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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]

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]

Research progress in the field of synthesis of graphene-like nanosheets has been expeditiously growing in the recent years because of their incredible properties in various fields offered by these two-dimensional nanostructures. Nano order thick graphitic flakes, one of the forms of graphene, can be used for many applications such as conductive inks, supercapacitors, nanofluids, gas sensing, etc. Synthesis of graphene flakes definitely the way to reach bulk quantity production. Preparation of stack layer graphene-like nanosheets from industrial waste carbon flake is important for scalable production at a low cost and societal uses. Our novel work surmised the fabrication of Nano order thick graphitic flakes from industrial waste using the modified hummer's method. The basic morphological characteristics have been examined by X Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Gas sensor was prepared by depositing a thin film on a figure-type interdicted electrode epoxy substrate. The sensing behavior was detected by monitoring the change in resistance after hydrogen gas exposure using a computer control indigenously developed hydrogen gas sensing unit. • This work presents novel synthesis of Nano order thick graphene-like nanosheets from industrial waste using hummer's method. • The qualitative and quantitative analysis of synthesize nanosheets have done by characterized physicochemical properties. • The synthesize nanosheets based chemiresistor type gas sensor was prepared and tested for hydrogen gas. • The sensor shows the faster response and higher sensitivity over a long period toward hydrogen gas at room temperature. [ABSTRACT FROM AUTHOR]

There is a growing interest in zirconia ceramics due to their high flexural strength, excellent corrosion resistance and good biocompatibility. The assembly of advanced zirconia material with functions of sensing, actuation and controlling to solve the problems that may arise during its use is critical to ensure long-term service and performance. Within this context, the objective of this work is to analyse the structural health of zirconia samples by screen-printing silver-based conductive ink on the surface subjected to maximum load under flexural testing. In doing so, silver conductive ink was formulated using silver nanoparticles where polyvinyl pyrrolidone acted as the capping agent. Silver ink was then screen-printed onto zirconia samples and sintered at 200 °C. The resistance of the sensors was measured and the sensing capabilities of printed conductive patterns were investigated using the four-point probe method. Experimental findings displayed a reproducible direct correlation between electrical resistance change and strain resulting from surface displacement under applied load in four-point bending. [ABSTRACT FROM AUTHOR]

An organic metamaterial absorber (OMA) with a total thickness of 2.98 mm composed by multi-layer flexible frequency selective surface (FSS) and worked in ultra wideband (UWB) is investigated. The proposed absorber is stacked on a metal substrate by organic materials layer by layer, such as polyimide and polyvinyl chloride. According to equivalent circuit and electromagnetic field analysis, periodic FSS patterns are printed on organic materials using organic conductive ink. The absorption rate of the structure is high up to 90 % and the fractional bandwidth (FBW) reached 147.7 % at 11.78–78.32 GHz, which shows incident angle insensitive within 50°. In addition, the fabricated prototype with a single unit cell of 0.17 g is measured in an anechoic chamber using free space method. Furthermore, the measurement is in great agreement with the simulation, which demonstrates the reliability and the practical application prospect of the provided OMA with flexible, lightweight and ultrathin construction. • An organic metamaterial absorber (OMA) is get by frequency selective surface (FSS). • Organic materials are stacked layer by layer on a metal substrate in this OMA. • Periodic FSS patterns are printed on organic materials using organic conductive ink. • The measurement of this OMA is in good agreement with the simulation at 8–67 GHz. • Simulated absorption above 90 % in 12–78 GHz and incident angle insensitive below 50°. [ABSTRACT FROM AUTHOR]

The conductive ink research area has attracted much interest from researchers. The possibility of fabricating flexible and simple electronic devices offers many advantages for electronic devices, such as energy storage, wearable devices, and smart devices. Graphene conductive ink has gained much attention from scientists owing to its excellent electrical, optical, and mechanical properties. Numerous scientists have reported the modification of graphene properties to meet the demand for the application. Among the presented graphene synthesis methods, the electrochemical exfoliation process is simple, low-cost, and environmentally friendly. Moreover, the electrochemical exfoliation approach can be conducted in a water solution, thus decreasing production costs and making it environmentally safe. This review article presents the progress in the electrochemical exfoliation of graphene to produce graphene-conductive ink. Progress on graphene conductive ink and its hybrid is also presented. In particular, the potential application of graphene in energy storage, sensors, and other possible applications is summarized in the last part. • Graphene-based conductive inks show promise for flexible, cost-effective electronics like energy storage and wearable devices. • Electrochemical exfoliation: A simple, eco-friendly method for large-scale graphene production, suitable for conductive inks. • Review of recent advances in electrochemically exfoliated graphene and hybrid inks, their properties, and applications. • Exploration of graphene ink applications in energy storage, sensors, and flexible displays for wearable electronics. [ABSTRACT FROM AUTHOR]

The possibility to print electronics by means of office tools has remarkedly increased the possibility to design affordable and robust point-of-care/need devices. However, conductive inks suffer from low electrochemical and rheological performances limiting their applicability in biosensors. Herein, a fast CO 2 laser approach to activate printed carbon inks towards direct enzymatic bioelectrocatalysis (3rd generation) is proposed and exploited to build biosensors for D-fructose analysis in biological fluids. The CO 2 laser treatment was compared with two lab-grade printed transducers fabricated with solvent (SB) and water (WB) based carbon inks. The use of the laser revealed significant morpho-chemical variations on the printed inks and was investigated towards enzymatic direct catalysis, using Fructose dehydrogenase (FDH) integrated into entirely lab-produced biosensors. The laser-driven activation of the inks unveils the inks' direct electron transfer (DET) ability between FDH and the electrode surface. Sub-micromolar limits of detection (SB-ink LOD = 0.47 μM; WB-ink LOD = 0.24 μM) and good linear ranges (SB-ink: 5–100 μM; WB-ink: 1–50 μM) were obtained, together with high selectivity due to use of the enzyme and the low applied overpotential (0.15 V vs. pseudo-Ag/AgCl). The laser-activated biosensors were successfully used for D-fructose determination in complex synthetic and real biological fluids (recoveries: 93–112%; RSD ≤8.0%, n = 3); in addition, the biosensor ability for continuous measurement (1.5h) was also demonstrated simulating physiological D-fructose fluctuations in cerebrospinal fluid. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Conductive, high adhesion and mechanical strength of 30MCP can be printed as conductive ink on flexible substrates to build flexible circuits. • 30MCP works not only as a friction layer but also as an electrode. • 30MCP is fully biodegradable, recyclable, and reusable. • The V oc of the KMCP-TENG prepared from recycled 30MCP reaches 90 % of the original TENG. Triboelectric nanogenerator (TENGs), which are capable of capturing high-entropy energy dispersed in the environment and converting it into electricity, have received significant attention for their potential as power sources for sensing networks and wearable portable electronics. Conventional triboelectric materials have serious limitations, which can be overcome by using nanostructured materials. Conductivity and semiconductor nanomaterials have been extensively studied as active components for this type of application, but need to be coupled to an elastic matrix, in order to be functional in flexible technologies. In this study, we prepared MWCNTs/PEO (MCP) films with conductive and biodegradable properties. MCP can be used as conductive ink printed on flexible substrates to fabricate flexible circuits. MCP is utilized as a high-performance positively charged material to construct a TENG (KMCP-TENG) with a maximum power density of 593 mW/m2. Furthermore, MCP can be degraded and recycled, and the output performance of the KMCP-TENG prepared using recycled MCP reaches 90 % of the original TENG. Additionally, the multi-array smart bandage (MASB) is designed and fabricated based on KMCP-TENG, which exhibits high sensitivity and stability. This MASB offers broad applications in health monitoring, motion tracking and human–computer interaction. [ABSTRACT FROM AUTHOR]

The modification on the surface of neural electrodes is critical for improving the signal-to-noise ratio (SNR) and prolonging the recording time. Electrodeposition is a simple and practical modification technique that has been applied to a wide range of materials. However, the traditional electrodeposition becomes increasingly inefficient as the electrode channels dramatically increase since it is performed one by one. Short-circuiting multiple electrode sites and then modifying them together can significantly improve efficiency. But it remains a significant challenge to reliably connect hundreds or thousands of electrodes before the electrodeposition and to safely and easily disconnect them afterward. An approach of removable electrical connection was adopted to solve this problem. A kind of silver nanowire (AgNW) conductive ink with water as the dispersion was chosen to connect all the electrodes for simultaneous electrodeposition temporarily electrically. This approach makes the electrodeposition process convenient and reliable. Above all, the proposed approach is compatible with a wide range of Multi-electrode arrays (MEAs) fabricated from different materials. [Display omitted] • This paper presents an efficient batch modification approach for large-scale neural microelectrode arrays based on an removable electrical interconnection. • This proposed method can modify hundreds or thousands of electrodes within minutes. • This proposed approach is compatible with many different types of microelectrode arrays and various modification materials. [ABSTRACT FROM AUTHOR]

• Deposition of conductive copper ink using the direct ink writing process. • The deposited track achieved an electrical conductivity of 1.21 × 106 S/m. • The electrical continuity of tracks was tested, and changes in conductance were observed while bending the samples. This work reports the fabrication and electrical characterization of conductive copper ink (CCI) deposited on flexible substrates using an in-house developed direct ink writing (DIW) technique. CCI tracks deposited on two flexible substrates were evaluated for uniformity, continuity, and electrical performance under various temperature and mechanical loads. The results indicated that with optimized printing parameters, uniform, and continuous tracks were successfully deposited, achieving a track width of 355 μm and an electrical conductivity of 1.21 × 106 S/m. Notably, bending caused little change in the electrical conductivity, whereas temperature had a greater effect. To demonstrate the practical applicability in electronics, a single conductive layer was printed by replicating the actual geometries of the printed circuit board. [ABSTRACT FROM AUTHOR]

Conductive inks have been widely used to develop electronic devices, such as sensors, RFID antennas, and transistors. Electronic utilization is a coating that forms conductive films for electromagnetic interference shielding (EMI Shielding). This process also can be employed to cover electronic modules called System in Package (SiP). A technology known as conformal shielding utilizes spray coating with metallic inks to form a conductive layer over the SiP. Traditionally, copper or silver inks have been the primary materials employed due to their high electrical conductivity. Conversely, these metallic inks are associated with significant costs, environmental impacts, and complex production methods. In this context, water-based graphene dispersion could be an alternative to EMI Shielding for electronic chips. Graphene is attractive due to its excellent electrical and thermal properties, reduced cost, and being an environmentally friendly material. In this study, a water-based graphene suspension was developed and applied via spray coating to form films for electromagnetic shielding. The graphene dispersion in water utilized Carboxymethyl cellulose (CMC). Characterizations of the graphene suspension, including morphology, particle size distribution, and chemical analysis, were conducted. The resistivity of the resulting films and their shielding effectiveness (SE) were measured. Electronic chip modules were painted to assess coverage. The study demonstrated the successful formulation of a stable water-graphene suspension exhibiting favorable electrical resistivity (2.8 × 10−2 Ω.cm) after drying at 300 °C for 1 h. The resulting film achieved a shielding effectiveness of −9 dB at 1.0 GHz. Graphene film completely covered the electronic chips, indicating an alternative conformal shielding. • The environmentally friendly method uses lab-scale equipment to produce a water-based graphene suspension for EMI shielding • Developing and applying water-based graphene suspension via spray coating on SiP modules • The film's shielding effectiveness is measured per the ASTM d4935 standard. [ABSTRACT FROM AUTHOR]

[Display omitted] • SPrGO-MoS 2 E exhibited greater electrocatalytic activity than SPCE. • The proposed sensors provided low detection limits of electroactive species. • The electrodes showed high reproducibility, repeatability, and good stability. In this work, a new and convenient fabrication process for screen-printed reduced graphene oxide-molybdenum disulfide electrode (SPrGO-MoS 2 E) was proposed. Reduced graphene oxide-molybdenum disulfide (rGO-MoS 2) 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-MoS 2 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-MoS 2 composite showed higher electrochemical sensing performance compared with electrodes containing only rGO or MoS 2. Cyclic voltammetry revealed that the SPrGO-MoS 2 electrode exhibited excellent electrochemical sensing performance toward several electroactive species, namely, potassium hexacyanoferrate (III) ([Fe(CN 6)]3−/4−), nicotinamide adenine dinucleotide (NAD+/NADH), and hydrogen peroxide (H 2 O 2) dissolved in 0.1 M PBS (pH 7.4). The limits of detection for [Fe(CN 6)]3−/4−, NAD+/NADH, and H 2 O 2 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-MoS 2 E could be an alternative material for advanced chemical and biological sensing applications. [ABSTRACT FROM AUTHOR]

For flexible electronics, conductive ink is a critical material with diverse applications. However, conventional inks, like those based on nano-silver, are expensive and result in printed patterns with limited conductivity stability. To address these limitations and enhance overall electrical performance, stability, and durability, this study developed a novel composite conductive ink incorporating liquid metal and silver microparticles. We fabricated conductive patterns and extensively investigated the sintering process, focusing on how liquid metal content and sintering techniques affect the resulting patterns' electrical performance and stability. Our findings reveal that incorporating liquid metal introduces a slight trade-off in the initial conductivity. However, subsequent thermal and hot-press sintering treatments significantly improve conductivity, with hot-press sintering leading to the most pronounced enhancement. Furthermore, the addition of liquid metal substantially bolsters the electrical stability of the patterns. Notably, conductive patterns fabricated using a 1:1 mass ratio of the ink exhibit ∆ R / R 0 values of only 1.72 and 0.432 after 5000 bending cycles, following thermal and hot-press sintering, respectively. This highlights the significant improvement in electrical stability and durability achieved by incorporating liquid metal into the conductive ink. [Display omitted] • Developed a composite conductive ink for flexible electronics by combining liquid metal with silver microparticles. • Conductive ink shows improved electrical stability and durability with liquid metal addition and hot-press sintering. • This research offers a solution to the trade-off between conductivity and stability faced with conventional silver-based inks and the complex processing of liquid metal inks. [ABSTRACT FROM AUTHOR]

Printed flexible electronics, developed through additive manufacturing techniques, aim to be a cost-effective, environmentally friendly, energy-efficient, and durable alternative to contemporary electronics. Conductive inks play a crucial role in printed electronic applications. Despite the availability of various conductive inks, there are persistent challenges, such as the use of toxic chemicals, low productivity, and complex production procedures, limiting their broader application due to the reduced financial viability of the resulting conductive inks. This comprehensive review provides essential information and requirements for the formulation of conductive inks in the context of printed flexible electronics. This review offers a summary of previous studies on etching-driven MXenes and their conductive ink formulations, highlighting the use of various solvents, including water, for environmentally friendly practices. Various applications of printed electronics are discussed. Additionally, this review addresses current challenges in the formulation of MXene-based conductive inks and provides recommendations for future research. MXenes are widely used in the development of various printed electronic devices. As a result, it can be concluded that MXene-based conductive inks are appropriate candidates for printed electronics applications due to their hydrophilic properties and high electrical conductivity. • MXenes boasts a high electrical conductivity up to 6500 Scm−1. • The important components of flexible printed electronics encompass conductive inks and polymer substrates. • MXenes conductive inks emerge as highly promising candidates for printed electronics applications. [ABSTRACT FROM AUTHOR]

Rheological modifiers enable direct ink writing of polymers with low viscosity such as epoxy without requiring light or heat. Modifiers that conduct electrons and phonons impart multifunctional properties to 3D printed polymers. Here, we report the development of printable nanocomposite inks comprised of epoxy, carbon fibers (CFs), and carbon nanotubes (CNTs) to achieve excellent mechanical properties and multifunctionality via high electrical conductivity required for next-generation light weight aerospace, electronics, and energy applications. CF and CNT concentrations of 8.5 and 1.7 wt%, respectively, render the material shear-thinning with a high yield stress, hence printable and self-supporting after being printed. An average electrical conductivity of 10−2 S/cm and thermal conductivity of 0.3 W/m.K were measured for the 3D-printed multi-layer structures. Furthermore, tensile modulus, tensile strength, flexural modulus, and flexural strength were measured to be 5.8, 0.08, 6.0, and 0.1 GPa, respectively. Compared with other 3D printed conductive polymer nanocomposites with reported electrical conductivity and elastic modulus, the structures here have the highest specific elastic modulus. They also possess the highest electrical conductivity among the 3D printed polymeric composites of carbon nanomaterials with an elastic modulus above 1 GPa. This is due to the outstanding combination of CNTs, CFs, and epoxy. The results expand the range of polymer properties for multifunctional applications. [ABSTRACT FROM AUTHOR]

The study presents the successful development of a new electrochemical sensor with low cost and disposability for application in nitrofurazone detection in environmental and pharmaceutical samples. The sensors were fabricated using materials obtained from local storage and conductive carbon ink. The modification of the screen-printed electrodes with the hybrid nanomaterial based on silver nanoparticles, carbon quantum dots, and carbon nanotubes showed synergistic contributions in the nitrofurazone electrooxidation, as observed in the wide linear range (0.008 at 15.051 μM), with a sensitivity of 0.650 μA/μM. The limit of detection obtained was 4.6 nM. Differential pulse voltammetry, cyclic voltammetry, X-ray photoelectron spectroscopy, X-ray diffraction analysis, and high-resolution transmission electron microscopy were used to evaluate the electrochemical and structural characteristics. Studies of possible interferences were considered with nitrofurazone in the presence of the ions and organic molecules. The results were satisfactory, with a variation of 93.3% ± 4.39% at 100% ± 2.40%. The low volume used in the analyses (50 μL), disposability, high sensibility, selectivity, and low limit of detection are advantages that make the proposed sensor an electrochemical tool of high viability for the NFZ detection in environmental matrices and pharmaceutical formulations. [Display omitted] • Novel disposable electrochemical device for nitrofurazone determination was developed. • Hybrid carbon dots, carbon nanotubes and Ag nanoparticles was used as modifier. • The sensor was applied in environmental and pharmaceutical real samples determination. • High sensitivity, selectivity and low-LOD was achieved with the new developed device. [ABSTRACT FROM AUTHOR]

A series of liquid crystal elastomer-based printed electronic devices has been innovatively crafted through modifying screen-printing patterns. [Display omitted] • A printed liquid crystal elastomer soft actuator with multi-stimuli responsiveness and self-sensing capabilities is achieved. • A printed liquid crystal elastomer near-infrared light array sensor is fabricated. • A series of printed functional devices are fabricated through simple modifications of the printing patterns. Liquid crystal elastomers (LCEs) are valuable in soft actuators, sensors and other emerging fields. However, it is still a huge challenge to build high-performance LCE-based functional devices in a simple and fast way to achieve the orderly and patterned integration of multiple functional layers and LCE. Herein, screen-printing technology is used to realize the multi-layer pattern deposition of silver fractal dendrites conductive ink (with excellent Joule heating effect and strain-sensing function) and carbon black conductive ink (with photothermal conversion ability) on the surface of LCE. A series of LCE-based electronic devices are prepared through customized printing patterns. The as-obtained actuator possesses excellent electric actuating performance (bending angle of 102° at 200 mA) and self-sensing function (maximum relative resistance changes of −55.0%), and also exhibits NIR light-driven self-sensing bending actuation behavior (bending angle of 81° at 1.43 W/cm2), which can be used to control the robotic arm. The as-printed NIR light sensing array system can accurately sense the intensity, spot size and position of NIR light, showing good application potential in the field of unmanned aerial vehicle flight safety. This work provides a new strategy for the efficient preparation of LCEs-based flexible electronics. [ABSTRACT FROM AUTHOR]

Although many high-performance wearable strain sensors have been developed, they are limited to uniaxial strain monitoring, which makes it challenging to meet the monitoring needs of complex multidimensional motion in practical applications. This study effectively constructed an anisotropic strain sensor by combining two materials that exhibit different responses to external stimuli (strain): liquid metal and conductive ink. In particular, the maximum gauge factors of this anisotropic strain sensor in conductive ink direction and liquid metal direction are 158.9 and 1.9, respectively. Both directions display outstanding dynamic stability, frequency independence, and durability over 3000 cycles. Furthermore, the integrated sensor formed by the orthogonal stack of two anisotropic strain sensors can distinguish the strain magnitude and direction (an outstanding selectivity of 3.7). The mechanism of the sensor's selective sensing ability is analyzed, and the broad application of the sensor in complex motion monitoring, human-computer interaction, and multi-component control is demonstrated. This research discovery provides new ideas and methods for constructing anisotropic wearable strain sensors. It creates conditions for the development and practical application of multifunctional wearable devices. [Display omitted] • Two functionally distinct materials are rationally assembled for highly sensitive and selective wearable strain sensors. • The cross-shape-integrated sensor has the ability to identify the magnitude and direction of unknown strains. • The potential applications of the developed strain sensor in health monitoring, human-computer interaction, and multidimensional control are demonstrated. • A novel approach to constructing anisotropic selective strain sensors is proposed. [ABSTRACT FROM AUTHOR]

Antennas operating at high frequency bands are sought after for applications in 5G, satellite, radar, and other communication systems. Graphene, a two-dimensional material known for its exceptional conductivity, mechanical strength, and chemical stability, is anticipated to serve as a viable substitute for copper in antenna applications. However, researches on graphene antennas at millimeter-wave and higher frequencies are mainly limited to theory and simulation, due to the fabrication challenges of achieving high-precision graphene patterns. Herein, we present the design and fabrication of a graphene folded reflectarray antenna (FRA) operating at millimeter-wave. The FRA is fabricated using screen-printing of graphene ink on an RT5880 substrate, followed by laser engraving for precise patterning. The main reflector has 918 patch units, and the polarizing grids have line widths and spacings of 100 μm. Measurements demonstrate that the antenna has a realized peak gain of 21.37 dBi at 37.5 GHz. The radiation patterns show a 3 dB beamwidth of 6° and 4° in the E-plane and H-plane respectively, with cross-polarization more than −18 dB. The laser-assisted screen-printing method provides a feasible strategy for the precision manufacture of graphene communication devices. [Display omitted] [ABSTRACT FROM AUTHOR]

• SE-tattoo is conformable, sweat permeable, and imperceptible on hairy skin. • Design a biocompatible water-based conductive ink for spray fabrication method. • SE-tattoo shows high adhesiveness, high conductivity, and fast curing ability (<20 s) • Reliable and versatile solution for bidirectional human–machine interaction. Biopotential signals recorded by skin surface electrodes reflect the state of the body and corresponding organ functions. These signals are commonly utilized in clinical diagnosis, health monitoring, sports training, and human–computer interaction. However, the utilization of conventional electrodes on hairy skin causes a number of issues, including suboptimal skin compliance, obstructed sweat secretion and impaired tactile perception, making it difficult to obtain long-term and high-fidelity biopotential recordings. Here, we propose an imperceptible spray-on electrode tattoo (SE-tattoo) with sweat-permeability, high adhesiveness, high conductivity, and fast curing ability (<20 s). The water-based conductive ink is sprayed directly on the hairy skin to form a conformable conductive tattoo that neither affects nor is affected by the skin hair. We demonstrate it for heart health monitoring, sports training, electro-tactile display and close-loop teleoperation control. The SE-tattoo offers a reliable and versatile solution to biopotential recordings and serves as a promising platform for bidirectional human–machine interaction. One-Sentence Summary: Imperceptible sweat-permeable SE-tattoo enables high-fidelity biopotential recordings for bidirectional human–machine interaction. [ABSTRACT FROM AUTHOR]

• All-in-one flexible photodetector (FPD) was facilely prepared. • The boronate ester polymer (BP) matrix achieves considerable interfacial adhesion. • The adaptation of FPD components is beneficial for interface charge transfer. • BP has a high binding affinity to conductive fillers to afford highly printable inks. • The resulting FPD exhibits stable photoresponse under severe mechanical deformation. Flexible photodetector (FPD) is a crucial component in modern wearable/flexible systems and plays a vital role in healthcare, environmental monitoring, flexible display, and other fields. However, achieving satisfactory interfacial adhesion among the electrode, photoactive material, and flexible substrate at the same time to fabricate FPDs with high flexibility, stretchability, stability, and mechanically compliance is still a challenge. In this study, we propose a green and eco-friendly water-system processing strategy to construct all-in-one FPDs, using borate ester polymers (BPs) as both the co-matrix of the photoactive layer substrate and the conductive ink. The flexible substrate exhibits a high adaptation to the conductive ink, and thus, efficient interface charge transfer with the complicated pattern electrode. The resulting FPD exhibits stable photoresponse under different bending angles and large mechanical strains. Even after 2000 cycles of light stimulation test at a whole device elongation of 50%, the FPD exhibits no significant decrease in the photoresponse performance. Such devices may provide new opportunities for multifunctional electronic skin and wearable electronic devices. [ABSTRACT FROM AUTHOR]

• Lab-made screen-printed electrode (LabSPE) was prepared for sensor applications. • TCS detection was performed with a Bluetooth-assisted connection. • The sensor was applied for TCS detection to various commercial samples. In this study, we prepared a facile and selective Bluetooth-assisted electrochemical sensor for the analysis of triclosan (TCS), which is a broad-spectrum antibacterial and antifungal compound. Initially, a laboratory-fabricated screen-printed electrode (LabSPE) was constructed by depositing various conductive inks (carbon and silver) onto a polycarbonate substrate surface using the screen-printing technique. Subsequently, the surface of the working electrode on the LabSPE was modified with a composite comprising Ni-doped Ag 2 S (Ni-Ag 2 S) and chitosan (Chit), rendering it suitable for the detection of TCS. The effect of Ni-Ag 2 S amount, Chit amount, composite film thickness, and pH of buffer solution on the electrochemical signal of the prepared sensor (Ni-Ag 2 S-Chit/LabSPE) was also optimized. The sensor displayed remarkable analytical performance in the range of 0.05 nM-90 μM TCS with a low detection limit of 0.02 nM. The sensitivities of Ag 2 S/LabSPE and Ni-Ag 2 S-Chit/LabSPE were found to be 0.0838 µAµM−1 and 0.1097 µAµM−1, respectively, proving the contribution of doped Ni to the performance of the present sensor. The selectivity, reproducibility, reproducibility, reproducibility and stability of the sensor as well as its practical applicability have been successfully in two commercial products. Triclosan detection via Bluetooth-assisted communication using Ni-Ag 2 S-Chit modified LabSPE. [Display omitted] [ABSTRACT FROM AUTHOR]

This work addresses two major challenges of MXene-based printing; that is, its low printing resolution (i.e., filament spreading >120%) and its inability to create structures with simultaneously high electrical conductivity and mechanical flexibility. We first report high-resolution extrusion printing of Ti 3 C 2 and composite of Ti 3 C 2 /poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The printing has a negligible filament spreading (<25%) and low thickness and width variations (<20%) compared to their average values. We then fabricate Ti 3 C 2 /PEDOT:PSS composite structures that possess simultaneously exceptional electrical conductivity and flexibility (conductivity of 1600 ± 400 S/cm for 80 wt% Ti 3 C 2 , which can withstand up to 3000 bending cycles). Addressing the two challenges expands the applications of MXene-based printing. For instance, micrometer-thick grids printed with our method show excellent EMI shielding effectiveness and superior specific EMI shielding effectiveness, reaching 38.4 dB and 43,000 dB cm2 g−1 in the case of pure Ti 3 C 2 and 28.1 dB and 32,000 dB cm2 g−1 for the composite containing 80 wt% Ti 3 C 2. The printed structures of pure Ti 3 C 2 also perform as highly-sensitive strain sensors with a gauge factor of 11,300 at a strain of 4%. The prepared sensors are capable of monitoring various human activities, including breathing, facial muscles movements, and talking. [Display omitted] • Aqueous and additive-free inks of pure Ti 3 C 2 and composites Ti 3 C 2 /PEDOT:PSS were developed. • High-resolution extrusion printing of Ti 3 C 2 -based inks was demonstrated. • Printed structures of Ti 3 C 2 showed simultaneously high conductivity and mechanical flexibility. • Printed grids of Ti 3 C 2 -based inks showed unique EMI shielding characteristics. • Printed structures of pure Ti 3 C 2 were performed as highly-sensitive strain sensors. [ABSTRACT FROM AUTHOR]

Sulfated nanocellulose (SNC) with high surface charge density (2362 μmol/g) is prepared and used as an efficient dispersant to non-covalently disperse single-wall carbon nanotubes (SWCNTs). The resulting SWCNT-SNC (CSNC) dispersions are extremely stable and redispersible, with the high dispersion limit of 80 wt% SWCNTs. As conductive inks, CSNC dispersions exhibit good compatibility with various printing processes and adaptability to multiple substrates. Furthermore, based on the good film formation of SNC and high SWCNTs content, ultra-highly conductive (1140 S/cm) nanocomposite films can be directly manufactured from CSNC dispersions. The obtained CSNC nanocomposite films not only have good mechanical and electrical properties, but also display outstanding thermal management performance and highly sensitive characteristic response to human respiration. [Display omitted] • Sulfated nanocellulose with high surface charge density (2362 μmol/g) is prepared. • High dispersion limit of 80 wt% SWCNTs is achieved by using SNC as a dispersant. • SWCNT-SNC dispersions exhibit excellent dispersion stability and redispersibility. • SWCNT-SNC films exhibit an ultra-high conductivity of 1140 S/cm. • SWCNT-SNC films have excellent Joule heating performance of over 170 °C at 2 V voltage. [ABSTRACT FROM AUTHOR]

Graphite, with many industrial applications, is one of the widely sought-after allotropes of carbon. Although the geometric design of the graphite in many of the applications could dictate its precision performance, conventional synthesis methods for formulating complex geometric graphite shapes are limited due to the intrinsic brittleness and difficulties of high-temperature processing. Here, we report the development of colloidal ink from commercial graphite powders that allows the fabrication of any complex architectures with tunable geometry and directionality via 3D printing at room temperature. The method is enabled via using very small amounts of clay as an additive, allowing the proper design of the graphite-based ink and subsequent binding of graphite platelets during printing. Sheared layers of clay are easily able to flow, adapt, and interface with graphite layers forming strong binding between the layers that make the larger structures. The direct ink writing of complex graphitic architectures without further heat treatments could lead to easy shape engineering and related applications of graphite at various length scales. The printed structures exhibit excellent thermal, electrical, and mechanical properties, and the clay additive does not seem to alter these properties due to the excellent inter-layer dispersion and mixing within the graphite material. [Display omitted] [ABSTRACT FROM AUTHOR]

• DI/PVP graphene ink exhibit high wetting, good stability and electrical conductivity. • Electrical conductivity increased with increasing number of printing cycle. • Insignificant drop in conductivity (about 0.2%) when the bending force was released after 100 bending cycles. Inkjet printing of graphene conductive inks plays a critical role in the technological advancement in flexible and stretchable electronics applications. In this study, water-based graphene conductive ink was fabricated and printed through inkjet printing on polyethylene terephthalate substrate. Deionized (DI) water and three different types of surfactants (sodium dodecyl sulfate (SDS), polyvinylpyrrolidone (PVP), and Gum Arabic GA)) were utilized in the preparation of graphene conductive inks. Among other conductive ink formulations, graphene conductive inks fabricated using the DI/PVP surfactant exhibit relatively higher wetting and stability properties. In addition, this formulation led to an increment of about 80% in electrical conductivity compared to DI water-based conductive ink. The results revealed an improvement of about 50 times in the electrical conductivity of the printed film when the number of the printing cycle was increased from 1 to 10. Furthermore, it was observed that under 50% tensile strain, the graphene film prepared using the PVP surfactant exhibited only a 0.12% drop in electrical conductivity. Therefore, it is inferred that the conductive inks prepared from DI/PVP surfactants are highly suitable for use in flexible and wearable electronics. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Conductive ink based on carbon nanomaterials and alkyd resin with good performance. • Nanomaterials have increased sensitivity and selectivity for phenolic pollutants. • Simultaneous electrochemical detection of catechol, bisphenol A and 4-nitrophenol. • Disposable carbon screen-printed electrode for on-site environmental monitoring. Disposable, flexible, and low-cost, lab-made screen-printed electrodes (SPEs) using conductive inks based on carbon nanomaterials were applied to determine environmental pollutants in water. Several compositions of carbon conductive inks were investigated, and the best one was composed of nanographite, graphene nanoplatelets, and alkyd resin (40:10:50%, w/w/w). Under optimized conditions using square wave voltammetry, calibration curves were constructed (individually and simultaneously) for detection of bisphenol A (BPA), catechol (CC), and 4-nitrophenol (4-NP), presented linear responses in the 2.5 to 200 µmol L–1 range. From the individual curves, the LODs obtained for BPA, CC, and 4-NP were 1.7, 6.9, and 2.8 µmol L–1, respectively. The proposed sensors were chemically and microscopically characterized and evaluated for their analytical performance, including stability (over 70 days, with RSD < 10%), reproducibility (RSD < 10% for 10 SPEs), possible interferences (relative error < 12%), and hazardous phenolic pollutants on-site analysis in water samples (RE < 10%). [ABSTRACT FROM AUTHOR]

• High sensitivity with printed graphene electrode modified with N-GQDs. • Improvement of surface area by N-GQDs leads to high electron mobility in electrode. • More efficiency in transferred electrons by catching through the N-GQDs. The improvement of electrochemical properties of graphene compounds can be achieved by using graphene quantum dots (GQDs) due to their high electron mobility, catalytic property and size corresponding to the active site of the enzyme. In this study, we developed a third-generation enzymatic amperometric biosensor based on nitrogen-doped graphene quantum dots (N-GQDs) and printed graphene electrodes (PGE) for the highly sensitive and selective detection of glucose. The PGEs modified with N-GQDs showed a high potential for the precise and sensitive electrochemical detection of glucose. Due to the high electron mobility and electrical conductivity, excellent electrocatalytic activity, large surface area and size compatibility of PGE and N-GQDs with biomolecules, a high sensitivity of 40.76 mA.mM-1.cm-2 and LOD close to 0.098 mM were achieved. The high enzyme surface coverage measured at 3.33 × 10–7 mol.cm-2 further confirmed the excellent enzyme loading capacity and immobilization tendency of the biosensor. Moreover, the N-GQD-based electrochemical biosensors were found to be highly specific and selective even in complex media, especially human blood serum. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] This article presents a Glossy Photo-Paper (GPP) based Screen-Printed Chemiresistive Interdigitate Electrode (SPCIDE) for enzymatic glucose sensing. A facile inexpensive screen-printing method was used to print the low sheet resistance Interdigitate Electrodes (IDEs) with graphene as conductive ink on the proposed GPP. The screen-printed IDE was functionalized with Polyaniline (PANI) material by drop-cast technique to create a chemiresistive matrix. Further, for selective sensing of glucose, Glucose Oxidase (GOx) enzymes with Green Synthesized Silver Nanoparticles (GS-AgNPs) were immobilized on the PANI material. The proposed GPP-based SPCIDE sensor was used to detect glucose using amperometric measurements. With a correlation coefficient (R2) of 0.9803 and a lower Limit of Detection (LOD) equal to 198 nM, the proposed SPCIDE glucose sensor displays a linear association between change in current and corresponding glucose concentration in the range of 198 nM to 30 mM. An experimental result shows that the created SPCIDE sensor has a sensitivity of 291.19 µA mM−1 cm−2. The study shows that the proposed method may be used to produce facile GPP-based glucose sensors that are inexpensive, eco-friendly, bio-synthesizable, and biodegradable. This may result in developing a Point-of-Care (PoC) diagnostic kit for glucose testing as needed. [ABSTRACT FROM AUTHOR]

Conductive polymers (CPs) are typically insoluble in solvents, and devising biocompatible hydrophilic CPs is challenging and imperative to expand the applications of CPs. Herein, sulfated chitosan (SCS) is used as a green dopant instead of toxic poly(styrene sulfonate) (PSS), and SCS:polypyrrole (SCS:PPy) conductive ink is prepared by in situ polymerization. Due to the complex structure between PPy and SCS polyanion, the synthesized SCS:PPy dispersion forms a well-connected electric pathway and confers superior conductivity, dispersion stability, good film-forming ability, and high electrical stability. As proof of our concept, electrochemical sensing utilizing an SCS:PPy-modified screen-printed carbon electrode (SPCE) was performed towards carbendazim (CBZ). The SCS:PPy on the SPCE surface displayed greater sensitivity to CBZ because the conductive complex structure eased the electrocatalytic action of SCS:PPy by dramatically increasing the current intensity of CBZ oxidation and notably ameliorating stability. The sensor unveils the lowest detection value of 1.02 nM with a linear range of 0.05 to 906 μM for sensing trace CBZ by utilizing the pulse voltammetry technique. Interestingly, this senor shows excellent selectivity towards CBZ due to the formation of substantial interactions between SCS:PPy and CBZ, as demonstrated by molecular simulation studies. Furthermore, this sensor can precisely monitor CBZ in actual fruit and river water samples with satisfactory results. This study sheds light on the design and synthesis of sustainable hydrophilic CPs in the fabrication of sensors. [ABSTRACT FROM AUTHOR]

Cu(II) di-n-dodecylbenzene sulfonates prepared from neutralization between CuO and n-dodecylbenzene sulfonic acid self-assemble into micro-micelles in water and reduced to CuNPs by sodium boron hydride. Energy dispersive x-ray spectra prove that CuNPs are covered by the unreactive HDBS and n-dodecylbenzene sulfonate (DBS-) and prevent the aggregation of CuNPs, keeping their sizes at tiny nanoscales and resulting in the λ max at 550–600 nm in the UV-Vis spectra. Without antioxidants or capping agents, the as-prepared CuNPs are well protected from oxidation by surfactants as confirmed by x-ray diffraction patterns. The micelle shapes of surfactant DBS- control the precipitated morphologies of the CuNPs. According to SEM and TEM micrographs, the average size of the CuNPs is at around 2–3 nm with a low melting point at ca. 140 °C measured by DSC and free from oxidation in the air below 140–150 °C by TGA thermograms. The surfactant-covered CuNPs are easily dispersed into a conducting ink and their electrical resistance drops sharply over 136 °C, attributable to the formation of a conducting network derived from the fusion of CuNPs. [Display omitted] • Prepare copper nanoparticle from micro-micelle. • Prepare pure Cu(ll) di-n-dodexylbenzene sulfonate. • Prepare low size, low melting point copper nanoparticles. • Facile way to print Cu circuit on PCB. • Significantly reduce Cu consumption on fabrication of PCB. [ABSTRACT FROM AUTHOR]

Flexible sensors are an important part of flexible electronic devices, and its application often relies on external power sources. However, traditional commercial batteries require repeated charging, lack of flexibility and potential leakage of electrolyte contamination, which seriously hinder the wearable smart electronic devices' develop of comfortable and portable integration. To overcome this key challenge. This paper combines energy harvesting technology, distributed energy storage devices and flexible electronics. This proposes a modular layout of friction nanogenerator (TENG), miniature solid-state supercapacitor (MSSC) and strain sensor. Three of modular components are constructed on a thermoplastic polyamide film. The basic conductive network is prepared through screen printing technique and graphene multiwall carbon nanotubes (G-MWCNTs) conductive inks. The TENG module is used to collect low-frequency and high-entropy mechanical energy from the surrounding environment for conversion into AC electrical energy. The MSSC module is used to store the electrical energy generated by the TENG and to continuously power the back-end flexible electronics. The strain sensor module has an asymmetric interlaced double-arc snake rib conductive structure inspired by the spotted snake. It enables multi-dimensional strain detection and ultra-sensitive sensing performance. Finally, as a concept proof, the prepared TENG, MSSC and strain sensors are composed to form a self-powered multimode distributed flexible sensing device. It can be used for human health monitoring in the areas of knuckle, elbow, hip and heel nodes. [Display omitted] • This proposes a modular layout of friction nanogenerator (TENG), miniature solid-state supercapacitor (MSSC) and strain sensor. The TENG outputs a maximum voltage of 15.36 V, a shortage current of 0.57 μA and a transferred charge of 5.70 nC. MSSC has a high area ratio capacitance of 7.09 mF cm-2. Capacitance retention up to 96.68% after 5000 volt-amp cycles. The strain sensor uses only 0.1061nW of power at a 0.001 V operating voltage. • The strain sensor module has an asymmetric interlaced double-arc snake rib conductive structure inspired by the spotted snake. It enables multi-dimensional strain detection and ultra-sensitive sensing performance. The sensor proposed in this paper achieves strain gauge factor (GF) of 6300.75 and 435% wide sensing range response. [ABSTRACT FROM AUTHOR]

Screen-printed electrodes (SPEs) based on hybrids of the conducting polymer poly(ortho-ethoxyaniline) (POEA), graphene oxide (GO) and reduced graphene oxide (rGO) were produced and characterized. The SPEs were produced from conductive inks based on graphite and alkyd resin and were modified with hybrids of POEA with GO, and rGO. The hybrids POEA-GO and POEA-rGO were produced by chemical polymerization of o -ethoxyaniline (orthophenitidine) in 1.0 mol L−1 with GO or rGO dispersed into the monomer solution. The SPEs were modified by the replacement of 5 % in mass of graphite by 5 % in mass of POEA-GO or POEA-rGO hybrids. The hybrids were characterized by Raman and FT-IR spectroscopies and XRD analyses. The modified SPEs, SPE/POEA, SPE/POEA-GO, and SPE/POEA-rGO were characterized by scanning electron microscopy, and by cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). The electrodes based on the rGO hybrid, SPE/POEA-rGO, showed a significant reduction of the charge transfer resistance obtained by EIS by a factor of 3 compared with SPE/POEA, from 4.62 kΩ to 1.48 kΩ, without changing the redox behaviour of POEA. The methodology used to produce SPE/POEA-rGO is a simple, effective, scalable, and low-cost alternative to produce POEA-based electrodes for applications such as in electrochemical sensors and charge storage devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Flexible and transparent conductors are essentially required in epidermal wearable devices such as electronic-skins (E-skins) that facilitate human interaction and biofeedback. However, due to the "trade-off" effect between high electrical conductivity and optical transparency, it is difficult to obtain transparent E-skins with high electrical conductivity. Furthermore, traditional transparent conductor is bulky and brittle which is not suitable for flexible and wearable applications. Herein, ultrathin two-dimensional (2D) titanium carbide (MXene) nanosheets with metallic conductivity, hydrophilic surface and excellent mechanical flexibility was proposed as a novel high-performance transparent conductor, which was further developed as wearable E-skins. Solution-processable MXene conductive ink was obtained by facilely etching Al from MAX phase for large-scale spray coating to obtain flexible transparent conductors. The flexible, transparent, and conductive MXene-based electrodes own a sheet resistance as low as 200 Ω/sq, while with high optical transparency of 60% @550 nm, which is sufficient for the applications of E-skins. Moreover, the transparent MXene-based soft E-skins also exhibits outstanding mechanical flexibility which could maintain its high opto-electrical performance even after 1000 cyclic bending tests. In addition, the robust flexible transparent MXene-based E-skins also could accurately identify the movements of human body including approaching, touching and pressing, which is essentially required in various application scenarios such as human-machine interactions, touch panels and healthcare sensors. The solution-processable flexible, transparent and conductive MXene-based E-skins holds tremendous potential in emerging wearable applications. Ultrathin two-dimensional T 3 C 2 T X -MXene nanosheets with metallic conductivity, hydrophilic surface and excellent mechanical flexibility was proposed as a novel high-performance transparent conductor, which was further developed as wearable E-skins. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, we have successfully developed a series of low-cost, environmentally friendly, and high-performance carbon-based conductive inks with a three-dimensional micro-nano structure through a simple dispersion and ball-milling process, offering an array of desirable characteristics. Significantly, the carbon-based conductive inks remained stable even after a 30-day settling period. Furthermore, the conductive film, produced using screen printing techniques, demonstrated an impressive conductivity of 1.99 × 103 S/m. This remarkable conductivity highlights the ability of the films to consistently maintain a robust conductivity network, even when subjected to 5000 mechanical bending/releasing tests. Expanding on the success of our carbon-based conductive inks, we harnessed their potential in the production of all-solid-state flexible Micro-supercapacitors (MSCs) with an interdigital structure, utilizing screen-printing technology. The resulting MSCs exhibited outstanding performance metrics, including a notable areal energy density of 1.47 µWh cm-2 and an area power density of 0.2 mW cm-2. Moreover, these MSCs demonstrated remarkable cycle stability, retaining 96.3% of their capacitance after 20,000 cycles. Additionally, their excellent mechanical flexibility was evident as they experienced only a minor 2.98% capacitance degradation after undergoing 5000 bending/releasing cycles. These findings highlight the enormous potential of our work in facilitating the scalable production of wearable and portable electronic products. • Synthesize a high-performance aqueous carbon-based ink. • Carbon black was attached to graphite flakes to construct an effective three-dimensional micro-nano structure. • The ink was applied in the field of planar micro-supercapacitors with screen printing technology, showing good electrochemical performances and excellent mechanical flexibility. [ABSTRACT FROM AUTHOR]

The development of conductive inks has increased in recent years, especially for applications in electronic devices. Inks can be applied by spraying on the IoT chips and forming a shield against electromagnetic interference (EMI). This technology is called conformal shielding, which reduces EMI on the component. Micro and nanoparticles of copper or silver are often used in the composition of the inks, but the high cost of silver and the oxidation of copper limit the application. Another option is using particles with a copper core covered by silver (Cu–Ag), as it overcomes both limitations of the pure metals mentioned. So, there is an opportunity to use these conductive inks as an alternative to traditional EMI shielding methods such as metal cans, sputtering coating, and electroless nickel. Therefore, this work synthesized Cu–Ag particles to use in a conductive ink applied by spray coating. The film's resistivity and shielding effectiveness (SE) were measured. The morphology, size, and chemical composition of the particles were evaluated. The particles presented an irregular shape with complete and partial coverage of silver over copper. The ink showed an electrical resistivity of ∼10−04 Ω cm at 200 °C in sintering. It was also tested on different substrates with better adhesion to PET. The shielding efficiency was −44 dB according to the ASTM d4935 norm. A painting on the chips with a low-thickness film covering all modules demonstrated suitability to conformal shielding. • Achieved copper-silver production via a straightforward two-step chemical synthesis in a water-based solution. • We developed an innovative spray coating method to apply an alternative conformal shielding to electronic chips. • We employed a coaxial method aligned with the ASTM d4935 standard to measure the shielding effectiveness of the film. [ABSTRACT FROM AUTHOR]

[Display omitted] The advent of cost effective printed smart devices has revolutionized the healthcare sector by allowing disease prediction and timely treatment through non-invasive real time and continuous health monitoring. Future advancements in printed electronic (PE) materials will continue to enhance the quality of human living. For any PE application, materials should possess proper mechanical integrity and resistivity while being non-toxic. In the case of sensing devices for physiological and biochemical signals, excellent conductivity is an essential requirement for obtaining high response signals. The emergence of the novel class of 2D materials called MXenes and their composites has resulted in structures and materials hugely relevant for healthcare devices. Exploiting solution based 2D MXene materials can expedite their practical application in PE devices by overcoming the present limitations of conductive inks such as poor conductivity and the high cost of alternative functional inks. There has been much progress in the MXene functional ink generation and its PE device applications since its discovery in 2011. This review summarizes the MXene ink formulation for additive patterning and the development of PE devices enabled by them in healthcare, biomedical and related power provision applications. [ABSTRACT FROM AUTHOR]

Cost-effective synthesis, portability, quick response and fascinating features of semiconducting metal oxide sensors have drawn much accredited to be utilized in wide variety of potential sensing applications. Herein, flexible acetone sensor was fabricated through spray coating method using different conductive inks of carbon nanotubes (CNTs), zinc oxide (ZnO) and silver (Ag) nanoparticles solutions on cellulose paper. Morphological analysis revealed the fiber like morphology of cellulose over which CNTs, ZnO and Ag nanoparticles are uniformly distributed. The energy dispersive X-ray spectroscopic analysis was performed to observe the elemental composition in the as-prepared samples. The recovery time toward acetone was greater for CNTs/Ag acetone sensor at 95% as compared to CNTs/ZnO/Ag sensor. Additionally, sensing time of the samples towards acetone was measured and the observed response time was greater for CNTs/ZnO/Ag (0.52 s) acetone sensor as compared to CNTs/Ag sensor (0.41 s). Hence, CNTs/ZnO/Ag can be easily employed for sensing applications due to quick response. [ABSTRACT FROM AUTHOR]

The exceptional high surface area and wide band gap ranges of semiconductor metal oxide nanostructures owe unique chemical, optical and physical properties that have grabbed their utilization for humidity sensing applications. In this framework, cost-effective sensors have been fabricated using a simple spray coating technique. Initially, the sonication was carried out for all the conductive inks such as carbon nanotubes (CNTs), zinc oxide (ZnO) and silver (Ag) nanoparticles (NPs) for 15 min in each case and then sprayed over conducting cellulose polymer substrate. Surface study demonstrated conducting networks of CNTs and cellulose polymer, and layers of ZnO and Ag NPs, as well. The analysis of elemental composition confirmed the required stoichiometric contents. Sensing measurement of CNTs/ZnO/Ag sample showed smaller resistance and enhanced current as compared to CNTs/ZnO sample. Hence, the device showed an efficient activity to sense humidity. [ABSTRACT FROM AUTHOR]

Among the conventional metallic inks used in the printing process, silver exhibits high conductivity and thermal stability. Nevertheless, due to the high cost of silver, it cannot be extensively used for the fabrication of inks. As a competitive alternative, copper can be considered as a substitute for silver; however, copper ink oxidizes under certain atmospheric conditions. To meet these shortcomings, a cost effective, highly conductive, and oxidation-free copper-based ink has been synthesized in this study, wherein, oxidation of the copper particles in the copper-based ink was prevented by using copper complexes. The copper ink thus fabricated was printed on chemically treated Si/SiO 2 substrates followed by the characterization of the printed copper films. The results of this study confirmed that the synthesized copper ink exhibited properties suitable for its use in the inkjet printing process for fabrication of various electronic devices. Image 1 • The cost effective, highly conductive, and oxidation-free copper-based ink was synthesized and characterized. • The prepared copper ink was printed on Si/SiO 2 substrates by using inkjet printing process. • The printed patterns on the substrates were characterized in terms of experimental conditions. [ABSTRACT FROM AUTHOR]

A sonication of graphite in polysaccharide (pullulan, chitosan and alginate) is one of the viable methods for the preparation of few-layer graphene. However, the effect of these adsorbed polysaccharides on the electrical performance of the produced graphene so far is not yet clear. In order to investigate the present effect of pullulan, chitosan and alginate on the electrical characteristic of resulted graphene, we have produced few-layer graphene using bath sonication of graphite in pullulan, chitosan and alginate medium for the application as electrical conductive ink in strain-sensitive. Data from the TEM reveals the appearance of folded few-layer graphene flakes after sonication for 150 min while the XPS data shows that the chitosan-based graphene possesses the highest carbon-oxygen ratio of 7.2 as compared to that of the pullulan and alginate-based graphene. By subjecting the produced graphene as the ink for paper-based strain sensor, we have discovered that the chitosan-graphene has the best resistivity value (1.66 × 10-3 Ω⋅cm) and demonstrate the highest sensitivity towards strain (GF: 18.6). This result interestingly implies the potential of the reported chitosan-based conductive ink as a strain-sensitive material for future food packaging. [ABSTRACT FROM AUTHOR]

The synthesis of few-layer graphene from graphite typically uses N, N methyl pyrrolidone (NMP) or dimethylformamide (DMF) due to the strong affinity of both solvents for graphite. However, NMP and DMF are known as carcinogens and a long-time exposure to these substances may subject users to potential risk of major health issue later. Therefore, a replacement with dispersing solvent that is not only harmless but also able to exfoliate graphite at an excellent concentration yield must be outlined for a sustainable mass-production of graphene. In this work, we have successfully exfoliated graphite to few-layer graphene with a recorded yield concentration of up to 0.75°mg/ml (2.5°h) just by using extracted red spinach/water mixture as an exfoliating medium. The prepared graphene was found to possess less structural defect (I D /I G : 0.5) and high C/O ratio (6.8) and can be used further as an electrical conductive ink for smart "Sticky Note" sensor. The fabricated device was able to detect strain and temperature with gauge factor and temperature coefficient resistance of 23.5 and −32.14 × 10-4°Ω/°;C, respectively. We believe that this study would be useful for the preparation of environmental-friendly graphene that is not only strain and thermally sensitive but also producible at low -cost. Image 1 [ABSTRACT FROM AUTHOR]

Cadmium (Cd) and lead (Pb) pollution is a significant environmental and human health concern, and methods to detect Cd and Pb on site are valuable. Stencil-printed carbon electrodes (SPCEs) are an attractive electrode material for point-of-care (POC) applications due to their low cost, ease of fabrication, disposability and portability. At present, SPCEs are exclusively formulated from graphitic carbon powder and conductive carbon ink. However, graphitic carbon SPCEs are not ideal for heavy metal sensing due to the heterogeneity of graphitic SPCE surfaces. Moreover, SPCEs typically require extensive modification to provide desirable detection limits and sensitivity at the POC, significantly increasing cost and complexity of analysis. While there are many examples of chemically modified SPCEs, the bulk SPCE composition has not been studied for heavy metal detection. Here, a glassy carbon microparticle stencil printed electrode (GC-SPE) was developed. The GC-SPEs were first characterized with SEM and cyclic voltammetry and then optimized for Cd and Pb detection with an in situ Bi-film plated. The GC-SPEs require no chemical modification or pretreatment significantly decreasing the cost and complexity of fabrication. The detection limits for Cd and Pb were estimated to be 0.46 μg L−1 and 0.55 μg L−1, respectively, which are below EPA limits for drinking water (5 μg L−1 Cd and 10 μg L−1 Pb) [1]. The reported GC-SPEs are advantageous with their low cost, ease of fabrication and use, and attractive performance. The GC-SPEs can be used for low-level metal detection at the POC as shown in the report herein. Image 1 • A low-cost and disposable glassy carbon stencil printed electrode (GC-SPE) was developed and characterized. • GC-SPEs exhibit desirable characteristics for anodic stripping voltammetry compared to conventional graphite SPCEs. • The GC-SPEs were applied to the sensitive detection of Cadmium (Cd) and Lead (Pb). [ABSTRACT FROM AUTHOR]

The demand for low-cost, efficient, selective, and sensitive analytical methods is increasing globally, making electroanalysis combined with screen-printed electrodes an appealing option. Gold, known for its excellent electrical conductivity and biocompatibility, improves the electrocatalytic activity of the sensors and reduces interference with other substances. Here, we propose the modification of disposable sensors with edible gold leaf, which is a cost-effective alternative to sputtering. The gold leaf was immobilized on the screen-printed electrode surface with chitosan. L-tyrosine, an amino acid, and an important biomarker for the diagnosis of various diseases was detected as a proof-of-concept. Using square-wave voltammetry for the determination of L-tyrosine, the disposable sensor modified with gold leaf showed a linear response in the range between 0.10 to 70 μmol L−1 with a limit of detection of 0.09 μmol L−1. Overall, the use of gold leaf to modify disposable electrochemical sensors for L-tyrosine detection represents a promising approach for electrochemical sensing. [ABSTRACT FROM AUTHOR]

Graphene-based printable inks are advanced and promising candidates for flexible printed electronic devices. To develop large-scale graphene-based highly conductive electronics based on existing printing approaches of the material, it is imperative to scale up its ink production methods and optimize the electrical properties of the printed films. Here, a sustainable approach is reported for preparing high-conductive screen-printing graphene ink by recycling cellulose solvents. The ink uses Cyrene solvent in circulation and produces highly concentrated and conductive graphene ink to conquer the limitation of graphene inks in massive industrial production brought by the high cost of the cellulose solvents. A systematic study of the sheet resistance variation with the number of cycles has been carried out. The average conductivity of the ink can exceed 3 × 104 S m − 1, with only a 2-h shear exfoliation process, which exhibits about the same conductivity of recent works (using toxic NMP solvent, complex centrifugation, ultrasonication, etc.) but with much more straightforward and cost-effective fabrication process. The formulation of graphene inks allows flexible metal-free far-field tag antenna to be screen-printed and integrated with an off-the-shelf sensory chip to achieve battery-free wireless UHF RFID far-field temperature sensing. The high responsiveness, accuracy, and sensitivity of the RFID sensing tag were observed with instantaneous detection of accurate and reliable wireless data transmission. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel flexible electrochemical sensor based on porous carbon nanosheets (PCNSs) nanozyme has been constructed for in situ and real-time monitoring of H 2 O 2 released by cells. The PCNSs are prepared with the integration of thermal transformation, thermal activation and sonochemical exfoliation by using zeolitic imidazolate frameworks as template. The PCNSs exhibit high electrical conductivity, electrochemical activity and peroxidase-like catalytic properties, which is beneficial to H 2 O 2 assay. With the transfer printing method, the flexible electrochemical sensor is obtained, which has excellent performances for H 2 O 2 electrochemical detecting with wide linear range from 1 μM to 20 mM and a low detection limit of 0.76 μM. Owing to the great biocompatibility, the flexible sensor guarantees the growth of living cells for 72 h and realizes in situ and real-time monitoring the release of H 2 O 2 from HeLa cells. The strategy of porous nanozyme preparation and flexible sensor construction provided a promising way for in situ and real-time assay of small molecules in the cellular microenvironment. [Display omitted] • A flexible electrochemical biosensor based on carbon nanozyme. • MOF-derived N-doped porous carbon nanosheets nanozyme. • Transfer printing method based on PCNSs conductive ink. • Great biocompatibility for HeLa cells growth. • Excellent properties for in situ and real-time monitoring H 2 O 2 released by cells. [ABSTRACT FROM AUTHOR]

The use of sustainable, multifunctional inks in printed electronics has great utility for various devices, particularly at soft biointerfaces. Here, we discuss the development of a multifunctional nanocomposite ink, termed PS-IO-N ink, designed for applications, principally in the field of flexible and bio-electronics. The ink combines electrically conductive properties with magnetic capabilities, offering a dual-functionality that facilitates both physical and electrical connections. The PSION ink is composed of two main components: poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), a conducting polymer with favorable biocompatibility, and iron oxide (Fe 3 O 4) nanoparticles known for their ferromagnetic properties. The ink is formulated as a stable water dispersion, making it eco-friendly and suitable for aqueous processing. Key findings include the optimization of components to balance electrical conductivity and magnetic behavior, allowing the ink to function as both a physical connector and a conductor. The addition of an adhesion promoter enhances the ink's water stability and surface adhesion. The ink's applicability is demonstrated in various scenarios, such as forming flexible circuits on substrates like paper and silk fibroin, creating temporary magnetic connections for electronic devices, and enabling stable connections to sensors for parameter monitoring. The PSION ink provides an innovative solution for flexible and bioelectronic applications, offering the potential for reversible, adaptable connections in both dry and wet environments. [Display omitted] • Discuss a multifunctional water based ink. • Stable dispersion with conductive and magnetic properties. • Can facilitate transient on/off connections. • Easily dispensed on variety of substrates as micropatterns. • Connections to sensors and other functional devices shown. [ABSTRACT FROM AUTHOR]

In present work, we report an eco-friendly, flexible and highly conducting cotton thread (CT) as a smart substrate for the development of biosensing platform towards ultrasensitive detection of swine flu serum amyloid A (SAA) biomarker. The biosensor was fabricated by optimized coating of CT with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) conductive ink followed by incorporation of nanodot zirconium trisulfide (nZrS 3) which helped in enhancing the electrochemical properties and improving stability of PEDOT:PSS polymeric film. The fabricated nZrS 3 /PEDOT:PSS/CT electrode was then used for sequential immobilization of monoclonal antibodies of SAA (anti-SAA) and bovine serum albumin (BSA). The synthesized nanomaterials and fabricated electrodes were characterized through X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy and contact angle analyser techniques. The electrochemical response of the fabricated smart thread based biosensor (BSA/anti-SAA/ZrS 3 /PEDOT:PSS/CT) was recorded against SAA using chronoamperometry technique which revealed superior sensitivity {30.2 μA [log (μg mL−1)]−1 cm−2}, excellent lower detection limit (0.72 ng mL−1) and prolonged shelf life up to 48 days. The response of the biosensor was also validated by analysing the electrochemical response of SAA spiked serum samples and the obtained results showed good correlation with that of standard samples. [ABSTRACT FROM AUTHOR]

Flexible electronic devices such as wearable strain sensors have drawn much interest in health monitoring systems. In the present study, hybrid ink-printed flexible strain sensors made of graphene and silver nanoparticles (AgNPs) were formulated. The main aim of the study is to investigate the effect of hybrid graphene and AgNP ratios on the properties of conductive inks and their performance as flexible strain sensors. The new conductive inks were printed on various types of flexible substrates: polyethylene terephthalate (PET), polyimide (PI), and polyvinyl alcohol (PVA). The performance of conductive ink on these substrates was evaluated. The results showed that the ratio of graphene/AgNPs influenced the properties of conductive inks. Graphene/AgNPs with a 0.3/0.2 wt% exhibit higher stability, wettability, and electrical conductivity than 0.4/0.1, 0.2/0.3, and 0.1/0.4 wt%. Hybrid graphene/AgNPs conductive ink printed on PI substrate showed better wettability and electrical performance compared to those on PET and PVA substrates. The gauge factors (GF) of the PI substrate are higher, 6.2% and 32%, compared to PET and PVA, respectively, at the 30% strain range. In short, the hybrid graphene/AgNPs strain sensor on PI that showed good linearity, sensitivity, and stability has a high potential to be used in low-strain health monitoring systems. • Graphene/AgNPs with 0.3/0.2 wt% exhibit higher stability, wettability, and conductivity than those others hybrid wt%. • Hybrid Graphene/AgNPs conductive ink printed on PI substrate showed better wettability and electrical conductivity. • PI substrate-based strain sensors showed high sensitivity and stability of hybrid graphene/AgNPs strain sensor. [ABSTRACT FROM AUTHOR]