Inkjet Printing Technique Research Articles

Controllable synthesis and sintering of silver nanoparticles for inkjet-printed flexible electronics

An effective and facile strategy was developed to successfully synthesize nearly uniform silver nanoparticles (AgNPs) with particle size of <10 nm, and demonstrated to achieve the sintering of AgNPs at room temperature for inkjet-printed flexible electronics. In such system, a series of different chain-length alkylamines were exploited as capped molecules to controllable synthesis of uniform AgNPs with the mean nanoparticle size in rang of 8.6 ± 0.9, 8.9 ± 1.2 and 9.2 ± 1.6 nm, and these ultra-small nanoparticles were very favorable to attain an excellent printing fluency. Based on the as-synthesized AgNPs, a sequence of flexible electrocircuits was successfully fabricated by ink-jet printing technique. After the dipped treatment, the printed AgNPs were achieved to spontaneous coalescence and aggregation at room temperature induced by preferential dissolution of capped molecules on AgNPs surfaces into methanol solution. These aggregated AgNPs demonstrated superior controllability, excellent stability and low resistivity in the range of 31.6–26.5 μΩ cm, and would have enormous potential in the application to be tailored for assembly of optoelectronics devices.

Controlled Ionomer Deposition into the Cathode Catalyst Layer By Inkjet Printer for PEM Fuel Cells

Proton exchange membrane (PEM) fuel cells are being intensively investigated as alternative energy conversion systems for both residential and automotive applications. In order for this technology to become fully commercial, the reduction of cost and improvements in performance and durability of PEM fuel cells membrane electrode assemblies (MEAs) are still required. The ionomer plays several important roles in the catalyst layer (CL), as the binder, proton conductor as well as oxygen transport media. It has been shown that amount of ionomer and its morphology and interaction with catalyst particles play an important role in Pt utilization and cell performance. However, controlling the ionomer structure and morphology inside the CL with conventional method of MEA preparation has been a challenge. There are several reports describing the effect of ionomer loading in catalyst layers on the fuel cell performance, ionic conductivity, and microstructure of MEA but less attention has been paid to the role of the distribution of ionomer within the catalyst layer [1–4]. It is conjectured that incorporating a graded distribution of ionomer such that its content is higher at the CL/membrane interface and lower at the CL/carbon paper interface might be beneficial to proton migration and mass transport, respectively. That is, the region of the catalyst layer possessing the highest ionic current density would be designed to possess the higher proton conductivity, and the region associated with the highest flux of gaseous oxygen would be bestowed with the higher porosity. Some studies that examined novel methodologies for MEA preparation have specifically tried to achieve a controlled ionomer distribution inside the CL [1–4], with the aim of improving three-phase boundary and catalyst utilization. For instance, Xie et al. [1] prepared a gas diffusion electrode (GDE) that contains a graded distribution of ionomer. The performance was improved when the Nafion® content in the GDE was higher toward the CL/membrane interface and lower toward the CL/carbon paper interface. It was hypothesized that this maximizes proton transport in the GDE in the region of greatest ion flux and maximizes porosity in the region of greatest gaseous flux, respectively. Shin et al. [2] impregnated lower ionomer content into a catalyst layer and coated additional higher ionomer content on its surface in order to increase proton conductivity at the catalyst layer/membrane interface. Cheng et al. [3] also suggested that impregnating the catalyst layer with additional Nafion® ionomer improves proton conduction. A theoretical study of PEMFC cathodes [4] suggested that the catalyst layer possessing a graded distribution of ionomer in which the Nafion® content was larger toward the catalyst layer/membrane interface should exhibit a slightly higher performance in fuel cells. Recently, great interest has arisen with respect to inkjet printing technology for manufacturing CL’s [5–7]. Our recent publications on inkjet printing techniques show great potential for increasing Pt utilization by reducing amount of ionomer [6]. The high-precision of inkjet printing allows for controlled catalyst deposition, especially for low Pt loadings, as well as ionomer patterning and gradient structures inside the CL. Therefore, in this work, inkjet printing technology was used to study ionomer distribution inside the CL. An experimental strategy is devised and implemented to examine the influence of a gradient of ionomer printed by inkjet nozzles into the CL and to verify the theoretical prediction of Wang et al. [4]. The effect of a graded distribution of ionomer content on ionic conductivity, active catalyst area, and porosity as well as performance results under different simulated automotive conditions are examined.

Evaluating silver tracks conductivity on flexible surfaces

The development of electric circuit fabrication on flexible polymer substrates has attracted significant interest as a pathway to low-cost, comfortable movement and large-area electronics among direct printing techniques. The term electronic textiles, or e-textiles, are used to denote the class of fabric structures that integrate electronic elements with textiles and can sense changes in its environment and respond to it. This new class of wearable electronic systems is being designed to meet new and innovative applications in the military, public safety, healthcare, space exploration, sports and consumer fitness fields. In this paper the inkjet printing technique (office thermal inkjet printer) was used as a simple method to chemically deposit silver Nanoparticles (85–300 nm) to the flexible surface. It is done by ejection of silver nitrate and ascorbic acid as a reducing agent to attain nanometals on the surface. Ink concentration and repeating the printing sequence of each ink determines molar ratio ejection of ink and is found to be necessary to be evaluated in order to attain the highest level of conductivity. The main purpose of this work is to gain the highest conductive printed tracks by using statistical design of experiment method on the fabric surface by applying inkjet technique. By optimizing the mentioned parameters, the highest conductivity of printed flexible tracks on the surface of paper is gained 8.0635 × 105 S/m and the result for polyester fabric is obtained 1.2417 × 104 S/m whereas metallic silver wire has a conductivity of 6.173 × 107 S/m.

Inkjet printed microwave circuits on flexible substrates using heterophase graphene based inks

Purpose – The purpose of this paper is to present the result of research on a new fabrication technology of printed circuits board and electronics modules. The new method is based on inkjet printing technique on flexible substrates using new generations of heterophase inks. New fabrications method was used to print microwave waveguides and signal splitters as new technology demonstrators. Design/methodology/approach – A fully Inkjet printed filter was printed on a flexible, transparent Kapton foil using heterophase inks developed in Instytut Technologii Materiałów Elektronicznych (ITME) for the purpose of this research based on graphene and silver nanoparticles. Findings – A microwave module was printed using two types of Inkjet printers – PixDro LP50 with KonicaMinolta 512 printhead – and developed in an Instytut Tele- i Radiotechniczny (ITR) laboratory printer using MicroDrop a 100-μm glass nozzle printhead. Fully printed microwave circuits were evaluated by their print quality and electrical properties. Originality/value – Fully Inkjet printed microwave circuits using the heterophase graphene ink were evaluated by their print quality and electrical properties.

Development of large-scale size-controlled adult pancreatic progenitor cell clusters by an inkjet-printing technique.

The generation of transplantable β-cells from pancreatic progenitor cells (PPCs) could serve as an ideal cell-based therapy for diabetes. Because the transplant efficiency depends on the size of islet-like clusters, it becomes one of the key research topics to produce PPCs with controlled cluster sizes in a scalable manner. In this study, we used inkjet printing to pattern biogenic nanoparticles, i.e., mutant tobacco mosaic virus (TMV), with different spot sizes to support the formation of multicellular clusters by PPCs. We successfully achieved TMV particle patterns with variable features and sizes by adjusting the surface wettability and printing speed. The spot sizes of cell-adhesive TMV mutant arrays were in the range of 50-150 μm diameter. Mouse PPCs were seeded on the TMV-RGD (arginine-glycine-aspartate)-patterned polystyrene (PS) substrate, which consists of areas that either favor (TMV-RGD) or prohibit (bare PS) cell adhesion. The PPCs stably attached, proliferated on top of the TMV-RGD support, thus resulting in the formation of uniform and confluent PPC clusters. Furthermore, the aggregated PPCs also maintained their multipotency and were positive for E-cadherin, indicating that the formation of cell-cell junctions is critical for enhanced cell-cell contact.

Underlying Mechanism of Inkjet Printing of Uniform Organic Semiconductor Films Through Antisolvent Crystallization

An underlying mechanism is reported for the formation of highly uniform crystalline organic semiconductor films by the double‐shot inkjet printing (IJP) technique utilizing antisolvent crystallization. It is demonstrated that the ability to form uniform films with this technique can be attributed to the unique nature of the initial contact dynamics between the chemically different microdroplets before occurrence of solute crystallization. Experiments are conducted systematically where a single microdroplet is over‐deposited by the IJP technique on a chemically different sessile droplet, for ten kinds of pure and miscible solvent combinations. The subsequent behavior is observed by high speed camera. The initial contact dynamics can be classified into three dramatically different cases that are respectively referred to as wetting, dewetting, and sinking. These phenomena are unique to microdroplets and the conditions for the occurrence of each type of phenomenon can be consistently explained by the fact that the initial contact dynamics are driven by the difference of surface tension of the liquids. Among the three kinds of dynamics, the wetting phenomenon creates a thin solution layer on the antisolvent droplet surface and can be used thus to manufacture uniform semiconductor films, where the coffee ring effect can be eliminated.

Facile synthesis of CuO nanosheets via the controlled delamination of layered copper hydroxide acetate

CuO nanosheets were prepared by the controlled delamination of layered copper hydroxide acetate followed by the in situ solvothermal transformation of hydroxide to oxide. The reaction was performed in 1-butanol in order to prevent recrystallization or nanoparticle aggregation. Analyses by small angle X-ray scattering, transmission electron microscopy, and atomic force microscopy revealed that the CuO nanosheets are approximately 1nm thin, corresponding to three to four stacked CuO6 octahedral layers. The average lateral size is approximately 5nm. The nanosheets form stable dispersions in 1-butanol that are suitable for the fabrication of transparent and homogeneous CuO thin films by spin-coating or inkjet printing techniques. The present synthesis is a rare example of the top down strategy leading to the nanometric two-dimensional nanosheets of non-layered oxide materials.

Development of fast response bi-luminophore pressure-sensitive paint by means of an inkjet printing technique

A novel fast response bi-luminophore pressure-sensitive paint (PSP) by inkjet printing of sensor-dot arrays on an anodized aluminum (AA) substrate has been developed for unsteady flow measurements. A bi-luminophore AA-PSP, which is a combination of PSP and temperature-sensitive paint (TSP), is essential for precise pressure measurements, because the PSP result needs the temperature correction. However, a conventional bi-luminophore AA-PSP prepared by a dipping method does not work well due to the interference between the PSP and TSP luminophores. To overcome this problem, we have developed isolated dot arrays of PSP and TSP formed on an anodized aluminum substrate by an inkjet printing method. In this study, platinum tetrakis (pentafluorophenyl) porphyrin (PtTFPP) and ZnS-AgInS2 (ZAIS) were employed as pressure- and temperature-sensitive dyes, respectively. A suitable solvent was chosen for each dye to form the dots with uniform, high luminescence intensity, and high sensitivity. The developed bi-luminophore AA-PSP could simultaneously measure pressure and temperature and could reduce the temperature effect of the PSP from −0.97%/K (without temperature correction) to −0.01%/K (with temperature correction). It showed a pressure response time of 17.8 ± 0.8 μs at 90% pressure rise to a step change of pressure, which is in the same range as a conventional AA-PSP.

Inkjet printing of conductive polymer nanowire network on flexible substrates and its application in chemical sensing

This work reports an inkjet printing technique for patterning a conducting polymer nanowire network on a flexible film for applications in chemical sensing. The novelty of this work is in the patterning capability of polymer nanowires to form a conducting path. Polyaniline nanowires were chemically synthesized in an aqueous solution and a surfactant was added to lower the surface tension which enabled the printing of the nanowires using a commercially available inkjet printer. The nanowire network-based patterns were printed on a flexible transparency film, and its morphology characterization, patterning ability as well as the electrical properties were investigated. Finally, as a proof-of-concept, a fully-printed chemical sensors were developed by using the proposed printing technique on flexible films. Two types of sensors were fabricated: a pH sensor and a hydrogen peroxide sensor. The results demonstrate that the developed sensors can be utilized as a low cost, disposable, and easily printable chemical sensors. The proposed technology may find applications in the development of a simple print-and-use biochemical sensing kit for potential use in point-of-care diagnostics.

Quantum Dots: Patterning Fluorescent Quantum Dot Nanocomposites by Reactive Inkjet Printing (Small 14/2015)

Semiconductor quantum dots have enormous potential as essential components in various optoelectronic devices. Patterned quantum dot nanocomposites such as quantum dot–polymers and quantum dot–photonic crystals are fabricated by Y. Song and co-workers on page 1649 through a reactive inkjet printing technique. Straightforward and efficient, this technique is capable of generating large-area patterns economically. It is anticipated that this concept will be broadened to the fabrication of other functional nanomaterials and optoelectronic devices.

K-space design of terahertz plasmonic filters

Wireless communication systems in the terahertz (THz) frequency range promise to dramatically increase available bandwidth in the electromagnetic spectrum. These wireless systems will require filtering techniques capable of operating in this relatively unused part of the spectrum. Here, we report a versatile technique for designing different classes of THz plasmonic filters based on a k-space methodology, in which the desired frequency response is mapped into two-dimensional (2D) k-space and then inverse Fourier transformed into the spatial domain. We use a recently developed inkjet printing technique to fabricate the spatial patterns allowing for grayscale conductivity variation. In general, any technique that allows for high-fidelity reproduction of the real-space grayscale variation in the fabricated plasmonic structure can be used. We demonstrate the flexibility of this approach by creating several classes of filters that allow for changes in the relative magnitudes in multiresonant filters; the polarization dependence, where the anisotropy can be carefully controlled; and the resonance bandwidth. We further demonstrate that, by cascading or adding filter functions together, even more complex filter designs can be achieved. We expect this approach to dramatically expand the design capabilities for filter technology for THz systems applications, such as THz wireless communications as well as applications in other spectral regions.

Controllable-density nanojunctions as SERS substrates for highly sensitive detection

A facile and efficient approach was designed to fabricate highly sensitive and reproducible SERS-active substrates based on the controllable-density nanojunctions with ink-jet printing technique. In this system, polyvinylpyrrolidone-capped silver nanoparticles (AgNPs) were ink-jet printed on substrates and subsequently dipped into sodium chloride solution. The capped molecules on the AgNPs surfaces were detached with the competitive absorption of chloride, and spontaneously triggered to form the controllable-density nanojunctions among the AgNPs aggregates. These formed AgNPs nanojunctions demonstrated excellent controllability, reproducibility, and a detection limit of 1×10−11M level for Rhodamine 6G probe molecules. This strategy could be expected to construct multifarious SERS sensors for highly sensitive detection in chemical and biological fields.

In-situ deposition of polyaniline and polypyrrole electroconductive layers on textile surfaces by the reactive ink-jet printing technique

A facile and original method of deposition of polyaniline (PANI) and polypyrrole (PPy) by reactive ink-jet printing on different textile fabrics is proposed. Polyaniline- and polypyrrole-coated conducting fabrics were obtained by chemical oxidation of aniline hydrochloride or pyrrole by ammonium peroxydisulfate on polyacrylonitrile (PAN), cotton, poly(ethylene terephthalate) (PET), cotton/PET, wool, and cotton/wool fabrics. The conducting fabrics were characterized chemically by means of Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and energy-dispersive spectroscopy (EDS). The morphology of the coatings was observed by optical microscopy and scanning electron microscopy (SEM). The conducting properties (surface resistance) of the fabrics were measured by means of the four-probe method. The optimal conditions of the PANI and PPy deposition on textiles by reactive ink-jet printing were established. The obtained results prove that the proposed method is very simple, practically could be carried out on the basis of water-containing inks, giving a very good adhesion of the in-situ formed conductive polymer to the substrate and ensuring a very low surface resistance. The variation of the surface resistance vs. concentration of aniline hydrochloride or pyrrole for different textile fabrics was obtained. The mechanism of the PANI and PPy deposition and adhesion on textiles based on the electrokinetic phenomena is proposed and proved by the changes in relative resistance of PANI/PAN and PPy/PAN composites during the multi-cyclic flexing, washing and dry-cleaning processes, and re-doping with HCl. An application of PANI and PPy conductive textiles in electromagnetic interference (EMI) shielding is proposed. The results showed that PANI/PAN and PPy/PAN composites achieved very good and moderate EMI shielding effectiveness, respectively.

Encapsulation of gold nanoparticles with PHB based on coffee ring effect

The hydrodynamic process of ring formation has been utilized to encapsulate gold nanoparticles in the matrix of PHB using an ink jet printing technique.

Realization of an Asymmetric Interdigitated Electrochemical Micro-Capacitor Based on Carbon Nanotubes and Manganese Oxide

Asymmetric interdigitated micro-supercapacitors with high resolution, dedicated to energy storage in embedded micro-systems, are fabricated using a simple micro-fabrication process based on the inkjet printing and electrolytic deposition techniques. The process is optimized to realize a carbon nanotubes (cathode)/manganese oxide (anode) hybrid micro-device with a resolution of 100 μm. The cell capacitance reaches a value of 2.4 mF.cm−2. Moreover, the use of the asymmetric configuration allows extending the working voltage of the device from 1 V to 1.8 V in an aqueous solution.

Impact of Pulse Thermal Processing on the Properties of Inkjet Printed Metal and Flexible Sensors

We report on the low temperature processing of environmental sensors employing pulse thermal processing (PTP) technique to define a path toward flexible sensor technology on plastic, paper, and fabric substrates. Inkjet printing and pulse thermal processing technique were used to realize mask-less, additive integration of low-cost sensors on polymeric substrates with specific focus on temperature, humidity, and strain sensors. The printed metal line performance was evaluated in terms of the electrical conductivity characteristics as a function of post-deposition thermal processing conditions. The PTP processed Ag metal lines exhibited high conductivity with metal sheet resistance values below 100 mΩ/□ using a pulse width as short as 250 μs. The flexible temperature and relative humidity sensors were defined on flexible polyimide substrates by direct printing of Ag metal structures. The printed resistive temperature sensor and capacitive humidity sensor were characterized for their sensitivity with focus on future smart-building applications. Strain gauges were printed on polyimide substrate to determine the mechanical properties of the silver nanoparticle films. The observed electrical properties of the printed metal lines and the sensitivity of the flexible sensors show promise for the realization of a high performance print-on-demand technology exploiting low thermal-budget PTP technique.

Thermovision and spectrophotometric analysis of ink volume and material characteristics influence on colour changes of heat treated printed substrates

Original scientific paper This paper presents experimental usage of updated control methods such as thermovision and spectrophotometric analysis in graphic industry. These methods were applied to research the influence of ink volume and material characteristics on colour and heat treated printed substrates. Samples used in these experiments were printed by digital ink jet printing technique using Mimaki JV22 printing machine and J-Eco Subly Nano inks. As printing substrates, three different types of materials were used. Materials were different in respect of fabric weight and thread count, while material composition was the same for all three materials. The appropriate test card consisting of fields of CMYK colours was printed, varying the number of ink layers applied. Samples were exposed to heat treatment after printing. The heat applied was measured by thermovision camera. Spectrophotometric measurements were conducted before and after heat treatment. Based on data gathered by spectrophotometric measurements colour difference ΔE76 was calculated. Results showed that increasing number of layers, as well as right choice of substrates, can improve behaviour of printed product during exploitation.

3D Printing Magnetic Material with Arbitrary Anisotropy

A process for 3D printing of magnetic materials with programmatically controlled anisotropy is presented. Using an experimental thermal inkjet printer magnetic structures with and without anisotropy are printed and characterized to demonstrate the unique advantage afforded by inkjet printing &#x2013; that of arbitrarily controlling the anisotropy orientation within the structure during printing. The technique will make possible 3D printed inductor and transformer cores with low losses, antenna loading materials and graded index lenses for processing microwave signals, and magnetic field sensors to name a few applications. In the inkjet printing technique presented here, a magnetic ink composed of magnetic nanoparticles in a UV curable resin is jetted on the substrate. The nanoparticles are then aligned in a magnetic field generated using a two-axis electromagnet and the ink cured to obtain a composite with the desired magnetic anisotropy. The process is repeated to fabricate a 3D structure of the desired shape and dimensions.

Structural characterisation of printable noble metal/poly(vinyl-alcohol) nanocomposites for optical applications.

In order to enable exploitation of noble metal/poly(vinyl-alcohol) nanocomposites for device fabrication, solutions of poly(vinyl-alcohol) suitable for piezo-driven inkjet printing techniques are identified and discussed in terms of their material properties. The printable poly(vinyl-alcohol) medium is then exploited as a host material through the formation of silver or gold nanoparticles in order to create nanocomposites that exhibit a surface plasmon resonance behaviour associated with the small metallic inclusions. To mitigate some of the material redistribution effects associated with the drying of printed droplets containing finely divided materials, the metallic nanoparticles are formed after the printing and drying process is completed, by way of an in situ reduction of an appropriate metal salt by the poly(vinyl-alcohol)-host matrix itself, which takes place at modest temperatures compatible with most substrate materials. An obvious application for such nanocomposites is in optical elements whereby the surface plasmon resonance associated with the metal is the functional aspect of devices such as sensors or active optical elements. High Resolution Transmission Electron Microscopy was used to examine the dimensions, distribution, morphology and crystal structure of the silver and gold nanoparticles in detail allowing discussion of their suitability for these applications and what further optimisation may be necessary to adequately control their formation.

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.