Direct Inkjet Printing Research Articles

Direct Printing of Disperse Dye Inks to Polyester Fabrics without Chemical Pretreatment.

Direct inkjet digital printing is a relatively green and environmentally friendly textile printing method with a wide range of applications in the textile printing and dyeing industry. However, pretreatment of the fabric is required before digital printing, which will generate certain energy consumption and wastewater. In this study, a digital direct inkjet printing method was developed to improve the printing accuracy of poly(ethylene terephthalate) (PET) fabrics without any pretreatment. A kind of direct inkjet printing ink was prepared by the response change in temperature viscosity. The increase in viscosity inhibits ink bleeding on the fabric, thereby improving printing accuracy. A thermosensitive direct inkjet printing disperse dye ink was prepared by adding cetyltrimethylammonium bromide (CTAB) and 3-methylsalicylic acid (3MS) to the ink. By evaluating the changes in the ink particle size, shear viscosity, and temperature viscosity, it was found that this thermosensitive ink has an excellent average particle size and special changes in viscosity with increasing temperature. When this heat-sensitive ink is printed on a polyester fabric, the fabric does not need pretreatment to improve the clarity of printing, and the printed fabric has satisfactory color fastness to friction and washing.

Inkjet-printed waveguide-coupled passive wedge-shaped microdisk resonator with refractive index tunability

We incorporate a passive wedge-shaped organic microdisk supporting spatially separated whispering gallery modes into an SU-8 photonic integrated circuit (PIC) by using direct inkjet printing. This innovative method allows the mixing of multiple organic materials, enabling tunability of the refractive index of microdisks, thereby overcoming limitations of single-material resonators from conventional lithography. In this study, the microdisk resonator, with a refractive index matching that of SU-8 by mixing hyperbranched polymers, is mounted horizontally to an optical waveguide, achieving directional coupling between the microdisk and PIC at a wavelength of 1550 nm. Geometrical conditions for successful coupling were obtained by measuring the cross-sectional profile of the fabricated structure’s surface via atomic force microscopy, determining ways to adjust the coupling efficiency.

Enhancement of hydrophilicity and color strength in plasma treated PET with water vapor post-exposure using a new in-line pilot scale DBD plasma

Due to its low hydrophilicity, direct sublimation inkjet printing on woven polyester fabric surfaces is challenging. This research experimentally studies the efficacy of dielectric barrier discharge (DBD) roll-to-roll plasma treatment with or without water vapor post-exposure as a novel method to modify polyethylene terephthalate (PET) surfaces to enhance hydrophilicity, color performance, and printing quality. The Response Surface Methodology (RSM) was used to design experiments, and the optimum conditions were analyzed through statistical calculations. Their results were examined using Optical Emission Spectroscopy (OES), Atomic Force Microscopy (AFM), field emission scanning electron microscopy (FESEM), Energy Dispersive X-ray (EDX), X-ray Photoelectron Spectroscopy (XPS), and Attenuated Total Reflectance Fourier Transform Infra-Red spectroscopy (ATR-FTIR) tests. Qualitative and quantitative tests for color performance and wicking test used for hydrophilicity assessment confirms the effectiveness of this Green inline pretreatment for industries to enhance direct sublimation inkjet printing quality on PET by a decrease in absorption time from 12051 to 202 s and an increase in the color depth to 12.49%, 25.89 and 18.07% for Cyan, Magenta and Key (black) respectively. One of the stable optimum conditions in which three printed colors: Cyan, Magenta, and Black (Key), show high-quality color performance is at 15 processing rounds, 2 m/min velocity in the absence or presence of water vapor post-exposure. Water vapor post-exposure exhibits a beneficial, economic effect along with plasma treatment. The results show that the chemical modification aspect of this treatment plays a more significant role in printing quality enhancement than its morphological modification.

Inkjet Printing-Manufactured Boron-Doped Diamond Chip Electrodes for Electrochemical Sensing Purposes.

Fabrication of patterned boron-doped diamond (BDD) in an inexpensive and straightforward way is required for a variety of practical applications, including the development of BDD-based electrochemical sensors. This work describes a simplified and novel bottom-up fabrication approach for BDD-based three-electrode sensor chips utilizing direct inkjet printing of diamond nanoparticles on silicon-based substrates. The whole seeding process, accomplished by a commercial research inkjet printer with piezo-driven drop-on-demand printheads, was systematically examined. Optimized and continuous inkjet-printed features were obtained with glycerol-based diamond ink (0.4% vol/wt), silicon substrates pretreated by exposure to oxygen plasma and subsequently to air, and applying a dot density of 750 drops (volume 9 pL) per inch. Next, the dried micropatterned substrate was subjected to a chemical vapor deposition step to grow uniform thin-film BDD, which satisfied the function of both working and counter electrodes. Silver was inkjet-printed to complete the sensor chip with a reference electrode. Scanning electron micrographs showed a closed BDD layer with a typical polycrystalline structure and sharp and well-defined edges. Very good homogeneity in diamond layer composition and a high boron content (∼2 × 1021 atoms cm-3) was confirmed by Raman spectroscopy. Important electrochemical characteristics, including the width of the potential window (2.5 V) and double-layer capacitance (27 μF cm-2), were evaluated by cyclic voltammetry. Fast electron transfer kinetics was recognized for the [Ru(NH3)6]3+/2+ redox marker due to the high doping level, while somewhat hindered kinetics was observed for the surface-sensitive [Fe(CN)6]3-/4- probe. Furthermore, the ability to electrochemically detect organic compounds of different structural motifs, such as glucose, ascorbic acid, uric acid, tyrosine, and dopamine, was successfully verified and compared with commercially available screen-printed BDD electrodes. The newly developed chip-based manufacture method enables the rapid prototyping of different small-scale electrode designs and BDD microstructures, which can lead to enhanced sensor performance with capability of repeated use.

Development of UV monomer-contained dye inks for high-quality printing application on polyester fabrics without pretreatment

The use of direct inkjet printing in the textile industry is an environmentally friendly option. However, the need for pretreatment of most fabrics before digital printing has been a major issue. In this study, a green and straightforward approach was developed that enhances printing accuracy without requiring any pretreatment. A novel waterborne disperse dye-based inkjet ink containing polyethylene glycol diacrylate (PEGDA) was developed that significantly improved the rheology of ink drops on the surface, resulting in superior printing quality on polyester fabric. The printing mechanism of the inks was thoroughly investigated by evaluating their conductivity, pH, particle size, surface tension, viscosity, and ink droplet formation. Real-time photo-rheological and low field nuclear magnetic resonance (LF-NMR) analyses were performed to investigate the behavior of the ink drops on the polyester fabric surface. Finally, the Kawabata evaluation system (KES) was employed to understand the impact of direct digital printing on fabric performance.

Aqueous MXene inks for inkjet-printing microsupercapacitors with ultrahigh energy densities

Although inkjet-printing technology has achieved significant development in preparing scalable and adaptable energy storage devices for portable and micro devices, searching for additive-free and environmentally friendly aqueous inks is a significant challenge. Hence, an aqueous MXene/sodium alginate-Fe2+ hybrid ink (denoted as MXene/SA-Fe) with solution processability and suitable viscosity is prepared for direct inkjet printing microsupercapacitors (MSCs). The SA molecules are adsorbed on the surface of MXene nanosheets to construct three-dimensional (3D) structures, thus effectively alleviating the two notorious problems of oxidation and self-restacking of MXene. Concurrently, Fe2+ ions can compress the ineffective macropore volume and make the 3D structure more compact. Moreover, the hydrogen and covalent bonding formed between the MXene nanosheet, SA, and Fe2+ effectively protects the oxidation of MXene and thus increases its stability. Thus, the MXene/SA-Fe ink endows the inkjet-printed MSC electrode with abundant active sites for ion storage and a highly conductive network for electron transfer. As a demonstration, the MXene/SA-Fe ink is used to direct inkjet-printed MSCs with an electrode spacing of 310 μm, which exhibit remarkable capacitances of 123.8 mF cm−2 (@5 mV s−1), good rate capability, an extraordinary energy density of 8.44 μWh cm−2 at a power density of 33.70 μW cm−2, long-term cycling stability of 91.4 % capacitance retention after 10,000 cycles, and surprising mechanical durability with 90.0 % of its initial capacitance retained after 10,000 bending cycles. Therefore, MXene/SA-Fe inks are expected to create various opportunities for printable electronics.

Lamination of inkjet-printed Ag electrodes for highly patternable and customizable polymer light-emitting diodes

Inkjet printing that ensures superior patternability and customizability can be fully exploited as top electrodes in thin-film-based light-emitting devices. However, direct inkjet printing onto multi-layered thin films severely damages the underlying functional layers due to intermixing with the ink solvents, resulting in poor device efficiencies. Here, we report a lamination of inkjet-printed Ag electrodes as a top cathode for polymer light-emitting diodes (PLEDs). The organometallic Ag ink was printed on surface-modified elastomers with stable wettability, and drop spacing was further optimized for low surface roughness. The lamination of Ag cathodes establishes intimate contact between the electrodes and the functional layers, allowing light emission of PLEDs along the printed patterns. Furthermore, additional heat treatment improves the electron injection, resulting in a reduction of turn-on voltage and higher current/power efficiencies. To illustrate the practicability of our laminated PLEDs, we demonstrate passive-matrix driven PLEDs with all-inkjet-printed electrodes by laminating the top cathode arrays crossing the bottom inkjet-printed anodes.

3D printable and stretchable PVA‐PAAm dual network hydrogel with conductivities for wearable sensors

AbstractConductive hydrogel has broad potential applications in wearable sensors and flexible electronic devices. However, due to the complicated and restrictive mold‐casting process, the manufacture of hydrogel‐based sensors is still facing great challenges. In this paper, we adopt direct inkjet printing (DIW) technology to fabricate three‐dimensional structures of chemically and physically cross‐linked hydrogels by integrating fumed silica as a rheological modifier into crosslinked poly(vinyl alcohol)/poly(acrylamide) (PVA/PAAm) network. Fumed silica not only enables hydrogels with excellent rheological properties, but also provides more hydrogen bond crosslinking sites, further improving mechanical properties. Meanwhile, calcium chloride (CaCl2) is supplemented to construct conductive channels in the hydrogel, which powers the hydrogel with good conductivity and strain sensitivity. The sensor assembled from 3D printed hydrogel shows cycle stability and accurate recognition ability in detecting mechanical deformation and various human movements (for example knee bending and frown). This work extends the application of 3D printing hydrogel in the field of wearable devices.

Direct Inkjet 3D Printing Microwires with Small Feature Size by Freezing, Sublimation, and Evaporation Induced Colloidal Nanoparticles Self‐Assembly Mechanism

AbstractThe feature size (FS) of inkjet printing is limited by nozzle size and drop spreading, which limits the realization of small optoelectronics devices and 3D microstructures. Some methods can realize small FS, but sacrifice advantages of inkjet technology. For instance, dewetting can reduce FS with all the advantages of inkjet technology kept, but is hard to print wires due to Rayleigh–Plateau instability. To solve these problems, in this paper, freezing and sublimation are introduced to direct inkjet printing wire processes. After optimizing the glycerol amount and adding tert‐butyl alcohol (TBA) in water‐based nanoparticle inks, condensed microwires of PS colloidal nanoparticles, graphene oxide (GO) nanosheets, and silver nanowires (AgNws) with small FS can be printed, respectively, by freezing, sublimation, and evaporation induced nanoparticle self‐assembly (FSE‐INS) mechanism. Using printhead with the nozzle size of 21 µm, the minimum feature size is only ≈2 µm for GO nanosheet samples. The FSE‐INS mechanism shows particle‐dimension dependent structure properties, introduces an additional particle manipulation freedom perpendicular to the substrate with sacrificial vertical solid surfaces, and exhibits great potential to realize small and novel devices and 3D structures, without sacrificing the advantages of inkjet technology.

Nitrogen and sulfur co-doped MXene ink without additive for high-performance inkjet-printing micro-supercapacitors

Although the evolution of inkjet printing in the extensible and configurable manufacturing of micro-supercapacitors (MSCs) is rapid, the performance of eco-friendly inks based on free additives need be improved. Meanwhile, MXenes, which are transition metal carbides and nitrides in two dimensions (2D), have received extensive attention due to their metallic conductivity, abundant functional groups, and extraordinary performance in applications such as energy storage. However, the pristine MXene (P-MXene) has various polar terminal groups and vacancy defects, resulting in poor environmental stability. Herein, the printable ink fabricated by doping nitrogen and sulfur on Ti3C2Tx MXene (N,S-MXene) is developed to improve the ambient stability and electrochemical properties; this ink is used to direct inkjet printing of the planar MSCs with an electrode spacing of 300 μm. These MSCs provide excellent performance, desirable customization, and seamless connection, delivering an extraordinary volumetric capacitance of 710 F cm−3, a remarkable energy density of 8.9 mWh cm−3 at a power density of 411 mW cm−3, and a long-term cycling stability up to 94.6 %, much better than previously reported MSCs fabricated by inkjet printing. These excellent properties are attributed to doping nitrogen and sulfur atoms that improve the redox reactivity, H+ adsorption, reaction kinetics, and antioxidation throughout the microelectrodes, depending on the results of DFT calculation and electrochemical tests. Therefore, this strategy makes the practical applications of MXenes more competitive, creating more possibilities for printed micro-electronics.

Editorial: Is Zirconia the Holy Grail of All-Ceramic Restorations?

Editorial: Is Zirconia the Holy Grail of All-Ceramic Restorations?

Direct Inkjet Printing of Digitally Designed 2D TiN Patterns

TiN is a non-oxidic ceramic widely employed as a hard coating material for cutting tools due to its high thermal and chemical stability. Among all 2D coating techniques, Inkjet printing (IJP) is one of the most promising for the fabrication of layers with customized designs. However, despite its advantages, this process has not been used so far with this material. In this work, we prepared TiN suspensions for their implementation in IJP with a nozzle of 70 μm. A complete study of the ink properties was performed to formulate a suitable ink with a high level of dispersion and to evaluate the jetting during the printing process. Moreover, after a sintering process at 1100 °C under vacuum, a complete hardness analysis of the coated discs was performed, resulting in values ranging from ~4 to 7 GPa, depending on the grid design.

3D printing of complex ceramic dental implant abutments by using Direct Inkjet Printing

The demand for dental implants has been steadily increasing in recent years. At the same time, the desire for patient-specific esthetic implant-supported reconstructions has also grown. The core element of an implant-supported reconstruction is the implant abutment, which performs as the base for the cementation of the implant crown. The abutment can be produced accurately and individually with the additive manufacturing process Direct Inkjet Printing, which is based on the layer-by-layer printing of ceramic suspensions. For the production of complex structures, such as abutments, a support structure is required, which can subsequently be removed without leaving any residue. In this project, a carbon black suspension was chosen as support material. To ensure the printed structures maintain their shape, the suspensions must not influence each other. Therefore, the rheological properties and printing behavior of the suspensions must be adjusted to each other, for which additives were investigated and printing tests performed. We demonstrated that proper additives (e.g. Triton X-100) and process parameters (e.g. component arrangement), allow the production of complex structures, like abutments, and may enable a new way of manufacturing dental implant abutments.

High Dynamic Range Smart Window Display by Surface Hydrophilization and Inkjet Printing

AbstractMechanoresponsive smart windows have been intensively investigated in recent years as they offer various applications for signage and light management. However, integrating a display functionality into such smart windows remains a challenge since the realization of pixels in these devices is difficult. In addition, mechanoresponsive smart windows with a high dynamic range are rarely demonstrated because they would suffer from complex fabrication processes and high costs. In this work, a novel surface modification process and digital encoding were developed for direct inkjet printing of micro‐etching‐masks on hydrophobic elastomers, and a pixelated haze distribution was realized. Compared to the traditional mechanoresponsive smart windows, which modify the optical performance by applied strain solely, here, a smart window with haze tunability in either static or strain‐applied state is demonstrated. The work enhances the potential of the fabricated smart window to be applied in high dynamic range signage displays.

Evaluation of solvent-based and UV-curing inkjet inks on the adhesion and printing quality of different aircraft surfaces coating

This work presents a study of digital inkjet printing technology for aerospace industry using different coatings on aluminum surfaces. The objective of this work is to understand the effect of some process parameters on digital inkjet printing technology in the aircraft industry for printing complex images, logos and other visual effects directly on the fuselage of aircraft with high quality, in order to replace conventional and manual aircraft painting processes. The consequent effects of the different coated surfaces on the properties of the printed images (e.g., adhesion, UV resistance, visual appearance and optical properties) were evaluated in order to understand how the coated surfaces affect these properties. For that purpose, solvent-based and UV-curing inkjet inks for industrial printing applications were used in the colors cyan, magenta, yellow and black on coated aerospace surfaces. The results show that the inkjet technology requires a white background substrate to match the conventional colors and there is an adhesion issue on conventional top coating used as a base for direct inkjet printing. The results reported here provide good evidence that the traditional aerospace surface used should be adjusted to improve the final print quality and paint film adhesion. The viscosity of UV-A inkjet ink is 2.1 times higher than UV-B ink and 2.4 times higher than solvent-based inkjet ink. The use of a new primer/top coating with clear coat is the optimal condition for maximizing the printed image properties, adhesion, UV degradation, low color variation (∆E*ab < 15) and improve the gloss effect (≥90GU). Although there are some challenges regarding this technology and these results create an effective strategy for the development of digital inkjet printing on aerospace surfaces with excellent final print quality.

Direct Sublimation Inkjet Printing as a New Environmentally Friendly Approach for Printing on Polyester Textiles

Polyester is one of the most important synthetic fibers extensively used in textile industry. Inkjet printing on polyester textile is performed either by direct or transfer approaches. The first method needs chemical surface treatment, while the latter uses transfer paper. In this article, direct sublimation inkjet printing (DSIP) on polyester textile has been studied to overcome the natural resource limitations and environmental problems by eliminating the need for transfer paper and chemical surface treatment. Polyester textile was surface treated using atmospheric-pressure plasma under air atmosphere. The effects of different factors including plasma speed, plasma power, and the number of treatments on the contact angle and K/S value have been investigated via experimental design method. Scanning electron microscopy (SEM), attenuated total reflection-fourier transform infrared (ATR-FTIR), and bleeding test showed that plasma power has the least effect on both K/S value and contact angle. The K/S values increased while the contact angle decreased by increasing the number of treatments and decreasing the plasma speed. Optical and scanning electron microscopy images also revealed that the treated textile using constant plasma power of 350 W, 60 plasma treatments and the plasma speed of 3 m/min showed the most printing thickness and the highest image resolution.

Additive manufacturing of zirconia ceramics by material jetting

The possibility of additive manufacturing of ceramics has been reported widely in scientific literature. This study investigates the potential of direct inkjet printing or material jetting of 3Y-TZP ceramics by assessing the microstructure and mechanical properties of the sintered printed parts. The technique allows to print in layers of 10.5 μm, with an as-printed green density of 58 % and nearly fully sintered density of 6.03 ± 0.1 g/cm3 (99.7 % TD). The dimensions of the green and sintered parts were highly accurate but showed an anisotropic roughness in function of the building direction, mainly due to the support structures. The biaxial bending and 4-point bending strength of the sintered material was found to be substantially higher in the XY direction than in the building (Z) direction. SEM and X-Ray computed tomography revealed the presence of delamination cracks, agglomerates and spherical pores, which were identified as fracture origins on fractured surfaces.

Innovative procedure for precise deposition of wrinkled hydrogel films using direct inkjet printing

This manuscript presents an inkjet-based strategy to fabricate wrinkled hydrogel surfaces with controlled characteristics (period and amplitude). For this purpose, a monomer mixture containing a crosslinking agent, a hydrophilic monomer, and a photoinitiator were deposited onto polycarbonate substrates. Upon UV irradiation and controlled drying under a vacuum atmosphere, either one-generation or hierarchical two-generation wrinkles were formed. More interestingly, the wrinkle characteristics depend on the crosslinking agent and monomer concentration in the solution so that larger wrinkles were observed in diluted solutions. Equally, the wrinkle period and amplitude also gradually grow by increasing the number of deposited layers. Atomic force microscopy was carried out to finely characterize the wrinkle dimensions as well as their eventual preferential orientation and distribution. Besides, hydrogel surfaces have been evaluated in terms of cytocompatibility, given their potential interest for biomedical applications.

In Situ Inkjet Printing of the Perovskite Single-Crystal Array-Embedded Polydimethylsiloxane Film for Wearable Light-Emitting Devices.

Metal halide perovskites are promising light-emitting materials for applications such as wearable lighting devices and flat panel displays because of their high photoluminescence efficiency, high color purity, and facile solution processability. However, the intrinsic ambient instability and crystal friability issues have fundamentally hindered the practical applications of perovskites. Here, we solve this problem through a liquid to liquid self-encapsulation inkjet-printing technique. Perovskite inks are directly inkjet-printed into the liquid polydimethylsiloxane (PDMS) precursor to in situ form the self-encapsulation perovskite single-crystal-embedded PDMS structure. We show that the space-confined effect of the liquid PDMS precursor can significantly retard the perovskite crystallization process and promote the embedded growth of perovskite single crystals in PDMS. Benefiting from the sealing function of PDMS, the printed perovskite single crystals show excellent ambient stability and flexibility. Furthermore, we demonstrate that wafer-scale air-stable and flexible perovskite fluorescent patterns can be produced in PDMS by direct inkjet printing, which is cost-effective and free of complex microfabrication processes. This method provides a facile approach to scalable fabrication of air-stable and wearable perovskite fluorescent patterns, which will be of great significance for potential application in perovskite light-emitting diode display.

Ultraviolet Photodetecting and Plasmon-to-Electric Conversion of Controlled Inkjet-Printing Thin-Film Transistors

Direct ink-jet printing of a zinc-oxide-based thin-film transistor (ZnO-based TFT) with a three-dimensional (3-D) channel structure was demonstrated for ultraviolet light (UV) and visible light photodetection. Here, we demonstrated the channel structures by which temperature-induced Marangoni flow can be used to narrow the channel width from 318.9 ± 44.1 μm to 180.1 ± 13.9 μm via a temperature gradient. Furthermore, a simple and efficient oxygen plasma treatment was used to enhance the electrical characteristics of switching ION/IOFF ratio of approximately 105. Therefore, the stable and excellent gate bias-controlled photo-transistors were fabricated and characterized in detail for ultraviolet (UV) and visible light sensing. The photodetector exhibited a superior photoresponse with a significant increase of more than 2 orders of magnitude larger drain current generated upon UV illumination. The results could be useful for the development of UV photodetectors by the direct-patterning ink-jet printing technique. Additionally, we also have successfully demonstrated that a metal-semiconductor junction structure that enables plasmon energy detection by using the plasmonic effects is an efficient conversion of plasmon energy to an electrical signal. The device showed a significant variations negative shift of threshold voltage under different light power density with exposure of visible light. With the ZnO-based TFTs, only ultraviolet light detection extends to the visible light wavelength.