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Pattern registration accuracy is a key property in printing processes, especially for miniaturized printed electronic devices that require the overlay of multiple layers. Except for inkjet and screen printing, various printing methods such as gravure offset, flexographic, and reverse offset printing typically use a roll-to-sheet type printer; however, registration has been limited, especially in the machine direction because of the speed variation in rotary motion of a cylindrical roll. We developed an arc-to-sheet type printer in which the rotary motion of an arc was realized by a trochoidal trajectory because such a mechanism can only be constructed using the translational motions of high-precision linear actuators. A prediction model for the behavior of the contact point of the arc during printing was also developed, along with a method for compensating for mechanical and assembly errors, which was verified by laser displacement measurements and torque exerted on the linear motor of table. Cu patterns reverse offset printed by the developed arc-to-sheet printer had positional errors of less than 3σ < 6 ppm with an optimized processing condition, achieving an unprecedented level of accuracy in printed electronics. • A novel arc-to-sheet printer was developed to provide a high-precision printed electronics. • The arc-to-sheet printer is offering 2-μm feature patterns. • The arc was rotated by the trochoidal motion of precision linear actuators. • Positional errors below 6 ppm at 3σ level were achieved with optimized parameters. • Registration accuracy was predicted by a point of contact model and a FEM simulation. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate a fully screen printed supercapacitor (SC) with a monolithic structure. The monolithic SCs were prepared by screen printing different SC layers on top of each other. After the layers were printed, an aqueous electrolyte was added to the screen printed separator, and the printed structure was sealed. The prepared monolithic SCs showed similar electrical characteristics to a face-to-face laminated stacked SC with a paper separator. Interfaces between the screen printed SC layers were observed with a scanning electron microscope. Results show that the screen printing process is reproducible and can be used to fabricate SCs reliably. This fabrication process also eliminates an assembly step that is common in laminated stacked SCs. Hence the introduced screen printing process shows feasible and scalable fabrication for the monolithic SCs. Advanced fabrication of the printed monolithic SCs can benefit different applications, such as wireless sensor devices with environmentally sustainable energy storage units, and the integration of an energy storage unit on the same substrate with the printed circuits. [Display omitted] • Development of a printable separator enables layer-by-layer fabrication. • Monolithic supercapacitors fabricated using screen printing. • Fully printed supercapacitor based on sustainable and non-harmful materials. [ABSTRACT FROM AUTHOR]

Colloidal droplet evaporation is an intriguing and intricate phenomenon that has captured the interest of scientists across diverse disciplines, including physical chemistry, fluid dynamics, and soft matter science, over the past two decades. Despite being a non-equilibrium system with inherent challenges posed by coffee ring formation and Marangoni effects, which hinder the precise control of deposition patterns, evaporative self-assembly presents a convenient and cost-effective approach for generating arrays of well-ordered structures and functional patterns with wide-ranging applications in inkjet printing, photonic crystals, and biochemical assays. In the realm of printed electronics and photonics, effectively mitigating coffee rings while achieving uniformity and orderliness has emerged as a critical factor in realising the next generation of large-area, low-cost, flexible devices that are exceptionally sensitive and high-performance. This review highlights the evaporative self-assembly process in colloidal droplets with a focus on the intricate mechanical environment, self-assembly at diverse interfaces, and potential applications of these assembling ordered structures. [Display omitted] • Complex mechanical environments of colloidal particles inside an evaporating droplet are presented in detail. • Advances in interfacial self-assembly at liquid-air, liquid-solid interfaces, and three-phase contact lines are described. • Applications in inkjet printing of functional materials and bio-chemical detection and analysis are demonstrated. • The challenges and future prospects of evaporative self-assembly of colloidal droplets are presented. [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]

• 2D MXenes are systematically reviewed as flexible electrodes. • Printing methods are discussed. • Applications of 2D MXenes for printing energy storage devices are summarized. • Future research directions in MXenes for printing electronics are suggested. MXenes, as a prominent class of two-dimensional (2D) materials have gained significant attention in various research fields over the past decade. In recent years, MXene-based materials have emerged as promising candidates for conductive electrodes in printed electronics due to their unique properties, including high electrical conductivity, mechanical flexibility, stability, compatibility, and large surface area. These attributes make MXenes highly desirable for flexible printable electronics. MXenes have demonstrated great potential in energy storage systems, particularly in supercapacitors (SCs) and batteries. This review provides an overview of recent advancements in MXene synthesis and their significance in energy storage applications. Specifically, it summarizes the electrochemical performance of SCs and batteries utilizing MXene-based materials. Moreover,the review highlights current challenges associated with MXene inks and shedding light on new opportunities for integrating MXenes into diverse electronic devices and systems. [ABSTRACT FROM AUTHOR]

Flexible electronics have gained significant interest due to their potential applications in wearable devices, biomedical sensors, and flexible displays. This study explores the combination of MXene and cellulose nanocrystals (CNC) for the development of flexible, conductive, and degradable materials. CNC and MXene are high-performance nanomaterials with known degradability. CNC can self-assemble into highly ordered layers and act as an ideal structural companion for enabling large surface MXene-based devices with outstanding performance. Three fabrication routes are explored in this work: self-assembly, drop casting, and dip coating. The mechanical and electrical properties of the CNC-MXene composite films were assessed. Tensile testing revealed that dip-coated films in high-loadings of MXene could exhibit enhanced toughness of up to 1.9 MJ‧m−3, higher than pure MXene or CNC. The electrical conductivity of the films varied depending on MXene concentration and drying, exhibiting superior conductivity in self-assembly with higher MXene loading and rapid drying that prevents oxidation. Self-assembled MXene-CNC with a 1:3 MXene-to-CNC ratio maintained high conductivity of 2.2 × 105 S‧m−1. Zeta potential measurements indicate that CNC enhances the stability of MXene dispersion. These findings demonstrate good synergy between CNC and MXenes for applications in flexible, transparent, and environmentally degradable electronic. Composites of cellulose nanocrystals with MXene were fabricated in three different ways: self-assembly, drop casting and dip coating. These composites can be used to tailor flexible, degradable and partially transparent films with controlled conductivity. [Display omitted] [ABSTRACT FROM AUTHOR]

• The mechanism of action of thermal bubbles at the solid–liquid interface was studied for the first time. • Unveiling the underlying mechanisms of liquid metal droplet ejection. • The potential of utilizing this technology to achieve multi-orifice liquid metal jetting was demonstrated. In this work, we introduced the pulsed laser-driven liquid metal arrayed printing technology. This study harnesses sub-millimeter-sized rapidly expanding bubbles generated by nanosecond pulsed laser irradiation at the solid–liquid interface as the power source for liquid metal printing, enabling efficient arrayed jetting printing of liquid metal. Utilizing high-speed imaging technology, this study investigates the expansion process of bubbles induced by nanosecond pulsed lasers at the solid–liquid interface and the jetting process of liquid metal, thereby revealing the mechanism of liquid metal jet ejection. The study systematically examines the influence of laser parameters on the jetting behavior of liquid metal, laying a theoretical and technical foundation for applications such as patterned printing in the field of liquid metal. This technology holds significant engineering implications for further advancing the application of liquid metal in fields such as flexible electronics and printed electronics. [ABSTRACT FROM AUTHOR]

[Display omitted] • A multifunctional gel was introduced to assist fabricating stretchable copper patterns. • The gel has a combination of stretchability, printability, moldability, and reducibility to Ag+. • The reduced Ag catalyst layer exhibits excellent uniformity, adhesion and catalytic ability. • Printed, straight, and omnidirectionally stretchable copper circuits were facilely fabricated. Printable, stretchable, and highly conductive metal conductors have emerged as potentially promising interconnects in the field of soft electronics. However, current techniques relying on geometric engineering have been criticized for complicated fabrication process and defective geometric structure. Here, we report a printed, straight, and omnidirectionally stretchable copper conductor, which is facilely fabricated on a flat substrate without requiring prestretching, assisted by a multifunctional gel medium layer. The PSS gel, composited by polydimethylsiloxane, Schiff base and fumed SiO 2 , offers a unique combination of stretchability, printability, and moldability. Additionally, this gel enables the reduction of silver ions directly on its surface by partially bonded crosslinker molecules. The fully exposed catalyst exhibits excellent activity in catalyzing electroless copper deposition reaction, on which high-quality copper coating is facilely achieved. The produced copper patterns exhibit high conductivity (4.93 × 107 S m−1) and excellent stretchability with fracture strains of ∼ 191 % and ∼ 135 % for the uni- and omni-directionally stretchable patterns respectively, which are superior to the majority of stretchable metals in published literature. The stretchable wrinkles derive form the gel medium layer molded by templates, realizing straight metal lines on flat substrate. This process combines the advantages of traditional in-plane and out-of-plane strategies, demonstrating great potential in practical application. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel photopolymerizable ink formulations based on conducting polymer were prepared. • DLP-based-3D printing of the formulation yields multi-functional hydrogels. • 3D-printed gels are mechanically robust and electrically conductive. • Printed gels resist freezing and maintain conductivity at sub-zero temperatures. • Gradient crosslinking of printed gels induces shape-morphing behavior. High-performance hydrogel-based electronic devices require conducting hydrogels. Conducting hydrogels that are stretchable, soft, and biocompatible are in much demand to fabricate human–machine interfaces, wearable devices, soft robotics, and many other applications. We present a new generation polymeric formulation to prepare hydrogels by digital light processing (DLP)-based three-dimensional (3D) printing technology with visible light that are anti-freezing, electrically conductive, tough, stretchable, and non-toxic. The printed conducting hydrogels have exceptional water-holding capability at atmospheric conditions and tolerance to freezing over a wide range of temperatures from − 80 to 45 °C. The inks are amenable to the manufacturing of four-dimensional (4D)-printed hydrogels that can elicit pre-programmed structural deformations. This work presents polymeric formulations for potentially designing ultrafast programmable electronic devices with printed hydrogel electronics in various biomedical applications, soft robotics, biosensors, flexible electronics, human–machine interfaces, and health monitors for use under extreme environmental conditions. [ABSTRACT FROM AUTHOR]

The increased interest in printed electronics necessitates the development of suitable sustainable substrates for them. In this study, the suitability of acetylated cellulose nanofiber (ACNF) films as substrates for printed electronics were examined through (I) the ink-substrates interaction, (II) print quality, and (III) electrical and (IV) mechanical properties of the printed pattern on the ACNF substrates. The results have been compared with cellulose nanofiber (CNF) and commercial reference material (CRM) substrates. The wetting of the silver nanoparticle (AgNP) ink on the ACNF substrate was found out to be excellent. The thickness of the printed pattern increased and the hole area fraction decreased with each consecutive layer of ink. The comparative investigations demonstrated that the electrical properties of the printed patterns were almost as good for 4 layers of ink on the ACNF substrate (1.6 Ω resistance) as the ones on the CRM substrate (1.2 Ω resistance). Additionally, the printed pattern on the ACNF substrate endured the adhesion and bending tests significantly better compared to the CRM substrate. Therefore, this study demonstrates that ACNF substrates could be a suitable candidate for printed electronics, which are more sustainable yet with similar functionalities in comparison with the conventional fossil based substrates. • The wetting of the silver nanoparticle (AgNP) ink on the acetylated cellulose nanofiber (ACNF) film was instant. • An increase in ink layers on the ACNF film increased the thickness and the root mean squared (RMS) height of the printed pattern. • The spreading of the ink was approximately double on the commercial reference material (CRM) film compared to the ACNF film. • The resistance for the AgNP ink pattern on ACNF (1.6 Ω) film was almost as low as for CRM film (1.2 Ω). • The adhesion and bending resistance of the printed pattern on the ACNF film were superior to that on the CRM film. [ABSTRACT FROM AUTHOR]

Technology convergence is considered one of the cornerstones of technological innovation as a phenomenon emerging at the intersection of two previously unrelated fields of technology. The new technological system is a new combination of knowledge types, technology components and intersections. For this matter, analyzing patents is an essential part for strategic decision making. However, the manual analysis of large amounts of patent semantics is often time-consuming, extensive, and difficult even for experts. To enhance manual patent analyses, new machine learning-based techniques are gaining increasing interest. This study aims to enrich this methodological research by developing and evaluating an unsupervised text-mining approach to automatically cluster patents of two knowledge types into four technology components. To this end, this study presents a five-step method including the comparison between different algorithms and design choices. This method is applied to printed electronics-relevant patents extracted from the Derwent World Patent Index and enables to draw recommendations for automated patent analyses. The findings show different significances for types of components: while components of the specialized knowledge type could be predicted with significance, components of the design knowledge types could not provide significant results. [ABSTRACT FROM AUTHOR]

[Display omitted] • All-printed solid-state micro-supercapacitors with MWCNTs and PEDOT:PSS. • Controlled PEDOT to PSS ratio, resulting in a four-fold increase in conductivity. • Synergy of polar solvent & temperature enhance dielectric screening, PSS segregation. • Achieved 97.5% decrease in charge transfer resistance & increased areal capacitance. • 99.7% capacitance retention (6,000 cycles), and stability (10,000 bending cycles) All solid-state micro-supercapacitors (S-MSCs) are pivotal for modern wearables as they offer rapid energy storage and release, with seamless integration into small, lightweight wearables. Developing all printed S-MSCs is a cost-effective alternative to traditional S-MSCs and can potentially revolutionize wearable energy storage technologies. This manuscript presents an innovative, substrate-friendly approach to enhance the conductivity and electrochemical performance of screen-printed electrodes for S-MSCs using multi-walled carbon nanotubes (MWCNTs): PEDOT:PSS (poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate)) composite ink. By incorporating various polar solvents into the ink formulation and optimizing printing and drying parameters, a four-fold increase in conductivity (5.5 × 103 S/m) was achieved. The synergy of polar solvent addition and temperature treatment on the dielectric screening, preferential solvation, and partial segregation of PSS were identified as the principal reason behind this enhancement. The optimally formulated ink was employed to create supercapacitor electrodes, demonstrating hybrid capacitive behavior with both liquid and gel electrolytes. An impressive 97.5 % decrease in charge transfer resistance (R CT) and a corresponding increase in areal capacitance and energy density were observed for these supercapacitors due to the segregation of PEDOT and PSS achieved by the synergistic effect. All printed S-MSCs were also fabricated with an impressive areal capacitance of 9.82 mF/cm2 @ 60 µA/cm2 and areal energy density of 1.964 µWh/cm2 at an areal power density of 63 µW/cm2. The fabricated S-MSCs exhibited impeccable capacitance retention of 99.7 % after 6,000 operation cycles and impressive stability upto 10,000 bending cycles, making them promising energy storage solutions for flexible and wearable devices. [ABSTRACT FROM AUTHOR]

Roll-to-roll printed electronics (R2RPE) is a low-cost and high-efficiency manufacturing method for high-density circuits printed on flexible substrates. Stable web tension control is essential for excellent printing quality. However, due to many uncertainties in terms of the model errors, roll machining errors, and external disturbances, etc., it is difficult to guarantee the tension control accuracy especially for conventional control methods. For this purpose, a nonlinear model predictive control (MPC) scheme is proposed to eliminate the tension disturbance of the R2RPE system. The dynamic model of the unwind roller is firstly established, and then the factors affecting the web tension are analyzed. The nonlinear dynamic matrix control (NDMC) based on an auto-regressive and moving average (ARMA) model is introduced to eliminate the tension disturbance. To evaluate the effectiveness of the proposed control method, the tension controls using the traditional proportional-integral-derivative (PID), fuzzy PID and proposed NDMC are simulated with MATLAB for performance comparisons. Finally, an R2RPE prototype is fabricated for performance tests. The experimental results validate the effectiveness of the proposed control scheme. Keywords: Roll-to-roll printed electronics, web tension control, dynamic modeling. • A nonlinear tension control is proposed to eliminate the tension disturbance of a roll-to-roll printed electronics system. • The proposed tension control only takes the easily collected tension signal as feedback. • The dynamic model of the unwind roll is established by considering the varying radius and inertia moment. • Experiments verify the effectiveness of the proposed method in controlling tension and suppressing disturbances. [ABSTRACT FROM AUTHOR]

Micro-drop ejection technology has been widely employed in cell analysis, drug delivery, microreactors, and various other fields due to its high accuracy and resolution, which can accurately control and dispense liquid materials. However, the current development of this technology faces challenges due to nozzle diameter limitations. Smaller droplets require finer nozzles for ejection. Nevertheless, fine nozzles cause significant fluid resistance, hindering micro-droplet ejection. Overcoming the constraint posed by nozzle and achieving high-precision micro-droplets ejection has become a challenging task for the industry. Inspired by the phenomenon of cavity collapse in nature, we have developed a micro-droplet ejection technology based on actively controlling the cavity collapse within the confined interface. By analyzing the formation and collapse of the liquid cavity, we have identified three ejection modes: no droplet, single droplet, and satellite droplet, and further delineated the boundary conditions for minimizing droplet size and ejecting satellite-free droplets. Using this technology, we achieved precise control over droplet size within a defined range, with the minimum droplet diameter reaching 34 % of the nozzle diameter. Furthermore, the continuous ejection of single droplets demonstrated excellent stability and repeatability. This innovative technology could provide a novel approach to achieve high accuracy and controllability in micro-droplets ejection, liberating it from nozzle constraints, thus expected to play a significant role in the fields of biomedical research, chemical engineering, and printed electronics. [Display omitted] • Proposed an innovative droplet ejection technique combining precise piezoelectric control with cavity collapse principle. • Identified three ejection modes and defined conditions for minimizing droplet size and eliminating satellites. • The minimum droplet size for controlled ejection is only 34 % of nozzle diameter. • Continuous micro-droplet ejection has excellent stability and repeatability. [ABSTRACT FROM AUTHOR]

The advent of flexible single-walled carbon nanotube thin-film transistors (SWCNT-TFTs) has transformed electronics, providing significant benefits like low operating voltage, reduced power consumption, cost-effectiveness, and improved signal amplification. This study focuses on leveraging these attributes to develop a novel flexible high-sensitivity and energy-efficient chloride ion sensors based on printed flexible SWCNT-TFTs utilizing polymers-sorted semiconducting SWCNTs (sc-SWCNTs) as the active layers and ion liquids-poly(4-vinylphenol as dielectric layers along with the evaporated deposition of aluminum electrodes and printed silver electrodes as the gate and source-drain electrodes, respectively. The sensors exhibit several operational advantages, including low voltage requirements (≤1 V), rapid response speed (5.32 s), significant signal amplification (Up to 702.6 %), low power consumption (0.31 μJ at 1 mmol chloride ion), good repeatability, high sensitivity for both low and high concentrations of chloride ion (up to 100 mmol/L) and excellent mechanical flexibility (No obvious changes after bending for 10,000 times with a 5 mm radius). The detection mechanism of chloride ions was analyzed using X-ray Photoelectron Spectroscopy (XPS). It was found that chloride ions react with silver nanoparticles (AgNPs) to form silver chloride (AgCl) on printed electrodes, impeding carrier transport and reducing the currents in SWCNT TFTs. Importantly, our sensors' compatibility with smart devices allows for real-time monitoring of chloride ion levels in human sweat, offering significant potential for daily health monitoring. High-sensitivity and energy-efficient chloride ion sensors based on flexible carbon nanotube thin-film transistors for real-time monitoring chloride ions in human sweat. [Display omitted] • Innovative design of high-sensitivity and energy-efficient chloride ion sensors. • Exhibiting rapid response speed and excellent mechanical flexibility. • Compatibility with smart devices for health monitoring applications. • Enabling real-time monitoring of chloride ions in human sweat. [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]

[Display omitted] • Co-based nanomaterials enabled inkjet-printed MSC with pseudocapacitance of 900 F‌/g. • Flexible MSCs employ highly stable ink on AgNW-modified paper with detailed pattern. • The areal capacitance of 35.7/23.6 mFcm−2 is achieved in symmetric/asymmetric device. • Robust cyclic and mechanical stability shows the potential for wearable electronics. Cobalt-based nanomaterials are among the most noticed candidates for manufacturing supercapacitive electrodes. Inkjet-printing is an emerging technique for fabricating miniaturized devices. In this work, highly flexible microsupercapacitors (MSCs) are manufactured, using a pseudocapacitive (C = 900 F‌ g−1 at 1 A g−1) Co-oxide-hydroxide water-based and ultra-stable (up to 12 months) ink on paper. The synthesized capacitive active material consists of cobalt-oxide nanocubes and cobalt-hydroxide hexagonal nanoflakes. Conductive (R s = 13 Ω/□) silver nanowire networks serve as current collectors, and the morphology of cobalt oxide-hydroxide structures and the developed ink features, allow for printing well-detailed and homogeneous patterns. The inkjet-printed symmetric and asymmetric devices show notable areal specific capacitances of 35.68 mF cm−2 and 23.60 mF cm−2 at a current density of 0.1 mA cm−2, respectively. The asymmetric devices deliver impressive energy and power densities of 2.76 μW h cm−2 (4.10 W h kg−1) and 646 μW cm−2 (959 W kg−1), respectively. A thorough study on the cyclic and mechanical stability of the flexible devices resulted in perfect capacitance maintenance of 94.3 % after 10,000 charge and discharge cycles and retention of over 80 % even after 1000 cycles of successive bending and folding. The extensive study of capacitance retention following folding under various obtuse and reflex angles, which can be regarded as an important step toward characterizing flexible devices suitable for being utilized in wearable electronics, is carried out for the first time to the best of our knowledge. The findings of this study clearly illustrate the prospects of using the inkjet-printing technique to fabricate high-performance MSC devices appropriate for integration with flexible and wearable electronics. [ABSTRACT FROM AUTHOR]

The emergent Internet of Things (IoT) market has increased the need of sensors, actuators and nanogenerators, demanding cost-effective and large-scale manufacturing methods to fabricate these devices. Printed electronics (PE), which consists of the application printing and coating technologies in the deposition of functional materials, is one of the ways to process low-cost lightweight, semi-transparent, and flexible devices, usually employing polymers as functional materials. In this work we present the fabrication of poly(vinylidene fluoride- co -trifluoroethylene) (P(VDF-TrFE)) copolymer-based printed piezoelectric devices applying different semi-transparent flexible conductive substrates as bottom electrodes. The screen-printing process was chosen as a large-scale cost-effective fabrication method at low-temperature processing. Printing and the laser scribing parameters were established, and the effectively use of silver and PEDOT:PSS as top electrodes was demonstrated. The final devices were electrically poled and characterized by Electrochemical Impedance Spectroscopy (EIS) and correlations among the device' performance regarding the different bottom and top electrodes were set up, leading to processing recommendations. Employing a cycle olefin polymer coated with silver nanowires (AgNW) as substrate, P(VDF-TrFE) as active material and silver as top electrode, a 223 µF/m2 capacitance was obtained when compressing at 2.37 KPa, demonstrating the devices charge storage capacity by the application of a mechanical stress. All the employed processing conditions can be easily integrated in a R2R pilot line, allowing high throughput, low-cost and large-area manufacturing. Additionally, the use of the polymer substrates enables the fabrication of flexible and lightweight devices. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper details how two new small molecules, based on phenanthrene, were developed, and tailored for light-emitting device applications. An account is provided of both the compound synthesis and the methodologies employed in device fabrication. The ink formulation was improved by the use of triflate counterions. Standard bottom emitting devices were constructed on ITO glass along with top emitting devices on a sputter coated silver on glass substrate. Both structures exhibit UV emissions from the synthesized molecules. Successful EL emission within the UV spectrum range has been achieved by spray coating these active molecules onto glass slides. The optimized solution-processed devices produce UV emission using a semi-transparent silver nanowire top electrode. This results in electroluminescence (EL) peaking at 398 nm, with a maximum EL emission intensity of 20.5 μW/cm2. [Display omitted] • Synthesized two novel UV light-emitting organic materials achieving high electroluminescent intensity of 20.5 μW/cm2. • Spray coating process suitable for top emitting OLECs with AgNW top electrodes demonstrated. • Hexyl imidazolium moiety enhances solubility and enables uniform spray-coated thin films without aggregation or pinholes. [ABSTRACT FROM AUTHOR]

• Micro-flaky gold particles were fabricated by directly chemical reducing method. • The flaky gold powder can improve the joining between the spherical gold powder. • Conductivity and sintering density of gold paste was improved remarkably. In this study, the gold precursors were rapidly reduced by hydroxy compound and micron-sized flaky gold powder was obtained under hydrothermal conditions. Isopropyl alcohol was selected as solvent and reducing agent after investigating the effect of reducing agent on the morphology of the gold powder. The influence of reaction concentration and temperature on the particle size and morphology of gold powder were researched. By controlling the reaction concentration and temperature, the prepared gold particles have regular flaky structure with the diameter of about 5 μm and the sintered gold conductor paste shows excellent conductivity and sintering density. [ABSTRACT FROM AUTHOR]

[Display omitted] • A kind of red hyperbranched conjugated polymers with four arms were designed and synthesized. • Hyperbranched polymers exhibited effective energy transfer and excellent thermally activated delay fluorescence character. • PFCz-(BZ-2Ac)50 had a maximum EQE of 4.88 % and a low roll-off (7 % decrease at 500 cd/m2). Wet-processable red luminescent materials with thermally activated delayed fluorescence (TADF) are essential in the field of printed electronics. Particularly, hyperbranched conjugated polymers with the advantages of large steric hindrance, effective energy transfer and good solubility had exhibited great potential application to prepare the high-performance solution-processed organic light-emitting devices, but it is still a great challenge. In this work, a novel kind of red hyperbranched conjugated polymers PFCz-(BTZ-DMAC)n (n = 1, 2, 10 and 50) were designed and synthesized using D-A-D-typed BTZ-DMAC as the red TADF cores and poly(fluorene-carbazole) as the backbone. The polymers owned more effective energy transfer process and reverse intersystem crossing that could simultaneously and effectively utilize the singlet and triplet excitons. The polymers also exhibited good thermal stabilities and film forming properties. At the same time, electroluminescent emission (about 650 nm) prominently enhanced and had an obvious red-shift with the increasing concentration of red cores. In the non-doped devices, PFCz-(BTZ-DMAC)50 with 50 mol‰ content of red TADF cores showed the best electroluminescent performance that a red chromaticity coordinate of (0.59, 0.39) and a maximum external quantum efficiency of 4.88 % were obtained. More importantly, it exhibited the low roll-off (7 % decrease at 500 cd/m−2) owing to the large steric hindrance. All results revealed that red TADF hyperbranched conjugated polymers had potential application for preparing the high-quality solution-processed organic light-emitting devices. [ABSTRACT FROM AUTHOR]

This paper presents an off-line programming approach for the automatic generation of trajectories and the printing program for a 6-axis robot in order to print accurate conductive paths on 3D objects using a silver microparticle solvent-based ink. The aim of this study was to develop a semi-predictive model in order to - Adapt the printing parameters of a 6-axis robot arm and a piezo jetting print head to the printing speed and substrate type. - Print 3D electronic circuits matching the targeted geometry and conductivity. For the jetting printing process, 2D patterns printed on substrates with different roughness and wettability were analysed as a function of the print head translation speed and jetting frequency which were used as base variables to develop correlations in order to predict line width, thickness and conductivity. The model was based on the assumption that the behaviour of a single drop impacting the printing substrate is close to that of a train of drops (i.e. lines). Thus, the diameter of individual drops on a specific substrate was used to account for support properties and jetting conditions. The study also proposes a methodology to tune the circuit morphology by adapting the jetting parameters as a function of the trajectory and the speed of the 6-axis robot. As a representative case study, a 3D circuit was printed on a disposable paper cup obtaining an excellent agreement between measured and predicted conductivity values. [ABSTRACT FROM AUTHOR]

The use of hydrogen as a clean and renewable energy source is increasing rapidly for both vehicle and stationary applications. There are safety concerns for the locations in which hydrogen is made, used, and transported (i.e., pipelines and tanker trucks). Sensors are needed to comply with safety regulations and to enable a smooth and safe rollout of hydrogen as an alternative energy. However, hydrogen sensors do not yet exist that have the combined features of small size and low power for easy deployment coupled with high-volume manufacturability and low cost. This is necessary to accommodate the emerging fixed and mobile markets while retaining critical metrological metrics, including measurement range, detection limits, selectivity, fast response, stability, and long lifetime. An amperometric gas sensor for hydrogen (AGS) has been developed using an innovative manufacturing method. The sensor was designed using scalable fabrication strategies based on "Printed Electronics" (PE) methodology which are compatible with large-scale production. Prototype sensors were batch fabricated with multiple individual elements on a substrate compatible in size with a standard 8-inch wafer to enable high-volume, low-cost manufacturing, thereby leveraging PE and semiconductor fabrication infrastructure. This novel AGS was instrumented with control circuitry and evaluated for hydrogen detection in the range of 0–5000 ppm v H 2 in air. Specific performance evaluations included assessment of the sensor measurement range, repeatability, and selectivity. [Display omitted] • Characterization of an electrochemical sensor for bridging the Cost-Performance Gap. • A low-cost/power H2 sensor is characterized in environmental and interferent tests. • An improved electrochemical H2 sensor is compared with other sensing technologies. [ABSTRACT FROM AUTHOR]

[Display omitted] • An alternating layered structure of CNT and GaInCu alloy (GCLA) is proposed. • Fibers with wrinkled GCLA layer show extremely high stretchability and conductivity. • Wrinkled GCLA layer enables fiber to achieve stable conductivity during stretching. • The GCLA structure can be patterned on hydrophilic and hydrophobic substrates. Liquid metal (LM) composites, known for their excellent conductivity and fluidity, hold great promise in the fields of printed electronics and wearable technology. However, their high surface tension and fluidity can lead to circuit instability, such as leakage during deformation, resulting in short circuits. Therefore, additional methods are necessary to enhance the stability of LM within composite material systems. In this paper, Carbon nanotube (CNT) was introduced as a transition layer to enhance the adhesion of gallium-indium-copper-alloy ink (GCLA) on different elastic substrates and to obtain interface fusion conductive layers. The modified GCLA conductive fibers achieved high conductivity (conductivity up to 3.13 × 105 S/m), ultra-stretchability (1580 % of ultra-large deformation, the resistance changes less than 3 Ω), and ultra-stability (within 200 % of large deformation, the change of resistance less than 1 Ω). In addition, we also demonstrated the operability of GCLA in forming patterns on hydrophilic and hydrophobic substrate surfaces and obtained conductive patterns through printing, transfer printing, and hand drawing, making it a promising candidate for flexible electronics. [ABSTRACT FROM AUTHOR]

We explored a novel design-for-recycling method for encapsulated printed electronics in an injection-molded package that improves disassembly at End-of-Life (EoL). To this end, a non-adhering disassembly layer (NADL) was applied onto the printed circuitry and light-emitting diodes prior to injection molding. Surprisingly, the devices with a disassembly layer remained fully functional after injection molding, despite exposure to high shear forces and elevated temperatures. Facilitating the disassembly of an encapsulated electronic device using a weak link in the adhesion strength of the overmolded encapsulant invokes a contradiction: the possibility to remove the injected plastic from any underlying coating goes against the requirement of high adhesion over the entire surface area for structural strength and integrity during the harsh conditions expected by industry. To achieve balance between disassemblability and reliability, the adhesion strength of the overmolded encapsulant was tuned using vias in the coating design. To the author's best knowledge, this is the first time design-for-recycling principles were successfully applied to such in-mold structural electronics devices. Accelerated lifetime tests at 85 °C/85% relative humidity for 1000 consecutive hours were conducted to study the reliability of devices realized with this design-for-recycling method. Mechanical disassembly of molded devices proceeded uniformly along the intended interface of NADL with molded polycarbonate resin and exposed the printed Ag and surface-mounted components, thereby demonstrating the possibility to perform subsequent and dedicated recycling on plastics and metals separately. • Dismantlable printed electronics; design-for-recycling method using non-adhering dismantling layers. • Adhesion of injection-molded polycarbonate made tunable by coating design. • Trade-off between recyclability and reliability; promising outcome for water-based non-adhering dismantling layers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metalloid nanoparticles (MNPs) of Mg–C and graphene fabricated via laser ablation. • Metalloid Mg–C nanoparticles inkjet printed for paper electronics. • Laser ablation used to alter the size and chemistry of nanoparticles after synthesis. Metalloid nanoparticles (MNPs) possess unique physicochemical properties but are challenging to create through biological or chemical routes. Using Pulsed Laser Ablation in Liquid (PLAL), Mg–C MNPs are fabricated from powders. The produced nanocolloids were ablated after the target was removed to tailor the particle size. MNPs with a mean size 300 nm could be reduced to 60 nm. Alternatively, MNPs with a mean size of 60 nm could be increased to 90 nm. The increase/decrease in size is controlled by the laser processing parameters and showcases the ability of PLAL for real-world applications that require meticulous control of size. The as-fabricated nanocolloids were successfully inkjet printed on paper, achieving a low resistivity of 75 Ω/square after 60 prints, highlighting their potential in printed electronics. To address a historical research gap, this article explored the impact of PLAL processing parameters, including fluence (1–2 J/cm2), pulse width (0.2–0.9 ns), repetition rate (10–20 kHz), and pH, factors often overlooked which is partly limiting applications. The influence of powder vs rod target on the PLAL process was addressed revealing that powders produce better size control and are easier to handle but they produce lower colloid concentrations. [ABSTRACT FROM AUTHOR]

In this study, we fabricated a thin-film light-emitting device to apply metronomic photodynamic therapy (PDT) in a weak light emitted by LED chips that showed the PDT effect at the cellular level. Thin-film light-emitting devices can operate an LED chip by the wireless power supply. This device has been developed by exploiting a flexible antenna coil made from Au nanoparticle ink printed on a 5-μm-thick poly(D, L-lactic acid) thin film. The weak light intensity of LED (10∼400 µW/cm2) can direct the cell death regions. Further quantification of mPDT at the cellular level as well as in vivo evaluation, will be carried out. [ABSTRACT FROM AUTHOR]

[Display omitted] • Permalloy nanoparticles are synthesized and made into a syringe printable ink with polyethylene glycol and glycerol in water. • Stability of permalloy nanoparticles with two different diameters is explored using various polymer coatings. • An inductor core is made by printing and drying the ink with a final concentration of > 35 vol%. Additive manufacturing has the potential to fabricate custom parts with complex shapes. For syringe printing, there is a possibility for printing filaments consisting of different materials on a single tool. Additively manufactured electronics is a major field of investigative research, where filaments contain nanoparticles to tailor properties, such as metal to improve magnetic permeability. This study investigates syringe printing parts with high magnetic permalloy (Ni 80 Fe 20) nanoparticle content (>35 vol%) and the properties of inductors printed from these inks. Two different metal alloy particle sizes of 250 nm and 30 nm are synthesized to observe the effect of particle size on stability. Zeta potential and settling behavior are observed to discern how coating procedures enhance particle stability in water. Permalloy nanoparticle inks are concentrated with polyethylene glycol (PEG) to increase viscosity and glycerol to decrease evaporation rates while printing. It is found that PEG and glycerol stabilize 30 nm permalloy nanoparticles in addition to increasing ink viscosity. Permalloy nanoparticle inks are printed into toroid shapes demonstrating the feasibility of fabricating useful three-dimensional magnetic structures. These inductors exhibited an inductance of 180 nH at 30 MHz. [ABSTRACT FROM AUTHOR]

The relentless advancement in nanomaterials and their concomitant micro- and nanoelectronic device technologies have engendered profound transformations within the domains of information technology, energy systems, and biomedicine. This progression is galvanizing the imminent realization of large-scale production for wearable, sustainable, and autonomously functional micro-nano-electronic systems. Amongst these novel technologies, Triboelectric Nanogenerators (TENGs) have emerged as a pivotal avenue for harnessing mechanical energy with remarkable energy conversion efficiency, compact device dimensions, robust longevity, and intrinsic compatibility with wearables and implantables. Such attributes render them highly promising for integration into micro-nano-systems. Despite the notable strides witnessed in the domain of friction nanomotors over the past decade, a formidable technical hurdle persists concerning their seamless integration with printed electronics and self-powered systems. This article undertakes a comprehensive critique of the research progression pertaining to printed TENGs employed as energy harvesting units to empower ancillary devices. The authors provide an evaluative overview of recent advances in the field of printed wearable nanomotors, as well as describe advances in printed electronics for the preparation of TENGs, the development of functionally customized e-ink materials for application to TENGs, and synergistic combinations of TENGs as energy harvesting mechanisms in composite device architectures. In conclusion, the discourse culminates with an appraisal of the challenges poised to the functionalization of printed TENGs, while concurrently discerning the latent opportunities that underpin their future trajectory within this dynamic paradigm. [Display omitted] • Analysis of pros and cons in various printed electronics techniques for TENG fabrication. • A comprehensive review of different material inks for the preparation of TENG was conducted. • Application and preparation of printed TENG in micro- and nanoelectronic systems. • Current challenges and future trends in printed TENG are discussed. [ABSTRACT FROM AUTHOR]

• Flexible solution-processed Organic Photovoltaics successfully produced and scaled-up. • Thicker active layer films leading to high indoor performances. • Fundamental role of layer's uniformity for high-indoor performances. • Importance of low light intensities study when evaluating devices for indoor applications. • The need of an in-depth study of Organic Photovoltaics structure dedicated to low light conditions. The recent development of 5G networks has enabled the internet of things (IoT) to emerge as a key factor in the growing global data network. For the IoT, not only are sensors required, but also alternative ways to supply them with the energy they need. Organic photovoltaics (OPV) are a promising solution for energy harvesting and self-generation for low-consumption sensors since they have excellent physical, optical and electrical properties, including being lightweight, having shape freedom, broad-range absorption spectra, semi-transparency, and they are highly efficient even in extremely low-light environments. Here, we report, encapsulated OPV module optimized for indoor applications delivering 18% power conversion efficiency (PCE) under 400 lx LED illumination. All modules were fabricated and encapsulated in air using totally scalable roll-to-roll (R2R) slot-die coating and screen-printing methods made on flexible substrates with non-toxic solvents. [ABSTRACT FROM AUTHOR]

In roll-to-roll continuous printing, given the limitations in the pattern engraving technique and the need for accurate contact angle control between the ink and substrate, printing fine lines in the 10-μm scale is a major hurdle that needs to be addressed to achieve mass production of printed electronic devices. To address this issue, we propose a novel printing method based on gradation engraving; this method allows for both greater control over the width decrement of printed patterns as well as narrower fine lines than those achieved using an engraved pattern in the printing roll. Our experimental results show that, using the proposed method, printed line widths could be decreased according to the curvature of the sidewall of the engraved cell, even in the same aspect ratio. Furthermore, the width of the printed pattern was decreased by up to 62%, as compared to that achieved via the engraved cell, and a fine printed line narrower than 10-μm could be achieved. The proposed method represents a suitable alternative for the fabrication of 10-μm, or even thinner, fine conductive lines via the roll-to-roll continuous printing process. • Novel method to control decrements in printed pattern widths is presented. • The method is based on the behavior of ink in different pattern depth profiles. • Printed lines 62% narrower than their engraved patterns could be achieved. • 10-μm, or even narrower, fine lines were achieved using this method. • This study represents a breakthrough in printing conductive lines via R2R printing. [ABSTRACT FROM AUTHOR]

The development of graphene-based materials with good light-curing ability and excellent electrical conductivity is the key to next-generation electronic devices. Herein, we demonstrate the molecular structure modification of photocurable graphene oxide (PGO) by reacting hydroxyl groups with isocyano groups, which is referred to as grafting of the photosensitive group on pristine GO, resulting in photosensitive PGO flakes that can be photocured during 3D printing using water as a solvent and a developer. Complex-shaped and highly precise 2D and 3D structures of GO as well as thin single-layer or few-layer GO films are obtained by optimizing the concentration and photocuring parameters of the PGO precursor. After thermal reduction of PGO microarchitectures, the reduced cross-linked GO (rCGO) exhibits a minimum square resistance of 213.74 mΩ sq−1, which is similar to that of graphene. Moreover, rCGO demonstrates excellent cell compatibility during cell culture experiments and superior hydrophilicity. The latter property can be exploited to prepare solution-based detection electrodes. The proposed strategy is used to print circuits and 3D bulk conductors, and can facilitate the formation of various electronic devices via photocuring 3D printing or photolithography process. [Display omitted] [ABSTRACT FROM AUTHOR]

• Copper nanoparticles covered by surfactant molecules prepared from CuO particles. • Beads milling was applied and the conditions to obtain highly dispersed paste. • The optimized condition of the beads milling is 1000 and 2000 rpm for 30 min each. • Excess milling resulted the formation of very large fused copper particles. Copper paste is considered as a promising candidate for printed electronics in replacement for silver paste. This is owing to copper which has anti-electromigration property, lower cost, and similar conductivity and compared with silver. We synthesize a copper nanoparticle (NP) paste that can be sintered at low temperature for high conductivity. The copper NP paste composes of 50 wt% copper NPs and dipropylene glycol (DPG) as the disperse medium. The effect of DPG coating and various conditions of milling with small beads on improving the dispersity of copper NPs has been investigated. The optimum conditions for milling are at 1000 and 2000 rpm for 30 min. This results in a volume resistivity of 6.62 × 10-6 Ω·cm after sintering the copper NP paste at 200 °C. [ABSTRACT FROM AUTHOR]

Flexographic printing, which involves high-speed contact of an inked stamp against a substrate, is of increasing interest for scalable manufacturing of electronics in new formats. However, the adaptation of flexography to thinner, finer features which are generally required for printed electronics requires improved understanding of stamp-substrate contact mechanics. Here, we present a desktop plate-to-roll (P2R) printing apparatus which enables the study of flexographic printing in a semi-continuous format that mimics industrial printing. In particular, we tailor the specifications of the machine to use nanoporous stamps which have been shown to enable flexographic printing of ultrathin ink features with micron-scale linewidth. Printing with nanoporous stamps requires precise control of stamp-substrate contact force (2–250 mN) and elimination of shear force at the interface among others; these are accomplished using a flexure-supported substrate, and by coordinated rotary-linear motion of the system. We detail the design and evaluation of the P2R machine and demonstrate printing of high-resolution features (<3 μm line width) with nanoporous stamps at speeds of up to 0.2 m/s. • A desktop plate-to-roll printing apparatus for flexographic printing. • Printing with nanoporous stamps by precise stamp-substrate contact force application and elimination of shear. • Flexure based contact force application and coordinated rotary-linear motion. • High-speed (>0.1 m/s) printing of high-resolution (<3 μm) features. [ABSTRACT FROM AUTHOR]

Printed Electronics (PE) involves additive deposition of functional materials on a substrate via printing processes to realize electronic circuits, interconnects, electrical components or devices. This methodology is opposite to the conventional microelectronics industry which is based on subtractive manufacturing techniques (e.g. etching). Some of the advantages of PE over conventional electronics are low prototyping costs, short time to market, less processing steps, etc. One of the features is the ability to manufacture flexible and customized products and devices. The applications of Printed Electronics apply to different sectors of industry like electronics, packaging, bio-medical, automotive, communication, etc. In this work, we present Aerosol Jet® Printing (AJ®P) and Screen Printing as two techniques for the realization of flexible and mass customized PE devices. Whereas the use of AJ®P is focused on rapid prototyping, Screen Printing allows to upscale for mass production. The two technologies are here implemented to realise conductive antennas on paper substrates, potentially to integrate into a delivery parcel box for the development of "smart packaging". This antenna design is based on the 13.56 MHz working frequency, which lies in the frequency spectrum of HF RFID/NFC applications. The print quality, electrical resistance and the basic functional characterization (working frequency) of these paper-based antennas are here investigated and reported. [ABSTRACT FROM AUTHOR]

There is great interest in carbon-based printed electronics as a promising technology to achieve lighter, thinner and flexible electronic devices at low-costs. Despite the surge of enthusiasm in this area, research advances in printed electronics are not yet able to realize diverse carbon structures yet. This is due to the limitations in conventional solution-based printing methods (e.g., inkjet printing, roll-to-roll, screen printing). Processes such as polymer phase-inversion offer one possibility but a much faster and efficient method should be devised for reliable production. Here, we demonstrate laser printing combined with intense pulsed-light (IPL) annealing as a novel and efficient technique which can form inter-connected carbon spheres electrode on flexible polymer substrate. Our observations show that the printed patterns from a laser printer consist of a solid-state polymer matrix with inorganic nanoparticles randomly embedded inside. Through ultrafast (5 ms) IPL treatment, core/shell type nanosphere arrays of carbon-coated SiO 2 were successfully fabricated, which could be used as a functional platform for highly selective NO 2 gas sensing. Image 1 [ABSTRACT FROM AUTHOR]

Electrochromic devices (ECDs) with reversible transmittance change represent a promising alternative to smart windows. However, the low−cost facile fabrication of ECDs, particularly flexible devices, remains challenging. In this study, novel NiO is synthesized by a solid state method, and the as−prepared NiO is introduced as an electrochromic anodic layer and fabricated onto a transparent conductive electrode (indium tin oxide, ITO or flexible silver nanowires, AgNW) by a sol–gel spin coating and low temperature annealing (80 °C-150 °C). The solvent, thickness of NiO, and annealing temperature are evaluated to obtain higher ECD performance. NiO/ITO ECDs exhibit very high transmittance variation (ΔT = ~84%) at 700 nm with applied potentials of −3.0 and 0 V. The stability and transmittance variation of NiO/ITO are significantly improved in the presence of a WO 3 cathodic electrode at lower applied voltages of 1.5 to 0 V. The low processing temperature of 80 °C demonstrates the potential of the flexible ECDs. The flexible NiO–WO 3 device achieves a transmittance variation of ~38% at 700 nm with applied potential of 2.0 and 0 V, and retains the ECD performance. The application of low−cost solution−processed NiO and NiO/WO 3 −based ECDs in flexible transparent conductive electrodes provides a new pathway for the fabrication of optical devices and printed electronics. NiO−based ITO and flexible devices are successfully developed from low-cost sol−gel spin-coating of NiO powder, which is prepared by a facile solid state method. The EC performance and stability of the flexible NiO device are significantly improved in presence of the WO 3 cathodic electrode at low voltage demonstrating the NiO/WO 3 as a potential flexible device for smart windows and optical devices. Image 1 [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]

Nanomaterial networks are attractive for a diverse range of printed device applications including electronics, sensing, energy capture and storage. At present, the influence of morphology on the network properties, such as electrical transport, is poorly understood. Here, we develop an understanding of structure-property relationships in these systems by performing size selection from bulk to few-layer graphene. We observe size-dependent electrical conductivity spontaneously during film formation, with the smallest nanosheets realizing electrical conductivity exceeding 105 S/m, a record value for liquid-exfoliated graphene and competitive with electrochemically-exfoliated graphene. Given the high electrical conductivity exhibited by these networks, and the applicability of graphene as a model layered nanosheet system, we explore the use of this size-selected graphene for thermoelectric applications. We interpret our understanding of the high conductivities obtained in terms of nanosheet packing and its influence on the number density and nature of inter-sheet junctions. This work represents an approach to overcome junction-limited electronic transport and enable nanoparticulate networks for printed device applications. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Robust packaging of printed flexible electronics (PFEs) to enhance their durability and reliability is still a major challenge. • Traditional polymer-based dielectric materials lack the required functionality to provide long-term adhesion and barrier protection to PFEs. • Novel cold atmospheric plasma (CAP) technology facilitates the deposition of SiO x (silica) coating under atmospheric conditions. • CAP deposited silica coating with optimum thickness serves as an effective intermediate layer enhancing adhesion and barrier properties of dielectric encapsulating materials. The ubiquity of printed flexible electronics (PFEs) spans diverse sectors, from healthcare to automotive, aerospace, agriculture, and consumer electronics, owing to their low cost, lightweight, flexibility, and conformability. However, addressing the critical challenge of ensuring robust packaging to enhance the durability and reliability of PFEs remains imperative. The limitation lies in the functionality of traditional polymer-based dielectric encapsulants, resulting in weak bonding between electrical components on the circuit and the encapsulant. As a consequence, when PFEs are exposed to harsh environmental conditions, water condensation occurs at the interface, leading to device failure. While hybrid multi-layer inorganic and organic encapsulation methods have demonstrated promise in providing robust packaging for electronic devices, the required deposition of inorganic coatings involves complex, time-consuming, and costly processes, rendering them unsuitable for scalable manufacturing of PFE devices. To address this challenge, a novel approach is investigated using cold atmospheric plasma (CAP) technology for the deposition of SiO x coatings as an intermediate layer between the printed circuit and the dielectric encapsulant coating. This effective intermediate layer promotes adhesion and enhances barrier properties of commonly used polymeric coatings in PFE devices. The CAP method enables selective deposition of high-quality and consistent SiO x thin films onto desired substrates under atmospheric conditions. Through a systematic study of CAP deposition conditions, the optimum thickness (∼820 nm) of the SiO x coating was determined, providing the required functionality to enhance barrier properties for corrosion protection of printed circuits while maintaining high mechanical flexibility. A remarkable 105-fold improvement in corrosion protection properties was observed through accelerated corrosion protection tests in saline water with the developed hybrid inorganic–organic coating process, compared to traditional encapsulation without the SiO x intermediate layer. As a proof-of-concept, the improved packaging of printed antennas, typically used in automobile rooftop shark fin applications, is showcased, highlighting the utility of the developed process in creating fully functional PFEs capable of reliable operation in harsh environmental conditions. This research represents a significant advancement towards scalable and cost-effective manufacturing of high-performance and reliable PFEs, introducing new possibilities for a broad range of applications. [ABSTRACT FROM AUTHOR]

• MXene composite materials were prepared with classical hydrothermal method. • MXene composites were used as the performance enhancers for conductive adhesives with silver-coated copper fillers. • The addition of the two-dimensional V 2 CT x composite connects the originally point-contact and disconnected Ag-clad Cu. 2D V 2 CT x was modified with Ag+ and rGO and doped into Ag copper-plated powder as a conductive filler to improve the conductivity of the conductive adhesive. The incorporation of 2D V 2 CT x composites connected the dispersed Ag copper-plated powder to form an effective conductive pathway. And as the content of 2D V2CTx composites increases, the resistivity of the epoxy conductive adhesives (ECAs) first decreases and then changes in an increasing trend. This is mainly because the right amount of 2D V 2 CT x can be established in conjunction with Ag copper-plated powder to form a conductive network inside the epoxy resin, but the increase in 2D V 2 CT x composite will accumulate in the epoxy resin, which in turn will impede the transmission of current, the resistivity can reach a minimum of 6.84 × 10-6 Ω·m. [ABSTRACT FROM AUTHOR]

Patients on long-term anticoagulation therapy require frequent testing of prothrombin time/international normalized ratio (PT/INR) to ensure therapeutic efficacy. Point-of-care (POC) PT tests for at-home monitoring eliminate the burden of visiting the clinic, but realizing a cost-effective and robust at-home POC test for PT has remained elusive. Recent demonstrations of printed PT sensors show promise for addressing the cost concerns; however, the printed sensors have lacked quality control to ensure reliability between tests. In this work, on-chip redundancy is introduced with fully printed impedimetric PT sensors by incorporating simultaneous testing with a single fingerstick volume of blood (8 µL). The influence of electrode dimensions and composition were studied, revealing an optimal electrode spacing of 200 µm and an unexpected dependence on the morphology of the electrodes. Three distinct silver morphologies were studied: aerosol jet printed silver nanoparticles (AgNPs), aerosol jet printed silver nanowires (AgNWs), and evaporated silver (Ag). In general, AgNPs exhibited the best PT sensor performance, due to relatively low conductance and high porosity. Overall, the printed impedimetric PT sensor functionalization was improved by incorporating simultaneous testing and, when combined with a handheld control device, shows promise for leading to a system that overcomes the challenges of commercial PT/INR coagulometers. • Fingerstick level volume of blood is proven capable for a printed PT test. • Novel 3-electrode design allows for on-chip redundancy for a printed PT sensor. • Relatively low-conductance and high-porosity Ag is ideal to not induce hemolysis. • Larger electrode gap width in sensor configuration reduces signal quality. [ABSTRACT FROM AUTHOR]

Sensing strategies adopting minimal electronic systems help in realizing REASSURED diagnostic tests. However, the challenge in developing such strategies escalates with demand in power and electronics during pursuit of reliable and accurate sensing. Herein, we present an electronic design strategy using a smart strip, operating with power generated from 3.5 μL of serum sample, to reveal glucose concentration through a response preserved in a capacitor. Further, by integrating an NFC tag alongside the strip, we devised a self-powered glucose measuring card, mobile-glucocard (or mGlucocard) for retrieving this stored digital response using smartphone, enabling 'connected mobile-health diagnostics'. The response from our device relates linearly to glucose concentration offering a sensitivity of 11.3 mV/mM and good correlation (R = 0.974) with colorimetric reference method. Interestingly, the design strategy uses only four components – two resistors, diode, and capacitor - of simple architecture likely transferable to printed technologies to deliver advanced self-powered sustainable devices. [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]

[Display omitted] • A facile and universally applicable additive copper patterning process was developed. • A prepared homogeneous Ag catalyst ink has virtues of granular and ionic catalyst. • Copper patterns with excellent electrical and mechanical properties were achieved. Additive strategy has been regarded as a promising approach for fabricating electronic copper patterns, since it has predominance over traditional lithography technology (subtractive strategy) in process simplicity, material economizing, and environmental protection. At present, the key challenge for additive strategy is how to precisely fabricate high-quality copper patterns adhering tightly to substrates, by facile and universally applicable process. Here a novel additive copper patterning process is explored by adopting a homogeneous Ag-based catalyst ink. The catalyst ink can be facilely patterned and tightly attached on various substrates by different patterning techniques, without any pre- and post-treatment procedures. In the catalyst ink formula, epoxy matrix contributes high adhesiveness and fixes ink form, valen Schiff base acts as a medium anchoring Ag catalyst, ethanol serves as both reductant and diluent, and polyethylene glycol improves hydrophility. The copper coating, forming on the catalyst layer by further electroless copper deposition process, exhibits compact structure and high electrical conductivity comparable to bulk copper. Moreover, the copper coating can be partially inserted into substrate body by porous surface design for substrates, thus achieving strong adhesion and high flexibility. This research contributes to the progress of next-generation copper patterning techniques. [ABSTRACT FROM AUTHOR]

The growing concern and demand for food safety in society dictate the necessity of developing intelligent portable devices for monitoring the whole food process from production to table. The development of flexible printed electronics provides one of the most promising paths for this challenge, as this technology brings together the unique advantages of various important technologies. Today, various specific products based on flexible printed electronics have been successfully developed, such as flexible printed sensors and radio frequency identification systems, which are excitingly able to meet various requirements for food safety, including ingredient detection, environmental monitoring, logistics tracking, and anti-counterfeiting and anti-theft. However, the current flexible printed electronics technology is still not mature enough. This review comprehensively introduces the different kinds of flexible substrates, printable conductive materials, and printing technologies involved in flexible printed electronics technology with their respective advantages and limitations, and then focuses on the application of flexible printed electronics technology in food quality monitoring and intelligent food packaging in recent years, intending to provide the latest reference for the development of intelligent food safety control. [ABSTRACT FROM AUTHOR]

The future flexible sensor technology will require low-temperature, fast processing 3D printing techniques that will rely heavily on the quality of nanoparticle (NP) Ink. Electrical conductivity has been found to decrease in majority of the 3D printed electronic wires. Herein we report a fundamental understanding in drop of electrical conductivity in processed silver (Ag) line wire, generally found in Ag-nanoparticle Ink, using large-scale atomistic molecular dynamics (MD) simulations of sintering of five different sizes of Ag NPs. To preserve the high conductivity of pure silver wires, the integrity of the pristine face-centered cubic (FCC) crystalline structure must be retained in the processed line wires. Simulations show that the pristine Ag FCC structures of the nanoparticles are not recovered after melting and resolidification, instead, the resolidified material is paracrystaline. The breakdown of pristine FCC structures might be the cause of the drop in conductivity of processed Ag wires. Simulation results suggest that the intermediate size nanoparticles retain highest percentage of the pristine silver face-centered cubic (FCC) structure after pulse treatments. Our results show that the most promising Ag-Ink should contain smaller to medium size silver NPs that can retain FCC structure after 3D printing of the Ag-Ink. • MD simulation of sintering of two silver nanoparticles (NP) of sizes 10nm to 100nm show breakdown of pristine silver crystalline structure. • Smaller NPs melts at lower temperature than pristine silver due nanoscale confinement effect on melting. • Breakdown of pure silver FCC structure results in undesirable conductivity drop, not recommended for 3D printed electronics. [ABSTRACT FROM AUTHOR]

• High AgNO 3 concentration and reaction temperature increased yield of AgNPs and subsequently increased electrical conductivity of ink. • Increased AgNO 3 concentration and reaction temperature increased yield of AgNPs and electrical conductivity of ink. • PVP was an effective stabilizing and capping agent for AgNO 3 , leading to greater stability of AgNPs for up to 45 days. • Findings provide insights for development of stable and high-performance waterbased AgNPs conductive inks for various applications. Developing conductive inks for printed electronics has gained increasing interest in recent years as a low-cost and environmentally friendly alternative to traditional organic metal-based inks. This study aims to investigate the influence of silver nitrate (AgNO 3) concentration at different temperatures and the effect of polyvinylpyrrolidone (PVP) surfactant concentration on the properties of the colloidal silver nanoparticles (AgNPs) conductive inks. In this study, water-based AgNPs were prepared using a chemical reduction method. The effect of AgNO 3 concentration, the reaction temperature, and the amount of PVP as a stabilizing agent on the size, shape, and purity of the synthesized AgNPs was investigated. The stability, thermal characteristics, and functional groups of the water-based AgNPs were also evaluated. The printed AgNPs patterns were examined for morphological and electrical properties. Results indicated that the concentration of AgNO 3 and reaction temperature influence the size of AgNPs particles and their clustering. A high concentration of AgNO 3 results in a higher yield of AgNPs and subsequently increases the electrical conductivity to 2.69×10° S/m. Adding PVP improves the stability of AgNPs for up to 45 days. Therefore, the development of water-based colloidal AgNPs conductive ink in this study can be used in inkjet printing to fabricate environmentally friendly printed electronics. [Display omitted] [ABSTRACT FROM AUTHOR]