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Solution-processed, large-area, and flexible electronics largely relies on the excellent electronic properties of sp2 -hybridized carbon molecules, either in the form of π-conjugated small molecules and polymers or graphene and carbon nanotubes. Carbon with sp-hybridization, the foundation of the elusive allotrope carbyne, offers vast opportunities for functionalized molecules in the form of linear carbon atomic wires (CAWs), with intriguing and even superior predicted electronic properties. While CAWs represent a vibrant field of research, to date, they have only been applied sparingly to molecular devices. The recent observation of the field-effect in microcrystalline cumulenes suggests their potential applications in solution-processed thin-film transistors but concerns surrounding the stability and electronic performance have precluded developments in this direction. In the present study, ideal field-effect characteristics are demonstrated for solution-processed thin films of tetraphenyl[3]cumulene, the shortest semiconducting CAW. Films are deposited through a scalable, large-area, meniscus-coating technique, providing transistors with hole mobilities in excess of 0.1 cm2  V-1  s-1 , as well as promising operational stability under dark conditions. These results offer a solid foundation for the exploitation of a vast class of molecular semiconductors for organic electronics based on sp-hybridized carbon systems and create a previously unexplored paradigm.

Nowadays, additive manufacturing technologies have impacted different engineering sectors. Three- and four-dimensional printing techniques are increasingly used in soft and flexible electronics thanks to the possibility of working contemporarily with several materials on various substrates. The materials portfolio is wide, as well as printing processes. Shape memory polymers, together with composites, have gained great success in the electronic field and are becoming increasingly popular for fabricating pH, temperature, humidity, and stress sensors that are integrated into wearable, stretchable, and flexible devices, as well as for the fabrication of communication devices, such as antennas. Here, we report an overview of the state of the art about the application of 4D printing technologies and smart materials in electronics.

This text discusses the synthesis of copper nanoparticles via a liquid phase reduction method, using ascorbic acid as a reducing agent and CuSO4·5H2O as the copper source. The synthesized copper nanoparticles are small in size, uniformly distributed, are mostly between 100–200 nm with clear boundaries between particles, and exhibit excellent dispersibility, making them suitable for metal conductive inks. 1. The copper nanoparticles are analyzed for good antioxidation properties, because their surface is coated with PVP and ascorbic acid. This organic layer somewhat isolates the particle surface from contact with air, preventing oxidation, and accounts for about 9% of the total weight. 2. When the prepared copper nanoparticles are spread on a polyimide substrate and sintered at 250 °C for 120 min, the resistivity can be as low as 23.5 μΩ·cm, and at 350 °C for 30 min, the resistivity is only three times that of bulk copper. 3. The prepared conductive ink, printed on a polyimide substrate using a direct writing tool, shows good flexibility before and after sintering. After sintering at 300 °C for 30 min and connecting the pattern to a circuit with a diode lamp, the diode lamp is successfully lit. 4. This method produces copper nanoparticles with small size, good dispersion, and antioxidation capabilities, and the conductive ink prepared from them demonstrates good conductivity after sintering.

Manufacturing technology of ion-selective electrodes (ISEs) for pH measurements is presented. Plasticized polyurethane membranes with tridodecylamine as a pH-selective ionophore were used as receptor layer, whereas electrodes printed with graphene nanoplatelets paste served as transducers. For preliminary experiments, sensors with screen-printed transducers and pH-selective membranes deposited manually or by direct-ink writing, were employed. However, the use of aerosol-jet printing (AJP) technique for the production of transducer as well as deposition of pH-selective polymeric membrane allowed substantial miniaturization of the sensors, leading to low-cost, automated fabrication of millimeter-scale ISEs. The pH sensors were printed on thermoplastic polyurethane (TPU) or polyethylene terephthalate (PET) substrate, the issues of compatibility of membrane and substrate materials were addressed. The average membrane thickness for the ISEs was 225.2 ± 8.0 μm with an additional 20 μm average thickness of other underlying printed layers. The planar dimensions of ISEs were 300 μm (width) by 2 mm, presenting an opportunity for even further miniaturization. Sensors fully printed with the AJP technique yielded a potentiometric response of −53.48 ± 4.26 mV/pH (N = 69) for PET substrate and − 46.71 ± 10.23 mV/pH (N = 66) for TPU substrate. Presented results are important for developing a fully operational electronic tattoo suitable for large-scale manufacturing.

Abstract Temperature correction for sensors is a critical aspect of ensuring accurate measurements in wearable devices, because skin and sweat temperatures vary between 20 and 40 °C depending on individual and time. Here, this study reports on the temperature dependence and correction techniques of printed Na+, K+, and pH sensors toward wearable applications. The ion sensor array is fabricated using a cost‐effective printing method. To enable temperature correction, a printed thermistor of crosslinked poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is monolithically integrated with the ion sensor array on a flexible plastic substrate. Temperature dependence of the potential response of the printed ion sensors exhibits a linear behavior with a slope of 1–2 mV °C−1 in the physiological skin temperature range of 20–40 °C. Applying temperature correction to the ion sensors, the maximum relative errors are reduced from 60% to 7.8% for the Na+ sensors and from 76% to 14.6% for the K+ sensors, while the maximum absolute error is reduced from 0.88 to 0.19 for the pH sensors, indicating the critical importance of temperature correction as a technology for wearable printed ion sensors.

Drop-on-Demand additive manufacturing could offer a facile solution for scalable on-site manufacturing. With an increasing number of functional materials available for this technology, there are growing opportunities for applications, such as electronics. Here we report on a novel printing strategy, Off-the-Grid (OtG), which enables refined positioning of individual droplets and enhanced resolution compared to the traditional printing strategy. We demonstrate successful printing of structures with feature position control smaller than a single droplet size, and hence enhanced shape fidelity for intricate designs. This strategy is extended to filled patterns, enabling improved layer coverage and customisable inter-layer droplet positioning to control surface morphology. The OtG strategy is applied to produce functional designs, such as conformable circuitry and miniaturized antennae, and is transferable to different materials, from metal nanoparticle and polymeric inks on inkjet platforms, to molten metals on a MetalJet printer. These results could advance exploitation of AM in electronics, wearable electronics, medical devices, and metamaterials.

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.

Multi-material manufacturing through the hybridisation of printed electronics and additive manufacturing has gained great interest recently. However, such hybridisation attempts are not trivial due to the need for functional material development and compatible process identification, as well as further performance understanding, comprehensive characterisation and long-term reliability evaluation of multi-material parts. While some multi-material structures from functional materials such as silver inks have been demonstrated via the integration of direct writing systems into stereolithography or material extrusion platforms, the performance assessment and characterisation of parts manufactured using such integrated systems is still required. Therefore, this research presents a comprehensive assessment of multi-material structures manufactured using syringe deposition and material extrusion platforms. Test specimens were subjected to various characterisation activities such as thickness measurement, resistance measurement, roughness tests, wettability measurement, adhesion tests, and morphological analysis. Results and statistical analyses suggested that the dry thickness and conductivity of deposited films were dependent on the substrate material. Adhesion between the conductive film and substrate was affected by both substrate material and ink deposition angle. Also, the interaction of conductive films with polycarbonate substrate was found to be noticeably better among all substrates due to low resistivity and enhanced adhesion at low thicknesses.

Defects are a major issue in 3D printed electronics because even a tiny inaccuracy will lead to a faulty electronic circuit. This article presents a novel approach to correct printing defects with a neural network based automatic error correction. The errors are detected during printing by recording images of each wire with a high-resolution camera and segmenting the wires using convolutional neural networks. The neural network is trained with a dataset of printed wires with marked wire positions. A novel error detection algorithm then identifies connection breaks and generates repair paths for every connection break in the circuit, which are then executed by the printer. Multiple objects with deliberately inserted defects were printed and automatically repaired on different substrates using a Neotech AMT PJ15X printer to evaluate the performance. The algorithm detected all connection breaks, generated repair paths, and successfully repaired the faulty wires. This article also shows this approach's limitations and areas for future research, like complex circuits printed on 5-axis machines. The automatic error correction is highly reliable and is an important step towards a first-time-right production.

The generation of electronic waste (e‐waste) poses a significant environmental challenge, necessitating strategies to extend electronics' lifespan and incorporate eco‐friendly materials to enable their rapid degradation after disposal. Foldable electronics utilizing eco‐friendly materials offer enhanced durability during operation and degradability at the end of their life cycle. However, ensuring robust physical adhesion between electrodes/circuits and substrates during the folding process remains a challenge, leading to interface delamination and electronic failure. In this study, electrohydrodynamic (EHD) printing is employed as a cost‐effective method to fabricate the eco‐friendly foldable electronics by printing PEDOT:PSS/graphene composite circuits onto polyvinyl alcohol (PVA) films. The morphology and electrical properties of the printed patterns using inks with varying graphene and PEDOT:PSS weight ratios under different printing conditions are investigated. The foldability of the printed electronics is demonstrated, showing minimal resistance variation and stable electronic response even after four folds (16 layers) and hundreds of folding and unfolding cycles. Additionally, the application of printed PEDOT:PSS/graphene circuit is presented as a resistive temperature sensor for monitoring body temperature and respiration behavior. Furthermore, the transient features and degradation of the PEDOT:PSS/graphene/PVA based foldable electronics are explored, highlighting the potential promise as transient electronics in reducing electronic waste. [ABSTRACT FROM AUTHOR]

Aerosol jet printing is a technology particularly suited for additive manufacturing of functional microstructures, offering resolutions as high as 10 μm, broad compatibility for electronic nanomaterials, and noncontact deposition, making it compelling for device prototyping and conformal printing. To adapt this method from thin film patterns to taller features, both ink rheology and drying kinetics require careful engineering. Printing in a solvent-rich, low-viscosity state commonly results in a puddle, with liquid-phase spreading and susceptibility to instabilities, whereas printing solvent-depleted aerosol results in a granular morphology with high overspray. Here, we demonstrate a strategy to mitigate this trade-off by tailoring the evolution of ink rheology during the process, using a graphene ink containing the nonsolvent glycerol as an exemplar. During droplet transport to the nozzle, evaporation of volatile primary solvents increases the glycerol concentration, resulting in gel formation. This switch in the ink rheology between the cartridge and substrate maintains the print resolution at high deposition rates. Moreover, multiple layers can be printed in rapid succession to build up high aspect ratio microstructures, as demonstrated by continuously printed cylindrical pillars with diameters on the order of ∼100 μm and aspect ratios as high as ∼10. Finally, the efficacy of this ink formulation strategy for a CuO nanoparticle ink confirms the generalizability of this strategy for a broader scope of colloidal nanomaterial inks. In addition to its utility for microscale additive manufacturing of 2.5D structures, this strategy provides insights into higher deposition rate patterning to improve scalability and throughput of aerosol jet printing. [ABSTRACT FROM AUTHOR]

Organic electronics is an emerging technology that enables the fabrication of devices with low-cost and simple solution-based processes at room temperature. In particular, it is an ideal candidate for the Internet of Things since devices can be easily integrated in everyday objects, potentially creating a distributed network of wireless communicating electronics. Recent efforts allowed to boost operational frequency of organic field-effect transistors (OFETs), required to achieve efficient wireless communication. However, in the majority of cases, in order to increase the dynamic performances of OFETs, masks based lithographic techniques are used to reduce device critical dimensions, such as channel and overlap lengths. This study reports the successful integration of direct written metal contacts defining a 1.4 μm short channel, printed with ultra-precise deposition technique (UPD), in fully solution fabricated n-type OFETs. An average transition frequency as high as 25.5 MHz is achieved at 25 V. This result demonstrates the potential of additive, high-resolution direct-writing techniques for the fabrication of organic electronics operating in the high-frequency regime. [ABSTRACT FROM AUTHOR]

Neural electrodes for electrocorticography (ECoG) recording and electrical stimulation are used for diagnosis and treatment of epilepsy, which are temporarily attached to the surface of cerebral cortex within the subdural space. However, conventional electrodes have a mechanical mismatch with the surface curvature of the brain cortex. Thus, it is necessary to develop a thin and flexible ECoG electrode to overcome the mechanical mismatch with cortex tissue and achieve long‐term ECoG measurement. Herein, a flexible thin‐film electrode is reported with a thickness of ≈8 µm by exploiting printed electronics. A simple fabrication method of conductive wiring is proposed by inkjet printing Au nanoink on a flexible elastomeric thin film consisting of polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS). The conductive wiring printed on the SBS thin film is encapsulated by another SBS thin film as an insulation layer, with laser‐processed micropatterns. The flexible thin‐film electrode is implanted on the cortical surface of rats and used for in vivo ECoG recording and electrical stimulation without the occurrence of severe inflammatory reactions after 6 weeks of implantation. The flexible electrode with 35 ECoG channels visualized the epileptiform activity in a drug‐induced epilepsy rat model, which demonstrates the potential application for the management of intractable epilepsy. [ABSTRACT FROM AUTHOR]

Pad printing is not a widely used printing technique, but it offers the possibility of a simple, fast, and low-cost production of various high-resolution electrode structures. Here, the pad-printed reduced graphene oxide (rGO) electrodes are prepared from pad-printable inks containing rGO powder and different concentrations of two cellulose-based polymers: ethylcellulose and cellulose acetate butyrate. The applicability of rGO inks for pad printing is analyzed according to their rheological parameters and printability. Based on viscosity, storage (G0) and loss modulus (G00) values, 10wt% of ethylcellulose and 15 wt% of cellulose acetate butyrate appear to be most suitable for pad printing. The effect of polymer concentration on rGO electrodes homogeneity and mechanical stability is also evaluated. Cyclic voltammetry measurements for [Fe(CN)6]3-/4-redox system are performed with rGO/cellulose inks pad-printed onto transparent conductive oxide substrates with the best results when using ethylcellulose as a binder. Finally, the square-wave voltammetric method assesses the viability of rGO electrodes for the fast detection of ascorbic acid (detection limit of 15 µM) coupled with satisfactory precision (4.5%, n = 5) and long-term stability during electrochemical measurements. [ABSTRACT FROM AUTHOR]

The widespread adoption of renewable and sustainable elastomers in stretchable electronics has been impeded by challenges in their fabrication and lacklustre performance. Here, we realize a printed sustainable stretchable conductor with superior electrical performance by synthesizing sustainable and recyclable vegetable oil polyurethane (VegPU) elastomeric binder and developing a solution sintering method for their composites with Ag flakes. The binder impedes the propagation of cracks through its porous network, while the solution sintering reaction reduces the resistance increment upon stretching, resulting in high stretchability (350%), superior conductivity (12833 S cm−1), and low hysteresis (0.333) after 100% cyclic stretching. The sustainable conductor was used to print durable and stretchable impedance sensors for non-obstructive detection of fruit maturity in food sensing technology. The combination of sustainable materials and strategies for realizing high-performance stretchable conductors provides a roadmap for the development of sustainable stretchable electronics. Printed stretchable electronics with sustainable elastomers are typically limited by their electro-mechanical performances. Herein, Lv et al. report a sustainable vegetable oil-based polyurethane-enabled printed conductor with high performance enabled by the porous binder and sintering of silver flakes. [ABSTRACT FROM AUTHOR]

As the market demand for products such as flexible displays, IoT devices, and healthcare devices increases, attention has been drawn to printed electronics by a roll-to-roll process that can continuously produce electronic products on flexible substrates using functional inks. In particular, printed patterns need to be uniform in terms of the line width and thickness, which requires uniform control of the contact pressure during the roll-to-roll process, in processes that require ultra-fine pattern printing such as thin-film transistors for flexible displays. Because the contact pressure is indirectly measured using load cells, the performance of the conventional contact pressure control method tends to deteriorate due to the occurrence of time-delay and magnitude errors. Using the transfer function between the actual contact pressure and load cell, the time-delay is measured and compensated. To achieve contact pressure uniformization, the individual drive cross-coupled control system with the time-delay compensation is proposed. [ABSTRACT FROM AUTHOR]

Featured Application: A basic framework for further large-area OLEDs via printed electronics. The effects of the solvent used for the active layer materials of an OLED based on TADF emitters play a fundamental role in solution-deposited devices. This work focuses on the effects on the performance of different solvents employed to fabricate a very simple two-organic-layer OLED based on a green TADF emitter, under the concept of host: guest matrix. From the different results of the main figures of merit, it was possible to conclude that the OLED that used toluene as a solvent for the active layer reached a maximum EQE of 14%, almost the maximum already obtained for this emitter in more complex device structures. With the analysis of the charge-transport processes, it was possible to establish an explanatory model for the obtained results. Through impedance spectroscopy, additional characterization of the nature of charge-transport processes was carried out. With these results, it was possible to correlate the relaxation times, with the electrical properties of the active layer, and make inferences about the interaction between the electrical charges and the defect levels, opening new possibilities for further development in printed OLEDs. [ABSTRACT FROM AUTHOR]

Amine ligand, as one of the essential components of the Ag–amine complex, is necessary to reduce the sintering temperature and time of conductive inks. Herein, we report the facile preparation of hybrid amine conductive silver ink, mainly composed of silver oxalate–hybrid amine complex and methanol–acetone solvent. The synergistic effect of long-chain and short-chain amines enhances the uniformity of silver nanoparticles in the silver film. A uniformly conductive silver film is obtained by spin-coating as-prepared ink on the polyimide film, followed by thermal sintering. Then, the influence of butylamine content and sintering parameters on the physical properties and microstructure of silver film is systematically investigated. The resistivity of silver films, sintered at 170 °C for only 20 min, is found to be 6.71 μΩ·cm, which is four times higher than bulk silver. In addition, silver films after bending and adhesion test exhibit low resistivity and excellent adhesion. These results indicate that the hybrid amine conductive silver ink can provide promising opportunities for fabricating highly conductive flexible printed electronics at low temperatures in short times. [ABSTRACT FROM AUTHOR]

Integration of organic thin‐film transistor (OTFT) devices with a wireless data transmission system such as 2.4‐GHz Bluetooth low energy (BLE) is a significant requirement for activating the Internet of Thing (IoT) ecosystem based on a vast number of sensors, while conventional OTFT circuits have problems with their high output impedance and the need for multiple power supplies. Here, a wireless, real‐time, and flexible sodium ion sensing system composed of a printed Na+ sensor, printed OTFT‐based amplifiers, inorganic passive elements, a BLE module, and a 3‐V sheet‐type battery is demonstrated. The printed organic amplifier circuits based on dual threshold technology and dual‐gate structure are combinable with a BLE module because of their low output impedance of 50 kΩ and operate with 3‐V single supply as well as improving operational stability under illumination. The sensitivity to Na+ concentration is improved from 53.7 to 242.5 mV dec−1 (4.5 times higher) by the OTFT‐based amplifier, and the data is transmitted in real‐time to a tablet via the BLE wireless communication. [ABSTRACT FROM AUTHOR]

Printed electronics (PE) have provided new material and application opportunities for devices and systems as well as new manufacturing routes that all need to be considered for commercialization. This paper introduces a case study with universally relevant manufacturing processes and applications in the PE area, focusing on the Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) of the Personal Activity Monitor (PAM) device. In the study, the PAM device's most important costs and environmental impacts during the prototype pilot production and device use phases are identified and assessed. Additionally, the potential environmental impacts of post‐consumption scenarios are considered. The LCA results indicate that the roll‐to‐roll (R2R) assembly of electronics and the R2R injection over‐molding are generally the most prominent production process steps affecting the results. From the LCC perspective, the capitial expenditure (CAPEX) contributor is the R2R assembly pilot line, due to its high investment cost and long operating time compare to other production assets. The traditional electronic components are the major operating expenditures (OPEX), especially the microcontroller units (MCUs) and accelerometers, in contrast to the low impact from the printed electronics. There are several advantages to applying LCA and LCC since they provide explanations of the relationships between cost, environmental, design, and manufacturing characteristics. [ABSTRACT FROM AUTHOR]

As an indispensable aspect of flexible and printed electronics, flexible strain sensors composed of silver nanowires (AgNWs) have attracted significant attention recently. However, low resolution and large wire‐wire contact resistance still impede the stability and sensitivity of AgNW‐based flexible strain sensors. Herein, self‐reduced soldered AgNW pattern is fabricated by combining the high‐resolution electrohydrodynamic (EHD) printing and joining of AgNWs. The resolution achieved by EHD printing is up to ≈20 µm. The contact resistance between AgNWs is greatly reduced by depositing Ag atoms at the AgNW junctions while EHD printing Ag ion ink on as‐prepared AgNW pattern. After self‐reduced soldering process, the sheet resistance decreases from 14.8 to 2.13 Ω sq−1. This process can be conducted under room temperature and ambient conditions and requires no external assistance from heat, light, or mechanical pressing. Furthermore, the deposited Ag atoms at the junctions remarkably improve the sensitivity (gauge factor 14.5–37.9) and stability (over 5000 stretching cycles with 25% strain). This superior sensitivity and stability occur because nano‐junctions induced by the self‐reduced soldering process significantly reduce the initial resistance and enable a robust network structure. This EHD‐based technique for nanojoining of AgNWs demonstrates its potential for flexible and wearable electronics. [ABSTRACT FROM AUTHOR]

Infrared (IR) technology plays a significant role in many application scenarios, such as satellite remote sensing, environmental monitoring, biomedical engineering, imaging, communications, and so on. Demands of the next generation IR photodetectors, including ease of fabricaation, low cost, high flexibility, and so on, greatly drive the development of colloidal IR quantum dots (QDs) as the most competitive candidate material for IR photodetectors. In this article, the progress of IR QD materials and photodetectors, the fundamentals of IR QDs, the integration of IR QDs with other materials for hybrid photodetectors, and the applications of the QD IR photodetectors are reviewed. [ABSTRACT FROM AUTHOR]

With the advent of printed electronics, electrode manufacturing has made significant progress. In contrast to the traditional lift-off method, printing methods offer several advantages. They are not limited by the shape, structure, or material of the substrate, allowing for the manufacturing of electrodes using a wider range of materials. The manufacturing process can be completed at low temperatures, and the cost is reduced due to less material consumption. Printing methods can be broadly categorized into plate printing and plateless printing. Screen printing is a representative plate printing method, while inkjet printing is a typical plateless method. The two techniques are widely used in electrode manufacturing due to their convenience and the easily customized graphics. Screen printing is particularly efficient for processing electrodes in large quantities, while inkjet printing offers greater flexibility, allowing for quick adjustments to the shape of electrodes. This paper reviews recent advances in electrode manufacturing based on printing, focuses on the characteristics of screen printing and inkjet printing, and makes discussions about the main issues and challenges and the potential solutions. [ABSTRACT FROM AUTHOR]

Pulsed laser ablation can be used to repair misprinted patterns in printed electronics. The properties of the conductive ink varied with sintering temperature. This property variation significantly affected the ablation process. Thus, we compared the pulsed laser scanning ablation of dried Ag nanoparticle (NP) layers, which were sintered at 150 ℃, and sintered at 200 ℃ with quantitative evaluations. With higher thermal diffusion, the AgNP layer sintered at higher temperatures had more protruding Ag parts at the ablated line boundary. Ablation threshold fluence values of 264, 547, and 1370 mJ/cm2 were obtained for the Ag NP layers that were dried, sintered at 150 ℃, and sintered at 200 ℃ using D2-law fittings, respectively. For the ablation process, the increase in the protruding Ag parts and the increase in the ablation threshold fluence would be problematic. For the sintered AgNP layers, D2-law predicted the ablation threshold fluence quite well. The sintering temperature of the Ag NPs affects the ablation phenomenon by changing the surface morphology and physical properties of the pre-sintered layer. [ABSTRACT FROM AUTHOR]

Multimaterial 3D printing is an attractive route for low‐cost fabrication of electronic systems having different types of embedded devices. Herein, tunable thermoplastic polyurethane (TPU)‐based conductive composite filaments are presented for development of either strain sensors or different circuit elements. The filaments are developed with two filler materials, namely, silver and multiwalled carbon nanotubes (MWCNT). The influences of filler aspect ratio (AR), concentration, functionalization, and morphology on the composites' mechanical, thermal, and electrical properties are studied. Printed tracks of the 10 wt% high‐AR MWCNT/TPU filament exhibit a maximum electrical conductivity of 0.92 S cm−1 and withstand powers >1 W and currents >100 mA. The filament shows negligible change in impedance over the frequency range 1 kHz–1 MHz and a change in the resistance of <5% with 90° bending. Conversely, printed tracks using filaments with 3 wt% low‐AR MWCNT exhibit a change in resistance of ≈30% with 90° bending, allowing a clear distinction between various bending angles, and thus could be used for embedded strain/bend sensors. These results suggest that, with the correct optimization, multimaterial additive manufacturing can be utilized with tunable conductive filaments to fabricate complex 3D electronic systems by constructing reliable circuit tracks, bendable interconnects, and sensors. [ABSTRACT FROM AUTHOR]

Despite advances in soft, sticker‐like electronics, few efforts have dealt with the challenge of electronic waste. Here, this is addressed by introducing an eco‐friendly conductive ink for thin‐film circuitry composed of silver flakes and a water‐based polyurethane dispersion. This ink uniquely combines high electrical conductivity (1.6 × 105 S m−1), high resolution digital printability, robust adhesion for microchip integration, mechanical resilience, and recyclability. Recycling is achieved with an ecologically‐friendly processing method to decompose the circuits into constituent elements and recover the conductive ink with a decrease of only 2.4% in conductivity. Moreover, adding liquid metal enables stretchability of up to 200% strain, although this introduces the need for more complex recycling steps. Finally, on‐skin electrophysiological monitoring biostickers along with a recyclable smart package with integrated sensors for monitoring safe storage of perishable foods are demonstrated. [ABSTRACT FROM AUTHOR]

Due to the low energy density of commercial printable dielectrics, printed capacitors occupy a significant printing area and weight in printed electronics. It has long remained challenging to develop novel dielectric materials with printability and high‐energy storage density. Herein, a novel strategy for inkjet printing of all aqueous colloidal inks to dielectric capacitors composed of carbon nanotube electrodes and polyvinylidene fluoride (PVDF)‐based dielectrics is presented. The formulated dielectric ink is composed of negatively charged PVDF latex nanoparticles complexed with cationic chitosan molecules. Beyond the isoelectric point, the PVDF@Chitosan particles demonstrate excellent printability and film‐forming properties. Chitosan serves as a strong binder to improve the printed film quality yet it introduces charged species. To mitigate the transport of mobile charges, the printed PVDF@Chitosan film is interlayered with a layer of boron nitride nanosheets. This layer is perpendicular to the electric field and serves as an efficient barrier to block the transport and the avalanche of charges, eventually leading to a recoverable energy density of 15 J cm−3 at 610 MV m−1. This energy density represents the highest value among the waterborne dielectrics. It is also superior to most of the state‐of‐the‐art dielectric materials printed from solvent‐based formulations. [ABSTRACT FROM AUTHOR]

A facile, ultralow‐cost, and up‐scalable printable manufacturing process of flexible, multifunctional sensors that respond to more than one external stimulus could have a pivotal role in low‐cost wearables and portable systems for Industry 4.0. Herein, using a low capex, in‐house spray coating system, the fabrication of a low‐cost photodetector that is tuneable by mechanical strain exploiting the piezo‐phototronic nature of defect‐free 2D In2Se3 nanosheets is reported. Moreover, force sensors that respond to different levels of applied force are spray‐coated by using In2Se3 nanosheets. Regarding the photodetector, a nonmonotonic and asymmetric effect of strain on photocurrent response is shown exhibiting a local maximum at the 23°–32° compressive angle range and a slight hysteresis. Forward compressive bending leads to a photocurrent enhancement by 27% at 32° and reverse by 31% at 23°, while tensile strain leads to a current suppression by 8–10% at 23°–32° angle. The resulting force sensor repeatably demonstrates discrete piezoelectric voltages in the millivolt scale upon different mass loads, opening the path for force and tactile sensing applications. Applying industrially compatible materials for the underlying flexible substrate and electrodes, combined with spray coating, removes manufacturing complexities that engage costly and energy intensive fabrication. [ABSTRACT FROM AUTHOR]

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]

Metal-oxide-semiconductor (MOS)-based thin-film transistors (TFTs) are gaining significant attention in the field of flexible electronics due to their desirable electrical properties, such as high field-effect mobility (μFE), lower IOFF, and excellent stability under bias stress. TFTs have widespread applications, such as printed electronics, flexible displays, smart cards, image sensors, virtual reality (VR) and augmented reality (AR), and the Internet of Things (IoT) devices. In this study, we approach using a low-temperature solution-processed hafnium zirconium oxide (HfZrOx) gate insulator (GI) to improve the performance of lanthanum zinc oxide (LaZnO) TFTs. For the optimization of HfZrO GI, HfZrO films were annealed at 200, 250, and 300 °C. The optimized HfZrO-250 °C GI-based LaZnO TFT shows the μFE of 19.06 cm2V−1s−1, threshold voltage (VTH) of 1.98 V, hysteresis voltage (VH) of 0 V, subthreshold swing (SS) of 256 mV/dec, and ION/IOFF of ~108. The flexible LaZnO TFT with HfZrO-250 °C GI exhibits negligible ΔVTH of 0.25 V under positive-bias-temperature stress (PBTS). The flexible hysteresis-free LaZnO TFTs with HfZrO-250 °C can be widely used for flexible electronics. These enhancements were attributed to the smooth surface morphology and reduced defect density achieved with the HfZrO gate insulator. Therefore, the HfZrO/LaZnO approach holds great promise for next-generation MOS TFTs for flexible electronics. [ABSTRACT FROM AUTHOR]

A novel approach to manufacture components with integrated conductor paths involves embedding and sintering an isotropic conductive adhesive (ICA) during fused filament fabrication (FFF). However, the molten plastic is deposited directly onto the adhesive path which causes an inhomogeneous displacement of the uncured ICA. This paper presents a 3D printing strategy to achieve a homogeneous cross-section of the conductor path. The approach involves embedding the ICA into a printed groove and sealing it with a wide extruded plastic strand. Three parameter studies are conducted to obtain a consistent cavity for uniform formation of the ICA path. Specimens made of polylactic acid (PLA) with embedded ICA paths are printed and evaluated. The optimal parameters include a groove printed with a layer height of 0.1 mm, depth of 0.4 mm, and sealed with a PLA strand of 700 µm diameter. This resulted in a conductor path with a homogeneous cross-section, measuring 660 µm ± 22 µm in width (relative standard deviation: 3.3%) and a cross-sectional area of 0.108 mm2 ± 0.008 mm2 (relative standard deviation 7.2%). This is the first study to demonstrate the successful implementation of a printing strategy for embedding conductive traces with a homogeneous cross-sectional area in FFF 3D printing. [ABSTRACT FROM AUTHOR]

Displays are one of the most mature technologies in the field of printed electronics. Their ability to be manufactured in large quantities and at low cost has led to their recent uptake into the consumer market. Within this article this technology is extended to electrochromic display stickers. This is achieved using a recent reverse display architecture screen printed on textile and paper sticker substrates. The electrochromic stickers are comparable to plastic control substrates and show little performance difference even when adhered to curved surfaces. The electrochromic display technology is extended to sticker labels for authentication applications by patterning either the dielectric or the graphical layer. A proof‐of‐concept prototype emulating a wax seal on an envelope is presented to show that other colors can be implemented in this technology. [ABSTRACT FROM AUTHOR]

This study provides a complete rheological characterization of bidimensional (2D) nanomaterial dispersions, employed as 2D-inks precursors in printed electronics. Three different 2D nanomaterials [molybdenum disulfide (MoS2), graphene, and hexagonal boron nitride (hBN)] were dispersed in a Newtonian fluid (toluene) and a viscoelastic fluid (toluene + ethyl cellulose) with different polymer concentrations. The presence of nanosheets does not change the shear rheology of the carrier fluid. Regarding the extensional rheology, the results showed that the pinch-off phenomenon is present in all toluene suspensions; however, the presence of the ethyl cellulose introduces elasticity in the system, even leading to the formation of beads-on-a-string, and the relaxation times of the suspensions depend on the kind of nanosheets present in the fluid. As controlling the droplet size when dispensing 2D-inks is of paramount importance for printed electronics as well as for many other applications, here it is presented a correlation between the rheological properties of these 2D-inks precursors and their droplet size when generated from a capillary nozzle in the dripping regime. [ABSTRACT FROM AUTHOR]

Novel technology systems, such as "fiber optics" and "printed electronics," increasingly emerge at the interface of hitherto unrelated technology areas. As such, new technology systems often arise through technology convergence, characterized by integrating technology components and knowledge from different technology systems, resulting in a novel system architecture. This phenomenon is of utmost societal relevancy but simultaneously poses tremendous challenges for firms' technology strategies. Firms must not only cope with unrelated knowledge rooted in hitherto different technologies but also have to decide deliberately how systemic (i.e., complete technology system) versus focused (i.e., single component of the technology system) their engagement in technology development in the converging technology system ought to be. In addition, firms need to decide strategically to what extent to develop specialized or design knowledge. Extant concepts of technology strategy fall short of capturing this complexity inherent in converging technology systems. Therefore, to address how technology strategies co‐evolve along with the emergence of new technology systems, this study adds a systems perspective to technology strategy by developing the concept of technology system coverage. This novel dimension of technology strategy is formed by the scope (i.e., focused vs. systemic coverage of the technology system) and type of technological knowledge (i.e., specialized or design knowledge). We empirically apply this novel angle of technology strategy to the convergence field of printed electronics. Based on a longitudinal set of 828 patents over 30 years, 74 relevant corporate actors are identified. The underlying taxonomy enables us to reveal four technology strategies and develop five propositions. The results indicate that all firms build design knowledge over time, whereas not all firms build specialized knowledge, no matter what technology strategy is pursued. In sum, this work advances literature by understanding technology strategy in emerging complex technology systems, introducing a systems perspective. [ABSTRACT FROM AUTHOR]

Inspired by decades of research in the compatibilization of fillers into elastomeric composites for high‐performance materials, a novel polyurethane‐based stretchable carbon ink is created by taking advantage of a Janus molecule, 2‐(2,5‐dimethyl‐1H‐pyrrol‐1‐yl)propane‐1,3‐diol (serinol pyrrole, SP). SP is used to functionalize the carbon and comonomer in the polymer phase. The use of SPs in both the organic and inorganic phases results in an improved interaction between the two phases. When printed, the functionalized material has a factor 1.5 lower resistance‐strain dependence when compared to its unfunctionalized analogue. This behavior is superior to commercially available carbon inks. To demonstrate the suitability of ink in an industrial application, an all‐printed, elastomer‐based force sensor is fabricated. This "pyrrole methodology" is scalable and broadly applicable, laying the foundation for the realization of printed functionalities with improved electromechanical performance. [ABSTRACT FROM AUTHOR]

Flexible hybrid electronics (FHE) offers potential for fast computation and communication needed in applications such as human–machine interfaces, electronic skin, etc. FHE typically comprises devices that can vary from nano‐ to chip scale, and their integration using a common process is often challenging. Herein, a printed electronics route is presented to integrate the ultrathin chips (chip‐scale) and nanowires (NWs)‐based electronic layers (nanoscale) on the same substrate. The fabrication process is categorized into three stages: i) direct transfer printing of ultrathin chips (UTCs), ii) contact printing of nanoscale structures, and iii) metal printing using the direct ink write (DIW) method to define electrodes/interconnects. The UTC printing process is carefully optimized by studying the performance of transistors present on them. Electrical data collected from 14 transistors located on 3 different chips show negligible variation in performance after they are transfer printed—thus confirming the efficacy of the printing technique. The superior grade quality of ZnO‐NWs‐based electronic layers printed on the same substrate is also demonstrated by constructing UV photodetectors using DIW printing. The photodetectors show high responsivity (≈2 × 107 A W−1) and specific detectivity (≈5 × 1015 Jones) at a low UV intensity of 0.5 µW cm−2. [ABSTRACT FROM AUTHOR]

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

Efficient, stretchable wiring electrodes are achieved when the resistance change during expansion and contraction is minimal. Herein, we prepared silver pastes specifically designed for screen printing on thermoplastic polyurethane films; they exhibit minimal resistance changes. The pastes were prepared using silver particles with sizes of 2 and 7 μm as well as a mixture of 2 and 7 μm silver particles (50:50 wt%). These pastes were analyzed using methods such as rheological measurements, thermogravimetric analysis, printability tests, tensile and torsion tests, and light-emitting diode (LED) tests. The most promising results were obtained when exclusively using 2 μm silver flake particles. The pastes demonstrated a viscosity of 24,880 cps, a thixotropic index value of 2.82, excellent printability, and consistent resistance measurements even after 100% stretch, thus indicating exceptional tensile properties. Moreover, the pastes exhibited substantial stability, with no change in brightness after the attachment of seven LEDs at 20% tension. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor was fabricated by means of solution-processed graphene oxide (GO) ink on fluorine-doped tin oxide (FTO), followed by rapid reduction of the GO surface to reduced graphene oxide (rGO) by cold diffuse atmospheric plasma generated in pure hydrogen gas. The FTO/rGO electrode was then employed in the detection of ascorbic acid, uric acid, dopamine, and acetaminophen molecules with low limits of detection; in these cases, 0.03, 0.06, 0.07, and 0.04 μM, respectively. While traditional methods for the reduction of GO are time-consuming, in the order of tens of minutes, and involve high-temperature (450 °C) sintering in argon, the novelty of this work lies in the rapid manufacture of the sensing material through cold plasma-assisted reduction of a GO surface. Since the temperature of the plasma procedure is below 70 °C, with the elapsed time lesser than 10 s, and the plasma unit is capable of processing an area of up to 160 cm2, FTO/rGO electrode preparation can be performed at high throughput. This fabrication method may be easily deployed in rapid and low-cost roll-to-roll manufacture, a factor essential for the future commercialization of cost-effective flexible and printed electronics based on a wide range of sensors. [ABSTRACT FROM AUTHOR]

Our recent development of a wireless humidity sensor system embedded in incontinence products enables new sensor applications to diagnose and supervise geriatric diseases (i.e., age-related diabetes mellitus type II). The measurement of glucose in urine, so-called glucosuria, is an early indicator for an incipient diabetes mellitus disease, whose symptoms are often age-related but misjudged. In this paper, an incontinence glucose sensor is printed with biocompatible ink and Prussian blue as an electron mediator on foil and functionalized with immobilized glucose oxidase. Inkjet printing of multiple layers of Nafion prevents large interference substances from diffusing into the measuring electrode and allows precise adjustment of the linear working range, which is significantly different from blood glucose measurement. Performance tests show the potential to detect minimum glucose values and store the sensor over a prolonged period at room temperature. The printed glucose sensor can be embedded into the absorber material of incontinence products, where capillary forces transport the urine analyte to the detection area. An attached readout module with an integrated potentiostat measures the glucose concentration in urine, which is transmitted wirelessly with incontinence events and stored in a cloud service for further analysis by medical staff and care workers.

The technology to jet print metal lines with precise shape fidelity on diverse substrates is gaining higher interest across multiple research fields. It finds applications in additively manufactured flexible electronics, environmentally friendly and sustainable electronics, sensor devices for medical applications, and fabricating electrodes for solar cells. This paper provides an experimental investigation to deepen insights into the non-contact printing of solder lines using StarJet technology, eliminating the need for surface activation, substrate heating, curing, or post-processing. Moreover, it employs bulk metal instead of conventional inks or pastes, leading to cost-effective production and enhanced conductivity. The effect of molten metal temperature, substrate temperature, standoff distance, and printing velocity was investigated on polymer foils (i.e., PET sheets). Robust printing parameters were derived to print uniform, bulge-free, bulk metal lines suitable for additive manufacturing applications. The applicability of the derived parameters was extended to 3D-printed PLA, TPU, PA-GF, and PETG substrates having a much higher surface roughness. Additionally, a high aspect ratio of approx. 16:1 wall structure has been demonstrated by printing multiple metal lines on top of each other. While challenges persist, this study contributes to advancing additively manufactured electronic devices, highlighting the capabilities of StarJet metal jet-printing technology.