Ink Layer Research Articles

Numerical simulation of the water-based ink transfer process in roll-to-roll gravure printing based on fluid–solid interactions

The roll-to-roll gravure printing ink transfer process plays an important role in enhancing printing quality and saving on costs. The static analysis and fluid–solid interaction method are used for the first time to conduct a systematic study on the coupling between the fluid flow state and the solid deformation in the whole process of roll-to-roll gravure printing. The static compression stage, the initial moment of ink transfer, and the process of ink passing through the gap between two rollers and the separation of the ink layer with the rotation of two rollers are considered. The effect of ink layer thickness on the ink transfer process is studied. At a printing pressure of 0.2 MPa and a printing velocity of 200 rpm, the ink thickness has a great influence on the ink flow state, which leads to backflow; the phenomenon causes irregularities in the effective ink transfer ratio. The critical ink layer thickness is 70 µm under the above gravure printing conditions. This should not be exceeded to ensure the stability of ink transfer. Under the above printing conditions, when the ink layer thickness is in the range of 30–50 µm, there is no ink backflow phenomenon and the width of the ink flow channel is relatively large, and the effective ink ratio is almost stable at 50%. This study is helpful for controlling the ink quantity in the gravure printing, providing strong theoretical support for the improvement of the gravure printing process, and promoting the application of the water-based ink.

A brief analysis of quality of printing in different substrates based on screen printing process

Screen Printing is a traditional and versatile process of transferring ink. A thick layer of ink can be deposited by this process which makes it ideal to print on broad range of substrates (both on porous & non porous). The purpose of this analysis is to focus on the quality of print on four different types of substrates: Paper, Plastics, Textile and Ceramic based on screen printing process. The work has been done using three different screen mesh of screen ruling 60, 120, 180 l/cm and two different squeegees of shore hardness: 60 shore A° & 90 shore A° to find out the factors influence the quality and probable solutions to achieve sharp and fine output with less amount of wastage.

Evaluation of electrical resistance of electrodes with conductive ink for agriculture applications using computer technology

The article presents the ongoing research, which aims to select suitable electrodes and mixtures of conductive inks, which will be used as a converter between the pressure and electrical quantities in the design of planar pressure transducers. In the described research, we continue our previous work and the work of other authors who have previously dealt with the properties of conductive inks and electrodes. Due to the only partial results in the given field, we decided to perform an extensive and original measurement of a total of 172 combinations of different electrode sizes, various conductive ink mixtures and ink layer thicknesses. Thanks to this, it will be possible, in the future, to select a suitable combination of electrodes and inks when designing pressure sensors for industrial and agricultural applications without the need to perform time-consuming preparatory measurements. The aim of the measurements is also to determine the usable working range of the pressures and the corresponding sensitivity for certain combinations of electrodes and inks, and to also exclude those variants which are unsuitable for the given purposes. This paper presents the introductory part of the measurements, which aims to verify the methodology of the measurements on a test plate at robotised workspace that is connected to a PC in real time via the program LabView. The described introductory measurements proved our methodology to be suitable to the given purpose; however, there minor problems emerged with the actual working pressure range of the transducer and the consequential necessary adjustments of the control program.

Reprogrammable, light-driven and sensing actuators based on Chinese ink composite: A synergetic use of shape-memory and self-healing strategies

Smart actuators have great prospects in soft robotics. Reprogrammable function is essential for shape-reprogramming of actuators to achieve arbitrary shapes and diverse deformations, which is a key feature for next-generation actuators. However, it remains a huge challenge to develop a facile strategy to prepare reprogramming and multi-functional actuators. Herein, we report a synergetic strategy to fabricate reprogrammable, light-driven and sensing actuators based on Chinese ink and waterborne polyurethane (PU) composite. The entire ink/PU actuator is self-healing, as both the ink and PU films can be self-healed with the aid of water. Through synergistically using the shape-memory of PU and self-healing property of ink/PU composite, the initial configurations of ink/PU actuators can be fixed and assembled into arbitrary shapes, including tendril-shape, heart-shape, accordion-shape, letter-shapes and so on. These programmed actuators demonstrate complex deformations reversibly under near-infrared light irradiation. Importantly, the same actuator can be reprogrammed and light-actuated again. Moreover, introducing conductive ink layer integrates temperature sensing function into the actuator. Finally, a bionic butterfly robot is constructed, which can not only flap wings under light irradiation, but also sense human touching. This study will open a new path to reprogrammable, self-healing, and light-driven soft robots with multi-functions and complex deformations.

Study of correlation between ink trapping and color difference in overprint

The ink trapping value is one of the important parameters affecting the appearance of secondary colors in overprint. Usually, the ink trapping parameter is traditionally calculated based on the solid density values of the primary colors and the overprint color. These density values are measured by the complementary color filter of the color final ink layer, and these ink trapping values can be calculated using the Preucil, Ritz, or Brunner formulas. Furthermore, the density measurement is more suitable for testing the color printing and not for overlapping assessment because these density values are measured by the complementary color filter of the second color ink. The ink has a specific transmittance, and light is not only absorbed but also scattered inside the ink layer, so the total density of the overlapping colors will be less accurate. As a result, the color measurement method is used to describe the effect of ink trapping of the second ink layer on the first layer of ink. The main idea is to use the color difference value to evaluate the ink trapping ability. In this paper, the author has quantitatively analyzed the correlation between the percentage value of ink trapping and the color difference parameter ΔEab*. The studied results show that the ΔEab* value has a linear correlation with the ink trapping value calculated according to the traditional methods based on density values. This result is also aimed at the fluctuant tolerance of ink trapping ratio during four-color printing to achieve the standard color value quickly.

Потенційна небезпека УФ-фарб в процесі друкування пакувань для харчової і фармацевтичної продукції

The article is devoted to the problem of the potential danger of UV-inks with radical mechanism of photoinitiated polymerization during printing and operation of packages for food and pharmaceutical products. Pointing to the high level of environmental friendliness of the technology the use of UV-inks, which do not contain volatile organic solvents, their problem is noted application due to the possible migration of components from the ink layer and accordingly the risk of product contamination during packaging. An analysis of the processes occurring during the reaction was carried out radical polymerization, the reasons for the migration of printing ink components and by-products as a result of undergoing photoinitiated polymerization in aerobic conditions Accordingly, small amounts of unreacted components remain embedded in a three-dimensional polymer mesh and constitute the bulk of those components which can freely diffuse from the ink layer. The factors as the reason were analyzed refusal to use some types of oligomers, monomers and photoinitiators for the creation photopolymerizable ink compositions. Unreacted component residues, diffusing and mixing, depending on the chemical structure, can have a toxic or carcinogenic effect on living organisms. The analysis made it possible to classify ways of minimizing migration components of UV-inks when printing packages, namely, ways to minimize migration. The properties of UV-inks components can be divided into two types: chemical and physical. At the chemical method is a careful selection of UV-inks components and introduction synergists, and in the case of physical - compliance with technological regimes, reduction the concentration of oxygen both in the atmosphere and in the liquid composition by creating an inert gas environment and the creation of effective barriers by lamination.

Development of a free-form piezo-resistive pressure sensor using advanced printing methods

The use of printed pressure sensors is becoming a popular alternative to conventionally made silicon-based pressure sensors in niche applications, ranging from automotive and aerospace to the biomedical industry. In this paper, a piezo-resistive pressure sensor is produced onto a free-form Polyamide (PA) substrate, by combining aerosol-based jet printing and screen-printing techniques. The result is a first study towards the implementation of printed piezo-resistive pressure sensors for biomedical applications.The piezo-resistive pressure sensor consists of silver interconnects which are printed onto the substrate and are connected through a layer of piezo-resistive ink. The sensor is printed onto a customized additive manufactured PA substrate, which is produced using Selective Laser Sintering (SLS). First, the interconnects are printed using silver ink, CUR AG-001, from Agfa N.V. Belgium, which is deposited using an aerosol-based jet printer, the Nebula 5X-100s, developed at the Advanced Manufacturing Laboratory (AML) of the KU Leuven. Next, the sensitive elements are printed using a piezo-resistive material, Carbon EMS CI 2050, which is applied across the sensor interconnects using an adapted screen-printing technique. An optimal ink composition for the two-component piezo-resistive ink was found at 40wt% CI-2050LR: 60wt% CI-2050HR, which are respectively low and high resistivity ink components. Both silver ink and printed piezo-resistive elements were sintered in an oven at 150°C for 240 and 45 min, respectively. Finally, a coupling for the sensor readout was provided using a silver conductive epoxy adhesive, which cures at room temperature, so that electrical connections could be attached to the sensor contact pads.Validation of the piezo-resistive pressure sensors was conducted using fingertip actuation, which showed a typical piezo-resistive behavior where the resistance of the sensor decreases in function of the applied pressure, and a maximal decrease in electrical resistance of 30.5Ω has been measured. These results show the feasibility of employing advanced printing techniques to produce piezo-resistive sensing devices onto free-form and additive manufactured substrates, for biomedical applications.

Determination of 18 photoinitiators in food paper packaging materials by FastPrep-based extraction combined with GC–MS

Extraction of photoinitiators (PIs) from food paper packages is difficult since they normally hide inside multiple ink layers. A one-step FastPrep-based extraction in combination with GC–MS was developed to simultaneously measure 18 PIs in food paper packaging materials. FastPrep-based extraction enabled direct and efficient release of PIs from raw paperboard in a minute without additional procedures. It was simple, high-throughput, consuming less solvent and not requiring heat or radiation. GC–MS using selected ion monitoring provided identification of PIs with high selectivity. The LODs and LOQs for 18 PIs ranged from 0.060 to 0.614 mg/kg, and 0.197–2.027 mg/kg, respectively. The method was successfully applied for various real samples, and the spiked recoveries using different real sample matrices ranged from 93.3% to 110.1%. The developed method can thus be used for the quality control of PI residues in paper packaging materials of food products.

Influence of procedural noise on the glossiness of 2.5D printed patches

Perlin noise, a type of procedural noise, was used for the design of elevation files for 2.5D printing. This printing method uses elevation data from a height map to create physical relief by superimposing layers of ink. In this experiment, the grayscale values of noise functions were used as elevation values to build different surface structures in UV curable ink by 2.5D printing. Printed samples with varying levels of Perlin noise were created and their reflectance properties were studied by measuring the values of specular gloss. The roughness and specular gloss of the printed surfaces were effectively influenced when varying the persistence and octaves of the noise functions. The aim of implementing the procedural approach to a high-resolution printing method has been to explore the reflectance properties of custom noise functions when transferred to the physical realm. This might contribute to better understand the effect of surface structure on the appearance of materials. Potentially, this approach will enable the use of relief printing to produce structures with a more natural appearance and a desired gloss value by using a low-cost computing process.

Preparation and application of water-based nano-silver conductive ink in paper-based 3D printing

PurposeIn 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/approachThe 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.FindingsThe 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/valueIn 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.

Carbon Particle-Doped Polymer Layers on Metals as Chemically and Mechanically Resistant Composite Electrodes for Hot Electron Electrochemistry

This paper presents a simple and inexpensive method to fabricate chemically and mechanically resistant hot electron-emitting composite electrodes on reusable substrates. In this study, the hot electron emitting composite electrodes were manufactured by doping a polymer, nylon 6,6, with few different brands of carbon particles (graphite, carbon black) and by coating metal substrates with the aforementioned composite ink layers with different carbon-polymer mass fractions. The optimal mass fractions in these composite layers allowed to fabricate composite electrodes that can inject hot electrons into aqueous electrolyte solutions and clearly generate hot electron-induced electrochemiluminescence (HECL). An aromatic terbium (III) chelate was used as a probe that is known not to be excited on the basis of traditional electrochemistry but to be efficiently electrically excited in the presence of hydrated electrons and during injection of hot electrons into aqueous solution. Thus, the presence of hot, pre-hydrated or hydrated electrons at the close vicinity of the composite electrode surface were monitored by HECL. The study shows that the extreme pH conditions could not damage the present composite electrodes. These low-cost, simplified and robust composite electrodes thus demonstrate that they can be used in HECL bioaffinity assays and other applications of hot electron electrochemistry.

A comparative study of the interaction between the dried ink layer andPLAfilm used for packaging purposes

AbstractThis research aims at comparing the interactions between the water‐based printing ink and polylactide (PLA) printing base. As a reference base, a polyethylene terephthalate (PET) film was chosen. The wettability of both films was investigated. The Owens–Wendt method was applied to calculate the surface free energy (SFE). The values of SFE and its polar and dispersive components were compared with the surface tension (ST) of the ink and the polar and dispersive components of ST. The wetting envelopes of the investigated PLA and PET films are presented. Finally, the bonding strength between the dried ink layer and the printing base was analyzed. The PET film exhibited higher values of SFE. However, the bonding strength between the dried ink layer and the printing base was higher for PLA films. Our results reveal that PLA films can be an excellent choice as packaging materials, with comparable or even better print quality than conventional fossil‐based plastics.

3D reactive inkjet printing of poly-ɛ-lysine/gellan gum hydrogels for potential corneal constructs

Corneal opacities are the 4th leading cause of blindness, and the only current treatment method is the replacement of damaged tissue with a donor cornea. The worldwide shortage of donor eye bank tissue has influenced research into biomaterial substrates for both partial and full thickness corneal implantation. Here, polymer hydrogels based on natural peptides, poly-ɛ-lysine and gellan gum, can be manufactured using reactive inkjet printing (RIJ). The inks used for printing were optimised based on their rheological properties. Printing alternating layers of ink forms a unique surface pattern, based on the immediate formation of ionic bonds between polymers of opposing charges. This surface pattern resembles a repeating honeycomb-like structure, visible by both optical and scanning electron microscopy. The structure of the printed hydrogels can be modified to include pores, a feature of interest for the tissue engineering of full thickness corneal constructs. Printed poly-ɛ-lysine/gellan gum hydrogels demonstrated a transparency of 80% and cyto-compatibility with both corneal epithelial and endothelial cells. Both corneal cell types demonstrated cell attachment across the surface of the printed hydrogel arrays, displaying their typical cell morphology. This gives confidence of the cyto-compatibility of these hydrogels in vitro. Reactive inkjet printing can produce 3D structures with a high resolution, producing printed tracks in the micron range. Additionally, RIJ demonstrates versatility, as constructs can be tailored to meet various dimension and thickness requirements. Furthermore, this work demonstrates for the first time that reactive inkjet printing can been used to produce hydrogel constructs based on these two inks, with the aim of producing constructs for corneal tissue engineering.

Reaction Products Affecting the PEFC Catalyst Ink Property

Catalyst ink is a key material of the catalyst layer in a proton exchange membrane fuel cell, but can be degraded as the reactions of alcohols are promoted by Pt in the ink. The present study quantitatively determined the concentrations of reaction products in an ethanol/water-based catalyst ink, and the effects of these substances on the ink and catalyst layer were investigated. The acetaldehyde concentration was found to be the key factor, as acetaldehyde caused particle agglomeration in the catalyst ink and micro-scale crack formation in the catalyst layer.

Effect of Plasma Surface Modification on Print Quality of Biodegradable PLA Films

PLA films, as non-absorbent materials, require modification of the surface before the printing process in order to improve the wettability of the substrate and to obtain proper ink adhesion to the substrate. In this paper, the surfaces of two kinds of PLA films were modified using plasma activation with parameters enabling high surface free energy (SFE) values, and then the films were printed on using different kinds of flexographic inks. Two gases, oxygen and argon, were used for activation, as these make it possible to obtain good hydrophilicity and high SFE values while having different effects on the roughness, or the degree of surface etching. Plasma-activated films were subsequently subjected to the measurements of: contact angle with water, diiodomethane and three printing inks, roughness, weight change, strength properties, color and gloss change, and SFE was determined. Unmodified and activated films were flexographically printed in laboratory conditions and then the quality of obtained prints was analyzed. The results showed a strong effect of activation with both oxygen and argon plasma on the SFE value of the films and the contact angles of water and inks, with the gas used for plasma activation and the type of film significantly influencing the thickness of the fused ink layer and the resultant color. Moreover, plasma activation had a especially favorable and significant effect on the quality of prints made with water-based inks, while it had little effect when printing with solvent-based inks.

Layout Estimation for Layered Ink of 3D Printer to Reproduce the Desired Line Spread Function of Skin using Simulated Data

Abstract In this article, the authors propose a method to estimate the ink layer layout for a three-dimensional (3D) printer. This enables 3D printed skin to be produced with the desired translucency, which they represent as line spread function (LSF). A deep neural network in an encoder‐decoder model is used for the estimation. It was previously reported that machine learning is an effective way to formulate the complex relationship between optical properties such as LSF and the ink layer layout in a 3D printer. However, although 3D printers are more widespread, the printing process is still time-consuming. Hence, it may be difficult to collect enough data to train a neural network sufficiently. Therefore, in this research, they prepare the training data, which is the correspondence between an LSF and the ink layer layout in a 3D printer, via computer simulation. They use a method to simulate the subsurface scattering of light for multilayered media. The deep neural network was trained with the simulated data and evaluated using a CG skin object. The result shows that their proposed method can estimate an appropriate ink layer layout that closely reproduces the target color and translucency.

Programmable Organic Chipless RFID Tags Inkjet Printed on Paper Substrates

In this paper, an organic, fully recyclable and eco-friendly 20-bit inkjet-printed chipless RFID tag is presented. The tag operates in the near field and is implemented by means of chains of resonant elements. The characterization and manufacturing process of the tag, printed with a few layers of a commercial organic ink on conventional paper substrate (DIN A4), are presented, and tag functionality is demonstrated by reading it by means of a custom-designed reader. The tags are read by proximity (through the near field), by displacing them over a resonator-loaded transmission line, and each resonant element (bit) of the tag is interrogated by a harmonic signal tuned to the resonance frequency. The coupling between the reader line and the resonant elements of the tag produce and amplitude modulated (AM) signal containing the identification (ID) code of the tag.

Ultra-wideband polarization- and angle-insensitive metamaterial absorber based on multilayer resistive ink

An ultra-wideband metamaterial absorber (MA) consisting of three layers of resistive ink separated by two layers of polymethacrylimide is proposed. The results of full-wave simulation show that the absorptivity is high up to 95% with a bandwidth ratio of 1:9.73 over the wide frequency range from 4.20 to 40.87 GHz, covering the whole C, X, Ku, K, and Ka bands. Moreover, the MA is insensitive to polarization and exhibits wide-angle stability, which is investigated by the full-wave simulation results as well as the analysis of multi-reflection interference theory. The fabricated prototype with a single unit cell of 0.081 g is tested using free-space measurement in an anechoic chamber, and the measured results are in good agreement with the simulation results, which prove the robustness of the design and indicates a practical application prospect of the proposed ultra-wideband MA with lightweight, simple, and compact structure.

Functional aqueous-based polyaniline inkjet inks for fully printed high-performance pH-sensitive electrodes

pH sensors are extremely useful in various applications such as health, food and environmental monitoring. Due to this fact the development of planar, low-cost and high-performance pH sensors that can be fabricated in large scale are highly appreciated. In this work we fabricated a polyaniline-based potentiometric pH sensor using two printing techniques. The working electrode was fabricated by printing a carbon ink layer onto Valox® by screen printing and subsequently modifying its active area by printing with a polyaniline ink by inkjet printing. Different water-based formulations of the polyaniline ink using acrylic dispersions as binders were tested in order to optimize printability, adhesion, rub resistance and functionality of the printed electrodes. These electrodes showed an outstanding sensitivity (up to 69.1 mV/pH), slightly higher than polyaniline electrodes fabricated by electropolymerization onto carbon paste electrodes and also comparable to glass electrodes. Moreover, their response to synthetic sweat was analyzed, demonstrating that there are suitable for application in wearable technology.

Method of multi-layer near-field electrohydraulic printing and sintering of nano-silver ink prepared by liquid phase reduction

The liquid phase reduction method has a wide application prospect because of its simple equipment and low cost. However, the disadvantages, such as uneven particle size distribution and easy agglomeration of particles, make it difficult to prepare high-concentration nanoparticle ink by this method, which limits its application in the manufacture of high-resolution electronic products. This paper presents a printing and sintering process for low-concentration ink prepared by the liquid reduction method. First, the set pattern is printed by the near-field electrohydraulic printing method. At the same time as multi-layer printing, the substrate is heated by the collecting plate to accelerate the evaporation of the solvent in the printed pattern. Then, the printed multi-layer micro-conductive pattern is solidified by a hot/pressure sintering machine. This method can overcome the edge diffusion effect caused by poor ink viscosity effectively and obtain printing patterns with high thickness, high conductivity, and high resolution. The drying time of different ink layers, the pressure and temperature of hot/pressure sintering, and other parameters were studied in this paper. The electrical conductivity and reliability of the pattern with different printing layers are also analyzed, which provides a reference for the printing and sintering of low-concentration ink in the future.