optimized C‐CNT ink is highly compatible with the conventional coating and printing processes on diverse substrates, thus finding potential applications in eco‐friendly, highly flexible, and stretchable electrodes is also demonstrated. [ABSTRACT FROM AUTHOR]

Natural polymer substrates are gaining attention as substitutes for plastic substrates in electronics, aiming to combine high performance, intricate shape deformation, and environmental sustainability. Herein, natural wood veneer is converted into a transparent wood film (TWF) substrate. The combination of 3D printing and origami technique is established to create programmable wood-based origami electronics, which exhibit superior flexibility with high tensile strength (393 MPa) due to the highly aligned cellulose fibers and the formation of numerous intermolecular hydrogen bonds between them. Moreover, the flexible TWF electronics exhibit editable multiplexed configurations and maintain stable conductivity. This is attributed to the strong adhesion between the cellulose-based ink and TWF substrate by non-covalent bonds. Benefiting from its anisotropic structure, the programmability of TWF electronics is achieved through sequentially folding into predesigned shapes. This design not only promotes environmental sustainability but also introduces its customizable shapes with potential applications in sensors, microfluidics, and wearable electronics. Wood-based electronics are typically constrained in their ability to undergo complex shape deformation. Here, authors integrate transparent wood film and cellulose-based conductive ink for flexible electronic origami devices that have been demonstrated as a proof-of-concept for human motion sensors. [ABSTRACT FROM AUTHOR]

Herein we introduce a novel water-based graphite ink modified with multiwalled carbon nanotubes, designed for the development of the first wearable self-powered biosensor enabling alcohol abuse detection through sweat analysis. The stencil-printed graphite (SPG) electrodes, printed onto a flexible substrate, were modified by casting multiwalled carbon nanotubes (MWCNTs), electrodepositing polymethylene blue (pMB) at the anode to serve as a catalyst for nicotinamide adenine dinucleotide (NADH) oxidation, and hemin at the cathode as a selective catalyst for H2O2 reduction. Notably, alcohol dehydrogenase (ADH) was additionally physisorbed onto the anodic electrode, and alcohol oxidase (AOx) onto the cathodic electrode. The self-powered biosensor was assembled using the ADH/pMB-MWCNTs/SPG||AOx/Hemin-MWCNTs/SPG configuration, enabling the detection of ethanol as an analytical target, both at the anodic and cathodic electrodes. Its performance was assessed by measuring polarization curves with gradually increasing ethanol concentrations ranging from 0 to 50 mM. The biosensor demonstrated a linear detection range from 0.01 to 0.3 mM, with a detection limit (LOD) of 3 ± 1 µM and a sensitivity of 64 ± 2 μW mM−1, with a correlation coefficient of 0.98 (RSD 8.1%, n = 10 electrode pairs). It exhibited robust operational stability (over 2800 s with continuous ethanol turnover) and excellent storage stability (approximately 93% of initial signal retained after 90 days). Finally, the biosensor array was integrated into a wristband and successfully evaluated for continuous alcohol abuse monitoring. This proposed system displays promising attributes for use as a flexible and wearable biosensor employing biocompatible water-based inks, offering potential applications in forensic contexts. A novel water-based graphite ink modified with multiwalled carbon nanotubes designed for the development of a wearable self-powered biosensor enabling alcohol abuse detection through sweat analysis. [ABSTRACT FROM AUTHOR]

The integration of electronics into textiles, commonly referred to electronic textiles (e-textiles), has sparked significant interest in recent years owing to their vast potential across diverse industries including healthcare, fashion, sports, and wearable technology. This review paper offers an extensive examination of the current landscape of e-textiles, focusing on their types, applications, conductive materials, and fabrication methods. Regarding fabrication methods, two primary approaches as main groups were introduced and are scrutinized in detail: (1) Fabricating/using conductive yarn/thread and inserting it into the textile using traditional textile techniques such as weaving, knitting, embroidery and so on. (2) Direct applying of conductive coatings onto existing textiles which include sub groups such as deposition techniques, wet coating techniques, printing techniques and in situ polymerization for integrated conductivity. Notably, this review not only elucidates these methodologies but also encapsulates the latest advancements in e-textile fabrication, serving as a vital resource for researchers and developers navigating this rapidly evolving domain. It also acknowledges the main challenges that need to be addressed to fabricate high efficent e-textile. These include ensuring durability with has direct relation with long-term washability and flexibility. Different strategies to improve durability such as using elastic substrates, stretchable conductive ink, improving adhesion between conductive layer and textile along with encapsulation of conductive layer on textile are discussed. By offering a comprehensive overview and highlighting recent innovations, this paper aims to propel further advancements in the realm of e-textiles, facilitating the realization of their full potential across various sectors. [ABSTRACT FROM AUTHOR]

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]

A modified polyol process was used to produce low-cost silver nanowires, which were analyzed using surface plasmon resonance, x-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. These nanowires were used to create silver ink with specific properties suitable for inkjet and aerosol printing. The ink's electrical resistivity was 140 µΩ cm on paper and 200 µΩ cm on polyethylene terephthalate and polypropylene. [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]

[Display omitted] • Achieve high-precision DIW printing using conductive hydrogel ink. • Conductive hydrogel electrodes have remarkable stretchability and self-healing capabilities. • Develop a self-powered strain sensing system employing conductive hydrogel electrodes. • Construct a complex internal structure within the electrode. • Remote human motion detection based on hydrogel strain sensors. With rapid advancements in health and human–computer interaction, wearable electronic skins (e-skins) designed for application on the human body provide a platform for real-time detection of physiological signals. Wearable strain sensors, integral functional units within e-skins, can be integrated with Internet of Things (IoT) technology to broaden the applications for human body monitoring. A significant challenge lies in the reliance of most existing wearable strain sensors on rigid external power supplies, limiting their practical flexibility. In this study, we present an innovative strategy to fabricate glutaraldehyde (GA)-poly(vinyl alcohol) (PVA)/cellulose nanocrystals (CNC)/Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) conductive hydrogels through multiple hydrogen bonding systems. Combining the advantageous rheological properties of the precursor solution and the high specific surface area after freeze–thaw cycling, we have created a self-powered sensing system prepared by large-area printing using direct ink writing (DIW) printing. The resulting conductive hydrogel exhibits commendable mechanical properties (411 KPa), impressive stretchability (580 %), and robust self-healing capabilities (>98.3 %). The strain sensor, derived from the conductive hydrogel, demonstrates a gauge factor (GF) of 2.5 within a stretching range of 0–580 %. Additionally, the resultant supercapacitor displays a peak energy density of 0.131 mWh/cm3 at a power density of 3.6 mW/cm3. Benefiting from its elevated strain response and remarkable power density features, this self-powered strain sensing system enables the real-time monitoring of human joint motion. The incorporation of a 5G transmission module enhances its capabilities for remote data monitoring, thereby contributing to the progress of wireless tracking technologies for self-powered electronic skin. [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%.

Fabricating high-conductive composites and constructing highly conductive networks are crucial for high-performance electrothermal film. In this study, an Ag nanowires/graphene (Ag/G) composite synthesized by liquid-phase exfoliation and in-situ photoreduction is mixed with carbon black (CB) to form a composite conductive ink, and a CB/Ag/G composite electrothermal film with a point-line-plane three-dimensional microstructure is obtained via blade coating process. Both the addition of Ag nanowires and a subsequent compression rolling treatment induce the establishment of the effective conductive network in the film, endowing it with an outstanding conductivity of 399.4 S cm−1. The film reaches a Ts of 204 °C with an input voltage of 3.0 V, and is successfully applied in water heating and de-icing, demonstrating its extraordinary electrothermal performance and vast potential for practical applications. The film is also used as an electromagnetic shielding film and heat dissipation substrate, showing exceptional electromagnetic shielding (42.5 dB) and heat dissipation properties. [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]

Conductive ink is an important component to fabricate printed electronics, such as flexible, stretchable, and wearable electronics. Solvents are essential for fabrication of conductive inks, but most of the organic solvents are expensive, toxic, and not environmentally friendly. In this review, stability, wettability, and electrical conductivity of different types of solvent- and water-based metal and carbon-based conductive inks are discussed. Further, the utilization of surfactants to facilitate aqueous homogeneous dispersion and stability of metal and carbon nanomaterial-based conductive material is discussed. Particularly, the solvent- and water-based surfactant-assisted conductive inks on the stability and electrical properties of metal- and carbon-based conductive materials are highlighted. In addition, the different characterization methods for assessing the dispersion and stability of conductive inks, such as zeta potential, UV–Visible, long-term stability, and wettability properties, were discussed in this review. [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]

Additive manufacturing of ceramics has attracted large interest due to its unique ability to rapidly prototype, low cost, and increased geometric complexity. Material extrusion technique is often considered for processing and shaping fine and dense ceramic structures because of the high solid loading in ink. In this work, 8 mol.% yttria-stabilized zirconia ink with 70 wt% ceramic loadings was prepared to print zirconia samples in horizontal and vertical directions, following two different filament orientations: 0/90° and ±45°. The study's main objective was to evaluate printing design influences on mechanical properties. This was assessed through flexural testing and digital image correlation analysis. Experimental findings showed that samples printed horizontally with ±45° filament orientation displayed the highest strength. A detailed inspection of fracture surfaces revealed that printing defects were the critical failure location sites formed after sintering and intimately related to printing design issues. After that, a conductive sensor was integrated into the surfaces of 3D-printed specimens by screen-printing silver-based conductive ink to analyze the structural health of zirconia samples. The sensing capabilities of printed conductive patterns were investigated using the four-point bending tests. The results demonstrated that the electrical resistance of the printed silver patterns increased as the applied load on zirconia substrates rose. It indicates that hybrid material extrusion and screen printing techniques are favored ways to manufacture sensors for structural detection of advanced 3D-printed ceramics. [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]

In this work, a new and convenient fabrication process for screen-printed reduced graphene oxide-molybdenum disulfide electrode (SPrGO-MoS2E) was proposed. Reduced graphene oxide-molybdenum disulfide (rGO-MoS2) composite was hydrothermally synthesized and then dispersed in deionized water and ethanol with a ratio of 2:3 (v/v) to form a conductive suspension. The suspension was then blended with carbon paste at a ratio of 0.1:9.9 (g/g) to obtain a screen-printable rGO-MoS2 conductive ink. An electrochemical sensing electrode was formed by screening this conductive ink onto a polyethylene terephthalate substrate. The characteristics of this electrode were investigated by scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffractometry, Raman spectroscopy, and electrochemical impedance spectroscopy. Overall, the conductive suspension comprising the rGO-MoS2 composite showed higher electrochemical sensing performance compared with electrodes containing only rGO or MoS2. Cyclic voltammetry revealed that the SPrGO-MoS2 electrode exhibited excellent electrochemical sensing performance toward several electroactive species, namely, potassium hexacyanoferrate (III) ([Fe(CN6)]3−/4−), nicotinamide adenine dinucleotide (NAD+/NADH), and hydrogen peroxide (H2O2) dissolved in 0.1 M PBS (pH 7.4). The limits of detection for [Fe(CN6)]3−/4−, NAD+/NADH, and H2O2 were 0.34, 0.25, and 1.36 μM, respectively. In addition, the reproducibility, repeatability, and stability determined from the relative standard deviations (RSDs, n = 7) of these analytes were less than 12.1 %, 8.6 %, and 7.4 %, respectively. Therefore, the ready-to-use SPrGO-MoS2E could be an alternative material for advanced chemical and biological sensing applications.

Highlights Naturally crosslinked carbonaceous liquid metal aqueous printable ink mediated by biopolymers. E-textile with conductivity, stability, wearability, and aesthetic characteristics. Multi-applications in health monitoring, pressure sensing, and energy harvesting.

The rapid development of ultrawideband (UWB) communication systems has resulted in increasing performance requirements for the antenna system. In addition to a wide bandwidth, fast propagation rates and compact dimensions, flexibility, wearability or portability are also desirable for UWB antennas, as are excellent notch characteristics. Although progress has been made in the development of flexible/wearable antennas desired notch properties are still rather limited. Moreover, most presently available flexible UWB antennas are fabricated using environmentally not attractive subtractive etching-based processes. The usage of facile additive sustainably inkjet printing processes also utilizing low temperature plasma-activated conductive inks is rarely reported. In addition, the currently used tri-notched flexible UWB antenna designs have a relatively large footprint, which poses difficulties when integrated into miniaturized and compact communication devices. In this work, a silver nano ink is used to fabricate the antenna via inkjet printing and an efficient plasma sintering procedure. For the targeted UWB applications miniaturized tri-notched flexible antenna is realized on a flexible polyethylene terephthalate (PET) substrate with a compact size of 17.6 mm × 16 mm × 0.12 mm. The antenna operates in the UWB frequency band (2.9–10.61 GHz), and can shield interferences from WiMAX (3.3–3.6 GHz), WLAN (5.150–5.825 GHz) and X-uplink (7.9–8.4 GHz) bands, as well as exhibits a certain of bendability. Three nested "C" slots of different sizes were adopted to achieve notch features. The simulation and test results demonstrate that the proposed antenna can generate signal radiation in the desired UWB frequency band while retaining the desired notch properties and having acceptable SAR values on-body, making it a viable candidate for usage in flexible or wearable communication transmission devices. The research provides a facile and highly efficient method for fabricating flexible/wearable UWB antennas, that is, the effective combination of inkjet printing processing, flexible substrates, low temperature-activated conductive ink and antenna structure design. [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]

Using a mixture of micro-copper and nano-silver in the production of screen-printed circuits has the potential to reduce material costs and cost variability. The fundamental premise of this study involved dispersing silver nanoparticles among the larger copper microparticles at selected ratios and subsequently sintering in order to establish their resultant electrical and physical performance. Commercial materials were mixed, printed, and sintered at two thermal regimes on fluorine-doped tin oxide (FTO)-coated glass substrate. The inclusion of 25% silver provided an appreciable reduction in electrical resistance from 4.21 Ω to 0.93 Ω, with further silver additions having less impact. The thermal regime used for sintering had a secondary impact on the final electrical performance. The addition of silver reduced the adhesion to the FTO substrate, with reduced film integrity. The results show that blending inks offers the advantage of enhancing material conductivity while simultaneously reducing costs, making it a compelling area for exploration and advancement in the field of electronics manufacturing. [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]

In the context of advancing flexible electronic technologies, conductive ink has garnered significant scholarly interest. Wherein, metal-organic decomposition (MOD) ink composed of silver precursors, complexing agents, and volatile organic solvents, has been widely studied due to its advantages such as simple preparation, long shelf life, high jetting stability, and low-temperature processing. However, the volumetric reduction of MOD ink frequently surpasses 80%, which typically could lead to multiple voids and breaks in the conductive film, resulting in poor conductivity. Meanwhile, a high temperature of above 180 °C is usually required for the MOD ink to be converted into conductive film. Nevertheless, it is imperative for the ink to be deposited onto substrates at low temperatures. Herein, a low temperature conducting ink with multiple silver source precursors has been developed. The results show that after sintering at 100 °C for 40 min on a polyimide (PI) substrate, the resistivity of the silver film was 16.8 µ Ω cm, which is only ten times higher than that of bulk silver, and the silver film with good uniformity and conductivity can be formed. Defects, such as voids and cracks, are significantly reduced through the gradient decomposition of different silver source during the sintering process. The formula of ink and the effects of sintering temperature on the microstructure and electrical properties of silver ink thin films have been studied in details using XRD, SEM, EDX, and four-probe techniques. [ABSTRACT FROM AUTHOR]

This paper addresses the bandwidth limitations inherent in microstrip patch antennas, which are commonly employed in radar applications owing to their compact size and integration convenience. To overcome these limitations, this study explores the application of Prosopis Africana conductive ink-based thick film, an innovative and environmentally friendly material. Originating from the African mesquite tree, this ink exhibits high conductivity owing to its elevated carbon content, presenting a compelling solution for enhancing microstrip patch antenna bandwidth. The research entails thoroughly examining microstrip antenna design principles and associated challenges, followed by exploring the unique properties of Prosopis Africana conductive ink. A detailed methodology outlines the fabrication process of the ink-based thick layer or film on the substrate, with simulation and measurements employed to evaluate its impact on impedance matching and radiation characteristics. Emphasizing the eco-friendliness of Prosopis Africana conductive ink aligning with green electronics trends, the study showcases its potential for advancing wireless communication systems while reducing ecological footprints. Results demonstrate a substantial bandwidth improvement exceeding 1.85 GHz, a simulation |S11| return loss value of -16.19 dB, and achieved 84.5% radiation efficiency of the operating frequency at 9.5 GHz and a peak realized gain of 7.10 dB. Hence, integrating Prosopis Africana conductive ink-based thick film is a viable strategy for augmenting microstrip patch antenna bandwidth, rendering them more adept for radar applications. [ABSTRACT FROM AUTHOR]

Highlights: Naturally crosslinked carbonaceous liquid metal aqueous printable ink mediated by biopolymers. E-textile with conductivity, stability, wearability, and aesthetic characteristics. Multi-applications in health monitoring, pressure sensing, and energy harvesting. Achieving flexible electronics with comfort and durability comparable to traditional textiles is one of the ultimate pursuits of smart wearables. Ink printing is desirable for e-textile development using a simple and inexpensive process. However, fabricating high-performance atop textiles with good dispersity, stability, biocompatibility, and wearability for high-resolution, large-scale manufacturing, and practical applications has remained challenging. Here, water-based multi-walled carbon nanotubes (MWCNTs)-decorated liquid metal (LM) inks are proposed with carbonaceous gallium–indium micro-nanostructure. With the assistance of biopolymers, the sodium alginate-encapsulated LM droplets contain high carboxyl groups which non-covalently crosslink with silk sericin-mediated MWCNTs. E-textile can be prepared subsequently via printing technique and natural waterproof triboelectric coating, enabling good flexibility, hydrophilicity, breathability, wearability, biocompatibility, conductivity, stability, and excellent versatility, without any artificial chemicals. The obtained e-textile can be used in various applications with designable patterns and circuits. Multi-sensing applications of recognizing complex human motions, breathing, phonation, and pressure distribution are demonstrated with repeatable and reliable signals. Self-powered and energy-harvesting capabilities are also presented by driving electronic devices and lighting LEDs. As proof of concept, this work provides new opportunities in a scalable and sustainable way to develop novel wearable electronics and smart clothing for future commercial applications. [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]

The conventional real-time screening in organs-on-chips is limited to optical tracking of pre-tagged cells and biological agents. This work introduces an efficient biofabrication protocol to integrate tunable hydrogel electrodes into 3D bioprinted-on-chips. We established our method of fabricating cell-laden hydrogel-based microfluidic chips through digital light processing-based 3D bioprinting. Our conductive ink includes poly-(3,4-ethylene-dioxythiophene)-polystyrene sulfonate (PEDOT: PSS) microparticles doped in polyethylene glycol diacrylate (PEGDA). We optimized the manufacturing process of PEDOT: PSS microparticles characterized our conductive ink for different 3D bioprinting parameters, geometries, and materials conditions. While the literature is limited to 0.5% w/v for PEDOT: PSS microparticle concentration, we increased their concentration to 5% w/v with superior biological responses. We measured the conductivity in the 3–15 m/m for a range of 0.5%–5% w/v microparticles, and we showed the effectiveness of 3D-printed electrodes for predicting cell responses when encapsulated in gelatin-methacryloyl (GelMA). Interestingly, a higher cellular activity was observed in the case of 5% w/v microparticles compared to 0.5% w/v microparticles. Electrochemical impedance spectroscopy measurements indicated significant differences in cell densities and spheroid sizes embedded in GelMA microtissues.

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.

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.

Electronic waste carries energetic costs and an environmental burden rivaling that of plastic waste due to the rarity and toxicity of the heavy-metal components. Recyclable conductive composites are introduced for printed circuits formulated with polycaprolactone (PCL), conductive fillers, and enzyme/protectant nanoclusters. Circuits can be printed with flexibility (breaking strain ≈80%) and conductivity (≈2.1 × 104 S m-1 ). These composites are degraded at the end of life by immersion in warm water with programmable latency. Approximately 94% of the functional fillers can be recycled and reused with similar device performance. The printed circuits remain functional and degradable after shelf storage for at least 7 months at room temperature and one month of continuous operation under electrical voltage. The present studies provide composite design toward recyclable and easily disposable printed electronics for applications such as wearable electronics, biosensors, and soft robotics.

Human exploratory missions to Moon or Mars are considered the next steps in human space exploration. Such activities result in the exposure of humans to the space environment for long time, especially under the constraints of orbital dynamics as with increasing distances from earth quick return possibilities are ruled out. Crews on these kinds of missions must be self-sustaining in medical treatments, as environmental conditions in space, such as the influence of altered gravity, radiation or isolation, raise health issues. Therefore, astronauts may use the here presented Handheld Bioprinter as part of the first-aid strategy for in situ wound treatment. The device consists of a handle capable of holding an exchangeable "Ink Printing Unit" containing two separate gel-like components (Bioink and Crosslinker), which are extruded during a printing process through a nozzle and form a skin-cell containing bioink band-aid. For ISS experiments cell simulants were used, as in-space experiments first demonstrated the general feasibility of handheld bioprinting under space conditions. On-ground human skin cells were mixed with the biogel, printed via the handheld bioprinter and cultivated, to demonstrate the overall feasibility of the "Bioprint FirstAid" technology. Concluding results were that a mobile, handheld tool like the bioprinter shows good applicability and offers a possibility of in situ wound treatment for in-space applications. The "Bioprint FirstAid" project was coordinated by the German Space Agency at the German Aerospace Center (DLR) in Bonn and funded by the Federal Ministry for Economic Affairs and Climate Action (BMWK). • Handheld Bioprinter offers possibility for in-situ wound treatment in future in-space applications • Human skin cells proliferate in biogels after printing with handheld bioprinter • The customizable Ink-printing unit and nozzle can be tailored to specific printing demands • Bioprinter device has low susceptibility to failure, has a robust design, no electronics, and maintenance-free mechanics • German Astronaut Matthias Maurer conducted the Bioprinting experiment successfully on board the ISS [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]

Liquid crystal elastomers (LCEs) are becoming increasingly popular as a shape memory material for soft robot actuators that operate in a contractile or flexural mode. There have been previously studies on the use of LCEs for reversible changes in surface topography. However, surface protrusions have typically been limited to the order of 1 μm or depend on light, heat, or electrical stimulation that are difficult to locally control or require relatively high voltage. This article presents a novel operation mode of LCE actuators based on the wrinkling behavior of an LCE‐elastomer bilayer architecture. Embedding a liquid‐metal‐based conductive ink within the LCE enables electrical control of surface wrinkling through Joule heating. The actuator cells can generate wrinkles with amplitudes ranging from 17 to 45 μm within 30 s under an input power of 2 W and a voltage on the order of 1 V. As the bilayer is composed entirely of soft materials, it is highly deformable, flexible, and can be integrated into a multi‐cell array capable of bending on curved surfaces. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic (EHD) printing technique, which deposits micro/nanostructures through high electric force, has recently attracted significant research interest owing to their fascinating characteristics in high resolution (<1 μm), wide material applicability (ink viscosity 1–10 000 cps), tunable printing modes (electrospray, electrospinning, and EHD jet printing), and compatibility with flexible/wearable applications. Since the laboratory level of the EHD printed electronics' resolution and efficiency is gradually approaching the commercial application level, an urgent need for developing EHD technique from laboratory into industrialization have been put forward. Herein, we first discuss the EHD printing technique, including the ink design, droplet formation, and key technologies for promoting printing efficiency/accuracy. Then we summarize the recent progress of EHD printing in fabrication of displays, organic field‐effect transistors (OFETs), transparent electrodes, and sensors and actuators. Finally, a brief summary and the outlook for future research effort are presented. [ABSTRACT FROM AUTHOR]

A wideband meta-material absorber with square and circular split rings that is based on a frequency selective surface of conductive ink is proposed. With over 90%absorptivity, the structure demonstrates broad absorption for the C, X, KU, and K bands, as well as polarization independent characteristics for both TE and TM, at angles of up to 45°. Research has been performed to better understand the absorption phenomenon by looking into real and imaginary permittivity, permeability, normalized impedance, and surface current density. The metamaterial absorber (MA) discussed in this study finds use in defense-related applications, such as radar surveillance, stealth technology, terrestrial and satellite communications. [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]

Aerosol jet printing (AJP) is a new non-contact direct writing technique designed to achieve precise and intricate patterns on various substrates. Specifically, the pneumatic AJP process breaks down the ink into fine particles, significantly reducing the risk of nozzle clogging and rendering it highly advantageous for industrial applications. This paper focuses on the optimization of the line electrode formation process using soluble silver clusters as the conductive ink, along with the aerosol formation procedure. The main parameters of the AJP process, namely sheath flow rate, atomizer flow rate, and dispensing speed, were identified and examined for their influence on line width and resistivity. Through this analysis, an operability window, including optimized conditions for printing high-quality lines using the AJP process, was established, along with a regression equation enabling the statistical estimation of line width. In summary, the outcomes of this investigation underscore the feasibility of an integrated printing system capable of precision control over line width, achieved through the optimization of AJP process parameters. Furthermore, it was established that pneumatic AJP offers robust process stability. The practical applicability of the proposed optimization techniques was assessed, highlighting their potential utilization in electrode formation processes within the electronic and display industry. [ABSTRACT FROM AUTHOR]

In this study, a screen-printed electrode (SPE) for nitrite (NO2 -) sensing was fabricated through an inkjet printing technique using a commercial printer machine and preparing an ink composite solution containing graphene oxide (GO) and poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS) as conductive materials. The optimum ink materials for SPE fabrication comprised GO and PEDOT:PSS with binders that resemble the viscosity of commercial ink. The surface topography of the fabricated SPE, which was characterized using scanning electron microscopy and atomic force microscopy, showed a smoother surface compared to the commercial screen-printed carbon electrode, with conductive ink materials deposited primarily from GO/PEDOT:PSS composites. This NO2 - sensor exhibited a linear response at the concentration range of 50-1000 µM, with limit of detection and limit of quantification as 25 and 50 µM, respectively. In addition, the stability, reproducibility, and selectivity of this sensor presented acceptable values in the analytical range. Furthermore, the performance of this sensor was compared with that of a spectrophotometry technique using synthetic water samples, and the results revealed its good analytical recovery at a confidence interval of 95%. Thus, our sensor based on SPE-modified GO/PEDOT:PSS, fabricated via the inkjet printing technique, can be potentially applied in monitoring NO2 - concentration in real samples. [ABSTRACT FROM AUTHOR]

A flexible printing electronical membrane is an electron equipment made by precisely spraying conductive metal ink such as silver on a soft membrane substrate. With its advantages of light weight and flexibility, it can adapt to changing working environments and is widely used in aerospace, wearable electronics and other fields. Nevertheless, during the manufacturing preparation of roll-to-roll printing membranes, the high-speed movement of printing electronical membranes under tension is affected by the impact of hot air from the drying oven and the electrostatic interference generated by friction in transmission, which restricts the overprint accuracy and preparation velocity of flexible electronical membranes. To address this issue, the nonlinear forced vibrational characteristics of a traveling flexible printing electronical membrane on temperature coupling subjected to nonlinear electrostatic force were investigated. The roll-to-roll printed intelligent RFID electron membrane is the research target. On the basis of the energy approach and the heat conduction equation considering the effect of deformation, the nonlinear vibrational equations of an axially traveling flexible printing electronical membrane coupled with temperature under the function of nonlinear electrostatical excitation force were derived. The Bubnov–Galerkin algorithm was applied to discretize the vibration partial differential equations; by making full use of the quartic Runge–Kutta numerical algorithm to calculate the approximate solution of equations, the phase portraits, Poincaré maps, time history diagrams, power spectra, and bifurcation plots of the nonlinear vibrations of the traveling printing electronical membrane were used to explore the effects of movement velocities, electrostatical field, and thermal coupling coefficients. The findings obtained the stable working domain and the divergence instability domain of the traveling flexible printing electronic membrane, which provided a theory fundamental for enhancing the stable craft of a printing electronical membrane. [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]