Complex Ink Research Articles

Synergetic Effect of Blended Alkylamines for Copper Complex Ink To Form Conductive Copper Films.

Cu(II) complex ink consisting of copper formate (Cuf) and a primary alkylamine could yield highly conductive copper films at low heating temperatures without a reducing atmosphere. A synergetic effect of the blended alkylamines on the formation of conductive films was observed. It was found that blending two types of amines with different alkyl chain lengths as ligands could improve the conductivity of copper films, compared with using one of these amines alone. The decomposition mechanism of the Cuf-amine complex and the role of amines with different alkyl chain lengths were investigated. It was found that the decrease in the decomposition temperature and the formation of copper films were attributed to the activating effect and capping effect of the amine, and these two effects were dependent on the alkyl chain length. The relative intensity of the dual effects determined the decomposition rate of the complex and the nucleation and growth of particles. The use of blended amines with different alkyl chain lengths as ligands could balance the two effects and lead to appropriate nucleation and growth rates, so that densely packed copper films with low resistivity could be obtained at low heating temperature in a short time. The Cuf-butylamine-octylamine (Cuf-butyl-octyl) ink with 1:1 molar ratio of the amines showed the best performance. The understanding of the synergetic effect could provide guidance to the design of copper complex inks to control the morphology of the films.

P-Type aliovalent Li(I) or Fe(III)-doped CuO hollow spheres self-organized by cationic complex ink printing: Structural and gas sensing characteristics

The p-type CuO hollow sphere films doped with aliovalent Li(I) or Fe(III) have been prepared directly on the substrate through a self-organization process in the printed films using the formulated cationic complex inks. The Li(I) or Fe(III) ions are substitutionally incorporated into CuO lattice with the variation in lattice parameters and act as a shallow acceptor or donor leading to the increase or decrease of the hole density, respectively. Such an electronic modification shifts the optical band gap and binding energy of Cu. The increased hole density by Li(I) doping reduces the overall sensor resistance and the width of hole-accumulation layer (λd) in CuO grains, resulting in the decrease in gas response toward the reducing ethanol gas to ca. 50% compared to that of undoped CuO. In contrast, the decreased hole density by Fe(III) doping increases the sensor resistance and λd, leading to the enhancement in gas response to ca. 150%, based on the electronic sensitization mechanism. These results show clearly that the substitutional doping of aliovalent cation is effective for the manipulation of electronic structure and gas sensing properties of p-type CuO.

Fabrication of 10 µm-scale conductive Cu patterns by selective laser sintering of Cu complex ink

A Cu complex ink was synthesized using copper formate as a precursor and its potential for laser patterning was investigated. The Cu ink was spin-coated onto a substrate and the coated film was space-selectively sintered using a nanosecond-pulsed ultraviolet laser. The unexposed Cu ink could be removed from the film by rinsing it with the dispersing agent used to synthesize the ink, disclosing a conductive Cu pattern. A minimum resistivity of 8.46×10−5Ωcm was obtained for the Cu lines with 10–20µm widths. The feasibility of this method for metallization was demonstrated by fabricating a complex Cu electric circuit on an indium tin oxide-coated glass substrate. The selective laser sintering approach provides a simple, cost-effective alternative to conventional lithography for the production of electrode or metallization patterns.

Self-reducible copper ion complex ink for air sinterable conductive electrodes

We introduce a novel self-reducible Cu ion complex ink, composed of formate, alkanolamine groups and poly alcohols, for the air sinterable, low-cost, environment-friendly fabrication of Cu conductive electrodes.

Effect of the Amine Concentration on Phase Evolution and Densification in Printed Films Using Cu(II) Complex Ink.

The nucleation and growth behavior of Cu nanoparticles during thermal heating of Cu(II) complex inks for printed Cu metallization were investigated, particularly focusing on the effects of the amine concentration on the microstructure evolution and electrical conductivity. Herein, the dual effects of hexylamine as a reducing agent dissociating the carboxyl group from the precursor and a capping agent hindering the subsequent growth of Cu nuclei were confirmed. On the basis of such dual effects of amine, the sufficient complexation of the Cu(II) precursor with a high amine concentration in the ink led to the single-route growth of Cu nanoparticles during thermal heating, which resulted in the dense film with a narrow particle size distribution exhibiting a high electrical conductivity. The electrical conductivity of the film could be further enhanced by a reducing atmosphere with formic acid. Significantly, the understanding of the ink chemistry and the nucleation and growth kinetics in the metal ion complex or metal-organic decomposition (MOD) ink can provide the design rules for the formulation of the solution-type inks to control the microstructure of printed metallization.

Surface Charge Reversal Method for High‐Resolution Inkjet Printing of Functional Water‐Based Inks

Printed electronics is a rapidly growing area of research being explored for the manufacture of large‐area and cost‐effective electronic devices by the patterned application of functional inks. There are challenges associated with processing the inks compatible with inkjet printing technology and developing efficient methods to successfully obtain the desired features, particularly when it comes to metal and metal–organic complex inks. Here, a reliable method is developed to achieve a sophisticated microstructured pattern using the inkjet printing technique assisted by a surface charge reversal effect. In addition, a procedure is formulated to obtain good quality, stable metal–organic water‐based inks compatible with salts of a variety of transition metals and rare earths, without the need for additional volatile solvents. A feasible and water‐based ink formulation combined with a simple and noninvasive surface charge reversal treatment constitutes a major step toward the manufacture of high‐resolution, inorganic patterned thin films on hydrophobic substrates using inkjet printing. These outcomes lead to the path of effective fusion of inorganic and organic heterointerfaces by simples designing and printing.

Fast and low-temperature sintering of silver complex using oximes as a potential reducing agent for solution-processible, highly conductive electrodes

Highly conductive, solution-processed silver thin-films were obtained at a low sintering temperature of 100 °C in a short sintering time of 10 min by introducing oximes as a potential reductant for silver complex. The thermal properties and reducibility of three kinds of oximes, acetone oxime, 2-butanone oxime, and one dimethylglyoxime, were investigated as a reducing agent, and we found that the thermal decomposition product of oximes (ketones) accelerated the conversion of silver complex into highly conductive silver at low sintering temperature in a short time. Using the acetone oxime, the silver thin-film exhibited the lowest surface resistance (0.91 Ω sq−1) compared to those sing other oximes. The silver thin-film also showed a high reflectance of 97.8%, which is comparable to evaporated silver films. We also demonstrated inkjet printed silver patterns with the oxime-added silver complex inks.

Annealed graphene sheets decorated with silver nanoparticles for inkjet printing

Abstract We report the preparation of annealed graphene nanosheets coupled with Ag organic complex inks by the approach of polymer stabilization and sonication, and the potential application of inkjet printing. The as-purchased graphene nanosheets were annealed as the main printing component which significantly increased the electrical conductivity of the inkjet printed track due to the highly reconstructed and nearly defect-free in-plane structures. Ag nanopaticles (NPs) were uniformly distributed on graphene nanosheets after post annealing process, which acted as superiorly conductive bridge to further decrease the contact resistance of graphene flakes and the resistivity of the inkjet printed track. The resistivity of 4.62 × 10 −4 Ω m (conductivity of 2.16 × 10 3 S/m) upon 15 printing times were achieved. The interwoven structured graphene nanosheets with Ag NPs formed a three-dimensional conductive network film with good mechanical robustness. The experimental results demonstrated the strategy of combining graphene nanosheets and nano-sized metal particles, which holds a possible pathway for the future application of flexible and maybe bendable inkjet printed electronic devices.

Synthesis of copper conductive film by low-temperature thermal decomposition of copper–aminediol complexes under an air atmosphere

The low-temperature synthesis of electrical conductive copper films under an air atmosphere was successfully developed by thermal decomposition using copper–aminediol complexes. Ink-mixed copper(II) formate and various types of aminediols were coated onto glass substrates, which were then calcined in air at various temperatures. Copper–aminediol complex inks were calcined with either 3-dimethylamino-1,2-propanediol or 3-diethylamino-1,2-propanediol at 165–180 °C to produce films with electrical conductivity and a minimum surface resistivity of 0.2 Ω sq−1. The film consisted of copper particles 1–3 μm in diameter. Aminediol adsorbed onto the surface of copper particles in the film prevented attacks from oxygen.

Enhanced surface coverage and conductivity of Cu complex ink-coated films by laser sintering

We here show that highly conductive copper films are obtainable from Cu complex ink by laser sintering. The synthesized Cu formate ink was spin-coated onto polyimide substrate and the coated films were scanned by an ultraviolet laser beam at 355nm. During the sintering process, N2 gas was blown into the irradiated area to prevent oxidation. Unlike the typical thermal process, laser sintering resulted in tightly packed, dense structures. This made it possible to produce highly conducting thin films with uniform thickness. A minimum resistivity of 1.92×10−5Ωcm was obtained.

Microstructure and electrical property of laser-sintered Cu complex ink

Abstract We show that highly conductive Cu films are obtainable from Cu complex ink by laser sintering. The Cu inks, synthesized using Cu formate as a precursor, were spin-coated onto polyimide substrate and scanned by an ultraviolet laser at 355 nm. The blowing of N 2 gas into the irradiated area prevented the film from being oxidized and a minimum resistivity of 1.70 × 10 −5 Ω cm was obtained. The laser-sintered film, composed mainly of nanorods, exhibited a much tighter structure than the one achieved by the typical thermal process. Although the thermal-sintered Cu film had a better crystalline quality, the minimum resistivity values available with both methods were almost identical. This is attributed to the more compact microstructure induced by laser sintering.

Direct Printing Synthesis of Self-Organized Copper Oxide Hollow Spheres on a Substrate Using Copper(II) Complex Ink: Gas Sensing and Photoelectrochemical Properties

The direct printing synthesis of metal oxide hollow spheres in the form of film on a substrate is reported for the first time. This method offers facile, scalable, high-throughput production and device fabrication processes. The printing was carried out via a doctor-blade method using Cu(II) complex ink with controllable high viscosity based on formate-amine coupling. Following only thermal heating in air, well-defined polycrystalline copper oxide hollow spheres with a submicrometer diameter (≤1 μm) were formed spontaneously while being assembled in the form of a film with good adhesion on the substrate. This spontaneous hollowing mechanism was found to result from the Kirkendall effect during oxidation at elevated temperature. The CuO films with hollow spheres, prepared via direct printing synthesis at 500 °C, led to the creation of a superior p-type gas sensor and photocathode for photoelectrochemical water splitting with completely hollow cores, a rough/porous shell structure, a single phase, high crystallinity, and no organic/polymer residue. As a result, the CuO hollow-sphere films showed high gas responses and permissible response speeds to reducing gases and high photocurrent density compared to conventional CuO powder films and the values previously reported. These results exemplify the successful realization of a high-throughput printing fabrication method for the creation of superior nanostructured devices.

Characterization of toners and inkjets by laser ablation spectrochemical methods and Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy

Detection and sourcing of counterfeit currency, examination of counterfeit security documents and determination of authenticity of medical records are examples of common forensic document investigations. In these cases, the physical and chemical composition of the ink entries can provide important information for the assessment of the authenticity of the document or for making inferences about common source. Previous results reported by our group have demonstrated that elemental analysis, using either Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) or Laser Ablation Induced Breakdown Spectroscopy (LIBS), provides an effective, practical and robust technique for the discrimination of document substrates and writing inks with minimal damage to the document. In this study, laser-based methods and Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS) methods were developed, optimized and validated for the forensic analysis of more complex inks such as toners and inkjets, to determine if their elemental composition can differentiate documents printed from different sources and to associate documents that originated from the same printing source. Comparison of the performance of each of these methods is presented, including the analytical figures of merit, discrimination capability and error rates. Different calibration strategies resulting in semi-quantitative and qualitative analysis, comparison methods (match criteria) and data analysis and interpretation tools were also developed. A total of 27 black laser toners originating from different manufacturing sources and/or batches were examined to evaluate the discrimination capability of each method. The results suggest that SEM-EDS offers relatively poor discrimination capability for this set (~70.7% discrimination of all the possible comparison pairs or a 29.3% type II error rate). Nonetheless, SEM-EDS can still be used as a complementary method of analysis since it has the advantage of being non-destructive to the sample in addition to providing imaging capabilities to further characterize toner samples by their particle morphology. Laser sampling methods resulted in an improvement of the discrimination between different sources with LIBS producing 89% discrimination and LA-ICP-MS resulting in 100% discrimination. In addition, a set of 21 black inkjet samples was examined by each method. The results show that SEM-EDS is not appropriate for inkjet examinations since their elemental composition is typically below the detection capabilities with only sulfur detected in this set, providing only 47.4% discrimination between possible comparison pairs. Laser sampling methods were shown to provide discrimination greater than 94% for this same inkjet set with false exclusion and false inclusion rates lower than 4.1% and 5.7%, for LA-ICP-MS and LIBS respectively. Overall these results confirmed the utility of the examination of printed documents by laser-based micro-spectrochemical methods. SEM-EDS analysis of toners produced a limited utility for discrimination within sources but was not an effective tool for inkjet ink discrimination. Both LA-ICP-MS and LIBS can be used in forensic laboratories to chemically characterize inks on documents and to complement the information obtained by conventional methods and enhance their evidential value.

Cu Salt Ink Formulation for Printed Electronics using Photonic Sintering

We formulate copper salt (copper formate/acetate/oleate) precursor inks for photonic sintering using high-intensity pulsed light (HIPL) based on the ink's light absorption ability. The inks can be developed through controllable crystal field splitting states (i.e., the ligand weights and their coordination around the metal centers). The inks' light absorption properties are extremely sensitive to the carbon chain lengths of the ligands, and the ink colors can drastically change. From the relationship between the ratios of C/Cu and the required sintering energies, it is possible to ascertain that the integral absorbance coefficients are strongly correlated with the photonic sintering behavior. These results suggest that the ink absorbance properties are the most important factors in photosintering. The wires formed by sintered copper formate complex ink via the HIPL method showed good electronic conduction, achieving a low resistivity of 5.6 × 10(-5) Ω cm. However, the resistivity of the wires increased with increasing contains carbon chain length of the inks, suggesting that large amounts of residual carbon have negative effects on both the wire's surface morphology and the electrical conductivity. We find in this study that high light absorptivity and low carbon inks would lead to a lower environmental load in future by reducing both energy usage and carbon oxide gas emissions.

Micro‐Raman spectroscopic analysis of inks and pigments in illuminated medieval old‐Slavonic manuscripts

Micro‐Raman spectroscopy was applied in characterisation of inks and pigments used in the text, illuminations and miniatures of two old‐Slavonic manuscripts: Vrutok four gospels (13th–14th centuries) and Benche four gospels (16th century). They were written in old‐Slavonic language with old Cyrillic alphabet. Both were decorated with ornaments in so called Balkan style characterised with intertwined rings and floral motifs. Only four colours/pigments were used in the simple miniature and ornaments in Vrutok book: orpiment, vermilion, organo‐copper complex and mixed ink. Much richer palette of pigments was revealed in the Benche book: calcite, gypsum, lead white, yellow ochre, pararealgar/realgar, vermilion, red lead, red ocra, organo‐copper complex, malachite, indigo, iron gall ink, carbon black and pure metallic gold. The use of pigments in ornaments compared with miniatures is somewhat different in Benche book, suggesting that either handwriting and ornamenting on one side and miniatures, on the other, were done by different persons/painters or depiction of sacral themes of the miniatures canonically required the use of more expensive/elaborate pigments.Micro‐Raman spectroscopy allowed in situ, non‐destructive, rapid and unambiguous identification of the majority of pigments used in the text, ornamentations and miniatures in the Vrutok and Benche four gospels. In case of uncertainty in identification of pigments, scanning electron microscopy–energy dispersive X‐ray analysis was applied. Copyright © 2012 John Wiley & Sons, Ltd.

Preparation and Spectral Analysis of Light Conversion Advanced Invisible Falsification-Resistant Ink

This paper discusses the structure design, light conversion agents, vehicles, colorants and the selection of other functional additives of light conversion advanced invisible falsification- resistant ink, the preparation of the light conversion falsification-resistant ink and rare earth metal europium complex, and analyzes rare earth metal europium complex, Eu(C5H7O2)3C12H8N2, through infrared spectrometer, element analyzer and fluorescence spectrometer. The results of the above analysis identify the composition of rare earth metal europium complex, its excitation spectrum ranging from 200nm to 400nm, and its emission spectrum ranging from 580nm to 640nm. Experiments suggest when the mixture of rare earth metal europium complex and white ink with titanium dioxide in a fixed proportion is printed on any objects, it appears reddish orange light under ultraviolet irradiation, which achieves the advanced invisible anti-counterfeiting effect.

Fabrication of aligned ultra-thin transparent conductive films of single-walled carbon nanotubes by a compression/sliding method

We demonstrate a novel, simple and scalable method for the fabrication of aligned ultra-thin transparent conductive films of single-walled carbon nanotubes (SWNTs). Pressing and sliding a thin liquid film of surfactant-stabilized SWNTs or SWNT–polymer complex ink between two parallel flat glass substrates provided a high order of directional alignment of nanotubes in the plane of the substrate along the sliding direction. The films showed high optical transmittances in the range of 95–98% at 550 nm and corresponding electrical resistances of 700–800 Ω □−1.

Effect of Complex Agent on Characteristics of Copper Conductive Pattern Formed by Ink-jet Printing

In this study, Cu ion complex ink was successfully synthesized by a modified electrolysis method in which the Cu ions generated from bulk metal plates by an electric field were coordinated with complex agents. The synthesized ink was ink-jet-printed on a flexible substrate and converted to a dense Cu pattern after sintering at 250 °C. The pattern was characterized by X-ray diffractometry, field emission scanning electron microscope, and four-point probe method to confirm the crystal structure, microstructure, and electrical conductivity, respectively. The effect of the type of complex agent on the characteristics of a Cu conductive pattern was also determined using the analysis results. Finally, we conducted the direct writing of conductive dots and lines using the Cu ion complex ink, and confirmed that fine patterning for application in electronics is possible with the Cu ion complex ink.

High Yield, Single Droplet Electrode Arrays for Nanoscale Printed Electronics

In this work we demonstrate two building blocks of a scalable manufacturing technology for nanoscale electronic devices based on direct-write printing: an architecture for high-yield printing of electrode gaps with 100 nm dimension and a low-temperature silver complex ink for integration of organic materials with high conductivity metal interconnects. We use single printed droplets that are made to dewet slowly from each other to allow reliable, high yield patterning even in the presence of certain surface defects.

Kodak's Stream Inkjet Technology and the Future of Digital Printing

The adoption of digital print continues to expand due in large part to the improvements in existing technologies as well as the development of new technologies that offer increasing levels of productivity, image quality, and economy. Eastman Kodak Company, a recognized leader in conventional and digital printing technologies, provides unified workflow solutions for a large number of diverse applications. In the area of inkjet printing, Kodak continues to pioneer ultra-high productivity inkjet technology for applications including, but not limited to, commercial, transactional, direct mail, packaging, and book publishing. Recent advancements in the ability to precisely control the instabilities in thermally stimulated microjets, coupled with advancements in MEMS technology, computer modeling of complex microfluidic systems, ink technology, and ink-substrate interactions, enabled the development and subsequent commercialization of a new continuous inkjet technology. This technology offers extremely high productivity with high image quality on a wide variety of substrates while maintaining a low total ownership cost. This technology, referred to as “KODAK Stream Inkjet Technology (or “Stream”),” forms the basis of a technology platform that is highly extensible, allowing participation in a broad range of markets that can effectively utilize high-speed digital print production. This paper will discuss the opportunities as well as the challenges of digital print and describe how Stream technology will play a significant role in this transformation.