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Indium tin oxide (ITO)-free solution-processed transparent electrodes are an essential component for the low-cost fabrication of organic optoelectronic devices. High-performance silver nanowires (AgNWs) ITO-free inverted organic photovoltaics (OPVs) usually require a AgNWs-embedded process. A simple cost-effective roll-to-roll production process of inverted ITO-free OPVs with AgNWs as a bottom transparent electrode requires solution-based thick metal oxides as carrier-selective contacts. In this reported study, we show that a solution-processed antimony-doped tin oxide (ATO)/polyethylenimine (PEI) electron-selective contact incorporated on the top of non-embedded AgNWs provides a high-performance ITO-free bottom electrode for non-fullerene acceptor (NFA) inverted OPVs.

The concept of the Light-based Internet of Things (LIoT) describes nodes that use light both to harvest energy to operate and to support full-duplex wireless communication. In this study, we investigate the design and implementation of a LIoT node using low power System-on-Chip based boards. The selection of the boards was carried out following performance and power consumption criteria. Benchmark tests included computational power and speed of executing I/O tasks, which are considered key performance metrics. The design considered the use of key components exploiting printed electronics (PE) technology to create a sustainable node solution. In the research, printed photovoltaic cells are used to harvest energy. However, the use of printed components poses some challenges, as the performance of these components is typically inferior to that of conventional components. Since the LIoT nodes are energy-limited, managing node energy is crucial to achieving energy autonomy. Thus, one of the main selections metric for the implementation of technology was the evaluation of power consumption during sleep modes. The paper discusses system architecture and design of the functionalities and provides a comparison between different System-on-Chip (SoC) based implementation platforms. The paper finally selects the most suitable SoC-based platform to implement a sustainable LIoT node supporting duplex communication operation.

Wearable sweat sensors are emerging as promising platforms for personalized and real-time tracking of evolving health and fitness parameters. While most wearable sweat sensors focus on tracking biomarker concentration profiles, sweat secretion rate is a key metric with broad implications for assessing hydration, cardiac, and neural conditions. Here we present a wearable microfluidic sensor for continuous sweat rate measurement. A discrete impedimetric sensing scheme relying on interdigitated electrodes within a microfluidic sweat collector allows for precise and selective sweat rate measurement across a broad physiological range. Integration of a manually activated pressure pump to expel sweat from the device prevents sensor saturation and enables continuous sweat rate tracking over hours. By enabling broad range and prolonged sweat rate measurement, this platform tackles a key obstacle to realizing meaningful and actionable sweat sensing for applications in exercise physiology and medicine.

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.

Printing techniques have been extensively studied as a promising route towards large-scale, low-cost and high-throughput manufacturing process for electronic devices. With the recently emerging applications in wearable electronics and customizable conformal electronics, it calls for the necessity to develop printed electronics that function on complex, 3D nonplanar architectures. In this study, aerosol printing and flash sintering of conformal conductors on nonplanar surfaces are demonstrated. Various printed patterns are fabricated by aerosol printing of conductive ink by copper nanoparticles (Cu NPs) on both planar and nonplanar surfaces. Pulsed flash light introduces rapid sintering of the printed Cu patterns in the ambient environment. For the nonplanar patterns, a back reflector is utilized to improve the uniformity of sintering. As a result, highly conductive customizable nonplanar Cu patterns with conductivity at 10%–12% of that of bulk Cu are obtained. Effects of different sintering conditions, including sintering voltage and mounting distance on the conductivity of sintered patterns are studied. For nonplanar patterns, conductivity values at different localized spots on the nonplanar rod are also investigated to evaluate the uniformity of nonplanar sintering. The processes of aerosol printing and flash sintering have provided a facile manufacturing route for conformal conductors on arbitrary nonplanar objects.

Soft robotics is gaining more interest because of the increasing demands in the manufacturing line to handle various types of delicate parts. The progress in the development of soft robotics does not only rely on the technology in the fabrication of the soft gripper structures, it also depends significantly on the integration of electronics such as the soft sensors and circuits. 3D printing technology is an important manufacturing tool for soft robotics due to its ability to fabricate designs with complex geometry and multi-material printing capability. Herein, the recently developed soft electronics such as sensors and circuits that involved the use of 3D printing technology are focused upon. In this article, the various designs of soft sensors, their fabrication techniques, and the materials used will be introduced. Besides, the design considerations and requirements for soft electronics will be presented. Lastly, the potential applications and the future outlook of soft electronics for soft grippers will be discussed. Agency for Science, Technology and Research (A*STAR) Submitted/Accepted version This research is supported by the Agency for Science, Technology and Research (A*STAR) under its IAF-ICP Programme ICP1900093 and the Schaeffler Hub for Advanced Research at NTU.

Fabrication of electronic devices on different flexible substrates is an area of significant interest due to low cost, ease of fabrication, and manufacturing at ambient conditions over large areas. Over the time, a number of printing technologies have been developed to fabricate a wide range of electronic devices on nonconventional substrates according to the targeted applications. As an increasing interest of electronic industry in printed electronics, further expansion of printed technologies is expected in near future to meet the challenges of the field in terms of scalability, yield, and diversity and biocompatibility. This chapter presents a comprehensive review of various printing electronic technologies commonly used in the fabrication of electronic devices, circuits, and systems. The different printing techniques based on contact/noncontact approach of the printing tools with the target substrates have been explored. These techniques are assessed on the basis of ease of operation, printing resolutions, processability of materials, and ease of optimization of printed structures. The various technical challenges in printing techniques, their solutions with possible alternatives, and the potential research directions are highlighted. The latest developments in assembling various printing tools for enabling high speed and batch manufacturing through roll-to-roll systems are also explored. Other information Published in: Hybrid Nanomaterials - Flexible Electronics Materials License: https://creativecommons.org/licenses/by/3.0/legalcode See chapter on publisher's website: http://dx.doi.org/10.5772/intechopen.89377

Printed electronics is an emerging research field and is going to play a vital role in our everyday-life in the near future. Luminescent printed electronic devices can be very thin and flexible, which makes them feasible for new applications. Such EL-devices are already being applied in automobiles. For the school-implementation of printed electronics the authors have developed a flexible EL-device, which can be hand-printed using low-cost materials and methods.

Advanced high-temperature materials, metals and ceramics, have been widely sought after for printed flexible electronics under extreme conditions. However, the thermal stability and electronic performance of these materials generally diminish under extreme environments. Additionally, printable electronics typically utilize nanoscale materials, which further exacerbate the problems with oxidation and corrosion at those extreme conditions. Here we report superior thermal and electronic stability of printed copper-flexible ceramic electronics by means of integral hybridization and passivation strategies. High electric conductivity (5.6 MS/m) and thermal stability above 400 °C are achieved in the printed graphene-passivated copper platelet features, while thermal management and stability above 1000 °C of printed electronics can be achieved by using either ultrathin alumina or flexible alumina aerogel sheets. The findings shown here provide a pathway toward printed, extreme electronic applications for harsh service conditions.

We report on the fabrication and characterization of electronic devices printed with inks of quasi-one-dimensional (1D) van der Waals materials. The quasi-1D van der Waals materials are characterized by 1D motifs in their crystal structure, which allow for their exfoliation into bundles of atomic chains. The ink was prepared by the liquid-phase exfoliation of crystals of TiS3 into quasi-1D nanoribbons dispersed in a mixture of ethanol and ethylene glycol. The temperature-dependent electrical measurements indicate that the electron transport in the printed devices is dominated by the electron hopping mechanisms. The low-frequency electronic noise in the printed devices is of 1/fγ-type with γ ∼ 1 near-room temperature (f is the frequency). The abrupt changes in the temperature dependence of the noise spectral density and γ parameter can be indicative of the phase transition in individual TiS3 nanoribbons as well as modifications in the hopping transport regime. The obtained results attest to the potential of quasi-1D van der Waals materials for applications in printed electronics.

Human environments are filled with large open spaces that are separated by structures like walls, facades, glass windows, etc. Most often, these structures are largely passive offering little to no interactivity. In this paper, we present Duco, a large-scale electronics fabrication robot that enables room-scale & building-scale circuitry to add interactivity to vertical everyday surfaces. Duco negates the need for any human intervention by leveraging a hanging robotic system that automatically sketches multi-layered circuity to enable novel large-scale interfaces. The key idea behind Duco is that it achieves single-layer or multi-layer circuit fabrication on 2D surfaces as well as 2D cutouts that can be assembled into 3D objects by loading various functional inks (e.g., conductive, dielectric, or cleaning) to the wall-hanging drawing robot, as well as employing an optional laser cutting head as a cutting tool. Our technical evaluation shows that Duco's mechanical system works reliably on various surface materials with a wide range of roughness and surface morphologies. The system achieves superior mechanical tolerances (0.1mm XY axis resolution and 1mm smallest feature size). We demonstrate our system with five application examples, including an interactive piano, an IoT coffee maker controller, an FM energy-harvester printed on a large glass window, a human-scale touch sensor and a 3D interactive lamp.

The enabling electrohydrodynamic (EHD) printing technology in a one-step forming, continuous, and controllable manner has gained wide attention in the field of flexible printed electronics. The evaporation characteristic of ink solvent during the EHD printing greatly affects the shape of the jet as well as the penetration and diffusion of inks on fabrics, which is crucial to the formation of high-quality printed electronics. However, few works have deeply investigated the control of ink solvent evaporation to adjust the formability of EHD printing electronics on rough and porous textiles. Here, conductive inks with different solvent evaporation rates are formulated. The effect of solvent evaporation on the motion of inks is evaluated by the contact angle over time. Furthermore, the morphology and electrical properties under different deformation of EHD-printed conductive lines are observed and measured. The results show that the morphology of conductive lines printed on fabric could be accurately controlled by the ratios of the solvent in inks, and the solvent evaporation rate has a significant inverse-parabolic effect on electrical resistance and its stability under deformation. Moreover, the serviceability of the optimal ink is demonstrated by the performance of an EHD-printed antenna for ultra-high frequency radio frequency identification tags, and its maximum reading range is 9.1 m under typical application examples. These findings will provide a guide for ink formulation and process control of EHD printing in flexible textile-based electronics.

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 ppmv H2 in air. Specific performance evaluations included assessment of the sensor measurement range, repeatability, and selectivity.

In this work, a novel microfabrication-compatible production process is demonstrated and used to fabricate UV photoresistors made from ZnO nanoparticles. It comprises a simple room-temperature production method for synthesizing and direct-writing nanoparticles. The method can be used on a wide range of surfaces and print a wide range of materials. Here, it is used to synthesize a ZnO photoresistor for the first time. The sensor shows a two orders of magnitude lower resistance under UV-C exposure compared to darkness. The low cost and simplicity of this synthesis method enables cheap integration of UV-C sensors for human exposure monitoring or UV-output monitoring of light sources.

Engineering the molecular structure of conjugated polymers is key to advancing the field of organic electronics. In this work, we synthesized a molecularly encapsulated version of the naphthalene diimide bithiophene copolymer PNDIT2, which is among the most popular high charge mobility organic semiconductors in n-type field-effect transistors and non-fullerene acceptors in organic photovoltaic blends. The encapsulating macrocycles shield the bithiophene units while leaving the naphthalene diimide units available for intermolecular interactions. With respect to PNDIT2, the encapsulated counterpart displays an increased backbone planarity. Molecular encapsulation prevents preaggregation of the polymer chains in common organic solvents, while it permits π-stacking in the solid state and promotes thin film crystallinity through an intermolecular-lock mechanism. Consequently, n-type semiconducting behavior is retained in field-effect transistors, although charge mobility is lower than in PNDIT2 due to the absence of the fibrillar microstructure that originates from preaggregation in solution. Hence, molecularly encapsulating conjugated polymers represent a promising chemical strategy to tune the molecular interaction in solution and the backbone conformation and to consequently control the nanomorphology of casted films without altering the electronic structure of the core polymer.

Next-generation printed electronics is required to be of high performance, cost-effective, multifunctional, sustainable, and environmentally benign. Herein, we report the manufacturing of a flexibl...

A new direction in 3D printing was investigated – prototyping of single-sided, double-sided and multilayer printed circuit boards. The current capabilities and limitations of 3D printed circuit board printing technology were identified. A comparative analysis of the characteristics of two desktop 3D printers presented in the industry for prototyping radio electronics, as well as the first professional machine DragonFly LDM 2020, which is a mini-factory for prototyping multilayer printed circuit boards, was carried out. The first practical experience of working and printing on DragonFly LDM 2020 supplied to the megalaboratory “3D prototyping and control of multilayer printed circuit boards” of the Institute of Radio Engineering and Telecommunication Systems MIREA – Russian Technological University is presented. The first samples of electronic boards printed on a 3D printer by the method of inkjet printing were obtained. An additive technology for the production of multilayer printed circuit boards is considered: printing with two printheads with conductive and dielectric nano-ink with two curing systems: an infrared sintering system for conductive ink and a UV curing system for dielectric ink. The LDM (Dragonfly Lights-out Digital Manufacturing) production method with the necessary maintenance is presented. The method allows the system to work roundthe-clock with minimal human intervention, significantly increasing the productivity of 3D printing and expanding the possibilities of prototyping. The materials used for 3D printing of multilayer printed circuit boards and their characteristics were investigated: dielectric acrylate nano-ink (Dielectric Ink 1092 – Dielectric UV Curable Acrylates Ink), conducting ink with silver nanoparticles (AgCite™ 90072 Silver Nanoparticle Conductive Ink). The research carried out allows us to compare the technological standards of printed electronics with traditional methods of manufacturing multilayer printed circuit boards for a number of parameters.

International audience; Printed electronics are expected to meet an increasing demand for improved functionality and autonomy of products in the context of Internet-of-Things. With this trend, the environmental performance of novel technologies is of growing importance. The current study presents the life cycle assessment of two novel devices: an anticounterfeit label based on the electrochromic display and a shock-detection tag based on the piezoelectric sensor, designed for the use in packaging of pharmaceuticals and luxury items to improve the safety and accountability in the supply chain. The devices are manufactured by means of energy-efficient printing techniques on a low-cost flexible and recyclable paper substrate. Comprehensive cradle-to-grave analysis contributes to industrial-scale energy and material life cycle inventories and identifies the main impact hotspots evaluated for a broad range of categories of the ReCiPe midpoint (H) impact assessment method. Results show that major impact burdens are associated with the near-field communication chip and radio-frequency identification antenna, while the impacts of solvents, process energy, electrochromic display/piezoelectric sensor, Li-ion battery, and substrate are comparatively small. In terms of their global warming potential, both the anticounterfeit label and shock-detection tag embody around 0.23 kg of CO2-equiv. Several material-use reduction and material-substitution strategies are quantified and discussed for their potential to reduce high impacts of the antenna.

International audience; The ohmic curing of two silver micro-particle inks was studied. Silver lines of 35 to 75 µm thick were printed on a mixture of polycarbonate and acrylonitrile butadiene styrene (PC+ABS) substrate and on a mineral reinforced Nylon 6 thermoplastic, using a laboratory-made system based on a volumetric dosing dispenser. After 48 h of stabilization in ambient conditions, a current is applied through the printed lines with an imposed intensity value and application time in order to cure the silver inks. Evolutions of the temperature and the resistivity of silver tracks were followed during the process. Printed thermoplastics were characterized at the end of the process in order to check the absence of deformation due to the curing treatment. The study showed that the ohmic curing led to better electrical performances than an oven process with a considerable time saving. Most of the printed line resistivity drop occurred in the first 30 s of the treatment. The ohmic curing induced a local increase of temperature located in the printed line and avoided damaging the substrates, which makes the process compatible with thermal sensitive substrates. Therefore, the ohmic curing is an efficient low-cost process to cure silver micro-particle inks that could be easily implemented at an industrial scale.

The flashlight annealing process has been widely used in the field of flexible and printed electronics because it can instantly induce chemical and structural modifications over a large area on an electronic functional layer in a subsecond time range. In this study, for the first time, we explored a straightforward method to develop strong self-adhesion on a metal nanowire-based flexible and transparent conductive film via flashlight irradiation. Nanowire interlocking, for strong mechanical bonding at the interface between the nanowires and polyamide film, was achieved by simple hot pressing. Then, by irradiating the nanowire-impregnated film with a flashlight, several events such as interdiffusion and melting of surface polymers could be induced along with morphological changes leading to an increase in the film surface area. As a result, the surface of the fabricated film exhibited strong interfacial interactions while forming intimate contact with the heterogeneous surfaces of other objects, thereby becoming strongly self-adhesive. This readily achievable, self-attachable, flexible, and transparent electrode allowed the self-interconnection of a light-emitting diode chip, and it was also compatible for various applications, such as defogging windows and transparent organic light-emitting diodes.

At present, screen printing is the most widely used technique in the printed electronics industry and the printed pattern can satisfy certain electronic application requirements. Ink development is the most important part of the printing process. In this paper, a new particle-free MOD ink (MOD = metal–organic-decomposition) was synthesized from silver malonate, diethanolamine (DEA) and ethylene glycol (EG). Silver malonate was the precursor of silver. DEA was the complexing agent that maked silver malonate soluble. EG acted not only as a solvent to regulate the rheological properties of the ink, but also as a reducing agent to reduce silver ions. The decomposition temperature was reduced from 210 °C to about 100 °C by the formation of silver-amine complex, thus the selection range of substrate could be broadened. The ink was spread on the polyimide (PI) substrate by screen printing. The silver film was formed after heat treatment at 150 °C for 1 h and its electrical conductivity can reach 1.0 × 104 S cm−1, which corresponded to one sixty-third of the theoretical conductivity of the bulk silver (6.3 × 105 S cm−1).

Active-matrices serve as the backplane circuitry for large-area display technologies and distributed sensors. Recently, there has been significant interest in developing flexible, additively manufactured active matrices for the burgeoning flexible electronics industry. Carbon nanotubes (CNTs) are prime candidate materials for semiconducting elements of transistors due to their solution processability, carrier mobility, and mechanical flexibility. There have been many recent accomplishments in the development of CNT inks and in their deposition via printing that enable their use in thin-film transistors (TFTs), and their appropriate performance make them suitable for use in large-area active matrices. In this review, we provide an overview of the field, with a specific focus on recent advancements in CNT sorting, ink preparation, and printing techniques. We also provide a benchmarking study of printed CNT devices presented in literature after 2017. Next, we discuss printable CNT-TFTs used for active-matrix applications. Finally, we provide a concluding perspective on the outlook and challenges for printed CNT-TFT active matrices.

The thermoelectric conversion capabilities and stabilities of carbon nanotubes (CNTs) in n-type organic semiconductors are important properties that urgently need improvement for large-scale and low-grade thermal energy applications. Importantly, conventional methods for preparing n-type CNT sheets are disadvantageous because they are incompatible with printing, which is an inherent advantage of organic materials for large-scale applications. Herein, we report the systematic preparation of CNT sheets containing dopant polymers using a drop-casting method that enhances thermoelectric performance and is adaptable to printing. The CNTs exhibit a large, negative Seebeck (S) value that depends on the level of the highest occupied molecular orbital of the dopant polymer, with the optimal poly(N-vinyl-2-pyrrolidone)-poly(vinyl alcohol) graft copolymer (PVP–PVA) providing a large negative S value and a power factor of 289 μW m−1 K−2. The inclusion of 1,2-diphenylhydrazine as a secondary dopant significantly improved the ZT value of the PVP–PVA/CNT from 5.26 × 10−3 for the undoped system to 1.34 × 10−2. Correspondingly, the power factor was ~20% more atmospherically stable after 31 d at room temperature compared to the undoped system. This excellent performance provides new avenues for the development of drop-cast fabricated n-type CNT films without the need for n-doping processes. For n-type organic semiconductors, low thermoelectric conversion properties are an issue that needs to be resolved, moreover current manufacturing methods are not compatible with printing technology. In this communication, we report the systematic preparation of carbon nanotube (CNT) sheets containing dopant polymers using a drop-casting method that enhances thermoelectric performance. The inclusion of 1,2-diphenylhydrazine as a secondary dopant significantly improved the ZT value of poly(N-vinyl-2-pyrrolidone)-poly(vinyl alcohol) graft copolymer/CNT, from 5.26 × 10−3 for the undoped system to 1.34 × 10−2. The developed approach, which is expected to provide on-demand manufacturing through printed electronics technologies.

Printed piezoresistive strain sensors based on stretchable roll-to-roll screen-printed silver electrodes on polydimethylsiloxane substrates and inkjet-deposited single-wall carbon nanotube micropatterns are demonstrated in this work. With the optimization of surface wetting and inkjet printing parameters, well-defined microscopic line patterns of the nanotubes with a sheet resistance of

Low-frequency noise is a critical characteristic of transistors, but there are only a few experimental works on the noise in printed electronics. In this work, we characterize the low-frequency noise of inkjet-printed electrolyte-gated thin-film transistors (EGTs) with indium-oxide semiconductors. We confirm that the carrier number fluctuation with correlated mobility fluctuation is the dominating noise generation mechanism. Also, we present the benchmark analysis on the noise level of various thin-film technologies. Notably, the extracted value of trap density near the insulator-channel interface is high, indicating an inferior quality of solution-processed and inkjet-printed thin-films. However, because of electrolyte-gating, the large areal gate capacitance compensates the negative effect of the high trap density, effectively reducing the flat-band voltage noise. As a result, the normalized drain current noise is considerably lower than solution-processed transistors and comparable with sputtered inorganic transistors with dielectric gating. This renders the electrolyte-gating approach useful in reducing the noise for printed/solution-based transistors, suitable for low-noise applications.

Sensors 22(16), 6119 (2022). doi:10.3390/s22166119 special issue: "Special Issue "Frontiers in Flexible Electronics and Sensors" / Special Issue Editors: Dr. Zhihui Zeng, Guest Editor; Dr. Shanyu Zhao, Guest Editor", Published by MDPI, Basel

Flexible sensing surfaces are the next frontier in large area electronics. Integrating sensors and electronics on flexible substrates it is possible to create surfaces that are capable of mapping the distribution of several quantities of practical interest: from pressure to X-rays, and from biopotentials to the infrared radiation generated by warm objects. In this paper we overview the main approaches and challenges in this field of research, focusing especially on solutions manufactured using organic materials.

Inkjet printing has proven to be a promising alternative method in the fabrication of printed electronics, besides screen printing and photolithography etching. In this work, we characterize the electrical performance of inkjet printed circuits on flexible PET and glossy photo paper. The electrical circuits were printed using a commercial Epson L310 piezoelectric printer, and the NB series silver ink and chemical-sintering PET substrate from Mitsubishi Paper Mills. This method allows rapid prototyping of electronic circuits (~ 30 min design, ~ 5 s fabrication) and quick iteration of prototypes. The system has a resolution of 250 µm electrodes and 300 µm electrical gaps, and on average, 1.5 ± 0.2 µm in thickness. The effect of printing on different substrates, geometry and overprinting on sheet resistance was also studied. It was found that double printing produced better electrodes with lower resistances. A stable conducting circuit has a sheet resistivity of

This article deals with the problem of printing current-conducting circuits on various substrates. The article provides an overview of modern technologies for solving this problem. The author describes a hybrid laser system that solves the problem under consideration. This device uses modern technologies and materials that show good results in research. A brief description of the software for preparing data for this system is also provided.

Metal nanoparticle pastes are useful for nanoinks to form fine conductive patterns in printed electronics. This study reports a novel method for room-temperature coalescence of Cu-Ag core-shell nan...

As a common type of microelectromechanical systems (MEMS) inertial sensors, comb-structured air-gap acceleration sensors have been applied to various industrial devices and systems. Printed electronics technology has emerged recently as an alternative for fabrication of flexible electronic devices with superior productivity and eco-friendliness to MEMS technology. However, air-gap structures are hard to realize through printing without etching process, and thus comb-structured acceleration sensors have been rarely reported in the printed electronics field in spite of many advantages. This study presents design of a comb-structured air-gap acceleration sensor and materials and processes for highly productive roll-to-roll printed electronic fabrication of the sensor. The sensor is designed to have multiple layers in two parts: fixed fingers are in the lower part while the movable mass and movable fingers in the upper part. Both parts are processed separately on different flexible PET substrates by roll-to-roll gravure printing and drying. Then the upper part is transferred and bonded to the lower one and air-gap structure is formed as a result. This paper also provides electrical characteristics of the proposed comb-structured acceleration sensor by testing capacitance change as a function of acceleration.

Polymer/oxide hybrid thin films, which have excellent electrical and mechanical performance, can be effectively fabricated through the sol-gel process, showing great potential in the future printed electronics. However, gelation of polymer/oxide ink systems can easily occur during a thermal process in which case capillary stress can lead to the crack of printed films due to the long period of stress accumulation. To solve this problem, the effect of different solvent systems on formed PAM/ZrOx hybrid films, which were printed by piezoelectric printing, was studied in this paper, including single solvent systems of glycol and binary solvent systems of glycol and water. The result showed that the microstructure characteristics and mechanical properties of hybrid nanostructures formed in different solvent systems varied significantly, and crack behavior can be regulated by simply adjusting the water volume ratio of the solvent system. The crack formation was significantly inhibited when the water volume ratio reached 25%.

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.

A stretchable conductor is one of the key components in soft electronics that allows the seamless integration of electronic devices and sensors on elastic substrates. Its unique advantages of mechanical flexibility and stretchability have enabled a variety of wearable bioelectronic devices that can conformably adapt to curved skin surfaces for long-term health monitoring applications. Here, we report a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-based stretchable polymer blend that can be patterned using an inkjet printing process while exhibiting low sheet resistance and accommodating large mechanical deformations. We have systematically studied the effect of various types of polar solvent additives that can help induce phase separation of PEDOT and PSS grains and change the conformation of a PEDOT chain, thereby improving the electrical property of the film by facilitating charge hopping along the percolating PEDOT network. The optimal ink formulation is achieved by adding 5 wt % ethylene glycol into a pristine PEDOT:PSS aqueous solution, which results in a sheet resistance of as low as 58 Ω/□. Elasticity can also be achieved by blending the above solution with the soft polymer poly(ethylene oxide) (PEO). Thin films of PEDOT:PSS/PEO polymer blends patterned by inkjet printing exhibits a low sheet resistance of 84 Ω/□ and can resist up to 50% tensile strain with minimal changes in electrical performance. With its good conductivity and elasticity, we have further demonstrated the use of the polymer blend as stretchable interconnects and stretchable dry electrodes on a thin polydimethylsiloxane (PDMS) substrate for photoplethysmography (PPG) and electrocardiography (ECG) recording applications. This work shows the potential of using a printed stretchable conducting polymer in low-cost wearable sensor patches for smart health applications.

Here, we report a previously unreported low-temperature curable barium strontium titanate (BaXSr1−XTiO3) or BST dielectric nanoparticle ink which shows a high dielectric tunability for printed electronics/additive manufacturing applications. The newly formulated BST ink is optimized to print in aerosol jet printers and can be cured at 150°C, which will allow the fabrication of tunable radio-frequency (RF) and microwave (MW) devices on a wide range of flexible substrates. Characterization of high-frequency dielectric properties showed a high dielectric tunability (~ 15% at 10 GHz with 10 V/µm) and a high dielectric constant (~ 16 at 10 GHz). The linear-reversible tunability, which is very important for tunable devices, was confirmed by the tunability testing at 10 GHz. Characterization of temperature-dependent dielectric properties found < 10% variations of the dielectric constant at 10 GHz from −50°C to 125°C for this BST ink. Detailed information on BST nanoparticle characterization, ink formulation and characterization of dielectric properties is discussed.

Printed electronics employing flexible substrate offers prospective features for various applications such as, tactile sensing, energy harvesting, wearable electronics and acoustic wave sensors. In this work, an acoustic FPW (flexural plate wave) sensor is printed on thin and flexible PZT-PDMS (lead zirconate titanate-poly dimethyl siloxane) composite film with silver ink. The prototype FPW resonator has a resonant frequency of 22.65 MHz with an attenuation of −1.552 dBm. Gravimetric mass sensitivity of the sensor was measured by applying PDMS layers in between the input and output interdigital transducers (IDTs). The mass sensitivity was measured to be −7.8 cm2/g. The sensor is highly responsive to VOCs (volatile organic compounds) with PDMS as a sensing layer. Gas sensitivities with acetic acid and toluene concentrations were measured to be 0.66 and 160.63 kHz/ppm, respectively. The limit of detection for acetic acid and toluene were 10.9 and 0.03 ppm, respectively. Further, the sensor shows good repeatability and response time with both the VOCs. The thermal stability and high piezoelectric charge coefficient of PZT-PDMS composite compared to other piezoelectric composite and polymer substrates are advantageous for the flexible printed sensor. The reported FPW gas sensor shows potential for low concentration measurement of VOCs.

Made available in DSpace on 2021-06-25T10:27:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-06-01 Wireless communication employing radio-frequency identification (RFID) tags is progressively more widespread in a variety of industrial and commercial sectors. Aspects as demanding specific needs regarding reading distance, production cost, and processability are requested for commercial applications. Nowadays, printing of optical barcodes is the most economically technology for short distance (up to ~30 cm) reading applications. However, the large-scale and low-cost printing of RFID tags would be a competitive alternative to barcode technology because it allows quicker identification with much less reading errors. Here we demonstrate a semi-transparent, screen printed RFID antennas using a non-metallic and environmentally friendly conductive paste. The variation of the film thickness (from 2.5 up to 15 µm) permitted the fabrication of antennas with reading range (0.84–3.29 m), sheet resistance (6.2–36 Ω/sq), and optical transmittance (0–32.3%), which are compatible to commercial or industrial applications aiming short to moderate reading distances. Indústria de Tintas Condutivas TICON Flextronics Instituto de Tecnologia (FIT) Institute of Geosciences and Exact Sciences Department of Physics São Paulo State University (Unesp) Institute of Geosciences and Exact Sciences Department of Physics São Paulo State University (Unesp)

In the field of printed electronics, carbon and its allotropes are today among the most studied materials due to their unique physical and chemical properties. In this work, carbon dispersions were used for the preparation of screen-printed carbon electrodes applied as counter electrodes (CEs) for the dye-sensitized solar cells and as working electrodes for electrochemical sensing. Following the simple and quick homogenization process, carbon dispersions were subjected to thermogravimetric analysis to closely examine drying, eventually sintering processes after printing. The influence of the graphite:carbon black ratio was investigated. The structure of composite carbon layers was analyzed by scanning electron microscopy and optical microscopy. The DSSC CEs printed from the dispersion containing 100 wt% of CB exhibited the highest catalytic activity for the effective reduction of oxidized triiodide I3− back to iodide I− within the solar cell. The highest conversion efficiency achieved for the high-temperature processed CE was 3.05% with the fill factor of 0.65. The same composition of the carbon WE was used for the quantitative analysis of neurotransmitter dopamine. Based on the cyclic voltammetry measurements, the sensor showed a limit of detection of 13.3 nM for dopamine.

Printed electronics such as solar cells, RFIDs, and display panels can be made using printed electronic technology by printing viscous liquids having various properties on films or insulating substrates. Among printed electronic production processes, the roll-to-roll process transfers functional ink to an insulation substrate by filling its engravings through repeated contact and rotation of two rolls. Extensive research has been conducted to commercialize this process because it offers several advantages such as low equipment investment and production cost, and high-speed mass production. However, the roll-to-roll process requires further development for commercialization because print quality precision and fine pattern formation are difficult to achieve, and print quality may be affected by processing precision errors and non-uniform printing pressure. Contact printing pressure is the pressure acting on the nip that makes contact with the two rolls, and is a factor that influences roll processing precision. That is, contact printing pressure uniformity must be maintained to enhance print quality. However, previous research on contact printing pressure failed to directly estimate the contact printing pressure due to structural problems, and only indirectly measured it by attaching a load cell at both ends of the impression roll. This study proposes a method of contact printing pressure estimation and control to enhance print quality. The processing precision of a roll can be measured by measuring the rotationally repeatable run-out after dividing the width of the impression roll and plate roll into 25 points. The relationship between the impression roll and the plate roll, with consideration of the contact printing pressure, rotationally repeatable run-out, and force measured by the load cell, is modeled in a manner similar to the relationship between a car body, suspension, and ground in a half-car model, and expressed using state-space equations. This model is then applied to an individual drive type cross-coupled control system for experiments on control of the contact printing pressure; pressure measuring films are used to check for actual improvement in uniformity of contact printing pressure.

We present a high-performance flexible bending strain sensor for directional motion detection of human hands and soft robotic grippers. The sensor was fabricated using a printable porous conductive composite composed of polydimethylsiloxane (PDMS) and carbon black (CB). The utilization of a deep eutectic solvent (DES) in the ink formulation induced a phase segregation between the CB and PDMS and led to a porous structure inside the printed films after being vapored. This simple and spontaneously formed conductive architecture provided superior directional bend-sensing characteristics compared to conventional random composites. The resulting flexible bending sensors displayed high bidirectional sensitivity (gauge factor of 45.6 under compressive bending and 35.2 under tensile bending), negligible hysteresis, good linearity (>0.99), and excellent bending durability (over 10,000 cycles). The multifunctional applications of these sensors, including human motion detection, object-shape monitoring, and robotic perceptions, are demonstrated as a proof-of-concept.

In nanoparticle-based printed electronic devices, the printability of the patterns constituting the device are crucial factors. Although many studies have investigated the printability of patterns, only a few have analyzed and established international standards for measuring the dimensions and printability of shape patterns. This study introduces an advanced algorithm for accurate measurement of the geometry and printability of shape patterns to establish an international standard for pattern dimensions and printability. The algorithm involves three core concepts: extraction of edges of printed patterns and identification of pixel positions, identification of reference edges via the best-fitting of the shape pattern, and calculation of different pixel positions of edges related to reference edges. This method enables the measurement of the pattern geometry and printability, including edge waviness and widening, while considering all pixels comprising the edges of the patterns. The study results revealed that the rectangle and circle patterns exhibited an average widening of 3.55% and a maximum deviation of 1.58%, based on an average of 1662 data points. This indicates that the algorithm has potential applications in real-time pattern quality evaluation, process optimization using statistical or AI-based methods, and foundation of International Electrotechnical Commission standards for shape patterns.

Successful precision agriculture decision making requires characterizing soil heterogeneity at high spatiotemporal resolution in real-time in order to optimize input (such as water and nutrient) amounts and location. In order to achieve this goal, a printed soil moisture sensor fabricated from biodegradable materials is demonstrated. These devices are intended to function during the growing season and then harmlessly degrade afterward, enabling high-density deployment, eliminating the need for sensor retrieval, and enabling the use of simple device structures and low-cost materials and fabrication techniques. A capacitive structure is used with a water-soluble zinc electrode printed onto a biodegradable substrate. Rapidly degrading substrate and electrode are encapsulated in a slowly degrading wax blend that protects the device, reduces drift, and controls degradation time. A linear capacitance response is observed for soil samples with a volumetric water content from 0 to 72%. Accelerated degradation testing demonstrates that the sensor responds predictably and stably until the encapsulation is breached, at which point the sensor fails rapidly, providing a clear distinction between the functional and nonfunctional lifetimes of the sensor. These results demonstrate the potential of biodegradable sensors to allow maintenance-free, affordable, and real-time soil moisture measurement at high spatial density for precision irrigation control.

This paper examines various ways of combining paper and glass as a laminate and the effects on transparency. Laminate in this context means a layer of paper sandwiched in between layers of glass held together with an adhesive. Different kinds of papers and adhesives were used to study the potentials of glass-paper-laminates as related to transparency and translucency. These laminates may find applications in building construction, safety glass, printed electronics and more. Utilizing a variety of adhesives and papers, qualitative evidence found that epoxy achieves the best with regards to transparency and adheres most effectively.

Sessile droplets of colloidal dispersions tend to exhibit the coffee-ring phenomenon in the drying process. The suspended particles are transported especially at the final stage of the drying process, which is called the rush hour. Conventional inkjet printers require the ink liquid to have a sufficiently low viscosity for inkjet discharge, but such liquids tend to be subject to the coffee-ring effect. The coffee-ring effect is an issue for conventional printing applications and drawing wires in printed electronics. We show by microscopy movie data analysis based on single particle tracking that the addition of a small amount of cellulose nanofibers (CNFs) to the colloidal dispersion works in such a way that the initial low concentration satisfies the low viscosity requirement, and the three-dimensional structural order of the CNFs formed during the final stage of droplet drying owing to the high concentration hinders the transport of particles to the periphery, suppressing the coffee-ring effect. This is a spatio-temporally controlled process that makes use of the inherent process of ordinary ink printing situations by the simple protocol. This is also an approach to seamlessly link the ink and substrate since CNFs are regarded as a promising substrate material for flexible devices in printed electronics because of their fine texture that keeps conductive nanoparticles on the surface.