Ink-jet Technique Research Articles

Development of fin-LEDs for next-generation inorganic displays using face-selective dielectrophoretic assembly

Micro-light-emitting diodes offer vibrant colors and energy-efficient performance, holding promise for next-generation inorganic displays. However, their widespread adoption requires the development of cost-effective chips and low-defect pixelation processes. Addressing these challenges, nanorod-light-emitting diodes utilize inkjet and dielectrophoretic assembly techniques. Nevertheless, the small volume and edge-directed emission of nanorod-light-emitting diodes necessitate brightness and light extraction improvements. As an alternative, we propose dielectrophoretic-friendly fin-light-emitting diodes, designed to enhance brightness and light extraction efficiency through face-selective dielectrophoretic assembly technology. Our results confirm the potential for next-generation inorganic displays, with a wafer utilization ratio exceeding 90%, a vertical assembly ratio of 91.3%, and a pixel production yield of 99.93%. Moreover, blue fin-light-emitting diodes achieve an external quantum efficiency of 9.1% and a brightness of 8640 cd m−2 at 5.0 V, which, even at this early stage, are comparable to existing technologies.

Metal Acetylene Dicarboxylates as Catalyst for Printable Low Temperature Carbon Precursors

The synthesis of various metal acetylene dicarboxylates (MxADC, M = Cu, Ag, Fe, Co, Ni) via new methods are reported. The previously unknown crystal structures for Ag2ADC and FeADC are presented. The behaviour of the different metal dicarboxylates and their role as graphitization catalysts in a printable highly energetic carbon precursor is investigated in detail. Despite the copper compound has the lowest decomposition temperature of all studied acetylene dicarboxylates and is significantly enhancing the conductivity of carbon thin films obtained at low pyrolysis temperatures, the catalytic effect of cobalt and iron on graphitizing carbon results in a superior conductivity in carbon thin films pyrolyzed at lower temperatures down to 600°C. The newly designed precursors are demonstrated to produce micro‐supercapacitors with a 3D‐piezoelectric inkjet technique at low pyrolysis temperature.

Scalable Fabrication of Flexible Supercapacitor Electrodes Using Sustainable Water‐Based Onion‐like Carbon Inks

AbstractThe increasing usage of electrical energy storage solutions demands for cost effective, scalable and sustainable manufacturing technologies. Deposition of functional inks, carrying electrochemically active materials is a suitable technique as it delivers material with selected properties only to required locations. However, the production of stable dispersions featuring high concentrations of active material ‐ necessary for effective deposition ‐ is challenging. Here we present an approach to print supercapacitor electrodes with onion‐like carbon as active material, using a simple, cost‐effective process as well as a water‐based ink. The ink is highly stable and can be deposited by spray and inkjet techniques. The fabricated electrodes offer a capacitance of up to 14 mF cm−2 (27 F g−1) and retained 97 % of their initial capacitance after 5000 cycles, demonstrating excellent performance and stability of the coating.

Inkjet printed acrylate-urethane modified poly(3,4-ethylenedioxythiophene) flexible conductive films

Abstract Flexible electronics is a new generation of electronic devices in which electronic components are integrated into flexible substrates. It is used in the fabrication of displays, solar cells, integrated circuits, and increasingly in the fabrication of electronic skin (E-skin), which can mimic the properties of human skin by being able to follow skin movements and flexures without loss of mechanical and electrical properties. E-skin is suitable for integrating various sensors to monitor personal health. Conductive polymers are used in flexible electronics due to their electrical conductivity, low mass, and stability. However, their main disadvantage is their brittleness, which is why they don’t possess flexibility property without modification. Therefore, in this work, the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) was used as the main chain and the side branches of poly(acrylate-urethane) (PAU) were grafted onto it by atom transfer radical polymerization (ATRP) onto it, obtaining the grafted copolymer PEDOT-g-PAU. In this way, the main chain of PEDOT retains the property of electrical conductivity without losing conjugation, while the side branches of PAU have the ability to crosslink non-covalently through hydrogen bonds with PAU side branches of adjacent polymer molecules due to the presence of oxygen in their structure. The presence of hydrogen bonds allows increasing the stretchability and flexibility of the material, and they also have the ability to spontaneously renew themselves when they break due to excessive stress. Three different synthesis conditions were used to obtain polymers of different structure, which were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and measurement of electrical conductivity with a four-point probe (4PP) method. The obtained graft copolymer was prepared in the form of ink and printed on a polyurethane (PU) substrate using inkjet technique. The conductivity of the printed layer, its elongation and adhesion were investigated, while possible delamination of the printed polymer layer was also monitored. The results showed that the PEDOT-g-PAU copolymer was successfully synthesized and inkjet printing on PU film was successful. The obtained material has satisfactory electrical and mechanical properties and could be used for the integration of fully functional biosensors with further optimization of the composition.

Printing MEMS: Application of Inkjet Techniques to the Manufacturing of Inertial Accelerometers.

In the last few years, the manufacturing of microelectromechanical systems (MEMS) by means of innovative tridimensional and bidimensional printing technologies has significantly catalyzed the attention of researchers. Inkjet material deposition, in particular, can become a key enabling technology for the production of polymer-based inertial sensors characterized by low cost, high manufacturing scalability and superior sensitivity. In this paper, a fully inkjet-printed polymeric accelerometer is proposed, and its manufacturing steps are described. The manufacturing challenges connected with the inkjet deposition of SU-8 as a structural material are identified and addressed, resulting in the production of a functional spring-mass sensor. A step-crosslinking process allows optimization of the final shape of the device and limits defects typical of inkjet printing. The resulting device is characterized from a morphological point of view, and its functionality is assessed in performing optical readout. The acceleration range of the optimized device is 0-0.7 g, its resolution is 2 × 10-3 g and its sensitivity is 6745 nm/g. In general, the work demonstrates the feasibility of polymeric accelerometer production via inkjet printing, and these characteristic parameters demonstrate their potential applicability in a broad range of uses requiring highly accurate acceleration measurements over small displacements.

Electrochemical Studies of Inkjet Printed Semi-Transparent NiCo2O4/ITO Supercapacitor Electrodes

Transparent supercapacitors find a large number of applications as components of many electronic devices and circuits. Mixed Ni–Co oxides (NCOs) are among the most promising supercapacitor electrode materials exhibiting high pseudo-capacitance and good electronic conductivity, while inkjet printing is a low cost and versatile technique for electrode printing. Surprisingly, although there have been many studies of NCO supercapacitor films on ITO glass substrates, these have not been prepared by the inkjet technique, and their optical properties were not fully characterized. Hereby, we report the fabrication and characterization of thin (295 and 477 nm thick; 0.017 and 0.035 mg cm−2 NCO loading) semi-transparent NiCo2O4/ITO supercapacitor electrodes, showing transparency to visible light (60–30%, from the thinner to the thicker electrode layers tested), typical mass specific capacitance for NCO-based supercapacitor electrodes (1294–829 Fg−1 at 1 mA cm−2 discharge current density) and high volumetric capacitance (746–608 F cm−3 at 1 mA cm−2). The NCO nanoparticles were prepared by hydrothermal synthesis followed by thermal treatment and ball milling (ZrO2 balls, 0.5 mm diameter), resulting in a cubic nickel–cobalt oxide structure and particle size in the 30–150 nm range, whereas the electrode layers were printed from water-propylene glycol solutions using a Dimatix DMP-2850 drop-on-demand (DoD) inkjet printer. Constant current charge–discharge experiments of the supercapacitor electrode (at ca 0.5 mA cm−2) for 1000 cycles confirmed stability of performance.

3D Printable Gelatin Methacryloyl (GelMA)-Dextran Aqueous Two-Phase System with Tunable Pores Structure and Size Enables Physiological Behavior of Embedded Cells In Vitro.

The restricted porosity of most hydrogels established for in vitro 3D tissue engineering applications limits embedded cells with regard to their physiological spreading, proliferation, and migration behavior. To overcome these confines, porous hydrogels derived from aqueous two-phase systems (ATPS) are an interesting alternative. However, while developing hydrogels with trapped pores is widespread, the design of bicontinuous hydrogels is still challenging. Herein, an ATPS consisting of photo-crosslinkable gelatin methacryloyl (GelMA) and dextran is presented. The phase behavior, monophasic or biphasic, is tuned via the pH and dextran concentration. This, in turn, allows the formation of hydrogels with three distinct microstructures: homogenous nonporous, regular disconnected-pores, and bicontinuous with interconnected-pores. The pore size of the latter two hydrogels can be tuned from ≈4 to 100µm. Cytocompatibility of the generated ATPS hydrogels is confirmed by testing the viability of stromal and tumor cells. Their distribution and growth pattern are cell-type specific but are also strongly defined by the microstructure of the hydrogel. Finally, it is demonstrated that the unique porous structure is sustained when processing the bicontinuous system by inkjet and microextrusion techniques. The proposed ATPS hydrogels hold great potential for 3D tissue engineering applications due to their unique tunable interconnected porosity.

Human gelatin-based composite hydrogels for osteochondral tissue engineering and their adaptation into bioinks for extrusion, inkjet, and digital light processing bioprinting

The investigation of novel hydrogel systems allows for the study of relationships between biomaterials, cells, and other factors within osteochondral tissue engineering. Three-dimensional (3D) printing is a popular research method that can allow for further interrogation of these questions via the fabrication of 3D hydrogel environments that mimic tissue-specific, complex architectures. However, the adaptation of promising hydrogel biomaterial systems into 3D-printable bioinks remains a challenge. Here, we delineated an approach to that process. First, we characterized a novel methacryloylated gelatin composite hydrogel system and assessed how calcium phosphate and glycosaminoglycan additives upregulated bone- and cartilage-like matrix deposition and certain genetic markers of differentiation within human mesenchymal stem cells (hMSCs), such as RUNX2 and SOX9. Then, new assays were developed and utilized to study the effects of xanthan gum and nanofibrillated cellulose, which allowed for cohesive fiber deposition, reliable droplet formation, and non-fracturing digital light processing (DLP)-printed constructs within extrusion, inkjet, and DLP techniques, respectively. Finally, these bioinks were used to 3D print constructs containing viable encapsulated hMSCs over a 7 d period, where DLP printed constructs facilitated the highest observed increase in cell number over 7 d (∼2.4×). The results presented here describe the promotion of osteochondral phenotypes via these novel composite hydrogel formulations, establish their ability to bioprint viable, cell-encapsulating constructs using three different 3D printing methods on multiple bioprinters, and document how a library of modular bioink additives affected those physicochemical properties important to printability.

The Use of Decor Techniques, Ink-Jet Decoration Techniques and Other Techniques in Dinnerware Ceramics

Seramik, insanlığın yerleşik hayata geçişinden bu yana yaşamın vazgeçilmez bir parçası olmuştur. Endüstriyel seramikler bunlardan biridir. Dünya genelinde rekabet gücü yüksek bir sektör olan endüstriyel seramik sektörü, üretici firmaların hayatta kalmak için hem tasarım hem de ARGE çalışmaları yaptıkları bir sektördür. Bu çalışmaların en başında, otomasyona uyumlu dekor oluşturma, farklı model geliştirme, sır ve renk çeşitliliğinin arttırılması gelir. Bu konuda bugüne kadar yapılan çalışmalardan biri olan dekorlama tekniklerinin incelenmesi ve özgün uygulama örneklerinin irdelenmesi bir ihtiyaç olarak kabul edilmiştir. Bu kapsamda tüketicilerin en çok satın alma eğilimi gösterdiği özgün dekor tasarımına sahip ürünlerin vazgeçilmez olduğu bu sektörde, bu özgünlüğü sağlayabilen farklı dekorlama teknikleri üzerinde durulmuştur. Ayrıca araştırmacılar tarafından farklı dekorlama tekniklerini bir arada kullanarak oluşturdukları ürünler incelenmiştir. Bu araştırma genel tarama modellerinden ilgili literatürün taranması, nitel yöntemlerden uygulama sürecinin analizi ve süreç sonrası oluşturulan ürünlerin irdelenmesi şeklinde gerçekleştirilmiştir. Elde edilen bulgulara göre, rekabetçi bir ortam olan endüstriyel sofra seramiği üretim sektöründe tutunabilmek ve pazar payını arttırabilmek için, farklı tekniklerin bir arada kullanılmasının avantajlar sağladığı bu sektördeki uzman kişiler tarafından belirtilmektedir. Sofra seramiği dekorlama tekniklerinde serigrafi, fırça dekoru, kazıma dekoru, astar dekoru, tampon baskı, sgrafitto, lüster, püskürtme dekoru ve dijital (Ink-Jet) tekniklerinin bazen ikisi, bazen de ikiden fazlasının bir arada kullanılmasıyla özgün ürünler oluşturulabildiği belirlenmiştir.

3D Bioprinting of Human Tissues: Biofabrication, Bioinks, and Bioreactors.

The field of tissue engineering has progressed tremendously over the past few decades in its ability to fabricate functional tissue substitutes for regenerative medicine and pharmaceutical research. Conventional scaffold-based approaches are limited in their capacity to produce constructs with the functionality and complexity of native tissue. Three-dimensional (3D) bioprinting offers exciting prospects for scaffolds fabrication, as it allows precise placement of cells, biochemical factors, and biomaterials in a layer-by-layer process. Compared with traditional scaffold fabrication approaches, 3D bioprinting is better to mimic the complex microstructures of biological tissues and accurately control the distribution of cells. Here, we describe recent technological advances in bio-fabrication focusing on 3D bioprinting processes for tissue engineering from data processing to bioprinting, mainly inkjet, laser, and extrusion-based technique. We then review the associated bioink formulation for 3D bioprinting of human tissues, including biomaterials, cells, and growth factors selection. The key bioink properties for successful bioprinting of human tissue were summarized. After bioprinting, the cells are generally devoid of any exposure to fluid mechanical cues, such as fluid shear stress, tension, and compression, which are crucial for tissue development and function in health and disease. The bioreactor can serve as a simulator to aid in the development of engineering human tissues from in vitro maturation of 3D cell-laden scaffolds. We then describe some of the most common bioreactors found in the engineering of several functional tissues, such as bone, cartilage, and cardiovascular applications. In the end, we conclude with a brief insight into present limitations and future developments on the application of 3D bioprinting and bioreactor systems for engineering human tissue.

Active Femtoliter Droplet Generation in Microfluidics by Confined Interface Vibration.

The precise and effective generation of micron-sized droplets is one of the most common and important issues for droplet-based microfluidics. Active droplet generation makes use of additional energy input in promoting interfacial instabilities for droplet generation. Here, we report a new technique for the active generation of femtoliter droplets in microfluidic systems using confined interfacial vibration (CIV). The CIV is formed at the orifice of a traditional inkjet nozzle first by pushing the liquid out and then pulling it back. Droplets are pinched off during the withdrawal process, and this is different from the current active droplet generation techniques, which only monodirectionally push the liquid out. Droplets with radius ranging from ca. 1 to 28 μm can be actively generated by CIV at an orifice with radius 30 μm, distinguishing from conventional active generation techniques in which the droplets are always comparable or slightly bigger than the orifice. Experimental results showed that the droplet volume can be customized by controlling the intensity of the CIV. The inherent digital nature of the inkjet technique enables easy and precise regulating of the droplet volume, making it seamlessly compatible with the digital microfluidic systems.

Radio & Wireless Week 2021 [From the Guest Editor's Desk

This focus issue of IEEE Microwave Magazine contains columns on topics being covered during IEEE Radio & Wireless Week 2021 (RWW 2021) and five overview feature articles dedicated to themes that represent the scope and purpose of the different subconferences within RWW. The five feature articles have been prepared by highly renowned authors in their research fields and address several timely technical topics, such as digital predistortion (DPD) in power amplifiers (PAs); integrated digital power amplifiers (DPAs) and transmitters; reflectionless filtering devices; emerging inkjet and 3D printing fabrication techniques for sensing, communication, and empowering tasks in modern Internet of Things (IoT) modules; and advanced receiver architectures with multiband, multifunction, and multimode operational capabilities.

Large-Area Patterning of Oil-Based Inks on Superhydrophobic TiO2 Nanotubular Layers by Photocatalytic Wettability Conversion

Patterning an oil-based ink on a solid surface based on a wettability difference is of significant importance for the application of offset printing. Herein, we describe a large-area patterning of oil-based ink on a self-organized TiO2 nanotubular layer based on a photocatalytic wettability conversion. The TiO2 nanotubular layer was fabricated by electrochemical anodization, which demonstrated a superhydrophobic wettability after modification with a self-assembled molecular layer. Subsequently, area-selective ultraviolet (UV) irradiation through a pre-designed pattern of water-based UV-resistant ink formed by an ink-jet technique was used to form a wettability difference. After removing the water-based ink, an oil-based ink was capable of depositing selectively on the superhydrophobic area to form the same pattern as the pre-designed pattern of water-based ink. This large-area patterning of an oil-based ink based on the photocatalytic wettability conversion is potentially applicable in offset printing.

Inkjet Bioprinting of Biomaterials.

The inkjet technique has the capability of generating droplets in the picoliter volume range, firing thousands of times in a few seconds and printing in the noncontact manner. Since its emergence, inkjet technology has been widely utilized in the publishing industry for printing of text and pictures. As the technology developed, its applications have been expanded from two-dimensional (2D) to three-dimensional (3D) and even used to fabricate components of electronic devices. At the end of the twentieth century, researchers were aware of the potential value of this technology in life sciences and tissue engineering because its picoliter-level printing unit is suitable for depositing biological components. Currently inkjet technology has been becoming a practical tool in modern medicine serving for drug development, scaffold building, and cell depositing. In this article, we first review the history, principles and different methods of developing this technology. Next, we focus on the recent achievements of inkjet printing in the biological field. Inkjet bioprinting of generic biomaterials, biomacromolecules, DNAs, and cells and their major applications are introduced in order of increasing complexity. The current limitations/challenges and corresponding solutions of this technology are also discussed. A new concept, biopixels, is put forward with a combination of the key characteristics of inkjet printing and basic biological units to bring a comprehensive view on inkjet-based bioprinting. Finally, a roadmap of the entire 3D bioprinting is depicted at the end of this review article, clearly demonstrating the past, present, and future of 3D bioprinting and our current progress in this field.

3D Printed Drug Delivery Systems Based on Natural Products.

In the last few years, the employment of 3D printing technologies in the manufacture of drug delivery systems has increased, due to the advantages that they offer for personalized medicine. Thus, the possibility of producing sophisticated and tailor-made structures loaded with drugs intended for tissue engineering and optimizing the drug dose is particularly interesting in the case of pediatric and geriatric population. Natural products provide a wide range of advantages for their application as pharmaceutical excipients, as well as in scaffolds purposed for tissue engineering prepared by 3D printing technologies. The ability of biopolymers to form hydrogels is exploited in pressure assisted microsyringe and inkjet techniques, resulting in suitable porous matrices for the printing of living cells, as well as thermolabile drugs. In this review, we analyze the 3D printing technologies employed for the preparation of drug delivery systems based on natural products. Moreover, the 3D printed drug delivery systems containing natural products are described, highlighting the advantages offered by these types of excipients.

Three-dimensional bio-printed constructs consisting of human umbilical-derived mesenchymal stem cells promote cell viability, proliferation, and differentiation in vitro

The aim of this study was to investigate the effect of three-dimensional (3D) bio-printed constructs consisting of human umbilical-derived mesenchymal stem cells (HUMSCs) on cell viability, proliferation and differentiation in vitro. Functional 3D bio-printed microspheres consisting of HUMSCs were constructed using electrostatic inkjet technique. The parameters used for the synthesis of 3D bio-printed tissue constructs were first optimized. The viability, proliferation and differentiation of 3D cultured HUMSCs were assessed. The results of scanning electron microscopy (SEM) showed that isolated HUMSCs exhibited fibroblast-like spindle adherent growth. The optimized printing parameters were 6 kV voltage, 10 mL/h flow, 15 cm receiving height, and alginate: water ratio of 1:1 mixed at 37 °C. Compared with 2D cultured HUMSCs, the 3D cultured HUMSCs have better viability, proliferation and differentiation ability. The results obtained in this study indicate that 3D bio-printed tissue constructs promote HUMSC viability, proliferation, and neural differentiation in vitro.

Fluidity measurement of human and synthetic analogous bloods using an electromagnetically spinning rheometry system

We developed an electromagnetically spinning viscometer and applied it to the rheological measurements for biohazardous samples such as bloods. Blood fluidity can be evaluated from the measurement of viscosity curves, which show shear thinning behaviors mainly due to deformation of blood cells. In this study, we fabricated gel-like microparticles with different softness using our inkjet technique and investigated the difference of fluidity for their dispersions. The results show that the viscosity curves depend on the softness of the dispersed particles: The fluidity for the dispersion of moderate soft particles is quite similar to that of the human blood.

The Research on Multi-material 3D Vascularized Network Integrated Printing Technology.

Three-dimensional bioprinting has emerged as one of the manufacturing approaches that could potentially fabricate vascularized channels, which is helpful to culture tissues in vitro. In this paper, we report a novel approach to fabricate 3D perfusable channels by using the combination of extrusion and inkjet techniques in an integrated manufacture process. To achieve this, firstly we investigate the theoretical model to analyze influencing factors of structural dimensions of the printed parts like the printing speed, pressure, dispensing time, and voltage. In the experiment, photocurable hydrogel was printed to form a self-supporting structure with internal channel grooves. When the desired height of hydrogel was reached, the dual print-head was switched to the piezoelectric nozzle immediately, and the sacrificial material was printed by the changed nozzle on the printed hydrogel layer. Then, the extrusion nozzle was switched to print the next hydrogel layer. Once the printing of the internal construct was finished, hydrogel was extruded to wrap the entire structure, and the construct was immersed in a CaCl2 solution to crosslink. After that, the channel was formed by removing the sacrificial material. This approach can potentially provide a strategy for fabricating 3D vascularized channels and advance the development of culturing thick tissues in vitro.

CONTROLLED ZnO DEPOSITS FOR GAS SENSORS

Zinc oxide (ZnO) is widely used for its capability to detect gases. There are several known methods to synthetize and deposit ZnO for gas sensor applications. We have developed a new process based on ZnO nanoparticles from Sigma Aldrich manufacturer deposited by an inkjet technique. The process achieved is based on stable ZnO nanoparticles ink obtained by mixing 10% weight of commercial powder with diethylene glycol (DEG). This ink has been deposited on Pamela Yoboue et al. 56 a microhotplate that can operate up to 550°C with a low power of consumption (less than 60mW). The gas tests presented in this article show good results concerning the sensor response and its stability in the presence of gases.

Oblique Electrostatic Inkjet-Deposited TiO2 Electron Transport Layers for Efficient Planar Perovskite Solar Cells

In this study, a new, simple, and novel oblique electrostatic inkjet (OEI) technique is developed to deposit a titanium oxide (TiO2) compact layer (CL) on fluorine-doped tin oxide (FTO) substrate without the need for a vacuum environment for the first time. The TiO2 is used as electron transport layers (ETL) in planar perovskite solar cells (PSCs). This bottom-up OEI technique enables the control of the surface morphology and thickness of the TiO2 CL by simply manipulating the coating time. The OEI-fabricated TiO2 is characterized tested and the results are compared with that of TiO2 CLs produced by spin-coating and spray pyrolysis. The OEI-deposited TiO2 CL exhibits satisfactory surface coverage and smooth morphology, conducive for the ETLs in PSCs. The power-conversion efficiencies of PSCs with OEI-deposited TiO2 CL as the ETL were as high as 13.19%. Therefore, the present study provides an important advance in the effort to develop simple, low-cost, and easily scaled-up techniques. OEI may be a new candidate for depositing TiO2 CL ETLs for highly efficient planar PSCs, thus potentially contributing to future mass production.