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Direct Ink Writing (DIW) has demonstrated great potential as a versatile method to 3D print multifunctional structures. In this work, we report the implementation of hydrogel meta-structures using DIW at room temperature, which seamlessly integrate large specific surface areas, interconnected porous characteristics, mechanical toughness, biocompatibility, and water absorption and retention capabilities. Robust but hydrophobic polymers and weakly crosslinked nature-origin hydrogels form a balance in the self-supporting ink, allowing us to directly print complex meta-structures without sacrificial materials and heating extrusion. Mechanically, the mixed bending or stretching of symmetrical re-entrant cellular lattices and the unique curvature patterns are combined to provide little lateral expansion and large compressive energy absorbance when external forces are applied on the printed meta-structures. In addition, we have successfully demonstrated ear, aortic valve conduits and hierarchical architectures. We anticipate that the reported 3D meta-structured hydrogel would offer a new strategy to develop functional biomaterials for tissue engineering applications in the future., Graphical abstract In this work, we demonstrate the implementation of hydrogel meta-structures using direct ink writing at room temperature, which seamlessly integrate large specific surface area, interconnected porous characteristics, mechanical toughness, biocompatibility, water sorption and diffusion capability. Robust but hydrophobic polymers and weakly crosslinked nature-origin hydrogels form a balance in the self-supporting ink, allowing us to directly print complex meta-structures without sacrificial materials and heating extrusion. Mechanically, the mixed bending or stretching of symmetrical re-entrant cellular lattices and the unique curvature patterns are combined to provide little lateral expansion and large compressive energy absorbance when external forces are applied on the printed meta-structures. In addition, we have successfully demonstrated ear, aortic valve conduits and hierarchical architectures. We anticipate that the reported 3D meta-structured hydrogel would offer a new strategy to develop functional biomaterials for tissue engineering and bone repair.Image 1, Highlights ⁃ We develop a self-supporting hydrogel ink to seamlessly integrate the mechanical toughness and 3D printability of direct ink writing scaffolds at room temperature, without extra sacrificial materials or UV irradiation curing ⁃ The ink based on nano-composites imparts water sorption and diffusion capability, biocompatibility and mechanical toughness, as well as superior 3D printability ⁃ We successfully print human ear, human aortic valve conduits and hierarchical Gyroid meta-structures with tunable density and infill pattern. ⁃ The printed structures show substantial compressive energy absorbance, excellent water sorption and diffusion capability, and bioactivity ⁃ Our method could be generalized to produce a wide combination of weakly crosslinked nature-origin hydrogel and biomedical thermoplastic polymers

Direct ink writing (DIW) provides a new route to produce SiC-based composites with complex structure. In this study, we additive manufactured short carbon fiber reinforced SiC ceramic matrix composites (Csf/SiC composites) with different short carbon fiber content through direct ink writing combined with liquid silicon infiltration (LSI). The effects of short carbon fiber content on the microstructure and mechanical properties of the DIW green parts and the final Csf/SiC composites were investigated. The results showed that the Csf content played an important role in maintaining the structure of the green parts. As the Csf content increases, the dimension deviation ratio of the sample decreased at all stages. With the Csf content of 40 vol%, the final Csf/SiC composite had low free Si content and high β-SiC content. The maximum density, tensile strength and bending strength of the Csf/SiC composites were 2.88 ± 0.06 g/cm3, 53.68 MPa and 253.63 MPa respectively. It is believed that this study can give some understanding for the additive manufacturing of fiber reinforced ceramic matrix composites.

Supercapacitors are widely used for powering flexible/wearable electronics owing to their excellent charge storage capabilities. In this study, MnO2 nanosheets were grown on the surface of graphene using a simple water bath method to prepare graphene/MnO2 composites for fabricating supercapacitors. In addition, two-dimensional black phosphorus was introduced as an additive into the electronic ink based on the as-prepared graphene/MnO2 composites. The characterization and electrochemical analyses results showed that adding black phosphorus considerably improved the capacitive performance of the material, yielding a high specific capacitance of 241.5 ​F ​g-1 at 0.1 ​A ​g-1 and an impressive rate capability improvement from 52.5% to 80.3%. Then the micro-supercapacitor having an area-specific capacitance of 20.15 ​mF ​cm-2 at a scanning rate of 2 ​mV ​s-1 was utilized to demonstrate the practical applicability of this material. To further evaluate the practical applicability of this micro-supercapacitor, the micro-supercapacitor was integrated with a flexible thin-film pressure sensor on paper and cloth through screen printing.

Pc-WLEDs are considered to play a spectacular role in future generation light sources in view of their outstanding energy efficiency. In this regard, Eu3+ activated BaY2ZnO5 phosphor was prepared and investigated by XRD, PL and SEM analyses. Rietveld refinement analysis was carried out to confirm the structure of the synthesized phosphor. The prepared phosphor shows an intense red emission around 627 nm under excitation by near UV light. The 5D0-7F2 transition intensity of the prepared phosphor is three times higher compared to the commercial (Y,Gd)BO3:Eu3+ red phosphor. The CIE colour coordinates of BaY2ZnO5:Eu3+ (9mol%) phosphor corresponds to be (0.6169, 0.3742) and it has a high 97.9 % colour purity. The obtained results reveal the utility of BaY2ZnO5:Eu3+ phosphor as an efficient red component in WLEDs, anti-counterfeiting and fingerprint detection applications.

Summary Ever since the first reports on metal halide perovskite solar cells, a fundamental claim regarded a straightforward solution processability of the material, allowing for affordable and scalable processing. Therefore, understanding perovskite ink properties is a fundamental requirement toward industrialization. However, the evolution over time of these inks, which has a tremendous impact on the final performances of devices, is not yet extensively addressed. Any minute change in the ink composition can result in large variations in the photovoltaic performances, because these directly influence crystallization dynamics and final material composition. This is particularly important for the recent complex ink formulations, where the presence of numerous chemical species implies the existence of diverse interconnected equilibria. In this perspective, recent discoveries on the perovskite ink modifications over time are critically discussed, and directions for future research are proposed, including a survey of the most effective diagnostic tools used so far to investigate such inks.

A new type of explosive ink formulation that can be quickly cured was prepared with unsaturated polyester as binder, styrene as active monomer, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide as photoinitiator, and hexanitrohexaazaisowurtzitane (CL-20) as the main explosive. Then the explosive ink direct writing technology was used to charge the micro-sized energetic devices, the curing mechanism of the explosive ink was discussed, and the microstructure, safety performance and explosive transfer performance of the explosive ink molded samples were tested and analyzed. Results indicate that the composite material has a fast curing molding speed, its hardness can reach 2H within 8 min. The crystal form of CL-20 in the molded sample is still e type. The CL-20 based UV-curing explosive ink formulation has good compatibility, its apparent activation energy is increased by about 3.5 kJ/mol. The composite presents a significant reduction in impact sensitivity and its characteristic drop height can reach 39.8 cm, which is about 3 times higher than the raw material. When the line width of charge is 1.0 mm, the critical thickness of the explosion can reach 0.015 mm, and the explosion velocity is 7129 m/s when the charge density is 1.612 g/cm3.

Este trabajo forma parte del proyecto “Escritura cotidiana. Alfabetización, contacto cultural y transformación social en Hispania Citerior entre la conquista romana y el final de la Antigüedad (EsCo)”, PID2019-104025GB-100., El objetivo de este trabajo es demostrar que los soportes habituales de las escrituras paleohispánicas fueron realizados con materiales orgánicos. Las inscripciones fueron una parte menor de la producción escrita, pero la única susceptible de conservarse por emplear materiales no orgánicos, como son la piedra y los metales. Esto significa que se ha perdido irremediablemente la gran mayoría de la producción escrita de estas sociedades, pues es posible afirmar, gracias a la presencia de instrumentos como cretulae, tinteros y estilos, que en la escritura cotidiana se usaron materiales de escritura como el papiro y las tablillas enceradas., The purpose of this work is to demonstrate that the material on which palaeo-Hispanic script was written was usually made of organic elements. While inscriptions represent but a minor part of the written production, they constitute the sole instances that could possibly be preserved because of the non-organic material used, i.e. stone and metal. The bulk of the written production from these ancient societies has inevitably disappeared yet the presence of implements such as cretulae, styluses and inkwells indicates that materials such as papyrus and wax tablets were habitually used for writing., PID2019-104025GB-100

Digital printing techniques are increasingly present in the field of textile printing. Particularly prominent is the inkjet printing technique using water-based inks, UV LED inkjet printing also increasingly being in use. UV LED inkjet is primarily not intended for direct clothing printing; however, it can be used especially as a hybrid solution in the soft signage market. It is a great option for the printers that are not engaged only in textile printing, and want a more versatile print portfolio, extending it to non-clothing textile products, e.g. soft signage and non-wearable products. As these types of products often require colour reproduction of logos, accurate colour reproduction, good ink adhesion and sharpness are important just like in other printing technologies. In order to evaluate the impact of UV LED radiation amount on colour differences, ink bleeding and abrasion resistance, six different fabric samples (five woven and one nonwoven) were printed using a UV LED inkjet printer. Based on the results of colour difference, it was established that a reduction of UV radiation (by half the manufacturer’s recommended amount) had no effect on this parameter. However, perceptible colour differences were observed with the use of different M measurement conditions defined by the international standard ISO 13655-2017. Reducing the amount of UV radiation had no effect on the adhesion and durability of the printed ink. Small differences detected in these two parameters were mainly a consequence of the properties of textile materials and not of decreased UV radiation.

The goal of this article is to investigate the printability of ethyl cellulose, a biomass derived polymer, using a custom-modified direct ink writing (DIW) printer. Ethyl cellulose is widely used as a thin-film coating in controlled-release vitamins and medical pills as well as a thickener in the food, cosmetics, and other industries, making it an attractive candidate biopolymer for 3D printing. In this work, ethyl cellulose was dissolved in an alpha-terpineol solvent at different solid contents to prepare inks with different viscosities. A custom DIW printer, retrofitted with an in situ infrared curing system, was designed, calibrated, and analyzed for printing ethyl cellulose. The results demonstrate that the printer can maintain a steady flow for a range of ethyl cellulose inks having different viscosities. In summary, DIW can be successfully deployed toward fabricating biopolymer parts.

Printed flexible electrical heaters with excellent heating performance and mechanical durability are highly desirable for deicing and wearable thermotherapy devices. However, the performance of the conventional heaters is stilled limited by low-resolution fabrication methods when applied in high-precision heating in desirable regions. Moreover, the poor conductivity and mechanical stability of the ink also increase the power consumption. Herein, a high-resolution (45 μm) heater with low power consumption was fabricated by a facile electrohydrodynamic (EHD) printing method. A highly printable and stable hybrid conductive ink was obtained by doping PANI nanoparticles into silver flake/thermoplastic polyurethane (TPU) composite. After adding 0.5 wt% PANI nanoparticles into 40 wt% silver flake/TPU composite and low temperature sintering (80 °C), the bulk resistivity decreased from 96.03 × 10−5 Ω·m to 1.26 × 10−5 Ω·m. Thanks to the ultrahigh conductivity of the ink, the EHD printed flexible heater shows high saturation temperature (127.0 °C) under low applied voltage (2 V), wide heating range (33.9 °C~127.0 °C) under a small range of driving voltages (0.5 V ~ 2.0 V), the rapid response time (20 s) and excellent repeatability during 10-time cyclic heating-cooling possess. Furthermore, the printed flexible heaters exhibit great flexibility and durability. The resistance of the heater remains stable after 3000 outer bending cycles with a radius of 0.5 mm, indicating outstanding mechanical stability. Moreover, the heater can be attached to the human body, showing the potential for emerging wearable electronic applications.

Pentingnya mengetahui tingkat kekeruhan air terutama dalam aktivitas penggunaan air konsumsi yang berupa air bersih menuntut adanya suatu alat yang digunakan untuk mengukur tingkat kekeruhan air. Pemanfaatan serat optik untuk mengetahui tingkat kekeruhan air dari nilai rugi daya diharapkan dapat menjadi suatu solusi untuk mengetahui tingkat kekeruhan air sebelum digunakan. Penelitian dilakukan dengan mengukur nilai loss daya pada dua ujung serat optik singlemode dan multimode yang dihubungkan dengan fiber coupler, kemudian diukur menggunakan Handheld Light Source dan Optical Power Meter. Fiber coupler dimodifikasi dengan memberi lubang sebesar 1mm pada titik tengah untuk melewatkan air yang diuji. Pengukuran dilakukan dengan kondisi dua ujung optik tanpa jarak, ujung optik diberi jarak sebesar 1mm, ujung optik diberi jarak sebesar 1mm melalui air jernih dan air dengan zat pengeruh berupa tinta. Didapatkan hasil loss pengukuran terbesar pada serat optik singlemode dengan pengeruh warna yellow sebesar 1.9dB. Pada serat optik multimode pengeruh warna yellow sebesar 2.81dB. Hasil grafik dan perhitungan loss daya menggunakan matlab menunjukkan adanya pengaruh penambahan zat pengeruh tinta terhadap daya terukur di OPM. Berdasarkan hasil pengukuran perubahan loss daya tidak konstan pada setiap penambahan 5ml zat pengeruh, dapat dikatakan sensor yang di desain memiliki sensitivitas rendah.

Flexographic technology usage is increasing in recent years. Predicted growth in the technology usage intensifies the demand for improved quality. It is expected that flexographic printing will achieve greater results than ever before. Since this technique is used in the printing of shrink sleeve packaging, it is imperative to meet the technical and economic requirements of the shrink sleeve product. This is primarily to ensure gliding of the white printing material. The amount of white should be as small as possible, making the sliding of the material optimal and the quality of the print better. Therefore, the quality of the printing was measured by changing the conditions of slippage and white color. This research has established a correlation between the thickness of the white layer and the reduction of print quality over thin lines.

In this work, dynamic pH-sensitive quick response code (QR code) labels have been successfully fabricated by inkjet-printing technology. Inks with roselle anthocyanins and curcumin natural dye are prepared, respectively. The rheological property, contact angle, and surface tension of the prepared inks are tested. Both inks show good printability with Newtonian fluid property. The QR code labels with different ratios of inks are fabricated, in which the ink ratio is controlled by automatic computer program. It can be seen that the color of all printed QR code labels is sensitive to the concentrations of ammonia solutions, demonstrating that the pH-sensitive QR code labels are achieved. The ammonia-dependent color difference is analyzed by L*a*b* digital images. It can be found that the color difference strongly depends on the ink ratio, which suggests that the QR code labels with different ink ratios can be applied for diverse food freshness monitoring in real time. Therefore, in future, combined with the QR code application program (QR code APP) of intelligent devices, the developed QR code labels can be used as data carrier and freshness sensor as well, which provides a convenient method to get comprehensive food information, including freshness, expected storage time, date and identification of product, etc.

It is key to understand powder blend characteristics in relation to tablet characteristics when using pharmaceutical 3D printing, in order to obtain 3D powder bed printed tablets that comply with the pharmaceutical specifications. There is limited literature available on excipient selection for 3D printing, even though the only marketed 3D printed drug is prepared with powder bed printing. In this study, the impact of different particle size distributions of lactose-starch base formulations on key critical material attributes such as wettability, consolidation and flowability was studied. It was found that fewer fines in the particle size of the blend is beneficial for a fast penetration time of the ink (liquid) into the powder bed. The impact of varying the print settings or binder type on primary tablet properties such as hardness and dissolution was studied using formulations with Acetaminophen or Diclofenac Sodium. It was found that optimizing the base formulation and print settings have to be in conjunction as they are closely related. This study shows in detail how hydrophilic/hydrophobic API's can be successfully formulated into 3D printed tablets taking into account the formulation considerations as described.

Since the discovery of two-dimensional (2D) transition metal carbides and nitrides, known as MXenes, research on these wonder 2D inorganic compounds has become increasingly intensified with their members quickly expanding. MXenes' state-of-the-art applications are heavily dependent on their processing strategies and manufacturing methods. Nevertheless, the solution processing of MXenes has not been comprehensively reviewed. This review summarizes progress regarding solution processing of MXenes over the past decade as well as outlines key perspectives for future scalable manufacturing strategies. Etching of MAX phases and delamination of MXene are briefly introduced. Rheological properties of MXene dispersions and wetting of the MXene inks, which are crucial for the achievement of high-resolution printing and homogeneous coating, are discussed in detail. We have discussed the ink formulation strategies and fine-tuning of the ink properties to match with that of the targeted substrates to yield efficient yet high-quality printed/coated films/structures. As such, we demonstrate a “map of guidelines” for solution-based processing of MXenes toward high-performance applications, such as electrochemical energy storage, conductive electrodes, electromagnetic interference shielding, and so on.

A new direction in 3D printing was investigated – prototyping of single-sided, double-sided and multilayer printed circuit boards. The current capabilities and limitations of 3D printed circuit board printing technology were identified. A comparative analysis of the characteristics of two desktop 3D printers presented in the industry for prototyping radio electronics, as well as the first professional machine DragonFly LDM 2020, which is a mini-factory for prototyping multilayer printed circuit boards, was carried out. The first practical experience of working and printing on DragonFly LDM 2020 supplied to the megalaboratory “3D prototyping and control of multilayer printed circuit boards” of the Institute of Radio Engineering and Telecommunication Systems MIREA – Russian Technological University is presented. The first samples of electronic boards printed on a 3D printer by the method of inkjet printing were obtained. An additive technology for the production of multilayer printed circuit boards is considered: printing with two printheads with conductive and dielectric nano-ink with two curing systems: an infrared sintering system for conductive ink and a UV curing system for dielectric ink. The LDM (Dragonfly Lights-out Digital Manufacturing) production method with the necessary maintenance is presented. The method allows the system to work roundthe-clock with minimal human intervention, significantly increasing the productivity of 3D printing and expanding the possibilities of prototyping. The materials used for 3D printing of multilayer printed circuit boards and their characteristics were investigated: dielectric acrylate nano-ink (Dielectric Ink 1092 – Dielectric UV Curable Acrylates Ink), conducting ink with silver nanoparticles (AgCite™ 90072 Silver Nanoparticle Conductive Ink). The research carried out allows us to compare the technological standards of printed electronics with traditional methods of manufacturing multilayer printed circuit boards for a number of parameters.

The combination of 3D printing technology and electrode materials make the design and manufacture of electrode structures more convenient and faster. Electrodes with the 3D structure have a large surface area and multiple ion transmission paths, which help the batteries to achieve a high areal capacity, energy density and power density. Here, we designed the 3D printed electrodes with a structure of square grid by Direct Ink Writing, and achieved an improvement of areal capacity (1.44 mA h cm−2 at 0.5C), better areal-energy density (18.06 J cm−2) and cycling stability (preserving ~80% capacity after 500 cycles at 5 C).

Aggregation-induced emission based organic heterocyclic luminogens bearing conjugated electronic structures showed much attention due to its excellent fluorescence in aggregation state. In this communication, a novel conjugated blue light emitting imidazole molecule is synthesized by one pot multicomponent reaction route is reported for the first time. The prepared molecule exhibits a strong fluorescence in aggregation state with exceptional properties, such as high purity, inexpensive, eco-friendly, large scale production, high photostability, etc. By considering these advantages, a new fluorescence based platform has been setup for in-situ visualization of latent fingerprints and its preservation by spray method followed by Poly(vinyl alcohol) masking. A clear and well defined fluorescence fingerprint images are noticed on variety of surfaces by revealing level 1–3 ridge features upon ultraviolet 365 nm light exposure. The dual nature of binding specificity as well as excellent fluorescence properties permits the visualization of latent fingerprints for longer durations (up to 365 days) with superior contrast, high sensitivity, efficiency, selectivity and minimal background hindrance. We further fabricated unclonable invisible security ink for various printing modes on valuable goods for protection against forging. The developed labels are displaying uniform distribution of ink and exceptional stability under various atmospheric environments. The development of long preservative information using aggregation-induced emission based luminogen opens up a new avenue in advanced forensic and data security applications.

Wearable multi-sensors based on nanocrystals have attracted significant attention, and studies on patterning technology to implement such multi-sensors are underway. Conventional patterning processes may affect material properties based on high temperatures and harsh chemical conditions. In this study, we developed an inkjet printing technique that can overcome these drawbacks through the application of patterning processes at room temperature and atmospheric pressure. Nanocrystal-based ink is used to adjust properties efficiently. Additionally, the viscosity and surface tension of the solvents are investigated and optimized to increase patterning performance. In the patterning process, the electrical, electrothermal, and electromechanical properties of the nanocrystal pattern are controlled by the ligand exchange process. Experimental results demonstrate that a multi-sensor with a temperature coefficient of resistance of 3.82 × 10-3 K-1 and gauge factor of 30.6 can be successfully fabricated using one-step inkjet printing.

China Scholarship Council (CSC) - UCL Joint research scholarship; Vest Scholarship of the US National Academy of Engineering (NAE)

Objectives: Paper documents are playing an increasingly important role in people's daily work with the development of economy, society and culture. In the practice of judicial appraisal, the sequence of the intersections of ink and seal on suspicious documents can often provide critical information for the detection of criminal cases. The examination of sequence of intersecting seal and ink lines is to judge the sequence of seal and ink mark formation by certain technical means.Methods: A representative black signature pen, ink, and specific paper are selected to prepare experimental samples. Under the given experimental conditions, the field emission scanning electron microscope is used to perform micro-morphology on the cross-sectional characteristics of the samples and all the characterization results obtained are systematically analyzed to summarize the specificity of the sample. Results: The results showed that the proposed method can efficiently discriminate the Permeation Characterization of the sequence of intersecting seal and ink lines.Conclusions: This research is expected to be applied to forensic investigation for counterfeiting documents and bring new developments in the field of document inspection.

要将荧光油墨应用于实际, 通常要求该油墨对环境友好且稳定, 并且具有良好的黏度和优异的发光性能. 本文中, 我们通过含有氨基的稀土钛氧簇Eu2Ti4-NH2 (1)与PEG (PEG = 甲氧基聚乙二醇琥珀酰亚胺碳酸酯, 2000 g mol−1)反应合成了稀土钛氧簇-高分子复合材料Eu2Ti4-NH2@PEG (2). 对2的相关表征表明, 1的结构在2之内是完整的. 1和2的发光性质表明其固态量子产率分别为50.91%和30.69%. 与化合物1相比, 2在极性溶剂中的溶解度和成膜性能大大提高. 当使用2的乙醇/乙二醇(v/v = 4/1)混合溶液用于喷墨打印的墨水时, 喷墨打印的标签显示出良好的隐蔽性和有效性.

Scanning electron microscopy (SEM) technology has been widely used in forensic science, which promotes the development of interdisciplinary science. This paper used SEM to observe the penetration degree of common black gel-ink on paper. The penetration morphology of the different black brands gel-ink has been observed. The relationship between the penetration process of gel-ink material and the dating of document has been observed after determining the measuring position. The results showed that the penetration depth of ink along Z direction on paper is significantly different, the penetration speed of ink is also different, which presents regular variety and gradually reaches a relatively stable state over time. The application of SEM will provide a useful exploration for judging the ink dating.

Slide coating is a precision method suitable for depositing multiple liquid-film layers simultaneously. Originally developed in the photographic film industry, it has been deployed for manufacturing of other products that benefit from multilayer coatings. One emerging application is the manufacture of polymer electrolyte membrane fuel cells (PEMFCs), which are used to produce electricity through electrochemical reactions of hydrogen and oxygen gas. The membrane-electrode assembly (MEA), in which key electrochemical reactions occur, consists of three layers that are typically deposited separately in serial fashion and then laminated together to form the three-layer MEA, i.e., three sequential steps of coat and dry. Adapting the process to simultaneous, multilayer slide coating of all three layers will save equipment cost and space while minimizing possible exposure to contaminants during transition between the steps. We are developing a three-layer slide coating model to aid the manufacturing process design of PEMFC. The model accounts for rheology of each layer, which typically exhibit shear thinning behavior. Model predictions are used to investigate simultaneous coatability of catalyst inks and to determine the best layer-by-layer ink selection.

We propose a layout estimation method for multi-layered ink using a measurement of the line spread function (LSF) and machine learning. The three-dimensional printing market for general consumers focuses on the reproduction of realistic appearance. In particular, for the reproduction of human skin, it is important to control translucency by adopting a multilayer structure. Traditionally, layer design has depended on the experience of designers. We, therefore, developed an efficient layout estimation to provide arbitrary skin color and translucency. In our method, we create multi-layered color patches of human skin and measure the LSF as a metric of translucency, and we employ a neural network trained with the data to estimate the layout. As an evaluation, we measured the LSF from the computer-graphics-created skin and fabricate skin using the estimated layout; evaluation with root-mean-square error showed that we can obtain color and translucency that are close to the target.

Commercial Chinese ink was employed to disperse pristine vapor-grown carbon nanofibers (VGCNFs) in aqueous suspensions via horizontal ball milling. The obtained suspension was used to fabricate conductive paper-based composites through filtration-deposition onto filter paper. It was found that the carbon black particles from the Chinese ink helped separate VGCNFs and acted as connection points between the VGCNFs, while the glue reinforced the conduction network. Thus, the VGCNF-ink/paper ternary composite showed sufficiently low sheet resistance. With merely 2.5 mg·cm−2 VGCNFs, the sheet resistance could be reduced to 4.5 Ω·sq−1. As a proof of concept, these paper-based composites were directly used as electrodes of solid-state symmetric electronic double-layer capacitors (EDLCs) and the substrate for the electrodeposition of MnO2 to achieve higher electrochemical performances. The EDLCs fabricated with 2.5 mg·cm−2 VGCNFs showed a specific capacitance of 224 mF·cm−2 at a current density of 1 mA·cm−2, which was retained by 86.4% after 10,000 charge-discharge cycles. Moreover, thanks to the high electrical conductivity and the porous structure, the MnO2 decorated paper-based composites exhibited dramatically enhanced specific capacitance. It is believed that our finding offers an idea to directly utilize commercial Chinese ink for the fabrication of electrode materials.

The paper investigates the influence of the mechanics of a friction printing pair on ink dusting in the printing process, taking into account the surface roughness of the printing plate. The aim of the study is to determine the influence of the surface roughness of the printing plate on the deformation of the deckle, as well as on the value of the total force in the area of the printed contact, the relative gear ratio and the relative speed of sliding of the deckle along the surface of the cylinder, which directly affects the dusting of the ink. It was found that when studying the mechanics of a printed pair, the influence of the microgeometry of the contacting surfaces on the parameters under study was not taken into account. The influence of microprotrusions of the surface roughness of the printing plate on the deformation of the deckle in the area of the printed contact has been substantiated and established. To determine the introduction of surface roughness irregularities, a discrete roughness model is used, presented as a set of identical spherical segments. To determine the influence of the surface roughness of the printing plate on the friction force arising in the contact zone, a calculation scheme is proposed that differs from analogs. A method is developed for calculating the parameters of a friction pair in the printing process, taking into account the roughness. Expressions are obtained for determining the total moment of tangential friction forces in the sliding sections when spherical irregularities are introduced. According to the proposed technique, the corresponding graphical dependences of the gear ratio on different parameters of the friction printed pair are shown. The advantages of this study in comparison with analogs are that at certain values of the parameters of the friction pair, taking into account the surface roughness of the printing plate, also at known values of the mechanical characteristics and thickness of the deckle, it is possible to determine the change in the length of the deckle of a given composition, which is necessary in the printing process. The proposed calculation method, which is carried out without taking into account the pressure in the printed contact zone, allows predicting the quality of printed impressions and the amount of ink involved in the formation of ink dusting, as well as correctly adjusting the printing press before the printing process.

Glass material used on a semiconductor device for isolating currents are one of the new breakthroughs of the modern world. Challenges are inevitable due to its complex characteristics and unique appearance. The study focuses on the phenomenon of reject glass die unrecognized, picked and bonded by die attach machine on good units of the semiconductor quad-flat no-leads (QFN) device in focus. This QFN device utilizes glass die as interposer on two active dice that separates the dielectric current of each die. During die attach process, machine photo recognition system failed to recognize and detect the glass die reject marking due to its unique transparent design and will be attached on good units. Thus, resulting to gross rejection and low process yield. Practical solutions to prevent the said phenomenon are simulated and determined by performing selection of variables like the contrast of the reject mark related to the product structure and compatibility through statistical analysis. The improvement drives to promote process robustness and scrap reduction that will help the manufacturing to be competitive through innovative resolutions on problems.

Purpose This study aims to examine on-site particle concentration levels due to emissions from a wide spectrum of additive manufacturing techniques, including polymer-based material extrusion, metal and polymer-based powder bed fusion, directed energy deposition and ink-based material jetting. Design/methodology/approach Particle concentrations in the operating environments of users were measured using a combination of particle sizers including the TSI 3910 Nano SMPS (10–420 nm) and the TSI 3330 optical particle sizer (0.3–10 µm). Also, fumes from a MEX printer during printing were directly captured using laser imaging method. Findings The number and mass concentration of submicron particles emitted from a desktop open-type MEX printer for acrylonitrile-butadiene-styrene and polyvinyl alcohol approached and significantly exceeded the nanoparticle reference limits, respectively. Through laser imaging, fumes were observed to originate from the printer nozzle and from newly deposited layers of the desktop MEX printer. On the other hand, caution should be taken in the pre-processing of metal and polymer powder. Specifically, one to ten micrometers of particles were observed during the sieving, loading and cleaning of powder, with transient mass concentrations ranging between 150 and 9,000 µg/m3 that significantly exceeded the threshold level suggested for indoor air quality. Originality/value Preliminary investigation into possible exposures to particle emissions from different 3D printing processes was done, which is useful for the sustainable development of the 3D printing industry. In addition, automatic processes that enable “closed powder cycle” or “powder free handling” should be adopted to prevent users from unnecessary particle exposure.

The presented work focused on the development of temperature sensors based on specially formulated carbon nanotube (CNT) and poly(3,4-ethylene dioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) based inks which are deposited directly onto the adhesive polyamide-based taffeta fabric with low-cost office-type inkjet printer. Stable and uniform dispersions of CNT and PEDOT:PSS with Triton X-100 were formulated to be used as temperature sensitive inkjet inks. Three kinds of temperature sensors were fabricated using sensitive materials including CNT ink, PEDOT:PSS ink, and CNT/PEDOT:PSS composite ink. Developed sensors are connected to the measuring devices via silver yarns and silver adhesive paste. Sensors are covered with translucent polyurethane welding tape for packaging and protection. All the sensors exhibit negative temperature coefficient (NTC) behavior and sensitivity of 0.15 %/degrees C for CNT, 0.41 %/degrees C for PEDOT:PSS, and 0.31 %/degrees C for CNT/PEDOT:PSS for temperatures varying from room temperature to 50 degrees C. CNT/PEDOT:PSS composite ink printed sensor achieved better sensing repeatability and demonstrated higher bending stability with a resistance change of 0.3 % up to 1000 cycles than CNT printed and PEDOT:PSS printed sensors. The softness, lightness, and capability to work on flexible or curved surfaces make the developed CNT/PEDOT:PSS composite ink printed sensor a robust candidate for wearable temperature sensor applications, especially in situations requiring continuous body temperature monitoring while satisfying comfort of the user.

Polymeric materials with a low dielectric constant are widely used in the electronic industry due to their properties. In particular, polymer adhesives can be used in many applications such as wafer bonding and three-dimensional integration. Benzocyclobutene (BCB) is a very interesting material thanks to its excellent bonding behavior and dielectric properties. Usually, BCB is applied by spin-coating, although this technology does not allow the fabrication of complex patterns. To obtain complex patterns, it is necessary to use a printing technology, such as inkjet printing. However, inkjet printing of BCB-based inks has not yet been investigated. Here, we show the feasibility of printing complex patterns with a BCB-based ink, reaching a resolution of 130 μm. We demonstrate that with a proper dilution, BCB-based inks enter the printability window and drop ejection is achieved without the formation of satellite drops. In addition, we present the conditions in which there is an appearance of the coffee ring effect. Inks that feature a too high interaction with the substrate are more likely to show the coffee ring effect, deteriorating the printing quality. We also observe that it is possible to achieve a better film uniformity by increasing the number of printed layers, due to redissolution of the BCB-based polymer that helps to level possible inhomogeneities. Our work represents the starting point for an in-depth study of BCB-based polymer fabrication using jet printing technologies, as a comparison of the bonding quality obtained with different materials and different technologies could give more information and broaden the perspective regarding this field.

In this study, the effects of the lacquer applied to the printing materials which were printed by electrophotographic printing method on printing quality were investigated. In practice, printing materials with the same weight and different optical properties were used and the study was carried out in three stages. The optical and physical properties of the printing materials used in the first part were determined, in the second part, the printing of these materials by electrophotographic printing method and printability tests were performed. In the third chapter, matte and glossy lacquers were applied to these printed materials and printability tests were repeated. As a result of the study, it was observed that the application of gloss and matte lacquer caused a decrease in the printing density values and also the application of matte lacquer caused a decrease in the gloss values.

Recycling of electric arc furnace dust (EAFD) has great potential for industrial applications, due to its useful metal contents, including zinc. In this study, aqueous cyan ceramic ink for ink-jet printing applications was synthesized using EAFD. More specifically, cyan ceramic pigments were synthesized using an empirical composition of Zn(EAFD)XCo1-XAl2O4, in which expensive cobalt oxide is replaced by Zn-enriched EAFD. Zn(EAFD)0.25Co0.75Al2O4, which has a vivid cyan color, was selected as the optimum composition of cyan ceramic pigments for synthesizing aqueous cyan ceramic ink for ink-jet printing applications. To prevent nozzle clogging during ink-jet printing, the cyan ceramic pigments were micronized. The micronized pigments were mixed with distilled water and dispersant to fabricate aqueous cyan ceramic ink. To determine the optimized jettability and printability of this ink, its rheological properties, including viscosity and surface tension, were adjusted and analyzed. It was concluded that the jettability and printability of aqueous cyan ceramic ink produced via ink-jet printing could be enhanced by appropriately adjusting its viscosity.

A vibration having a character of self-excited chatter oscillation known from machine tools is observed during intermittent motion of ink rollers of offset printing machines. This vibration occurs under specific operating conditions and is often accompanied by an increased noise level. To explain this unusual vibration behavior, a simple analytical model of two rollers interaction is derived. The calculated oscillation is compared with the measurement of ductor roller displacement. The model results confirm the possibility of self-excited vibration development in the presence of viscous forces, negative damping effects and continuous supply of external energy from roller rotation.

In this review paper, we focus on the 3D printing technologies that consist of the extruding of fluid material in lines to form structures for electro- and biomechanical applications. Our paper reviews various 3D print technologies, materials, sensing technologies and applications of extrusion-based 3D printing. We also discuss how to overcome some of the challenges with 3D printed sensors, such as the anisotropy of the conductors as well as the drift and nonlinearity of the materials.

Summary Phase change materials (PCMs) are an attractive option to passively control building heating and cooling. We present a facile method to produce and print PCM-filled inks by a direct ink writing (DIW) technique that leverages spherical PCM particles as viscosity modifiers in a matrix of photocurable resin. We successfully print inks with up to 63 wt% PCM, which have excellent thermal regulation capacity and nearly no leakage over 200 melting/solidifying cycles. A hollow house printed with PCM-filled ink maintained a 40% lower temperature than the external environment when heated. PCMs with different melting points can be simultaneously integrated into resin and printed without detriment to the structure or integrity. Our approach uses PCM particles as both viscosity modifiers for 3DP and passive thermal management to produce effective thermal buffers and is compatible with a wide range of photopolymer matrices and PCMs, without requiring prior microencapsulation of the PCMs.

Digital Image Correlation (DIC) is a popular experimental technique for measuring full-field deformations in materials. Accurate motion and displacement field reconstruction in DIC depend heavily on the intrinsic material texture or speckle patterns painted on the material prior to deformation. Many traditional techniques such as spray painting, ink stamping, or manual texturizing have provided adequate performance but are often challenging to apply on highly compliant, porous or non-planar surfaces. To address this challenge we present a new, robust and efficient technique to print DIC speckle dot patterns on both planar and non-planar sample surfaces using a custom-modified 3D printer in an automated fashion. In this new technique, a 3D printer is modified by replacing the conventional extrusion head with a syringe filled with ink. The motion of the 3D printer is controlled via customizable G-code scripts, precisely controlling both the extrusion volume and spatial positioning of the print head in a well-controlled and predictable fashion. The printed speckle dots have radii on the order of O( $$10^2$$ ) $$\upmu$$ m, and the subsequent DIC reconstructed deformations have an accuracy on the order of O( $$10^{-2}$$ ) pixels and O( $$10^{-4}$$ ) in measuring displacements and strains, respectively. Furthermore, we demonstrate that this technique has the capability to print suitable patterns for tracking large and heterogeneous deformations in highly compliant and porous materials, as well as materials with significant 3D topographies.

New ink compositions for direct ink writing (DIW) printing of hydrogels, combining superior rheological properties of cellulose nanocrystals (CNCs) and a water-compatible photoinitiator, are presented. Rapid fixation was achieved by photopolymerization induced immediately after the printing of each layer by 365 nm light for 5 s, which overcame the common height limitation in DIW printing of hydrogels, and enabled the fabrication of objects with a high aspect ratio. CNCs imparted a unique rheological behavior, which was expressed by orders of magnitude difference in viscosity between low and high shear rates and in rapid high shear recovery, without compromising ink printability. Compared to the literature, the presented printing compositions enable the use of low photoinitiator concentrations at a very short build time, 6.25 s/mm, and are also curable by 405 nm light, which is favorable for maintaining viability in bioinks.

Objective: To synthesize the easily erasable, user-friendly, and low-cost whiteboard ink from the locally available raw sources. Methods: The ink was prepared by mixing the Neem-gum, n-butanol, dyes of different colours in different ratios, and the mixture thus obtained was heated at constant temperature and then was cooled to room temperature and filtered. Findings: Out of different combinations three different ink formulations SH1, SH2, and SH3 were obtained, and later they were tested to different physiochemical analysis. The results thus obtained for SH1, SH2, and SH3 respectively were pH (5.9, 4.7, and 3.4), viscosity (0.0011628 Ns/m2, 0.0086425Ns/m2and 0.0046242Ns/m2) and drying time (5.24 seconds, 18.04 seconds and 8.22 seconds). Samples SH1 and SH3 depict the best properties like drying time, viscosity, and erasability. To know the elemental concentration in the samples, the XRF analysis was conducted and the results thus obtained were on par with that of the standard ink available in the market. Novelty: Ink manufacturers of international repute often synthesize them with chemicals that might harm the users like teachers and other professionals if they come into improper contact with it. So we prepared an ink from the naturally available neem gum which is both user-friendly and eco-friendly. Keywords: Azadirachta indica; erasability; ink; Phenolphthalein; viscosity; XRF analysis

Quantum dot light-emitting diode (QLED) can be directly patterned for pixel array by solution processing, while the limitation of resolution and device stability exists unless a proper solvent system and multilayer design are established. With a small-sized nozzle inkjet printing process, solvent formulation effects on the morphology and precision of printing for the quantum dot layer were investigated. Drop formation as well as ink spreading and wetting behavior on the non-crosslinked organic hole-transporting polymer were optimized with a non-erosive solvent formulation composed of octane and cyclohexane. While the ink composition formed low-contact angle droplet on the surface and was not completely ideal for the defectless pixelating process of high-resolution inkjet, its controllability of wetting at a small-scale nozzle, uniform drying, and orthogonal characteristics with an effective hole transport layer resulted in a high-performance green inkjet QLED with 6.13 cd/A at 19,550 nits highly bright region. This amounted to about 50% of efficiency performance compared to an identical device prepared with spin-coating, but one of the best green inkjet QLED properties reported with less than 120-μm sub-pixel pitch.

© 2021 Elsevier Ltd and Techna Group S.r.l. Titanium dioxide is widely used in numerous industries and with the newly developed titanium manufacturing technique, referred to as the Near-net-shape Electrochemical Metallisation (NEM) Process, the rapid and precise production of titanium dioxide components is highly sought-after. This manuscript presents the rheological investigation and extrudability tests of titania inks, to establish the improved production of titanium dioxide components via Direct Ink Writing. The extrudability tests indicated that despite an unfavourable increase in viscosity during the high shear rates (dilatancy peaks), the best-performing ink had a weight ratio of 1:0.8:0.1 TiO2:H2O:PEG, and the dilatancy peaks were smoothed out with the addition of 0.1 wt ratio of oleic acid to the ink, dramatically improving the quality of the product. To further improve the green bodies a new printing approach was also introduced, removing the necessity for specialised printing bed, by printing a removable support into the green body and allowing for drying without any cracks and warping.

The order of laying down homogeneous intersecting strokes of ball-point inks has been assessed using a range of different spectroscopic and analytical techniques for recent inks and for inks with a time difference of 4 years. These techniques are infrared reflectance photography with luminescence, fluorescence micro-spectrophotometry, Fourier transform infrared spectrometry, high resolution liquid chromatography and gas chromatography with mass spectrometry. This paper presents a combined method applicable to forensic cases aimed at resolving homogenous intersecting strokes of ball-point ink to determine whether they were made at the same time or, on the contrary, they were intersecting strokes laid down with an acute time difference, taking four years as an age reference.

Lab-on-Chip is a technology that aims to transform the Point-of-Care (PoC) diagnostics field; nonetheless a commercial production compatible technology is yet to be established. Lab-on-Printed Circuit Board (Lab-on-PCB) is currently considered as a promising candidate technology for cost-aware but simultaneously high specification applications, requiring multi-component microsystem implementations, due to its inherent compatibility with electronics and the long-standing industrial manufacturing basis. In this work, we demonstrate the first electrolyte gated field-effect transistor (FET) DNA biosensor implemented on commercially fabricated PCB in a planar layout. Graphene ink was drop-casted to form the transistor channel and PNA probes were immobilized on the graphene channel, enabling label-free DNA detection. It is shown that the sensor can selectively detect the complementary DNA sequence, following a fully inkjet-printing compatible manufacturing process. The results demonstrate the potential for the effortless integration of FET sensors into Lab-on-PCB diagnostic platforms, paving the way for even higher sensitivity quantification than the current Lab-on-PCB state-of-the-art of passive electrode electrochemical sensing. The substitution of such biosensors with our presented FET structures, promises further reduction of the time-to-result in microsystems combining sequential DNA amplification and detection modules to few minutes, since much fewer amplification cycles are required even for low-abundance nucleic acid targets.

Among the available additive manufacturing (AM) technologies, fused filament fabrication (FFF) technique—broadly used in academia—seems to be a promising alternative to injection molding process in industry regarding physical prototypes. This is partially due to its accessibility, fast responsiveness and the substantial development of low-cost and open-source machines and filament materials. However, beyond the ongoing research efforts related to this material extrusion technique, the inherent layer-by-layer deposition strategy leads to lower mechanical performances compared to traditional formative and subtractive manufacturing processes. Indeed, recurrent anisotropic material properties and fracture strength still remains as the key challenges to be tackled in FFF, so as to get close to mechanical performances obtained by injection molding. In such a context, the main objective of the article is to extend mechanical parts’ performances by improving fracture strength of FFF printed parts. To do so, an innovative hybrid additive manufacturing platform—combining FFF and direct ink writing (DIW) techniques—is proposed. The proposed platform is implemented through a dedicated digital workflow covering process planning algorithms and a new modular concept of hybrid 3D printer. The added value of the proposal is demonstrated with tensile strength tests and opens the door to multi-material 3D printing.

Here, we report a previously unreported low-temperature curable barium strontium titanate (BaXSr1−XTiO3) or BST dielectric nanoparticle ink which shows a high dielectric tunability for printed electronics/additive manufacturing applications. The newly formulated BST ink is optimized to print in aerosol jet printers and can be cured at 150°C, which will allow the fabrication of tunable radio-frequency (RF) and microwave (MW) devices on a wide range of flexible substrates. Characterization of high-frequency dielectric properties showed a high dielectric tunability (~ 15% at 10 GHz with 10 V/µm) and a high dielectric constant (~ 16 at 10 GHz). The linear-reversible tunability, which is very important for tunable devices, was confirmed by the tunability testing at 10 GHz. Characterization of temperature-dependent dielectric properties found < 10% variations of the dielectric constant at 10 GHz from −50°C to 125°C for this BST ink. Detailed information on BST nanoparticle characterization, ink formulation and characterization of dielectric properties is discussed.