Printable Electronics Research Articles

Inkjet‐Printed Xerogel Scaffolds Enabled Room‐Temperature Fabrication of High‐Quality Metal Electrodes for Flexible Electronics

AbstractInkjet‐printed metal electrodes with desirable morphologies and electrical properties are indispensable cornerstones for printable and flexible electronics. However, methods to fabricate metal electrodes nowadays mostly request the sintering of printed metal particles, which not only will easily damage heat‐sensitive plastic substrates, but also is difficult to achieve a smooth, neat, and highly adhesive electrode structure. Herein, a room‐temperature, solution‐processable copper (Cu) electrode is demonstrated to overcome the above issues. The key is to inkjet print a stable xerogel scaffold with high porosity, good uniformity, and smoothness for growing high‐quality Cu via electroless deposition. Xerogel‐based Cu electrodes exhibit a bi‐layer architecture, consisting of an upper thin‐film Cu (with an electrical conductivity of ≈1.2 × 107 S m−1) and a bottom Cu‐polymer interpenetrated network. The electrodes show an excellent uniformity, surface smoothness, high interfacial energy to the plastic substrates (690–970 mJ m−2), and good flexibility. Taking these merits, the electrodes can be patterned onto various plastic substrates and fabricate all‐solution‐processed electronic devices such as organic thin‐film transistors and organic electrochemical transistors with stable electrical performance.

Recent Advances of Self-Healing Electronic Materials Applied in Organic Field-Effect Transistors.

Self-healing materials play an essential role in the field of organic electronics with numerous stunning applications such as novel integrated and wearable devices. With the development of stretchable, printable, and implantable electronics, organic field-effect transistors (OFETs) with a self-healable capability are becoming increasingly important both academically and industrially. However, the related research work is still in the initial stage due to the challenges in developing robust self-healing electronic materials with both electronic and mechanical properties. In this mini-review, we have summarized the recent research progress in self-healing materials used in OFETs from conductor, semiconductor, and insulator materials. Moreover, the relationship between the material design and device performance for self-healing properties is also further discussed. Finally, the primary challenges and outlook in this field are introduced. We believe that the review will shed light on the development of self-healing electronic materials for application in OFETs.

Stretchable inkjet-printed electronics on mechanically compliant island-bridge architectures covalently bonded to elastomeric substrates

Herein, we present an approach that allows versatile combination of inkjet-printed electronics and stretchable substrates. For this, we created a hybrid platform made out of stretchable Ecoflex covalently bonded via silane monolayers to flexible polyethylene terephthalate islands interconnected by bridges. The islands served as platforms where conductive lines, capacitive sensors and electrochromic devices (ECDs) were fabricated by inkjet printing. The robustness of the approach is highlighted by the minor influence of strain on the conductivity of printed Ag electrodes, which changed the resistance only by 1.3% at an applied strain of 50%. Furthermore, we demonstrated capacitor sensors capable of responding to strain changing their capacitance from 0.2 to 1.6 pF. To further show the applicability of the approach for multilayer/multimaterial optoelectronic elements, we processed ECDs capable of displaying information on the stretchable platform. Thus, we demonstrate how this digital and additive concept can be applied for the scalable integration of printed optoelectronic devices onto stretchable systems without relying on lithographic processes.

The Influence of Application of Local-wisdom-based Modules toward Peace-loving Characters of Elementary School Students

The purpose of this study was to compare the application of printed modules and electronic modules based on local wisdom of ngubat padi to see indicators of the Peaceful Love character. This type of research is quantitative research. This study used a sample of 44 students in class VA and class V B at SDN 76/I Sun-gai Buluh. Data analysis used descriptive and inferential statistics. The peace-loving character of students can be seen in the application of electronic modules and print modules. From the two teaching materials, the peace-loving character of students with the application of the E-Module is dominant in the very good category, while the peace-loving character of students with the application of the printed module is domi-nantly good.

Journal of Selected Topics in Quantum Electronics on Photonic Electronic Co-Integration and Advanced Transfer Printing

Journal of Selected Topics in Quantum Electronics on Photonic Electronic Co-Integration and Advanced Transfer Printing

Current Developments in Conductive Nano-Inks for Flexible and Wearable Electronics

Nanoparticles are progressively being incorporated into the printing industry and research is underway to enhance their use to boost innovation and competitiveness. Precursors or metallic nanoparticles replace ink pigments in printed electronics, imparting electrical conductivity to the resulting printed patterns. Many types of conductive inks have diverse characteristics that are best suited to specific applications and have different preparation techniques. Conductive inks are a pertinent element of the broader functional printing area, which is currently expanding and is seen as one of the most pertinent future technologies in the printing industry. In this review, the aspects of selecting, functionalizing, and making nanomaterials based conductive inks for printable, flexible and wearable electronics. Various methods and mechanisms for developing conductive inks based on nanomaterials, such as Ag nanoparticles, Cu@Ag core-shell nanoparticles, graphene conductive ink, biocompatible CNT ink, conductive indium tin oxide (ITO), proposed by various research groups are summarized. We have also attempted to provide insights into enhancing printing ink parameters such as uniformity, flexibility, resolution, and durability which are considered to be very important aspects for any printable inks. Finally, the applications of the conductive ink in thin film transistors (TFT), dye sensitized solar cells (DSSC), Radio Frequency Identification (RFID) tags, and sensors are summarized.

Study on Influence of Adhesion Properties in Screen Printing Electronic Ink Transfer

Printing electronic components by screen printing with the excellent printing quality, high efficiency, and environmental protection has broad application prospects in additive manufacturing. However, because conductive-ink blocks the screen, printing efficiency and quality decreased in the printing process. Thus, it is pivotal to explore adhesion factors from the interaction of conductive ink and screen. Herein, according to the transfer process of screen printing ink, solid-liquid wetting theory, and adhesion mechanism, we establish a liquid bridge adhesion model between two plates and obtain the functional relationship between the adhesion force and its influencing factors. Fluent software verifies the adhesion force model's conclusion to get the influence trend of the adhesion force on the ink residue. At last, by establishing a liquid bridge tensile fracture test, we gain experimental results consistent with the theoretical model and numerical simulation results. It is demonstrated that solid-liquid contact angle, tensile distance, and liquid volume are the main factors affecting the change of solid-liquid adhesion. The increase of tensile distance and contact angle will affect the adhesion force. The smaller the maximum solid-liquid adhesion during the initial stretching of the liquid bridge, the less the residual amount remained on the solid surface. By means of screen modification, the adhesion between conductive ink and screen can be reduced; meanwhile, the efficiency and quality of printed products can be improved. What's more, it also provides a valuable reference for the modification of screen printing electronics.

Solution Printing of Electronics and Sensors: Applicability and Application in Space

To ensure the safety and reliability of increasingly frequent, long‐duration, and long‐distance space missions, a sufficient and timely supply of the electronics and sensors that are essential in the maintenance and regeneration of spacecraft in space has become urgent. Solution‐based printing (SP) in space can be considered a disruptive technology for in situ manufacturing and maintenance of functional devices during the long duration and endurance of space exploration and crewed spaceflight. Herein, the origin and overview of the printing techniques in space are first introduced and further the printing processes in extreme space environments are discussed; then, its potential space applications in flexible solar cells, soft and wearable sensors, and space‐based antennas are forecast; finally, survivability for printed electronics in space is analyzed. Overall, a comprehensive description of the applicability and application of the SP techniques for manufacturing electronics and sensors in space is given.

Formulation of conductive inks printable on textiles for electronic applications: a review

Printed electronics (PE) is one of the most dynamic technologies in the world. It proposes low-cost electronic network production in flexible substrates by numerous printing techniques, (screen printing, gravure, offset, flexographic, and inkjet printing), used in various industries. In PE, ink pigments are replaced by metallic particles or precursors that transmit electrical conductivity to the printed patterns such as carbon, polymers and conductive pigments. Conductive inks play an important role in printed electronics, and despite the number of conductive ink types available on the market, there are still issues to be addressed. Some of these restrictions include the use of toxic chemical reagents and solvents and complicated manufacturing protocols, which often make the industrialization of conductive inks an even more distant goal. In particular, conductive inks based on silver nanoparticles, Graphene and PEDOT:PSS are widely studied thanks to their high electrical conductivity. On the other hand, there is still work to be done to show the interest of inks based on phthalocyanine pigments, in particular copper phthalocyanine. Nevertheless, problems related to stability, dispersion and annealing temperature often limit the application of these four types of fillers. In this review, we present general information on available conductive fillers used for the formulation of conductive inks, focusing on metallic particles, carbon fillers, pigments and polymers. The influence and technical requirements of the regularly used printing techniques, as well as the post-processing treatments to achieve the targeted performance in the obtained inks have been discussed. In addition, the surface characteristics of the various types of extensible and flexible substrates used in portable electronics are described. Moreover, some types of printed flexible electronic components as well as notable applications of electronic textiles in various sectors are exhibited. Next, the major challenges for the manufacturing of printed flexible electronics and recommendations for future research are discussed in this review

High-performance hysteresis-free perovskite transistors through anion engineering

Despite the impressive development of metal halide perovskites in diverse optoelectronics, progress on high-performance transistors employing state-of-the-art perovskite channels has been limited due to ion migration and large organic spacer isolation. Herein, we report high-performance hysteresis-free p-channel perovskite thin-film transistors (TFTs) based on methylammonium tin iodide (MASnI3) and rationalise the effects of halide (I/Br/Cl) anion engineering on film quality improvement and tin/iodine vacancy suppression, realising high hole mobilities of 20 cm2 V−1 s−1, current on/off ratios exceeding 107, and threshold voltages of 0 V along with high operational stabilities and reproducibilities. We reveal ion migration has a negligible contribution to the hysteresis of Sn-based perovskite TFTs; instead, minority carrier trapping is the primary cause. Finally, we integrate the perovskite TFTs with commercialised n-channel indium gallium zinc oxide TFTs on a single chip to construct high-gain complementary inverters, facilitating the development of halide perovskite semiconductors for printable electronics and circuits.

A Review on Printed Electronics with Digital 3D Printing: Fabrication Techniques, Materials, Challenges and Future Opportunities

The introduction of 3D printing technology has revolutionised the manufacturing and electronic product design in the past few years, where it is used to even produce printed circuit boards. Printed electronics is one of the fastest-growing additive manufacturing technologies and is becoming invaluable to various industries. The evolution of several contact and non-contact types of fabrication techniques have been reported in the recent past. Leveraging these technologies, various types of printed electronic components have been realized. One method is inkjet printing technology, which has been widely accepted for printed electronics manufacturing. As 3D printing uses only those materials which are essential to create the product, it eliminates waste production, with a smaller equipment cost and minimizes the number of process steps, resulting in lower manufacturing costs with reduced turnaround time. Various kinds of conductive and non-conductive materials have emerged in the recent past in conjunction with many manufacturing techniques for printed electronics. Herein, we review the most commonly used substrates, electronic printing materials, and the widespread printing techniques employed at the industrial level, giving an overall vision for a better understanding and evaluation of their different features. The technical challenges of several contact and non-contact techniques with corresponding solutions are also presented. Finally, status on advances in the production of various kinds of materials employed in 3D printed electronics and the methods for producing them, shortcomings, technical challenges, applications, benefits, and the future opportunities pertaining to printed electronics are discussed in detail.

Challenges, Prospects, and Emerging Applications of Inkjet-Printed Electronics: A Chemist's Point of View.

Driven by the development of new functional inks, inkjet-printed electronics has achieved several milestones upon moving from the integration of simple electronic elements (e.g., temperature and pressure sensors, RFID antennas, etc.) to high-tech applications (e.g. in optoelectronics, energy storage and harvesting, medical diagnosis). Currently, inkjet printing techniques are limited by spatial resolution higher than several micrometers, which sets a redhibitorythreshold for miniaturization and for many applications that require the controlled organization of constituents at the nanometer scale. In this Review, we present the physico-chemical concepts and the equipment constraints underpinning the resolution limit of inkjet printing and describe the contributions from molecular, supramolecular, and nanomaterials-based approaches for their circumvention. Based on these considerations, we propose future trajectories for improving inkjet-printing resolution that will be driven and supported by breakthroughs coming from chemistry. Please check all text carefully as extensive language polishing was necessary. Title ok? Yes.

Improvement of discharge system in cool plasma sintering method for copper fine traces

As a wiring material for printed electronics (PE), copper is strongly needed instead of silver. For a sintering method of copper traces, we have developed the method using oxygen pump and atmospheric pressure plasma, and demonstrated the ink composed of nanoparticles can be sintered to bulk-like structure. In this study, we have improved the sintering system to make it effective especially for copper inks made of submicron particles. We have tried to increase the thickness of the sintered layer and decrease the resistivity by changing the power supply system of plasma discharge and increasing the plasma density. The improved system has successfully demonstrated that a copper trace at least 4 μm thick can be sintered and that the resistivity decreases to approximately 3.3 μΩ·cm. These results can lead to huge breakthroughs in PE based on copper.

Recent Progress in Printed Physical Sensing Electronics for Wearable Health-Monitoring Devices: A Review

Printed electronics (PEs), as a fast-growing advanced manufacturing technology in recent years, plays an essential role in development of wearable electronic sensors, flexible displays, human-machine interaction, and thin electronics owing to its low cost, high throughput, and the possibility to be fabricated on diverse thin substrates with good flexibility and stretchability. Various PEs have been developed, such as physical sensing devices, electrochemical sensors, wearable supercapacitors and energy harvesters, stretchable electrodes, thin-film transistors (TFTs), and printed transceiving circuits. In this work, recent progress on physical sensing devices and their interface circuits developed by the printing process are reviewed in terms of their functions, printing methods, materials, and performance. The printed physical sensors used for monitoring the basic biometric parameters through physical sensing mechanisms, such as temperature sensors for skin temperature, pressure sensors for human pulse wave, strain sensors for human motions, biopotential electrodes for electrocardiogram signals, and multiple-function physical sensing platforms, have been studied and highlighted with their good designs and advanced materials. The state-of-the-art printed interface circuits for the wearable sensors such as interconnects, TFTs, digital circuits, amplifiers, oscillators, and antennas have been reviewed in terms of their structures and functions from basic to advanced levels. The challenge and suggestions of the printed wearable devices for future developments are discussed and end with a conclusion.

Performance enhancement of solution-processed InZnO thin-film transistors by Al doping and surface passivation

Solution-processed oxide semiconductors have been considered as a potential alternative to vacuum-based ones in printable electronics. However, despite spin-coated InZnO (IZO) thin-film transistors (TFTs) have shown a relatively high mobility, the lack of carrier suppressor and the high sensitivity to oxygen and water molecules in ambient air make them potentially suffer issues of poor stability. In this work, Al is used as the third cation doping element to study the effects on the electrical, optoelectronic, and physical properties of IZO TFTs. A hydrophobic self-assembled monolayer called octadecyltrimethoxysilane is introduced as the surface passivation layer, aiming to reduce the effects from air and understand the importance of top surface conditions in solution-processed, ultra-thin oxide TFTs. Owing to the reduced trap states within the film and at the top surface enabled by the doping and passivation, the optimized TFTs show an increased current on/off ratio, a reduced drain current hysteresis, and a significantly enhanced bias stress stability, compared with the untreated ones. By combining with high-capacitance AlO x , TFTs with a low operating voltage of 1.5 V, a current on/off ratio of > 10 4 and a mobility of 4.6 cm2/(V·s) are demonstrated, suggesting the promising features for future low-cost, low-power electronics.

Machine learning-enabled feature classification of evaporation-driven multi-scale 3D printing

The freeform generation of active electronics can impart advanced optical, computational, or sensing capabilities to an otherwise passive construct by overcoming the geometrical and mechanical dichotomies between conventional electronics manufacturing technologies and a broad range of three-dimensional (3D) systems. Previous work has demonstrated the capability to entirely 3D print active electronics such as photodetectors and light-emitting diodes by leveraging an evaporation-driven multi-scale 3D printing approach. However, the evaporative patterning process is highly sensitive to print parameters such as concentration and ink composition. The assembly process is governed by the multiphase interactions between solutes, solvents, and the microenvironment. The process is susceptible to environmental perturbations and instability, which can cause unexpected deviation from targeted print patterns. The ability to print consistently is particularly important for the printing of active electronics, which require the integration of multiple functional layers. Here we demonstrate a synergistic integration of a microfluidics-driven multi-scale 3D printer with a machine learning algorithm that can precisely tune colloidal ink composition and classify complex internal features. Specifically, the microfluidic-driven 3D printer can rapidly modulate ink composition, such as concentration and solvent-to-cosolvent ratio, to explore multi-dimensional parameter space. The integration of the printer with an image-processing algorithm and a support vector machine-guided classification model enables automated, in situ pattern classification. We envision that such integration will provide valuable insights in understanding the complex evaporative-driven assembly process and ultimately enable an autonomous optimisation of printing parameters that can robustly adapt to unexpected perturbations.

Dry Printing and Additive Nanomanufacturing of Flexible Hybrid Electronics and Sensors

AbstractThe growing demand for flexible and wearable hybrid electronics has triggered the need for advanced manufacturing techniques with versatile printing capabilities. Complex ink formulations, use of surfactants/contaminants, limited source materials, and the need for high‐temperature heat treatments for sintering are major issues facing the current inkjet and aerosol printing methods. Here, the nanomanufacturing of flexible hybrid electronics (FHE) by dry printing silver and indium tin oxide on flexible substrates using a novel laser‐based additive nanomanufacturing process is reported. The electrical resistance of the printed lines is tailored during the print process by tuning the geometry and structure of the printed samples. Different FHE designs are fabricated and tested to check the performance of the devices. Mechanical reliability tests including cycling, bending, and stretching confirm the expected performance of the printed samples under different strain levels. This transformative liquid‐free process allows the on‐demand formation and in situ laser crystallization of nanoparticles for printing pure materials for future flexible and wearable electronics and sensors.

Study on nonlinear vibration of flexible electronic membrane engendered by high-precision imprinting system

In the process of guide roller transmission, the geometric nonlinearity caused by the lateral vibration of the flexible electronic membrane will result in the divergence and instability of the membrane velocity, thus affecting the printing accuracy. In this paper, in order to engineer the exact condition that affecting the printing accurancy, the Elliptic integral method, whose effectiveness has been verified for its soluted result, is consistent with the one concluded from L-P method and He's Frequency formula while soluting the nonlinear vibration equation, respectively, on basis of Von Karman’s large deflection theory and Hamilton’s principle, is mainly applied, and thus provide a theoretical support for the design and manufacture of high-precision flexible electronic printing press.

Accuracy control for roll and sheet processed printed electronics on flexible plastic substrates

For the first time, the necessity to thermally pre-treat ubiquitously used PET substrates for printed electronics, to improve dimensional stability during manufacturing, is clearly defined. The experimental results have proven this phenomenon for both roll-to-roll (R2R) and sheet-to-sheet (S2S) processing of printed electronics. The next generation of electronics manufacturing has pushed the boundaries for low-cost, flexible, printed, and mass produced electronic components and systems. A driving force, and enabling production method, are the R2R printing presses. However, to produce electronics with increasing complexity and high yield in volume production, one must have a highly accurate process. In this article, R2R processing accuracy of printed electronics is evaluated from the point of dimensional accuracy of the flexible polyester substrate (DuPont Teijin Films’ PET Melinex ST504 with and without indium tin oxide, Melinex ST506, and Melinex PCS), precision of printing, and accuracy of layer-to-layer registration with stages that involve tension and elevated temperatures. This study has confirmed that dimensional changes during R2R processing will occur only in the first processing stage and that if a thermal pre-treatment run for the substrate is made—at identical temperature and tension of the processing stage—there is improved stability originating from a new-level strain in the crystalline PET film structure and freezing it in at the tensions and temperatures it is exposed to (i.e. 1400 μm machine direction stretching reduced to 8 μm). Furthermore, it is explained how the dimensional accuracy can be improved and reproducibly maintained in multilayer printing of electronics devices such as organic photovoltaics (OPV). These devices provide a valuable baseline of how the layer-to-layer alignment accuracy plays a crucial role in fully printed electronics devices, which lessons can be applied in all aspects of this field including hybrid systems and system fabrication involving multiple processing methods.

Accelerating sustainable development and production of nanomaterials and printed electronics

Printed and embedded electronics are considered game changing for electronics industry, and various R&D groups worldwide have already achieved remarkable progress. In the EU, limited access to these developments for industry and businesses still hampers wide rollout. Additionally, technology evaluation is often strictly focused on performance, i.e. whether technical functionalities meet specified requirements. For multiple reasons, a more holistic evaluation could contribute to more sustainable innovation. The EU-funded LEE-BED project has therefore created an open innovation test bed for printed electronics (PE), offering a time-efficient three-step process accessible via an online single entry point for easy involvement. The approach fosters evaluating ideas, developing prototypes, and transferring knowledge to interested parties from SMEs to global OEMs with or without previous involvement with PE. The first step (LEE-BED Phase 1) includes a multi-dimensional assessment of technical feasibility, economic viability, environmental sustainability, safety, and intellectual property before developing any prototype. This has successfully been applied to industry partners from construction, automotive, labelling, and luxury brands, offering novel functionalities and additional aesthetics through PE in their business practices. In this way, LEE-BED has established a collaborative platform for PE innovation sharing key learnings and opportunities.