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Introductions: Ink based on metallic nanoparticles has been widely used so far for the fabrication of electronic circuits and devices using printing technology. This study aimed at the analysis of the effect of the silver shell thickness of nickel@silver core@shell (Ni@Ag) nanoparticles (NPs) on the fabrication and conductive properties of deposited coatings.Methods: The process of the synthesis of Ni@Ag NPs with various silver shell thicknesses was developed. The physicochemical properties (size, stability against aggregation process) of synthesized Ni@Ag nanoparticles were analyzed. The films based on ink containing Ni@Ag NPs with different silver shell thicknesses were fabricated and sintered in a temperature range of 120– 300 °C and at times from 15 to 90 min. The dependence of their conductive properties on the applied temperature and time as well as silver shell thickness was evaluated.Results: Ni NPs were coated with 10, 20, 30, 35, 45, and 55 nm silver shell thickness. The resistivity of coatings based on obtained NPs depends on the thickness of the Ag shell and the sintering temperature. After sintering at 300 °C, the highest decrease in its value (at an optimal sintering time of 60 min) from about 100 μΩ·cm to 9 μΩ·cm was observed when the thickness of the shell increased from 10 to 55 nm. At the lowest sintering temperature (120 °C) the highest conductivity (about 50% of that for bulk nickel) was obtained for films based on Ni@Ag NPs with 45 and 55 nm of the silver shell thickness.Discussions: The analysis of the resistivity of the sintered films showed that higher conductivity was obtained for the coatings formed from Ni@Ag NPs with the thicker Ag shell; moreover, thicker shells allowed a lowering of sintering temperature due to higher conductivity and a lower melting point of silver in comparison to nickel NPs. [ABSTRACT FROM AUTHOR]

Efforts to miniaturize and customize electronic devices have attracted considerable amounts of attention in many industrial fields. Recently, due to its innovative printing technology with the capability of printing fine features onto non-planar substrates without masks, aerosol jet printing (AJP) is emerging as a promising printed-electronics technology capable of meeting the requirements of various advanced electronic applications. In this research, a novel manufacturing process based on AJP is proposed in order to fabricate highly flexible and conductive customized temperature sensors. To improve the flexibility and conductivity of the printed tracks, a silver nanoparticle/carbon nanotubes composite ink is developed. Customized temperature sensors are then designed and fabricated based on the optimized process parameters of AJP. It was found that the CNTs served as bridges to connect silver nanoparticles and defects, which could be expected to reduce the contact resistivity and enhance the flexibility of the printed sensor. [ABSTRACT FROM AUTHOR]

We studied the conductive properties of ink coatings composed of a mixture of Ni–Ag core–shell nanoparticles (NPs) at the size 70 nm and 250 nm. The metallic ink films were deposited on glass substrates by using bar coating and screen printing methods. The effect of the type of deposition method of ink coatings, as well as the temperature and time of the sintering process on their conductivity, was investigated. The most conductive films were obtained after thermal sintering at 300 °C. The obtained conductivity was about 20% of that for a bulk nickel, more than 80% higher than for films formed with any single type of particles. [ABSTRACT FROM AUTHOR]

Poly(tartaric acid) is a relatively recently described polymer that can be easily synthesized and scaled up from a readily available renewable material (tartaric acid). This article demonstrates its use in a green synthesis of gold nanoparticles, silver nanoparticles, copper particles, and magnetite nanoparticles. In this case poly(tartaric acid) acts both as a reductant and as a coating agent. To our knowledge this is the first green synthesis of several different types of nanoparticles using only one reagent (polytartrate) as both reductant and coating. The resulting particles were analyzed by XRD, TEM/SEM, EDX, FTIR, DLS, zeta-potential, XPS, and UV/VIS spectroscopy. Preliminary studies of the thermal behavior of mixtures of different types of particles with poly(tartaric acid) were also conducted. The obtained particles show different sizes depending on the material, and the coating allows for better dispersibility as well as potential further functionalization, making them potentially useful also for other applications, besides the inclusion in polymer composites. [ABSTRACT FROM AUTHOR]

This research paper presents the results of an investigation into the formulation of silver conductive ink for use in inkjet printing. The aim of the study is to develop an environmentally friendly and cost-effective ink using a simple and scalable method. To achieve this, silver nanoparticles (AgNPs) were synthesized through a co-reduction approach using starch and temperature, and their physical and chemical properties were examined. The silver conductive ink was prepared with different amounts of AgNPs, using a sodium alginate/ Polyethylene glycol (Na-alginate/PEG) suspension matrix. In order to ensure the suitability of ink for the inkjet printing technique, the viscosity measurement was performed. According to the results, three formulations were produced and printed on Polyurethane-coated polyester (PU-coated PET) by a syringe disposition system. The electrical measurements showed that the minimum sheet resistance of printed patterns prepared with 3%wt of AgNPs was 0.008 Ω/cm and 0.205 Ω/cm with 20wt% and 40wt% of Na-alginate, respectively. These values are sufficient to power an LED connected to the printed coated fabric. Furthermore, the electrical properties of the printed patterns remained acceptable for electronic applications even after mechanical stress up to 20%. This research has the potential to pave the way for several future applications of printed electronic textiles where environmentally friendly, low-cost, and higher electrical performance inks are required. [ABSTRACT FROM AUTHOR]

Low‐temperature bonding (≤300 o C) using Ag nanoparticles (Ag NPs) is considered to be the new generation of bonding technology in power electronics. The oxygen‐accelerated sintering has been observed by many researchers which is attributed to the decomposition of organics covered on Ag NPs. In this work, organic‐free Ag NPs are fabricated to eliminate the influence of organics, and it is found that the accelerated bonding process by oxygen is strongly correlated to the self‐confined amorphous Ag‐O compound shell on the surface of Ag NPs. In experiments, the sintering process is apparently accelerated by the elevating oxygen content, and the amorphous shell is observed after sintering, which do not grow thicker even in pure oxygen ambient for a long time while performing active chemical evolutions. In simulations, the results match well with the experiments and indicate that the amorphous shell performed the dynamic oxidation and decomposition process. This dynamic equilibrium is caused by the instability of silver oxides, which would enable the amorphous shell to activate the mobility of the surface mass flow and promote the surface diffusion. The shear strength of SiC chip increased by 354% when bonding in pure oxygen, targeting a broad variety of applications in electronic packaging. [ABSTRACT FROM AUTHOR]

Hybrid nanocomposites of silver nanoparticles and multiwalled carbon nanotubes (AgNPs/MWCNTs) were successfully synthesized by a green one-step method without using any organic solvent. The synthesis and attachment of AgNPs onto the surface of MWCNTs were performed simultaneously by chemical reduction. In addition to their synthesis, the sintering of AgNPs/MWCNTs can be carried out at room temperature. The proposed fabrication process is rapid, cost efficient, and ecofriendly compared with multistep conventional approaches. The prepared AgNPs/MWCNTs were characterized using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The transmittance and electrical properties of the transparent conductive films (TCF_Ag/CNT) fabricated using the prepared AgNPs/MWCNTs were characterized. The results showed that the TCF_Ag/CNT film has excellent properties, such as high flexible strength, good high transparency, and high conductivity, and could therefore be an effective substitute for conventional indium tin oxide (ITO) films with poor flexibility. [ABSTRACT FROM AUTHOR]

The field of printed electronics for highly integrated circuits and energy devices demands very fine and highly conductive electric interconnections. In this study, conductive lines having a high cross-sectional aspect ratio were printed via the inkjet printing of Ag nanoparticle inks assisted by a laser-induced selective surface wetting technique: a hydrophobic layer of self-assembled monolayer-treated ZnO nanorods was coated on a glass substrate and selectively ablated by a laser to form micro-channels for the inkjet, whose surface energy changed from 36.3 mJ/m2 to 51.5 mJ/m2 before and after the laser irradiation. With the varying width of the laser-ablated channels and pitch of jetted ink drops, the 3D shapes of the printed silver lines were measured to investigate their effects on the widths, heights, and uniformities of the printed patterns. The results showed that the present technique realized a uniform line of 35 μm width and 0.46 μm average thickness, having an aspect ratio of 0.013, which is 7.6 times higher than that printed on bare glass. [ABSTRACT FROM AUTHOR]

The large-scale manufacturing of flexible electronics is nowadays based on inkjet printing technology using specially formulated conductive inks, but achieving adequate wetting of different surfaces remains a challenge. In this work, the development of a silver nanoparticle-based functional ink for printing on flexible paper and plastic substrates is demonstrated. Amphiphilic silver nanoparticles with narrow particle size distribution and good dispersibility were prepared via a two-step wet chemical synthesis procedure. First, silver nanoparticles capped with poly(acrylic acid) were prepared, followed by an amidation reaction with 3-morpholynopropylamine (MPA) to increase their lipophilicity. Density functional theory (DFT) calculations were performed to study the interactions between the particles and the dispersion medium in detail. The amphiphilic nanoparticles were dispersed in solvents of different polarity and their physicochemical and rheological properties were determined. A stable ink containing 10 wt% amphiphilic silver nanoparticles was formulated and inkjet-printed on different surfaces, followed by intense pulsed light (IPL) sintering. Low sheet resistances of 3.85 Ω sq–1, 0.57 Ω sq–1 and 19.7 Ω sq–1 were obtained for the paper, coated poly(ethylene terephthalate) (PET) and uncoated polyimide (PI) flexible substrates, respectively. Application of the nanoparticle ink for printed electronics was demonstrated via a simple flexible LED circuit. [ABSTRACT FROM AUTHOR]

Over the last decade, an extensive range of consumer products containing manufactured silver nanoparticles (AgNPs) have been progressively used. The unfitting usage and discharge of these materials can enable passage of AgNPs into the aquatic ecosystem causing prospective toxicological consequence. The present study shed new lights on the phycotoxicity of small (8.47–17.66 nm) and stable Oscillatoria reduced gelatin-capped silver nanoparticles (OG-AgNPs) fabricated using a completely green synthetic technique. In this work, estimating of the possible toxic effects of OG-AgNPs on two freshwater microalgae Chlorella vulgaris and Chlorella minutissima was carried. This study found that, the growth of cells and photosynthetic pigment inhibitory effects of OG-AgNPs exhibit a significant increase with increasing time and concentration compared to control. Based on the IC50 value C. vulgaris (3.705 μg/mL) was found to be more sensitive to OG-AgNPs than C. minutissima (5.8 μg/mL). This study revealed that OG-AgNPs exhibit potent phycotoxic effect against Chlorella species. Finally, the negative effect of OG-AgNPs on aquatic algae and these modifications might have severe effects on structure and function of aquatic ecosystems. Besides, the biosynthesized OG-AgNPs showed a catalytic activity in the reduction of hydrogen peroxide, one of the reactive oxygen species that represent a major threat to biological systems. This method pretends an auspicious non-skill dependent technique with a good sensitivity for determination of H2O2 concentration, particularly at trace ppm level for applying in numerous domains such as medical and industrial processes. [ABSTRACT FROM AUTHOR]

Sintered silver (Ag) die-attach has attracted much attention in power systems with high power density and high operating temperature. In this paper, we proposed a novel surface modification method for Ag nanoparticles with organic amines as a coating agent for enhancing the pressureless sintering performance. This work systematically introduced the Ag nanoparticle modification process, Ag paste preparation, and sintering process and compared the changes in the sintering performance of Ag nanoparticles after modification with four different alkyl chain lengths of amines. The study showed that the sintered films of Ag nanoparticle pastes modified with n-octylamine (NOA) can achieve the lowest resistivity of the sintered film and the highest shear strength of the bonded joints. The resistivity of the sintered Ag film is affected by the grain size and microscopic morphology, and the strength of the bonded joints is also related to the sintering density and the amount of organic residues. The thermal behavior of the Ag particles coated with different amines is measured by thermal analysis. Finally, the mechanism of NOA-modified Ag nanoparticles to improve the sintering performance is proposed. This study can provide effective data and theoretical support for the further promotion and application of nano-Ag pressureless sintering. [ABSTRACT FROM AUTHOR]

Silver particles are key materials for the production of conductive inks, which are typically thermally sintered to obtain high conductivity. However, it remains a big challenge to achieve high conductivity at temperatures lower than 150 °C, for the protection of heat‐sensitive components in printed electronic devices. In this study, a novel frigid synthesis strategy at subzero temperature (Celsius) to produce Ag NPs with rich, rose‐like nanostructures (Ag nano‐flowers) is developed. The growth mechanism of Ag nano‐flowers under frigid conditions is analyzed and discussed. Due to the fine nanoscale structure of Ag nano‐flowers, they exhibit low sintering temperature below 120 °C. The electrical conductivity of printed Ag nano‐flower foil reaches 8.64 × 104 S cm−1 at 120 °C, and 1.20 × 105 S cm−1 at 150 °C. This study provides an attractive approach to the facile fabrication of Ag nano‐flowers with high electronic conductivity sintered at low temperatures and grants new insights into nanocrystallization under low‐temperature conditions. [ABSTRACT FROM AUTHOR]

Silver nanoparticle (NP) inks have been widely used in the ink-jet printing field because of their excellent properties during low-temperature sintering. However, the organic dispersant used to prevent the aggregation and sedimentation of NPs can hinder the sintering process and result in the high resistivity of sintered films. In this study, silver thin films derived from silver NP ink with polyvinylpyrrolidone (PVP) dispersant were sintered in different atmospheres of pure nitrogen, air, and pure oxygen. The effect of the oxygen content in the sintering atmosphere on the thermal properties of the ink, the electrical resistivity and microstructure of the sintered films, and the amount of organic residue were studied by using differential scanning calorimetry, the four-point probe method, scanning electron microscopy, Fourier transform infrared spectroscopy, etc. The mechanism of optimizing the film resistivity by influencing the decomposition of the PVP dispersant and the microstructure evolution of the silver thin films through the sintering atmosphere was discussed. The results demonstrated that an oxygen-containing atmosphere could be effective for silver NPs in two ways. First, the oxygen content could enhance the diffusion ability of silver atoms, thus accelerating the stage transition of microstructural evolution at low temperatures. Second, the oxygen content could enable the PVP to decompose at a temperature much lower than in conditions of pure nitrogen, thus helping to finalize the densification of a silver film with a low resistivity of 2.47 μΩ·cm, which is approximately 1.5-fold that of bulk silver. Our findings could serve as a foundation for the subsequent establishment of ink-jet printing equipment and the optimization of the sintering process for printing silver patterns on flexible substrates. [ABSTRACT FROM AUTHOR]

Nano-silver conductive ink meets the development demands of the flexible printed electronic products. The size of silver nanoparticles (AgNPs) was closely connected with the conductivity of the printed pattern. In this study, AgNPs were prepared, correlated with its conductivity. AgNPs were characterized by SEM, HR-TEM, UV–Vis, and XPS. The sintering methods of AgNPs were compared. The results showed that the optimum conditions of AgNPs with high conductivity were as follows: the molar ratio of polyvinylpyrrolidone to silver nitrate was 1.8:1, the concentration of silver nitrate was 0.05 mol/L, and the concentration of hydrazine hydrate was 2 mol/L. The particle size of AgNPs with a face-centred cubic structure was around 60 nm. Using sodium chloride as sintering agent at room temperature, AgNPs could get close to each other and sinter faster in comparison with the sintering at high temperature, and the sheet resistance of nano-silver film arrived at 1.2 × 10–5 Ω m. [ABSTRACT FROM AUTHOR]

Nowadays, inkjet-printed devices such as transistors are still unstable in air and have poor performances. Moreover, the present electronics applications require a high degree of reliability and quality of their properties. In order to accomplish these application requirements, hybrid electronics is fulfilled by combining the advantages of the printing technologies with the surface-mount technology. In this work, silver nanoparticle-based inkjet ink (AgNP ink) is used as a novel approach to connect surface-mount devices (SMDs) onto inkjet-printed pads, conducted by inkjet printing technology. Excellent quality AgNP ink-junctions are ensured with high resolution picoliter drop jetting at low temperature (~150 °C). Electrical, mechanical, and morphological characterizations are carried out to assess the performance of the AgNP ink junction. Moreover, AgNP ink is compared with common benchmark materials (i.e., silver epoxy and solder). Electrical contact resistance characterization shows a similar performance between the AgNP ink and the usual ones. Mechanical characterization shows comparable shear strength for AgNP ink and silver epoxy, and both present higher adhesion than solder. Morphological inspections by field-emission scanning electron microscopy confirm a high quality interface of the silver nanoparticle interconnection. Finally, a flexible hybrid circuit on paper controlled by an Arduino board is manufactured, demonstrating the viability and scalability of the AgNP ink assembling technique. [ABSTRACT FROM AUTHOR]

Purpose: In flexible electronics applications, organic inks are mostly used for inkjet printing. Three-dimensional (3 D) printing technology has the advantages of low cost, high speed and good precision in modern electronic printing. The purpose of this study is to solve the high cost of traditional printing and the pollution emissions of organic ink. It is necessary to develop a water-based conductive ink that is easily degradable and can be 3 D printed. A nano-silver ink printed circuit pattern with high precision, high conductivity and good mechanical properties is a promising strategy. Design/methodology/approach: The researched nano-silver conductive ink is mainly composed of silver nanoparticles and resin. The effect of adding methyl cellulose on the ink was also explored. A simple 3 D circuit pattern was printed on photographic paper. The line width, line length, line thickness and conductivity of the printed circuit were tested. The influence of sintering temperature and sintering time on pattern resistivity was studied. The relationship between circuit pattern bending performance and electrical conductivity is analyzed. Findings: The experimental results show that the ink has the characteristics of low silver content and good environmental protection effect. The printing feasibility of 3 D printing circuit patterns on paper substrates was confirmed. The best printing temperature is 160°C–180°C, and the best sintering time is 30 min. The circuit pattern can be folded 120°, and the cycle is folded more than 60 times. The minimum resistivity of the circuit pattern is 6.07 µΩ·cm. Methyl cellulose can control the viscosity of the ink. The mechanical properties of the pattern have been improved. The printing method of 3 D printing can significantly reduce the sintering time and temperature of the conductive ink. These findings may provide innovation for the flexible electronics industry and pave the way for alternatives to cost-effective solutions. Originality/value: In this study, direct ink writing technology was used to print circuit patterns on paper substrates. This process is simple and convenient and can control the thickness of the ink layer. The ink material is nonpolluting to the environment. Nano-silver ink has suitable viscosity and pH value. It can meet the requirements of pneumatic 3 D printers. The method has the characteristics of simple process, fast forming, low cost and high environmental friendliness. [ABSTRACT FROM AUTHOR]

The need for more sustainable printed electronics has emerged in the past years. Due to this, the use of nanocellulose (NC) extracted from cellulose has recently been demonstrated to provide interesting materials such as functional inks and transparent flexible films due to its properties. Its high specific surface area together with the high content of reactive hydroxyl groups provide a highly tailorable surface chemistry with applications in ink formulations as a stabilizing, capping, binding and templating agent. Moreover, NC mechanical, physical and thermal properties (high strength, low porosity and high thermal stability, respectively) provide an excellent alternative for the currently used plastic films. In this work, we present a process for the production of water-based conductive inks that uses NC both as a template for silver nanoparticles (Ag NPs) formation and as an ink additive for ink formulation. The new inks present an electrical conductivity up to 2 × 106 S/m, which is in the range of current commercially available conductive inks. Finally, the new Ag NP/NC-based conductive inks have been tested to fabricate NFC antennas by screen-printing onto NC-coated paper, demonstrating to be operative. [ABSTRACT FROM AUTHOR]

Otitis Media (OM) is the most common reason for US children to receive prescribed oral antibiotics, leading to be a potential to cause antibiotic resistance. To minimize oral antibiotic usage, we developed polyvinylpyrrolidone‐coated silver nanoparticles (AgNPs‐PVP), which completely eradicated common OM pathogens, that is, Streptococcus pneumoniae and nontypeable Haemophilus influenzae (NTHi) at 1.04 and 2.13 μg/ml. The greater antimicrobial efficacy against S. pneumoniae was a result of the H2O2‐producing ability of S. pneumoniae and the known synergistic interactions between H2O2 and AgNPs. To enable the sustained local delivery of AgNPs‐PVP (e.g., via injection through perforated tympanic membranes), a hydrogel formulation of 18%(w/v) P407 was developed. Reverse thermal gelation of the AgNPs‐PVP‐P407 hydrogel could gel rapidly upon entering the warm auditory bullae and thereby sustained release of antimicrobials. This hydrogel‐based local delivery system completely eradicated OM pathogens in vitro without cytotoxicity, and thus represents a promising strategy for treating bacterial OM without relying on conventional antibiotics. [ABSTRACT FROM AUTHOR]

The properties of silver nanoparticles (AgNPs) synthesized using compounds exhibiting biological activity seem to constitute an interesting issue worthy of examination. In these studies, two types of AgNPs were synthesized by a chemical reduction method using well‐known antioxidants: gallic acid (GA) and ascorbic acid (AA). Transmission electron microscopy (TEM) and atomic force microscopy (AFM) revealed that the AgNPs were spherical. The average size was equal to 26 ± 6 nm and 20 ± 7 nm in the case of ascorbic acid‐silver nanoparticles (AAgNPs) and gallic acid‐silver nanoparticles (GAAgNPs), respectively. Surface‐enhanced Raman spectroscopy (SERS) confirmed that the AgNPs were not stabilized by pure forms of applied antioxidants. Changes in mitochondrial activity and secretion of inflammatory and apoptosis mediators after the exposure of human promyelocytic (HL‐60) and histiocytic lymphoma (U‐937) cells to the AgNPs were studied to determine the impact of stabilizing layers on nanoparticle toxicity. The GAAgNPs were found to be more toxic for the cells than the AAgNPs. Their toxicity was manifested by a strong reduction in mitochondrial activity and induction of the secretion of interleukin‐6 (IL‐6), tumor necrosis factor‐α (TNF‐α), and caspase‐9. The addition of pure antioxidants to the AgNP suspensions was found to influence their toxicity. There was a significant positive effect in the case of the mixture of AA with AAgNPs and GA with GAAgNPs. The results obtained suggest that the presence of stabilizing agents adsorbed on the surface of AgNPs is the main factor in shaping their toxicity. Nevertheless, the toxic effect can be also tuned by the introduction of free antioxidant molecules to the AgNP suspensions. Cytotoxic activity of AgNPs strongly depends on chemical structure of stabilizing layers. Ascorbic acid‐silver nanoparticles (AAgNPs) are less toxic than gallic acid‐silver nanoparticles (GAAgNPs). The presence of free antioxidants modify toxic effects induced by AgNPs. [ABSTRACT FROM AUTHOR]

A unique atmosphere using formic acid was introduced to sinter silver (Ag) nanoparticles (NPs) for conductive patterns applicable for flexible electronics. Printed Ag NP patterns on flexible polyimide sheets using Ag NP ink were sintered in the atmosphere selected from air, N2, or N2-bubbled formic acid (N2-FA). Microstructures, organic residues, and electrical and mechanical properties of the sintered Ag patterns were compared, depending on sintering parameters including atmosphere, temperature, and time. The Ag NP patterns sintered in N2-FA atmosphere revealed an effective decomposition of organic materials, resulting in lower electrical resistivities and improved mechanical properties. For the Ag NP patterns sintered in N2-FA, organic residues were obtained below 5 wt% and grain sizes increased to 30–31 nm when the sintering temperature increased from 80 to 140 °C and sintering time increased up to 12 min. Less amount of organic residues and larger grain sizes contributed to achieving lower electrical resistivity of 15.7 μΩ-cm and higher hardness and modulus with their respective values of 0.184 and 8.405 GPa. The Ag NP patterns sintered in N2-FA resulted in improved electrical and mechanical properties in comparison with those sintered in air or N2. The Ag NP patterns sintered in N2-FA had enough electrical conductivity to operate light emitting diode lamps and were used to fabricate a radio frequency identification (RFID) antenna tag. From the measurement of the return loss (S11) in the RFID tags, the antenna showed a dual-band feature with two resonance frequencies of 27.76 and 33.50 MHz, which gave the ability to receive and send information in both frequencies. [ABSTRACT FROM AUTHOR]

A new broadband UV light‐based processing method for a screen printable silver oxalate molecular ink is developed that enables structural electronics to be produced on complex thermoformed 3D objects. The production of these 3D devices is driven by the light‐induced reduction of silver oxalate to form an interfacial silver nanoparticle layer that allows the ink to transition to a viscous liquid intermediate and elongate up to 50% without cracking during thermoforming. Ultimately, this enables the development of 3D electronics devices with significantly less limitations on geometry, shape, size, and depth in comparison to commercially available inks. UV processing is also effective for 2D traces on low temperature PET substrate, where in situ produced silver nanoparticles can subsequently absorb light and further facilitate the rapid conversion of the silver oxalate to metallic silver through a self‐limiting thermal decomposition. The resulting traces have superior electrical properties and are produced in significantly less time in comparison to thermal sintering. Together, UV processing and the silver oxalate molecular ink serve as a platform for both the rapid production of conductive silver traces on low temperature substrates and the development of novel thermoformed 3D human‐machine interface devices, areas of interest for both academia and industry. [ABSTRACT FROM AUTHOR]

Additive manufacturing methods have shown great potentials to substitute the costly and time‐consuming conventional subtractive methods in the processing of electronically conductive materials for applications in flexible and stretchable electronics. Herein, additive manufacturing of highly conductive, sandwich‐structured conductors with high‐temperature processibility and versatility in applicable substrates is reported. The sandwich‐structured conductors with silver nanoparticles (Ag NPs) as electronic conductors and polyimide (PI) as encapsulation are layer‐by‐layer deposited by aerosol printing into PI/Ag/PI composites. A high annealing temperature of 250 °C contributes to the high electronic conductivity of the Ag layer at 1.14 × 107 S m−1, which is in the same order of magnitude to the conductivity of bulk Ag at 6.3 × 107 S m−1. The high annealing temperature also significantly improves the interfacial bonding between the Ag and PI layers. For applications in flexible and stretchable electronics, the sandwich‐structured conductors are transferrable to various substrates through a thiol−epoxy bonding process, including polystyrene (PS), polyethylene terephthalate (PET), Kapton, and polydimethylsiloxane (PDMS) thin films. The sandwich‐structured conductors transferred to flexible and stretchable substrates exhibit highly retained electronic conductivity under deformations such as bending and stretching. [ABSTRACT FROM AUTHOR]

Silver (Ag) nanoparticles with a mean diameter of about 24.3 nm were synthesized by electroless deposition in an aqueous solution using PAA-Na and ascorbic acid as protective and reducing agents, respectively. The Ag nanoparticles were utilized as conductive ink and sintered at room temperature using different halide solutions (NaCl, NaBr, NaI, LiCl, KCl) at varying concentrations. A significant increase in particle size of about 174–990% was observed after sintering depending on the type of halide solution used. This also led to an increase in the electrical conductivity of the printed Ag pattern. Halide solutions with smaller ionic sizes generally promote the fusing of Ag nanoparticles, which results in larger Ag particles (NaCl > NaBr > NaI) and higher electrical conductivity. The use of an ionic stabilizer (PAA-Na salt) is more effective as a capping agent for Ag nanoparticles. Sintering is also more significant in samples stabilized by PAA-Na compared to those with PAA only. [ABSTRACT FROM AUTHOR]

Flexible, transparent and conductive films (TCFs) were prepared with silver nanowires (AgNWs) and the conductivity was enhanced via tuning junction resistance between nanowires treated by different surfactants and encapsulated by poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS). The results showed that the conductivity of AgNW TCFs was obviously enhanced after being immersed into surfactant solutions because the AgNWs would approach each other directly after dislocating away from polyvinyl pyrrolidone (PVP) and the junction resistance sharply decreased. Moreover, the transmittance of AgNW TCFs immersed into different surfactant solutions just decreased little because the halogen ions induced the formation of silver nanoparticles on the surface of AgNWs. Besides, the conductivity of AgNW TCFs encapsulated by PEDOT:PSS was also enhanced because the charges can transfer between PEDOT chains and AgNWs with the little decrease of optical transmittance. Graphical abstract [ABSTRACT FROM AUTHOR]

We show that it is possible to tailor the gap separation and interface geometry between adjacent Ag nanoparticles (NPs) by controlling fluence when irradiating with pulses from a fs laser. Unirradiated samples extracted from aqueous solution consist of networks of Ag NPs coated with polyvinylpyrrolidone (PVP). At low laser fluence, bonding between NPs occurs via the formation of an intervening hydrogenated amorphous carbon (α-C:H) layer resulting from the laser-induced decomposition of PVP. This occurs when electrons are emitted at hot-spots created by the trapping of plasmons. The thickness of the α-C:H layer determines the minimum separation between NPs. Ag NPs with different contact geometries can be produced by irradiation of the networks in solution at fluences exceeding the threshold for the formation of α-C:H. At fluences between 200 and 380 μJ/cm2, the α-C:H interface layer is replaced with a metallic neck. Surface enhanced Raman scattering (SERS) has been used to quantify the electromagnetic field enhancement in joined NP samples. We find that Ag NPs bonded by α-C:H and exhibiting a narrow gap possess the highest SERS enhancement. [ABSTRACT FROM AUTHOR]

Pressure-assisted die bonding at 250 °C in air using a paste containing 2 µm Ag-coated Cu particles (Cu@Ag) and 350 nm Cu particles was demonstrated for power device bonding. At a Cu@Ag-to-Cu mixing ratio of 6:4, the sinter-bonded dies showed a considerable average shear strength that approached 25 MPa after only 5 min of bonding. Furthermore, a near-full-density bondline and excellent strength, greater than 30 MPa, were achieved after only 10 min. The remarkably rapid improvement in the strength and microstructure was attributed to the generation of pure Cu nanoparticles on the Cu surfaces by in situ reduction during heating for the bonding. [ABSTRACT FROM AUTHOR]

Recently, there have been considerable interests in strain sensors that are flexible and stretchable, due to their potential for use in wearable electronics applications. Herein, a facile approach has been employed to produce synergistic strain sensor, taking advantage of the salient properties of hybrid conductive inks produced from graphene and silver nanoparticles (AgNPs). The hybrid ink was inkjet-printed on a polyvinyl alcohol (PVA) substrate. The effect of factors such as amount of graphene, annealing time and printing cycle on the performance of the hybrid conductive ink was investigated. The results showed that an increase in the amount of graphene from 0.1 to 0.5 wt% produced about 90% enhancement in the electrical conductivity of the hybrid ink. However, the change in electrical conductivity values of the hybrid ink at 0.5 wt% and 0.7 wt% graphene content is negligible. On the other hand, it was observed that the electrical conductivity was notably influenced by the number of printing cycle, as well as the annealing time. Significantly, the sensitivity performance of the printed hybrid graphene/AgNPs strain sensor is higher than that of individual graphene and AgNPs printed strain sensors under the strain range up to 20%. [ABSTRACT FROM AUTHOR]

In this work, inkjet printing of porous graphene/silver composite with low temperature vapor phase reduction was studied. Silver precursor and graphene oxide (GO) with a low weight ratio were used as ink for inkjet printing into a film. After vapor phase reduction, the inserted silver nanoparticles between reduced graphene oxide (RGO) layers acted as physical separators to prevent agglomeration of the RGO and reduce the Van Der Waals force between graphene sheets. The fabricated RGO/Ag electrode presented a high electrical conductivity of 2.9 × 105 S/m, and could keep stable after multiple bending. Meanwhile, the reducing agent vapor entered the interior of the RGO during the vapor reducing process, which generated porous channels in the RGO/Ag electrode. The porous channels could facilitate the penetration of the electrolyte into the graphene/silver electrode, resulting in a good electrochemical performance with a specific capacitance of 60.6 mF/cm2 at a scan rate of 5 mV/s, which greatly improves the property compared with the previous reports. [ABSTRACT FROM AUTHOR]

Flexible electronics can be developed with a low-cost and simple fabrication process while being environmentally friendly. Conductive silver inks have been the most applied material in flexible substrates. This study evaluated the performance of different conductive ink formulations using silver nanoparticles by studying the material properties, the inkjet printing process, and application based on electrical impedance spectroscopy using a buffer solution. Silver nanoparticles synthesis was carried out through chemical reduction of silver nitrate; then, seven conductive ink formulations were produced. Properties such as resistivity, viscosity, surface tension, adhesion, inkjet printability of the inks, and electrical impedance of the printed electrodes were investigated. Curing temperature directly influenced the electrical properties of the inks. The resistivity obtained varied from 3.3 × 100 to 5.6 × 10−06 Ω.cm. Viscosity ranged from 3.7 to 7.4 mPa.s, which is suitable for inkjet printing fabrication. By using a buffer solution as an analyte, the printed electrode pairs presented electrical impedance lower than 200 Ω for all the proposed designs, demonstrating the potential of the formulated inks for utilization in flexible electronic devices for biological sensing applications. [ABSTRACT FROM AUTHOR]

2D metallic grids that consist of various nanomaterials that are suitable for the replacement of indium tin oxide in transparent electronics (TEs) manufacturing. High‐resolution conductive grids with large open areas are often required while considering high transmittance. However, previous research shows that this kind of TE often cannot have high transmittance and low sheet resistance simultaneously; it hinders the fabrication techniques and materials from practical applications. Herein, direct fabrication of a high‐performance TE through electrohydrodynamic jet 3D printing technique is reported. Micro‐scale 3D metallic grids with an aspect ratio of above‐5 were printed on a polyester film using Ag nanoparticles. The metal grids with high aspect ratios exhibit an average sheet resistance of 3 Ω sq−1 and transparency of 96%. Both optical and electrical performances are significantly enhanced for which the large cross‐section of the metallic grid is contributed. Furthermore, the flexibility of printed TE is also characterized by the bending and recovering test. It is believed that the printed flexible TE, which utilize a high aspect ratio, 3D metallic grids may replace the conventional ITO glass for which both high transmittance and conductivity are achieved with economic efficiency. [ABSTRACT FROM AUTHOR]

Stable silver nanoparticles have been obtained in reverse micelles of known and available nonionic surfactants, sorbitan monooleate (Span 80) and tetraethoxylated dodecanol and p-nonylphenol (Brij 30 and Tergitol NP-4, respectively), in n-decane. The obtained nanoparticles have been characterized using a number of physicochemical methods. The stability, hydrodynamic diameter, and electrokinetic potential of the nanoparticles have been studied as depending on the amounts of added water; chloroform; and an anionic surfactant, sodium bis(2-ethylhexyl)sulfosuccinate (AOT). It has been shown that, for different surfactants, AOT should be introduced in different ways to provide the nanoparticles with the electrokinetic potential values sufficient for enhancing their stability and ensuring the possibility of concentrating them by nonaqueous electrophoresis. In the case of Brij 30, it is preferable to introduce AOT after the synthesis as a "charging additive," while, in the case of Tergitol NP-4, it should be added as a cosurfactant at the stage of the synthesis. The nanoparticles synthesized in Span 80 micelles have a rather high electrokinetic potential even in the absence of the additives. In this case, the use of AOT as a cosurfactant decreases the electrokinetic potential of the nanoparticles, while, being added after the synthesis, it increases the potential. [ABSTRACT FROM AUTHOR]

In this paper, humic acid (HA) was used as stabilizer to prepare silver nanoparticles (Ag NPs) by chemically reducing silver salts in water phase, which were employed to produce Ag NPs inks for inkjet printing conductive silver patterns. The obtained silver nanoparticles stabilized with HA (HA-Ag NPs) were all in spherical shape and the particle size was about 7–12 nm. By re-dispersing HA-Ag NPs in ultrapure water, conductive ink with excellent storage stability was prepared, which can be placed at room temperature for 30 days without any precipitation. The as-prepared HA-Ag NPs conductive ink was printed onto photopapers to fabricate conductive silver patterns with a domestic inkjet printer. The resistivity of the printed pattern could reach 135 μΩ cm after printed for 40 layers and sintered at 180 °C for 60 min. In addition, the printed conductive silver patterns could be integrated into a LED device or alarm apparatus, indicating it could be widely used in flexible printing electronics. [ABSTRACT FROM AUTHOR]

In recent years, Moore's law had a remarkable effect on predicting the development of semiconductor technology. As the size of devices shrinks to micro scale or nano scale, Intel's newest 10-nm logic technology is scheduled to start product shipments before the end of 2017. Moore's law will not die out, as the research scale reaches the atomic scale, "new devices" and new interconnection methods are urgently needed. In this paper, based on emerging interconnection requirement, the contribution to the advanced electronic packaging containing novel nano-materials, such as the carbon nanotubes, nanoparticles sintering, interconnection of nano-solder, nano-silver and surface plasma nano-welding are discussed. For the next 5–10 years, two new types of interconnect solutions are gaining attentions: solder joint alternatives and Cu electrode alternatives. The former uses new materials such as graphene, carbon nanotubes and nanowires to replace traditional solder joints. The latter uses optical media to replace the traditional Cu metal. In general, advanced materials will make more and more outstanding contributions in the development of electronic packaging in the next 10–20 years. [ABSTRACT FROM AUTHOR]

Stable silver organosols with a particle diameter of 7 nm containing up to 0.1 M metal have been prepared in water-in-oil dynamic emulsions stabilized with a surfactant, sodium bis(2-ethylhexyl) sulfosuccinate. Liquid-phase concentrates with silver concentrations up to 8 M have been obtained from them by nonaqueous electrophoresis. Thin films and powdered redispersible composites with silver contents up to 75 wt % have been prepared by solvent evaporation. Conductve lines with a width of nearly 70 μm have been formed by selective laser sintering of the thin films of these composites. The specific electrical conductivity of the lines is about 20% of the conductivity of bulk silver. It has been shown that the unsintered composite may be used repeatedly. [ABSTRACT FROM AUTHOR]

In this investigation, bamboo (Dendrocalamus giganteus Munro) timbers were coated selectively into vascular vessel bundles with a potential antimicrobial colloidal solution of silver nanoparticles (Ag-NPs). Electric charge and size of Ag-NPs, with different charged organic ligands (trisodium citrate and chitosan), affect their self-sorting in different anatomical structures of bamboo when submitted up to 20 impregnation cycles through a vacuum system. Physicochemical characterization of Ag-NPs was performed by spectroscopic techniques and electron microscopy. Confocal laser scanning microscopy and scanning electron microscopy were employed to characterize natural bamboo. Qualitative and quantitative determination of the metal coating in bamboo specimens was performed with X-ray microtomography (μCT), energy-dispersive X-ray spectroscopy, and X-ray diffraction. μCT revealed a gradient deposition of citrate-capped Ag-NPs into the parenchyma tissue with the higher concentration at the outer part of the bamboo. On the other hand, the chitosan-capped Ag-NPs were deposited mainly in the vessel bundles. [ABSTRACT FROM AUTHOR]

Well-dispersed silver nanoparticles (AgNPs) were synthesized using a benign, one-pot process based on a low-cost wet chemistry technique. Monoethanolamine was used as a strong reducing agent and poly(acrylic acid) (PAA) was used as a stabilizing agent. After the addition of these reagents to a reaction system, one-pot synthesis of AgNPs was completed in ∼45 min at 75 °C with a reaction efficiency of 92.4%. The average particle size of the aqueous dispersion of AgNPs was 14.83±5.96 nm, and the dispersion remained stable even after 14 months in an ambient dark environment, which may be due to the electrostatic repulsion of the carboxylate anions of the stabilizing agent. The role of PAA in the stabilization of the AgNPs was analyzed via Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy. The highly stable AgNPs in the aqueous system showed high catalytic activity for the reduction of methylene blue and p-nitrophenol in the presence of sodium borohydride as the reducing agent based on pseudo-first-order kinetics. [ABSTRACT FROM AUTHOR]

The promising and extraordinary properties of graphene have attracted significant interest, making graphene an alternative to replace many traditional materials for many applications, particularly in conductive ink for the fabrication of flexible electronics. For the past 10 years, numerous studies have been reported on the synthesis of graphene conductive ink for printing on flexible substrates for various electronic applications. The development of graphene-based ink is reviewed, with the main focus on the types of graphene-like materials in conductive inks, and the compositions and important properties of those inks. Another intention behind this review is to compare the pros and cons of graphene-based ink with those using other common conductive materials, such as gold nanoparticles, silver nanoparticles, copper nanoparticles, conductive polymers and carbon nanotubes. Recent works on graphene hybrid-based ink containing other metallic nanoparticles as an alternative way to improve the electrical properties of the conductive inks are also reported. Brief comparisons between inkjet printing and other printing techniques for the fabrication of flexible electronics are discussed. [ABSTRACT FROM AUTHOR]

A silver (Ag) composite paste was fabricated based on Ag nanoparticles (NPs) and Ag microflakes (MFs). Robust interconnections were achieved after sintering in the temperature range of 150-225 °C. The shear strengths of the Ag MF + NP joints before and after thermal shock from − 50 to 150 °C for 1000 cycles were 155.7 ± 14.5 MPa and 78.4 ± 20.8 Mpa, respectively. The results show that the Ag composite paste not only has similar sintering properties to the Ag NP pastes but also exhibited superior mechanical reliability due to the addition of the Ag MFs. In addition, the sintered properties of different Ag pastes were discussed in terms of the coating organics, thermal behaviour and microstructure. The fracture modes after the shearing tests were analysed in detail. The Ag composite paste provides a potential solution for high-temperature applications. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to study the repeatability of path manufacturing in the drop on demand inkjet printing process and the influences of environmental and application factors on path resistance. Design/methodology/approach: Paths were printed as multiline paths in packets one-, two- and three-layer paths on polyimide substrates using nanoparticle silver ink. The sintering conditions were determined experimentally. The paths were subjected to climatic and shock exposures and to bending processes. The resistance, profile and width of the paths were measured and analyzed. The temperature distribution for electrically heated paths was measured to identify the defects. Findings: This research shows the repeatability of printing processes and identifies the sources that cause diversification in path parameters after the whole technological process. The influence of shock, climatic and mechanical exposures on path electrical properties is indicated. An effective method for identifying defects thermally is shown. Research limitations/implications: The research could have limited universality by arbitrarily use of substrate material, ink, printhead, process parameters and kind of sample exposures. Practical implications: The research includes practically useful information about the width, thickness, defects and resistances and their changes during a typical application for a path printed with different technological parameters. Originality/value: This research presents the results of original empirical research on problems concerning the manufacture of paths with uniform parameters and shows how path parameters will change under exposures that may occur in a typical application. The research combines both production and application aspects. [ABSTRACT FROM AUTHOR]

Direct write (DW) technologies offer a potential avenue towards reducing existing long lead times required for fabrication of prototypes and evaluation of new materials and integrated circuit designs. Nanostructured metallic DW inks are widely utilized due to their excellent electrical conductivity which dictates the performance of printed sensors and circuits. Besides controlling the surface chemistry and rheology of these inks to control the print resolution, the essential joining of these conductive nanomaterials to create functional sensors and devices remains a challenge. Low-temperature interconnecting techniques are required to minimize the deleterious heat effects on the shape of printed conductive networks and electronic components. Therefore, the reduced melting temperatures characteristic of metallic nanomaterials offer opportunities to bridge this technological gap. Amongst the reported low-temperature sintering approaches, the chemically-induced sintering method emerges as a readily scalable approach with relatively low energy input. By uncovering the underlying relationship between particle size effects and the role of the ionic salts used to induce sintering under ambient conditions, we aim to elucidate the compatible chemistries (i.e., size and salt) to achieve optimal chemically-induced sintering. The sintering of polyacrylic acid-modified Ag nanoparticle-based DW inks of different size distributions (bimodal vs. monodispersed distribution) and average sizes (e.g., 5 nm and 17 nm) was systematically investigated to elucidate the role of a commonly used salt, NaCl, in the chemically-induced sintering process. An observed enhancement in our ink conductivities by about 4 orders of magnitude for the monodispersed 17 nm and bimodally distributed 9 and 170 nm particles resulted mainly from the sintering between neighboring Ag nanoparticles. In the case of monodispersed 5 nm nanoparticles, a low electrical resistivity was observed despite an increase in grain size which indicated successful sintering. The low measured electrical resistivity was mainly due to significant AgCl formation that had a lower electrical conductivity. Our results show that the chloride ions played an active role in triggering first the oxidative decomposition of Ag to Ag+ resulting in AgCl formation which subsequently led to the sintering between neighboring Ag nanoparticles. The difference in the results for the 5 nm and 17 nm monodispersed Ag nanoparticles was attributed to the differences in the size-dependent surface reactivities and relative amounts (i.e., packing density, thickness) of the polymeric PAA coating. [ABSTRACT FROM AUTHOR]

Printed electronics based on nanomaterials has been a potential alternative to conventional electronic technology and is favorable for flexible polymer substrates. However, a printed circuit has insufficient electrical performance and mechanical reliability under flexible stress. We designed hybrid Ag pastes containing Ag nanoparticles (NPs, 30–50 nm) and Ag flake (F, 2.5–3.5 μm in diameter) particles to overcome the obstacles of printed electronics. Six types of Ag paste (Ag NPs-x wt% F paste, x = 0, 10, 25, 50, 75, and 100) were screen-printed onto a polyimide substrate and sintered at 200 °C for fabricating a flexible circuit. We simulated a coplanar waveguide pattern before measuring the S-parameter using high frequency structural simulation. To investigate the radio frequency characteristics of various Ag circuits under sliding stress, a network analyzer and Cascade’s probe system in the frequency range from 1 to 10 GHz were employed before and after 100,000 sliding cycles. Hybrid Ag circuits showed stable electrical conductance and signal transmission, while pure Ag particle circuits showed a definite drop of electrical conductance (over 30% increase of electrical resistance) under cyclic sliding stress. The microstructural crack behavior demonstrated that the Ag F content within the Ag hybrid circuits effectively suppressed crack propagation, leading to improved flexibility of the sintered Ag circuit. [ABSTRACT FROM AUTHOR]

Silver nanoparticles with small particle size distribution and good dispersibility were synthesized through a facile chemical reduction method. In the progress, AgNO3 was used as the precursor, polyacrylic acid and ethanol amine were introduced as the protective agent, hydrazine hydrate was chosen as the reduce agent. Diameter of the resulted monodisperse silver nanoparticles is between 50 and 70 nm. Then, the obtained silver nanoparticles were well dispersed in the oil-based ink, which can be printed on a flexible polyimide substrate to form the conductive printed circuit board through following low temperature annealing treatment. A lowest electricity resistivity of 5.6 × 10−8 Ω m is obtained which is only 3.5× higher than that of bulk silver. [ABSTRACT FROM AUTHOR]

A printable hybrid hydrogel is fabricated by embedding poly(N-isopropylacrylamide) (PNIPAm) microparticles within a water-rich silica-alumina (Si/Al)-based gel matrix. The hybrid gel holds water content of up to 70 wt%, due to its unique Si/Al matrix. The hybrid hydrogel can respond to both heat and electrical stimuli, and can be directly printed layer-by-layer using a commercial 3-dimensional printer, without requiring any curing. The hybrid ink is printed onto a transparent, flexible conductive electrode composed of silver nanoparticles and sustains bending angles of up to 180°, which enables patterning of various flexible devices such as smart windows and a 3D optical waveguide valve. [ABSTRACT FROM AUTHOR]

Inkjet ink based on silver nanoparticles with sizes of 11.1 ± 2.4 nm has been developed. Test images are printed on a laboratory inkjet printer, followed by sintering the printed patterns with a diode laser having a wavelength of 453 nm. The structure and electrical properties of the resulting films are studied depending on the parameters of laser sintering. It is found that under optimal conditions, an electrically conductive film with a low resistivity of 12.2 μΩ· cm can be formed. [ABSTRACT FROM AUTHOR]

Monodispersed mixtures of 6-nm Cu and Ag nanoparticles were prepared by electrochemical reduction on electrochemically polymerized poly-Fe(vbpy)3(PF6)2 film electrodes on glassy carbon. Conversion of the complex to poly-Fe(vbpy)2(CN)2 followed by surface binding of salts of the cations and electrochemical reduction gave a mixture of chemically distinct clusters on the surface, (Cu)m,(Ag)n|polymer|glassy carbon electrode (GCE), as shown by X-ray photoelectron spectroscopy (XPS) measurements. A (Cu)2, (Ag)3,(80-monolayer-poly-Fe(vbpy)32+|GCE electrode at -1.33 V vs. reversible hydrogen electrode (RHE) in 0.5 M KHCO3, with 8 ppm added benzotriazole (BTA) at 0 °C, gave acetate with a faradaic efficiency of 21.2%. [ABSTRACT FROM AUTHOR]

Facile networked alignment of AgNPs was attained by employing a graft copolymer bearing C=S moieties prepared via combination of free radical polymerization and polyaddition. The self-assembly induced the formation of the networked structure with cavities leading to translucency. The vertical conductivity depended on contact force, and suggests potential applications for printable devices such as touch screens. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to study the packing density of printed paths on different substrate materials. It presents problems which appear when the necessity of printing one or more narrow paths occurs.Design/methodology/approach A piezoelectric printhead containing nozzles with a diameter of 35 µm was used for printing nanoparticle silver ink on different polymer substrates which were treated by plasma or not treated at all. The shape, defects, resistance and printing parameters for the printed paths were analysed.Findings The obtained results allow the identification of the sources of the technological problems in obtaining a high packing density of the paths in a small area of substrate and the repeatable prints.Research limitations/implications The study could have limited universality because of the chosen research method; printhead, ink, substrate materials and process parameters were arbitrarily selected. The authors encourage the study of other kinds of conductive inks, treatment methods and printing process parameters.Practical implications The study includes practically useful information about widths, shapes, defects and the resistance of the paths printed using different technological parameters.Originality/value The study presents the results of original empirical research on problems of the packing density of inkjet printed paths on a small area of substrate and identifies problems that must be resolved to obtain effective interconnections in the inkjet technology. [ABSTRACT FROM AUTHOR]

AlO-to-Cu/3 μm Ni/1 μm Au assemblies were direct-sintered with a paste consisting of micron-sized AgO particles and a reducing solvent that provokes AgO-to-Ag reduction during processing accompanied by the formation of Ag nanoparticles. The variation of process temperature, pressure and time resulted in different porosity and shear strength. This experimental data set was used to calibrate a finite element model of the assembly considering the elasto-visco-plastic joint properties and the joint porosity. Local analyses within the sintered Ag layer yielded a damage function D and a damage criterion that could assess the joint strength as a function of geometry, microstructure and process conditions. The developed damage model introduced a parameter ζ, i.e. the product of equivalent creep strain ε and stress triaxiality η, that balanced the tolerable equivalent plastic strain ε at fracture. A Fortran subroutine (UVARM) visualized the damage distribution over the sintered layer. The predominant crack initiation and propagation were identified in good agreement with the experimental fracture behavior. A numerical parameter study subsequently revealed the complex interaction between the ceramic-metal interfacial porosity, the total bulk porosity and the shear strength. [ABSTRACT FROM AUTHOR]

We describe herein the significance of a sodium citrate and tannic acid mixture in the synthesis of spherical silver nanoparticles (AgNPs). Monodisperse AgNPs were synthesized via reduction of silver nitrate using a mixture of two chemical agents: sodium citrate and tannic acid. The shape, size and size distribution of silver particles were determined by UV-Vis spectroscopy, dynamic light scattering (DLS) and scanning transmission electron microscopy (STEM). Special attention is given to understanding and experimentally confirming the exact role of the reagents (sodium citrate and tannic acid present in the reaction mixture) in AgNP synthesis. The oxidation and reduction potentials of silver, tannic acid and sodium citrate in their mixtures were determined using cyclic voltammetry. Possible structures of tannic acid and its adducts with citric acid were investigated in aqueous solution by performing computer simulations in conjunction with the semi-empirical PM7 method. The lowest energy structures found from the preliminary conformational search are shown, and the strength of the interaction between the two molecules was calculated. The compounds present on the surface of the AgNPs were identified using FT-IR spectroscopy, and the results are compared with the IR spectrum of tannic acid theoretically calculated using PM6 and PM7 methods. The obtained results clearly indicate that the combined use of sodium citrate and tannic acid produces monodisperse spherical AgNPs, as it allows control of the nucleation, growth and stabilization of the synthesis process. [ABSTRACT FROM AUTHOR]

Electrically conductive films are key components in most printed and flexible electronics applications. For the solution processing of conductive films, inks containing silver nanoparticles (AgNPs) remain important because of their relatively easy processing and generally low resistivity after a sintering procedure. Because the commonly used, moderate sintering temperatures of 150-300 °C are still too high for most low-cost flexible substrates, expanding the knowledge of surface-ink interactions that affect the sintering temperature is desirable. It is known that chloride ions can assist the sintering of AgNP films by displacing capping agents on the surfaces of AgNPs. However, very little is known about other possible Cl-AgNP interactions that affect the resistivity and no interaction having the opposite effect (sintering inhibition) has been identified before. Here we identify such a Cl-AgNP interaction giving sintering inhibition and find that the mechanism involves the formation of AgCl nanocrystals within the AgNP film. The AgCl formation was observed after inkjet-printing of AgNP inks with polyvinylpyrrolidone (PVP) as the capping agent onto papers with quick-absorbing coatings containing 0.3 wt % KCl. Our findings show that chloride can have opposite roles during sintering, either assisting or inhibiting the sintering depending on the prevalence of AgCl formation. The prevalence of AgCl formation depends on the absorption properties and the capping agent. [ABSTRACT FROM AUTHOR]