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Abstract Conductive polymer hydrogels (CPHs) are promising in cutting‐edge applications including bioelectronics and tissue engineering. However, the precise regulation of the spatial distribution of the conductive polymer (CP) in the hydrogel network is still an issue for designing a smart material. Herein, we propose a facile method for preparing CPH‐based smart materials by controlling the distribution of Fe3+ initiator with UV light irradiation. Thus, designable polypyrrole (PPy) conductive patterns in the polyvinyl alcohol/sodium alginate (PVA/SA) semi‐interpenetrating hydrogel network are demonstrated by controlling the concentration of Fe3+ ions coordinated with carboxylate groups. Depending on the irradiation time, the reduction of Fe3+ to Fe2+ occurs in different extents. As a result, the controllable polymerization of pyrrole only initiated by Fe3+ is achieved to form desirable CPH patterns, which are confirmed by the characterization results of Fourier transform infrared spectrometry, X‐ray photoelectron spectroscopy, and scanning electron microscopy. Moreover, the developed hydrogel with PPy patterns is illustrated for the application in smart conductive circuit and information encryption. The simple procedure and the controllable conductive patterning of the proposed method make it a promising route in developing smart hydrogel materials, which can be extended to other Fe3+ initiated CP patterns.

• A conductive polythiophene composite film containing copper and silver is formed. • Cu/Ag-PT film serves as seed layer to directly electrodeposit on insulating substrate. • A multi-dimensional conductive pattern is obtained by Cu/Ag-PT direct electroplating. Conductive polymer direct electroplating technology is one of the research hotspots in printed circuit board manufacturing. In this work, we designed a simple, efficient and environmental friendly chemical polymerization method to form a conductive polymer-based metal-mixed composite film where the polymer was polythiophene and the metals included copper and silver (PT-based Cu/Ag composite film). The work function of the PT-based Cu/Ag composite film decreased from 4.822 eV of pure PT to 4.638 eV, which serves as a seed layer to prepare conductive circuits by the additive process. The method without the metal etching and photolithography steps solves the problems of conventional subtractive processes for forming conductive patterns. Besides, the PT-based Cu/Ag composite film is able to increase the roughness of the substrate to improve the bonding force between the electroplated copper layer and the substrate. Moreover, due to the particularity of oxidation solution for preparing the PT-based Cu/Ag composite film, conductive lines and patterns can be selectively formed on insulating substrate with arbitrary shapes by the additive process. [Display omitted] [ABSTRACT FROM AUTHOR]

We reported a simple, high yield and large-scale preparation method for silver nanoparticles. Silver nanoparticles with 8–13 nm in diameter were successfully synthesized by silver nitrate as raw material, sodium borohydride as reducing agent, dispersan-5040 (polycarboxylate sodium salt) as surface modifier in aqueous solution. The effects of sodium borohydride and dispersan-5040 on the morphologies of silver nanoparticles were investigated. Further, the conductive inks were prepared with as-synthesized silver nanoparticles as conductive fillers in the presence of deionized (DI) water and additives. The effects of conductive fillers and additives on the pH, conductivity, surface tension and viscosity of the inks were investigated. The conductive patterns were fabricated by inkjet printer and their performances were studied. The sheet resistances of the printed pattern with seven-layer was 1.2 Ω / □ when the printed pattern was heat-treated at 120 ∘ C for 60 min. We succeeded in printing a simple conductive circuit on photographic paper, which can light three 0.06 W LED beads. The successful fabrication of the functional circuit proves the feasibility of the ink and provides some ideas for future paper-based circuits. [ABSTRACT FROM AUTHOR]

Printed circuit boards are part of electronic devices and affect the functioning of today's society. At present, printed circuit boards are manufactured for relatively long periods of time using the same methods. The presented article focuses on the design of the possibility which eliminates errors arising from the development and etching of PCBs. It describes the theoretical design of the use of hydrodynamic continuous water jet machining in PCB production. The proposal points to the possibility of using positive water jet properties are as such: no heat-affected zone, thin separation gap, absence of dust particles and toxic fumes. [ABSTRACT FROM AUTHOR]

For the conductive patterns of electronic textiles (e-textiles), it is still challenging to maintain low electrical resistance, even under large or cyclic tensile deformation. This study investigated a double-layered pattern with different crack configurations as a possible solution. Patterns with single crack growth exhibit a low initial resistance and resistance change rate. In contrast, patterns with multiple crack growth maintain their conductivity under deformation, where electrical failure occurs in those with single crack growth. We considered that a double-layered structure could combine the electrical characteristics of patterns with single and multiple crack growths. In this study, each layer was theoretically designed to control the crack configuration. Then, meandering copper patterns, silver ink patterns, and their double layers were fabricated on textiles as patterns with single and multiple crack growths and double-layered patterns, respectively. Their resistance changes under the single (large) and cyclic tensile deformations were characterized. The results confirmed that the double-layered patterns maintained the lowest resistance at the high elongation rate and cycle. The resistance change rates of the meandering copper and silver ink patterns were constant, and changed monotonically against the elongation rate/cycle, respectively. In contrast, the change rate of the double-layered patterns varied considerably when electrical failure occurred in the copper layer. The change rate after the failure was much higher than that before the failure, and on the same order as that of the silver ink patterns.

Directly printing conductive ink on textiles is simple and compatible with the conventional electronics manufacturing process. However, the conductive patterns thus formed often show high initial resistance and significant resistance increase due to tensile deformation. Achieving conductive patterns with low initial resistance and reduced deformation-induced resistance increase is a significant challenge in the field of electronic textiles (e-textiles). In this study, the passivation layers printed on conductive patterns, which are necessary for practical use, were examined as a possible solution. Specifically, the reduction of the initial resistance and deformation-induced resistance increase, caused by the curing shrinkage of passivation layers, were theoretically and experimentally investigated. In the theoretical analysis, to clarify the mechanism of the reduction of deformation-induced resistance increase, crack propagation in conductive patterns was analyzed. In the experiments, conductive patterns with and without shrinking passivation layers (polydimethylsiloxane) cured at temperatures of 20–120 °C were prepared, and the initial resistances and resistance increases due to cyclic tensile and washing in each case were compared. As a result, the initial resistance was reduced further by the formation of shrinking passivation layers cured at higher temperatures, and reduced to 0.45 times when the curing temperature was 120 °C. The cyclic tensile and washing tests confirmed a 0.48 and a 0.011 times reduction of resistance change rate after the 100th elongation cycle (10% in elongation rate) and the 10th washing cycle, respectively, by comparing the samples with and without shrinking passivation layers cured at 120 °C.

Screen printing is widely used to form conductive patterns due to its simple process, inexpensive equipment and masks, and fewer printing errors. In the field of electronics, there has recently been a growing demand to print both low-width and high-thickness electrodes, not only on flat surfaces but also on cylindrically curved ones. However, screen printing cannot form fine patterns due to ink bleeding, and in principle, printing on concave surfaces is impossible with conventional screen printing. Further, overprinting forms a thick pattern that requires subjecting the conductive ink to a drying process before printing the next layer of ink, leading to longer processing times. To address these issues, we developed an advanced screen printing technique called screen-offset curved-surface printing to form fine patterns on a curved substrate. In this method, ink is screen-printed onto a roll-type silicone blanket, and the ink is then transferred from the blanket onto a final substrate. During the transfer process, the roll-type blanket is moved in the vertical direction with a rotational motion along the surface of the curved substrate. It is this compound motion of the blanket that enables printing on a curved surface. Moreover, a simple overprinting technique for thick patterns was successfully performed on the curved substrate. This technique leverages the fact that the silicone blanket absorbs the organic solvents in the ink; the increase in the viscosity of the first layer of ink, owing to the solvent absorption, enables the next layer of ink to be easily overprinted on the blanket. In this paper, the developed printing method is presented in detail. [ABSTRACT FROM AUTHOR]

Conductive patterns on textiles are one of the key components for electronic textiles (E-textiles). The patterns with deeper permeation of inks into the textiles show better durability against cyclic tensile deformation. However, other requirements for improving the durability and the behavior of resistance under deformation are still unclear. In this study, the resistance during cyclic tensile deformation was measured with changing conditions, and the resistance variation was analyzed while considering the stress variation. Silver inks were printed on a plain weave, and the pattern width and tensile direction against weft yarns were changed. Measurements confirmed that the resistance increased less with wider pattern widths and when the tensile direction was horizontal to the axis of the weft yarns. Through scanning electron microscopy (SEM) observation, we also confirmed that the growth rate of cracks, at the crossing point of yarns, was changed by the tensile direction. These results indicate that the durability is improved when the electricity path redundancy within the pattern is robust, and the crack growth rate at the yarn crossing points is low. The analysis also confirmed both increasing and decreasing behavior of resistance during stretching in the cyclic tensile deformation, indicating the behavior results from the stress variation of a plain weave.

We report a fabrication method of the conductive pattern based on in situ reactive silver precursor inks by inkjet printing. The reactive silver precursor inks were prepared with ethylene glycol and deionized water mixture as the solvent, and silver nitrate as silver source. Sodium borohydride solution as the reducing agent was first coated on photographic paper by screen printing process, and then dried at 50 °C for 4 h. Furthermore, the reactive silver precursor inks were printed on a photographic paper coated with sodium borohydride using inkjet printing to form silver nanoparticles in situ due to redox reaction, and thus a conductive pattern was obtained. The effects of the reactive silver precursor ink concentration and printing layer number and treatment temperature on the electrical properties and microstructures of the printed patterns were investigated systematically. The size range of in situ-formed silver nanoparticles was 50−90 nm. When the reactive silver precursor ink concentration was 0.13 g/mL, the five-layer printed pattern exhibited a sheet resistance of 4.6 Ω/γ after drying at room temperature for 2 h; furthermore, the sheet resistance of the printed pattern decreased to 1.4 Ω/γ after drying at 130 °C for 2 h. In addition, the display function circuit was printed on the photographic paper to realize the display of the numbers 0−99. It provides new research ideas for the development of environmentally friendly and low-cost flexible paper-based circuits.

Nanoscale patterns with high conductivity based on silver nanoparticle inks were fabricated using spray coating method. Through optimizing the solution content and spray operation, accurate nanoscale patterns consisting of silver nanoparticles with a square resistance lower than 1 Ω /cm were obtained. By incorporating in situ sintering to substitute the general post sintering process, the time consumption could be significantly reduced to one sixth, qualifying it for large-scale and cost-effective fabrication of printed electronics. To testify the application of spray-coated silver nanoparticle inks, an inverted polymer solar cell was also fabricated, which exhibited a power conversion efficiency of 2.76%. [ABSTRACT FROM AUTHOR]

A simple patterning process to prepare conducting circuits in the atmosphere with the irradiation of laser and complex Cu nano-colloid was demonstrated. Stable Cu nano-colloids with a particle size of less than 10 nm were produced by an electrical wire explosion process in anhydrous ethanol. Uniform Cu film without cracks was prepared by using a Cu nano-colloid with copper(II) nitrate trihydrate. Various kinds of conductive Cu patterns on a flexible substrate were prepared by laser irradiation in air. The Cu pattern on a flexible polyimide substrate showed about 40 Ω/square of electrical sheet resistance. [ABSTRACT FROM AUTHOR]

Screen printing is a useful method for fabricating electrodes or signal wires of electronic devices. However, finer patterns, e.g., 50-μm-wide, are difficult to form. Herein, we introduce a newly developed printing technique called “screen-offset printing,” as a candidate method for solving this problem. In this process, first, ink patterns are screen-printed on a silicone-resin blanket; they are then transferred from the blanket to an object. In the present study, we analyze the features of screen-offset printing by observing printed conductive patterns, and elucidate the impact of this method by comparing the experimental results of screen-offset printing and conventional screen printing. In addition, we demonstrate the fabrication of fine patterns with a line and space ( L / S ) of 50/50 and 30/30 μm. [ABSTRACT FROM AUTHOR]

Highlights: [•] Mixed stabilizers and reductants resulted in reduced the size of Cu particles. [•] Refined Cu NPs exhibited an enhanced density upon sintering. [•] The enhanced particle density decreased the resistivity of the Cu pattern. [ABSTRACT FROM AUTHOR]

Air-stable Cu nanoparticles (NPs) with an average diameter of 6.5 nm were synthesized under ambient conditions using polyvinylpyrrolidone and cetyltrimethylammonium bromide as a mixed capping agent, for preparing nano-Cu ink applicable for direct writing on photo paper using a roller pen. The size, morphology, and air-stability of the Cu NPs were characterized by TEM, SEM, XRD, etc. The mixed capping agent was effective in reducing the aggregation, size of the Cu NPs and improving their air-stability. The reduced size and enhanced air-stability of the Cu NPs resulted in an improved particle density upon sintering, which was mainly responsible for the increased conductivity of the Cu patterns. The resistivity of Cu patterns sintered at 160 °C for 2 h was 11 ± 0.8 μΩ cm, 6.40 times the bulk resistivity. A sample RFID antenna and a decorative logo were successfully made and the Cu patterns or lines exhibited excellent integrity and good conductivity, which were experimentally tested. [ABSTRACT FROM AUTHOR]

An unusual kind of transparent and high-efficiency organic silver conductive ink (OSC ink) was synthesized with silver acetate as silver carrier, ethanolamine as additive, and different kinds of aldehyde-based materials as reduction agents and was characterized by using a thermogravimetric analyzer, X-ray diffraction, a scanning electron microscope, and a four-point probe. The results show that different reduction agents all have an important influence on the conductive properties of the ink through a series of complex chemical reactions, and especially when formic acid or dimethylformamide was used as the reduction agent and sintered at 120°C for 30 s, the resistivity can be lowered to 6 to 9 µΩ⋅cm. Furthermore, formula mechanism, conductive properties, temperature, and dynamic fatigue properties were investigated systematically, and the feasibility of the OSC ink was also verified through the preparation of an antenna pattern. [ABSTRACT FROM AUTHOR]

Pulsed electrohydrodynamic printing (EHDP) is used to fabricate conductive silver patterns with micrometer resolution. The silver ink pendant experiences swelling, pulsation, and ejection under an applied pulse voltage of 20 Hz. The droplet deposition frequency is equal to the applied voltage frequency so that the EHDP can deposit silver ink on demand. A low applied voltage favors uniform and non-scattering silver patterns while a high applied voltage results in ink scattering. Discrete droplets with 45-55 μm in diameter and continuous tracks with 60 μm in width are generated by using a 110-μm-cailber nozzle. The feature size of deposited patterns is about half of the nozzle caliber, and a finer resolution can be achieved with the introduction of smaller nozzle calibers. Furthermore, the appropriate curing condition is investigated for sufficient combustion of ink solvent. The minimum resistivity of 3.3 μΩ cm is demonstrated for a continuous track cured at 200°C for 10 min. Eventually, several passive electrical components, such as coated resistors, interdigitated capacitors (6 pF), and spiral inductors (0.6 μH), are successfully fabricated. [ABSTRACT FROM AUTHOR]

Abstract: Direct stamping of functional materials has been developed to reduce the number of processes and cost, and to increase throughput. However, there remain several challenging issues. One of the challenging issues is the residue-remaining problem after direct stamping. This significantly reduces reliability of stamping of micro-patterns and life-span of stamps. Here we present that direct stamping of silver nanoparticle generated conductive pattern with super-oleophobic stamp. A stamp was fabricated with UV-curable urethane rubber modified by perfluorinated silane. A master fabricated by photolithography and Bosch type etching enabled us to obtain a stamp patterned with a 2D array of voids with nano-scale re-entrant walls. And complete residue-free direct stamping of silver nanoparticles onto a glass substrate has been achieved using the stamp for little contact between the silver nanoparticle ink and the stamp was allowed by super-oleophobicity which resulted from the stamp material and pattern. [Copyright &y& Elsevier]

Abstract: This paper investigates fabrication of large-area Ag–Pd conductive patterns on ferrite substrate using laser micro-cladding for microwave device application. The effects of the scan line spacing (i.e., beam overlapping factor) on the quality of the fabricated conductive film were studied in detail. Results showed that surface morphologies and electrical characteristics of laser-sintered conductive films were highly dependent on the value of the scan line spacing and the critical beam overlapping factor lay between 20% and 40%. [ABSTRACT FROM AUTHOR]

Abstract: Ink-jet printing of metal nanoparticles is an attractive method for direct patterning conductive metal lines owing to low-cost, low-waste, and simple process. While most of the researches here focused on novel metals such as gold and silver, we have developed a conductive ink containing copper nanoparticles as an alternative that is inexpensive conductive material. Copper particles with a size of 40–50 nm were synthesized by polyol process, from which the well-dispersed conductive ink with low viscosity was prepared. We have successfully demonstrated a direct writing of the conductive lines using Cu conductive ink. The ink-jet printed copper patterns exhibited metal-like appearance and became highly conductive upon heat treatments. The resistivity of the film reached to 17.2 μΩ cm at 325 °C for 1 h in vacuum. [Copyright &y& Elsevier]

Abstract: We have developed a conductive ink containing silver nanoparticles from which the electrodes for organic thin film transistor were directly patterned by ink-jet printing. Nano-sized silver particles having ∼20 nm diameter was used for a direct metal printing. Silver conductive ink was printed on the heavily doped n-type silicon wafer with 200-nm thick thermal SiO2 layer as a substrate. To achieve a high line resolution and smooth conductive path, the printing conditions such as the inter-drop distance, stage moving velocity and temperature of the pre-heated substrates were optimized. After the heat-treatment at temperatures of 200 °C for 30 min, the printed silver patterns exhibit metal-like appearance and the conductivity. To fabricate a coplanar type TFTs, an active material of semiconducting oligomer, α,ω-dihexylquaterthiophene (DH4T) in a chlorobenzene was deposited between the ink-jet printed silver electrodes by drop casting. The OTFT with the ink-jetted source/drain electrodes shows general performance characteristics with good saturation behavior and no significant contact resistance as compared to the one with vacuum deposited electrodes. The electrical characteristic parameters of OTFT show the mobility of 1.3×10−3 cm2 V−1 s−1 in the saturation regime, on/off current ratio over 103, and threshold voltage of about −13 V. [Copyright &y& Elsevier]

We have developed a conductive ink applicable to ink-jet printing to fabricate conductive lines on flexible substrates. Nano-sized silver particles with ∼⃒21 nm diameter were used for the direct metal printing. Silver conductive ink was printed on polymer substrates for the application to flexible electronics. The printing conditions of pulse amplitude, head frequency, xy-stage moving velocity and substrate temperature were optimized to achieve smooth conductive track with high resolution. After heat-treatment at temperature of 100 ∼⃒ 300°C for 30 min, the printed silver patterns exhibit metal-like appearance and high conductivity. The influence of the printing conditions on the microstructure and conductivity of the conductive track was investigated. [ABSTRACT FROM AUTHOR]

Diabetes is one of the most serious diseases affecting human health worldwide. Maintaining a certain level of glucose concentration is key for diabetes. Driven by the increasing demand for simply prepared, low-cost, and flexible sensing systems, we developed reduced graphene oxide (rGO) patterns-based amperometric sensor for glucose determination. The rGO patterns were produced by stamping of patterned graphene oxide (GO) on polyethylene terephthalate (PET) substrates using filtration/wax-printing method and then reducing to rGO for providing conductivity. The prepared graphene-based patterns were modified by glucose oxidase (GOx) and used as an excellent working electrode for electrochemical enzymatic determination of glucose, as a model sensing. The proposed biosensor exhibited an ultra-fast response time of 0.37 s and the sensitivity of 11.2 μA mM−1 cm−2 with a linear concentration range of 1.0–25.0 mM and a satisfactory low detection limit of 0.32 mM. Besides, it showed good reproducibility, stability, selectivity, and anti-interference ability in glucose determination. The results present that the fabricated platform can be employed for the determination of glucose in human serum, which indicates its promising applicability in the real sample analysis. The effective proof-of-concept for the determination of glucose can be applied to different (bio)sensing systems to miniaturize of detection instrument. Unlabelled Image • Demonstration of sensor preparation via patterning of reduced graphene oxide (rGO) • Wax-printing and filtration method have been employed. • rGO patterns-based amperometric sensor for glucose determination has been achieved. [ABSTRACT FROM AUTHOR]

• Found that the pattern of conduction of many gold nanorods contains a low conductivity central region. • It was found that this was not an artefact of the CAFM technique. • The concavity images from sensitive AFM modes strongly support the BSWG mechanism of nanorod growth. • The possibility of 50 nm gold nanotube formation has been demonstrated. • The reversible connection and disconnection of polycrystalline nanorod embedded inside porous alumina. Nanowires and nanotubes composed of layered or nonlayered materials have been fabricated via different techniques, among which Anodic Aluminium Oxide (AAO) template-based electrodeposition technology provides a versatile technique for synthesizing one or two-dimensional nanostructured materials. Herein, Conductive Atomic Force Microscopy (CAFM) has been used to image and characterise the nanorods for nanorods with diameter of 50 nm ± 5. Given that only one previous study using CAFM on gold nanorods exists [1], recording the difficulties encountered with this technique will be of wider interest to the scientific community. This work details experiments on electrical response as a function of applied force on the AFM tip and contamination on the top surface on nanorods. We report a novel observation, revealing a hollow shaped conductive pattern of some of our gold nanorods. This is explained with reference to competing growth rates in horizontal and vertical directions inside the pores. [ABSTRACT FROM AUTHOR]

For the conductive patterns of electronic textiles (e-textiles), it is still challenging to maintain low electrical resistance, even under large or cyclic tensile deformation. This study investigated a double-layered pattern with different crack configurations as a possible solution. Patterns with single crack growth exhibit a low initial resistance and resistance change rate. In contrast, patterns with multiple crack growth maintain their conductivity under deformation, where electrical failure occurs in those with single crack growth. We considered that a double-layered structure could combine the electrical characteristics of patterns with single and multiple crack growths. In this study, each layer was theoretically designed to control the crack configuration. Then, meandering copper patterns, silver ink patterns, and their double layers were fabricated on textiles as patterns with single and multiple crack growths and double-layered patterns, respectively. Their resistance changes under the single (large) and cyclic tensile deformations were characterized. The results confirmed that the double-layered patterns maintained the lowest resistance at the high elongation rate and cycle. The resistance change rates of the meandering copper and silver ink patterns were constant, and changed monotonically against the elongation rate/cycle, respectively. In contrast, the change rate of the double-layered patterns varied considerably when electrical failure occurred in the copper layer. The change rate after the failure was much higher than that before the failure, and on the same order as that of the silver ink patterns. [ABSTRACT FROM AUTHOR]

Directly printing conductive ink on textiles is simple and compatible with the conventional electronics manufacturing process. However, the conductive patterns thus formed often show high initial resistance and significant resistance increase due to tensile deformation. Achieving conductive patterns with low initial resistance and reduced deformation-induced resistance increase is a significant challenge in the field of electronic textiles (e-textiles). In this study, the passivation layers printed on conductive patterns, which are necessary for practical use, were examined as a possible solution. Specifically, the reduction of the initial resistance and deformation-induced resistance increase, caused by the curing shrinkage of passivation layers, were theoretically and experimentally investigated. In the theoretical analysis, to clarify the mechanism of the reduction of deformation-induced resistance increase, crack propagation in conductive patterns was analyzed. In the experiments, conductive patterns with and without shrinking passivation layers (polydimethylsiloxane) cured at temperatures of 20–120 °C were prepared, and the initial resistances and resistance increases due to cyclic tensile and washing in each case were compared. As a result, the initial resistance was reduced further by the formation of shrinking passivation layers cured at higher temperatures, and reduced to 0.45 times when the curing temperature was 120 °C. The cyclic tensile and washing tests confirmed a 0.48 and a 0.011 times reduction of resistance change rate after the 100th elongation cycle (10% in elongation rate) and the 10th washing cycle, respectively, by comparing the samples with and without shrinking passivation layers cured at 120 °C. [ABSTRACT FROM AUTHOR]

Conductive patterns on textiles are one of the key components for electronic textiles (E-textiles). The patterns with deeper permeation of inks into the textiles show better durability against cyclic tensile deformation. However, other requirements for improving the durability and the behavior of resistance under deformation are still unclear. In this study, the resistance during cyclic tensile deformation was measured with changing conditions, and the resistance variation was analyzed while considering the stress variation. Silver inks were printed on a plain weave, and the pattern width and tensile direction against weft yarns were changed. Measurements confirmed that the resistance increased less with wider pattern widths and when the tensile direction was horizontal to the axis of the weft yarns. Through scanning electron microscopy (SEM) observation, we also confirmed that the growth rate of cracks, at the crossing point of yarns, was changed by the tensile direction. These results indicate that the durability is improved when the electricity path redundancy within the pattern is robust, and the crack growth rate at the yarn crossing points is low. The analysis also confirmed both increasing and decreasing behavior of resistance during stretching in the cyclic tensile deformation, indicating the behavior results from the stress variation of a plain weave. [ABSTRACT FROM AUTHOR]

We report a fabrication method of the conductive pattern based on in situ reactive silver precursor inks by inkjet printing. The reactive silver precursor inks were prepared with ethylene glycol and deionized water mixture as the solvent, and silver nitrate as silver source. Sodium borohydride solution as the reducing agent was first coated on photographic paper by screen printing process, and then dried at 50 °C for 4 h. Furthermore, the reactive silver precursor inks were printed on a photographic paper coated with sodium borohydride using inkjet printing to form silver nanoparticles in situ due to redox reaction, and thus a conductive pattern was obtained. The effects of the reactive silver precursor ink concentration and printing layer number and treatment temperature on the electrical properties and microstructures of the printed patterns were investigated systematically. The size range of in situ-formed silver nanoparticles was 50–90 nm. When the reactive silver precursor ink concentration was 0.13 g/mL, the five-layer printed pattern exhibited a sheet resistance of 4.6 Ω/γ after drying at room temperature for 2 h; furthermore, the sheet resistance of the printed pattern decreased to 1.4 Ω/γ after drying at 130 °C for 2 h. In addition, the display function circuit was printed on the photographic paper to realize the display of the numbers 0–99. It provides new research ideas for the development of environmentally friendly and low-cost flexible paper-based circuits. [ABSTRACT FROM AUTHOR]

Inkjet printing of functional inks on textiles to embed passive electronics devices and sensors is a novel approach in the space of wearable electronic textiles. However, achieving functionality such as conductivity by inkjet printing on textiles is challenged by the porosity and surface roughness of textiles. Nanoparticle-based conductive inks frequently cause blockage/clogging of inkjet printer nozzles, making it a less than ideal method for applying these functional materials. It is also very challenging to create a conformal conductive coating and achieve electrically conductive percolation with the inkjet printing of metal nanoparticle inks on rough and porous textile and paper substrates. Herein, a novel reliable and conformal inkjet printing process is demonstrated for printing particle-free reactive silver ink on uncoated polyester textile knit, woven, and nonwoven fabrics. The particle-free functional ink can conformally coat individual fibers to create a conductive network within the textile structure without changing the feel, texture, durability, and mechanical behavior of the textile. It was found that the conductivity and the resolution of the inkjet-printed tracks are directly related with the packing and the tightness of fabric structures and fiber sizes of the fabrics. It is noteworthy that the electrical conductivity of the inkjet-printed conductive coating on pristine polyethylene terephthalate fibers is improved by an order of magnitude by in situ heat-curing of the textile surface during printing as the in situ heat-curing process minimizes the wicking of the ink into the textile structures. A minimum sheet resistance of 0.2 ± 0.025 and 0.9 ± 0.02 Ω/□ on polyester woven and polyester knit fabrics is achieved, respectively. These findings aim to advance E-textile product design through integration of inkjet printing as a low-cost, scalable, and automated manufacturing process.