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Carbon-based conductive inks, with their low cost, ease of fabrication, and environmental friendliness, have a wide range of applications. In this study, we present the development of a candle-soot-based conductive ink through a simple and cost-effective synthesis process. The composite was formulated by incorporating candle-soot with PVDF-HFP polymer using DMF as a solvent. The study evaluates the performance of different amounts of carbon present in a candle-soot-polymer composite. The conductive ink was also filled in a ballpoint refill, circuits were drawn, and I–V responses were studied. The conductive films were thoroughly characterized using SEM, EDX, TGA, and IV characteristics. XRD and FTIR analyses were performed to assess the properties of the conductive film (CPC4) and candle-soot. Four distinct conductive ink formulations were synthesized by varying the percentage of candle-soot. I-V studies revealed that the electrical resistance of the composite films decreased with increasing candle-soot content. The results demonstrated excellent conductivity, enabling the fabrication of simple and functional conductive circuits on paper using the developed CPC4 ink. Candle-soot, as filler, exhibited promising results comparable to expensive conductive fillers such as graphene and multi-walled carbon nanotubes. The developed conductive ink shows promising performance in flexible electronic devices, offering a cost-effective and environmentally friendly alternative. [ABSTRACT FROM AUTHOR]

The integration of electronics into textiles, commonly referred to electronic textiles (e-textiles), has sparked significant interest in recent years owing to their vast potential across diverse industries including healthcare, fashion, sports, and wearable technology. This review paper offers an extensive examination of the current landscape of e-textiles, focusing on their types, applications, conductive materials, and fabrication methods. Regarding fabrication methods, two primary approaches as main groups were introduced and are scrutinized in detail: (1) Fabricating/using conductive yarn/thread and inserting it into the textile using traditional textile techniques such as weaving, knitting, embroidery and so on. (2) Direct applying of conductive coatings onto existing textiles which include sub groups such as deposition techniques, wet coating techniques, printing techniques and in situ polymerization for integrated conductivity. Notably, this review not only elucidates these methodologies but also encapsulates the latest advancements in e-textile fabrication, serving as a vital resource for researchers and developers navigating this rapidly evolving domain. It also acknowledges the main challenges that need to be addressed to fabricate high efficent e-textile. These include ensuring durability with has direct relation with long-term washability and flexibility. Different strategies to improve durability such as using elastic substrates, stretchable conductive ink, improving adhesion between conductive layer and textile along with encapsulation of conductive layer on textile are discussed. By offering a comprehensive overview and highlighting recent innovations, this paper aims to propel further advancements in the realm of e-textiles, facilitating the realization of their full potential across various sectors. [ABSTRACT FROM AUTHOR]

Conductive ink is an important component to fabricate printed electronics, such as flexible, stretchable, and wearable electronics. Solvents are essential for fabrication of conductive inks, but most of the organic solvents are expensive, toxic, and not environmentally friendly. In this review, stability, wettability, and electrical conductivity of different types of solvent- and water-based metal and carbon-based conductive inks are discussed. Further, the utilization of surfactants to facilitate aqueous homogeneous dispersion and stability of metal and carbon nanomaterial-based conductive material is discussed. Particularly, the solvent- and water-based surfactant-assisted conductive inks on the stability and electrical properties of metal- and carbon-based conductive materials are highlighted. In addition, the different characterization methods for assessing the dispersion and stability of conductive inks, such as zeta potential, UV–Visible, long-term stability, and wettability properties, were discussed in this review. [ABSTRACT FROM AUTHOR]

In the context of advancing flexible electronic technologies, conductive ink has garnered significant scholarly interest. Wherein, metal-organic decomposition (MOD) ink composed of silver precursors, complexing agents, and volatile organic solvents, has been widely studied due to its advantages such as simple preparation, long shelf life, high jetting stability, and low-temperature processing. However, the volumetric reduction of MOD ink frequently surpasses 80%, which typically could lead to multiple voids and breaks in the conductive film, resulting in poor conductivity. Meanwhile, a high temperature of above 180 °C is usually required for the MOD ink to be converted into conductive film. Nevertheless, it is imperative for the ink to be deposited onto substrates at low temperatures. Herein, a low temperature conducting ink with multiple silver source precursors has been developed. The results show that after sintering at 100 °C for 40 min on a polyimide (PI) substrate, the resistivity of the silver film was 16.8 µ Ω cm, which is only ten times higher than that of bulk silver, and the silver film with good uniformity and conductivity can be formed. Defects, such as voids and cracks, are significantly reduced through the gradient decomposition of different silver source during the sintering process. The formula of ink and the effects of sintering temperature on the microstructure and electrical properties of silver ink thin films have been studied in details using XRD, SEM, EDX, and four-probe techniques. [ABSTRACT FROM AUTHOR]

Printed flexible electrical heaters with excellent heating performance and mechanical durability are highly desirable for deicing and wearable thermotherapy devices. However, the performance of the conventional heaters is stilled limited by low-resolution fabrication methods when applied in high-precision heating in desirable regions. Moreover, the poor conductivity and mechanical stability of the ink also increase the power consumption. Herein, a high-resolution (45 μm) heater with low power consumption was fabricated by a facile electrohydrodynamic (EHD) printing method. A highly printable and stable hybrid conductive ink was obtained by doping PANI nanoparticles into silver flake/thermoplastic polyurethane (TPU) composite. After adding 0.5 wt% PANI nanoparticles into 40 wt% silver flake/TPU composite and low temperature sintering (80 °C), the bulk resistivity decreased from 96.03 × 10−5 Ω·m to 1.26 × 10−5 Ω·m. Thanks to the ultrahigh conductivity of the ink, the EHD printed flexible heater shows high saturation temperature (127.0 °C) under low applied voltage (2 V), wide heating range (33.9 °C~127.0 °C) under a small range of driving voltages (0.5 V ~ 2.0 V), the rapid response time (20 s) and excellent repeatability during 10-time cyclic heating-cooling possess. Furthermore, the printed flexible heaters exhibit great flexibility and durability. The resistance of the heater remains stable after 3000 outer bending cycles with a radius of 0.5 mm, indicating outstanding mechanical stability. Moreover, the heater can be attached to the human body, showing the potential for emerging wearable electronic applications. [ABSTRACT FROM AUTHOR]

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

The fabrication of environmentally friendly printed flexible sensors is still an emerging technology, but with vast potential applications. Among the available printing techniques, inkjet printing is considered as a promising technique for flexible electronics because it enables high volume and versatile manufacturing, at low environmental impact. This study demonstrates a simple and facile method of preparing an environmentally benign water-based conductive ink, by dispersing functionalized and non-functionalized multi-walled carbon nanotubes (MWCNTs) in aqueous solution with the help of a biopolymer surfactant. The concentration of CNTs in the ink formulation was varied from 0.25 to 0.75 wt%, and additives such as triton-x 100, polypropylene glycol, and defoamer were added to achieve desirable ink properties. Inkjet printable ink was produced, and it was observed that the conductivity of the printed pattern is dependent on the printing pass. In addition, it was found that as the number of printing layer increases, there is higher synergy between concentration and number of printing pass in F-MWCNTs printed ink to produce higher electrical conductivity, compared to MWCNTs printed ink. Generally, the findings of this study could potentially open opportunities for global economic growth through the applications of printed, low cost and environmentally friendly flexible sensors. [ABSTRACT FROM AUTHOR]

In printing electronics, graphene is used as a functional material due to its excellent physical properties. Therefore, to prepare a conductive graphene ink that contains non-toxic and environment-friendly solvent is very important. Direct preparation of graphene from graphite using liquid-phase exfoliation process is beneficial since it is simple and easy to use. Here in this work, we have synthesized the graphene dispersion using ethanol and water by liquid-phase exfoliation method and prepared a conductive graphene ink that shows an absence of coffee ring formation during the evaporation of solvents. A film has been prepared using the prepared ink which shows the electrical resistivity 1.06 Ω-cm at temperature 300 °C. [ABSTRACT FROM AUTHOR]

This paper presents the production and the characterization of the multi-walled carbon nanotube (MWCNT) printed flexible temperature sensors for high-precision reading in temperature sensing applications. The temperature sensor was fabricated using the inkjet printing method by depositing carbon nanotube (CNT) ink on soft taffeta fabric. An aqueous CNT-based conductive ink was formulated for the inkjet printing process. A translucent polyurethane (PU) welding tape was used as an encapsulation layer on the surface of the sensors to protect sensors from various environmental effects during usage and testing. The fabricated sensors function as thermistors, as the conductivity increases with temperature linearly. The performances of differently patterned three temperature sensors were compared. The highest obtained temperature coefficient of resistance (TCR) and the thermal index are −1.04%/°C and 1135 K, respectively. The fabricated sensors possess a high-temperature sensitivity between room temperature and 50 °C and perform better than the typical commercial platinum temperature sensors and most of the recently reported CNT-based temperature sensors in the literature. [ABSTRACT FROM AUTHOR]

Inkjet printing conductive ink was prepared with the as-prepared silver nanoparticles as conductive fillers and deionized water as the solvent and leveling agent (MY-3000) and silicone defoamer (NXZ) and wetting agent (TRITONX-405) and moisturizer (glycerol) as functional additives. We investigated the effects of viscosity and surface tension of conductive ink and the inkjet print parameters including number of nozzle, print speed, and ink droplet spacing on inkjet printability of conductive ink. The research results show that the inks with the viscosity range of 2.8–9.1 mPa·s and the surface tension of 33.4 mN·m−1 are suitable for inkjet printing. The printing accuracy of the print pattern is related to the number of nozzles and droplet space and the printing layer, but not to the printing speed, but can be changed appropriately to improve the print efficiency. When the mass content of silver nanoparticles is 6.91 wt%, the sheet resistance of the printing pattern with four layers is 2.71 Ω·cm−1, which is in appropriate printing conditions of the inkjet printing voltage of 21 V, printing speed of 60 m· S−1, ink droplet space of 20 μm, and nozzles of 2. The systematic studies of printability and electrical conductivity of inkjet printing silver nanoparticles conductive ink prove the feasibility of the ink and provide some ideas for future applications. [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]

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]

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]

A comparative study of inkjet-printed graphene films (IPGFs) with mechanically exfoliated, highly crystalline graphene platelets have been conducted. Inkjet-printed graphene films were obtained using liquid-phase exfoliation of bulk graphite, while crystalline, residue-free graphene was obtained from highly-oriented-pyrolytic-graphite (HOPG) using mechanical exfoliation through a viscoelastic transfer process. Optical absorption spectroscopy was used to infer the density of platelets in the graphene-based ink dispersion. Temperature-dependent Raman spectroscopy revealed the presence of the defect D-band peak in the IPGFs, which was not observed in the HOPG-based samples at room temperature, confirming the higher crystalline quality of the latter. Full-width-half-maximum (FWHM) of the G-band was measured to be ~ 26.4 cm−1 for IPGFs compared to ~ 18.6 cm−1 for HOPG-based samples. Moreover, the D-band intensity decreased as temperature increased up to 600 °C for IPGFs, suggesting the possibility of annealing effects that may arise at these temperatures to reduce defect densities. In both HOPG-based samples and IPGF patterns, the G-band and G′-band red-shifted with increasing temperature which can be attributed to elongation of the C–C bond due to thermal expansion, resulting in the anharmonic coupling of the phonon modes. Moreover, a power study demonstrated the IPGFs even with printing passes as low as 10 passes, dissipate ~ 1.03 mW of power at 1 V, which was similar to the power dissipated in the HOPG samples (~ 1.05 mW at 1 V) suggesting good adherence of graphene platelets and high conductivity in IPGFs, which suggests that the inks are favorable for use in interconnects for device platforms in printed electronics. A natural follow-on from this work, was the use of the conductive graphene inks as an interconnect in devices, specifically WS2-based photodetectors, where prototype devices were fabricated and characterized that are also discussed here. [ABSTRACT FROM AUTHOR]

Cu-based conductive inks are more cost effective than silver-based ones for flexible electronics. However, it is challenging to simultaneously ensure the mechanical flexibility, environmental oxidation durability, and low resistance of the sintered Cu electrodes. To achieve this goal, Cu-based conductive inks including silane coupling agents are developed and used to produce flexible Cu electrodes on cellulose paper after air–atmosphere sintering. The key factor to achieve the mechanical flexibility and environmental oxidation durability at the same time is the use of aminoethyl-aminopropyltrimethoxysilane (AEAPTMS) or 3-glycidoxypropyltrimethoxysilane (GPTMS). Negligible resistance change is observed in the sintered Cu electrode with AEAPTMS, even after 1000 repeated bending cycles with a bending radius of 5 mm and exposure at 60 °C/80% RH for 7 days. Especially, Cu electrodes produced using GPTMS show improved flexibility with negligible resistance change even after 10,000 bending cycles. To demonstrate the applicability of these Cu electrodes, a flexible paper-based movement sensor is successfully fabricated from the present Cu-based ink. This approach using silane coupling agents will contribute to the reliable operation of Cu-based flexible devices with high mechanical and environmental durability. [ABSTRACT FROM AUTHOR]

Copper–silver hybrid conductive inks can combine the advantages of lower cost, better conductivity and long-term stability of the copper or silver ink, which have attracted wide research interest in the development of materials for flexible electronics. Although Cu–Ag nanoparticle based inks, such as Cu–Ag core–shell nanoparticle inks and Cu–Ag bimetallic nanoparticle inks, have already been developed and applied to produce conductive patterns using different deposition methods, they are still not ideal because of the complex and time-consuming synthetic process, low yield and high sintering temperature for good conductivity. In this paper, we report synthesis and characterization of novel self-catalyzed Cu–Ag organic complex inks with reduced sintering temperature via a simple one-step method. The effects of Cu–Ag ratio on the thermal property, stability and electrical performance of the formulated inks were investigated, where the Cu1–Ag1 ink was found to be ideal in terms of cost, conductivity and thermal behavior. The presence of silver oxalate in the copper complex ink was beneficial to the thermal decomposition of the Cu complex and able to decrease the sintering temperature by 30 °C due to the catalytic function of silver, making it more compatible with flexible polymer substrate materials. Meanwhile, the addition of a small amount of silver oxalate could improve the conductivity of the Cu ink. The sintered Cu–Ag films showed favorable conductivity which is comparable to the value of the reported Cu–Ag nano inks but with a lower sintering temperature. The Cu1–Ag1 hybrid ink with self-catalyzing capability is a balanced choice when considering the cost and conductivity. [ABSTRACT FROM AUTHOR]

A microwave-assisted two-steps method was proposed for the facile and fast preparation of silver nanoparticle conductive ink. The nanoparticles in the ink are of multi-sized, which is beneficial to getting higher packing density and better conductivity of the printed/written pattern. The effects of the reaction parameters of microwave and additives on the written pattern resistivity were studied on the basis of scanning electron microscope, X-ray diffraction and surface porosity results. Both of the microwave energy and the addition of PVP as the capping agent were found to be critical for the formation of face-centered cubic silver nanoparticles in the conductive ink. The surface porosity and the pore distribution form were also demonstrated to affect the pattern conductivity. The electrical resistivity or the pattern written with the ink prepared at microwave irradiation time of 90 s was calculated to be 364 μΩ cm. The second step of simple centrifugation process could improve the pattern conductivity effectively. After concentrated the conductive ink for two times, the electrical resistivity of the written pattern reduced from 364 to 77 μΩ cm. The proposed two-steps of microwave combined with centrifugation method is a simple and useful way for the preparation of silver nanoparticle conductive ink that can be used in printed electronics. [ABSTRACT FROM AUTHOR]

Flexible electronics is of considerable interest for many applications due to the distinctive features of low-cost, flexibility and light weight capabilities. However, in translating the technology from research to practical applications one faces many challenges. One of them is to formulate suitable ink materials where the selection of functional components, for example in the case of organic silver ink, the silver precursor, complexing agent and volatile organic solvent, are very critical because these constituents determine the final properties of the ink. In this paper, a new type of silver organic ink with decomposition and self-reduction mechanisms (10 wt% silver content) was formulated. It is shown that the ink is capable of producing silver films with good uniformity and conductivity on a polyimide substrate after sintering at 155 °C. The effect of solvent on the thermal property of the formulated ink have been investigated by differential scanning calorimetry (DSC) and UV–Vis spectrscopy, where the active roles of the solvents and the underlying chemical reactions in the ink during heating were studied. The reaction mechanism between the complexing agent and the silver precursor was confirmed by FT-IR measurements. The effects of sintering temperature and time on the microstructure and electrical properties of the silver ink films have been studied in detail using XRD, SEM/EDX and 4-probe based techniques. The defects such as voids and cracks as well as the coffee rings, which are often associated with films produced from organic silver inks, were reduced significantly by using both decomposition and self-reduction mechanisms in film formation. [ABSTRACT FROM AUTHOR]

Conductive ink can be widely applied in printed electronics to print high conductivity and flexible electrodes, especially for large-area formats with low cost considerations. In this article, we demonstrated that the in situ prepared silver nanoparticles decorated graphene conductive ink was suitable for flexible electronics. By using liquid phase exfolication method and reducing the silver salt to nano silver at the same system which addressed the heterogeneous issue of silver decorated graphene. The inkjet-printed graphene features attained low resistivity of 20 ± 1Ω/□ after a thermal anneal at 400 °C for 30 min while showed uniform morphology, compatibility with flexible substrates. [ABSTRACT FROM AUTHOR]

Due to low melting temperature, low price and high conductivity, copper nanoparticles have great potential to substitute conductive polymers, silver and gold nanoparticles and others in conductive inks. Here we developed a new, simple and green method to synthesize copper nanoparticles, which have the average size of around 140 nm and show remarkable ability to prevent oxidation. Using the copper nanoparticles for conductive ink, the electrical performance of copper film by depositing copper ink on polyimide was also investigated with the sintering temperature from 150 to 400 °C. The electrical resistivity is around 17.0 μΩ cm under sintering temperature of 250 °C, and can reach as low as 5.7 μΩ cm under the temperature of 400 °C. The proposed approach to synthesize copper nanoparticles for high performance conductive ink presents potential applications in flexible electronics. [ABSTRACT FROM AUTHOR]

In this study, we present a new simple method using formic acid pretreatment to achieve low temperature sintering of Cu nanoparticles, and the Cu nanoparticles have been successfully prepared with a modified polyol method. For formic acid pretreatment, the spherical Cu nanoparticles with an average size of 30 nm were saturated with a mixed solution of formic acid and absolute ethanol directly. The surface composition analysis indicated that the initial oxide on the surface of Cu nanoparticles was completely removed, and formate was generated as a by-product which could decompose at low temperature. According to the thermal analysis results, it was found that the sintering temperature of Cu nanoparticles with formic acid pretreatment was reduced to 160 °C. And the corresponding microstructures further demonstrated that the emerging small exothermic peak of thermal curve over the temperature range between 120 and 160 °C was caused by the formation of sintering necks. The formic acid treated Cu nanoparticle films sintered at 260 and 320 °C exhibited an electrical resistivity of 6.1 and 3.6 μΩ cm respectively. [ABSTRACT FROM AUTHOR]

The electrical performance of the ink-jet printed conductive tracks composed of silver particles was investigated. Three different shapes silver particles were synthesized via chemical reduction method in the presence of poly vinyl pyrrolidone, and then they were used to study the shape influence on the electrical property and thermal stability of the conductive tracks. The resistivity variation and microstructure of the silver conductive tracks was monitored as a function of fillers content using a four-point probe and scanning electron microscopy as well as thermal analysis. In addition, we proposed the possible formation mechanism of conductive tracks with different fillers. It demonstrated that the conductive tracks filled with silver nanorods and nanoparticles could achieve the volume electrical resistivity of ~3.2 × 10 Ω cm after sintering at 160 °C for 15 min. Finally, we fabricated highly conductive silver patterns on a glass substrate by ink-jet printing. [ABSTRACT FROM AUTHOR]