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The study of Frequency Selective Surface (FSS) by Direct ink writing (DIW) has attracted much attention due to the convenience and effectiveness of 3D printing technology. However, the limited printing precision of DIW has heavily restricted its applications as the electromagnetic performance is highly sensitive to it, especially the precision at the microscale. Herein, the ultra-high printing precision of FSS was achieved through DIW by the uniformly dispersed graphene sheets to deeply modify the rheological behavior and the steric hindrance effect. Thus, the highly precision of the printed filament width as thin as 67 μm with a space of only 42 μm were achieved, which is difficult for conventional DIW, and no structural distortion is found after 3D printing, no matter it was 2D printed on a flat surface or the sharply skewed hook face, or even 3D printed to architectural structures. According to the highly improved precision, the electromagnetic performance matching between the designed model and the printed physical FSS device was perfectly achieved, reducing the center frequency error less than 0.3 GHz, and the transmission coefficient error less than 0.046. Our work promises an effective and easy preparation of high-quality FSS from the aid of graphene.

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.

The possibility of printing conductive ink on textiles is progressively researched due to its potential benefits in manufacturing functional wearable electronics and improving wearing comfort. However, few studies have reported the effect of conductive ink formulation on electrodes directly screen-printed on flexible substrates, especially printing UV curable conductive ink on common textiles. In this work, a novel UV curable nano-silver ink with short-time curing and low temperature features was developed to manufacture the fully flexible and washable textile-based electrodes by screen printing. The aim of this study was to determine the influence of ink formulation on UV-curing speed, degree of conversion, morphology and electrical properties of printed electrodes. Besides, the application demonstration was highlighted. The curing speed and adhesion of ink was found depending dominantly on the type of prepolymer and the functionality of monomer, and the type of photoinitiator had a decisive effect on the curing speed, degree of double bond conversion and morphology of printed patterns. The nano-silver content is key to guarantee the suitable screen-printability of conductive ink and therefore the uniformity and high conductivity of textile-based electrodes. Optimally, an ink formulation with 60 wt% nano-silver meets the potential application requirements. The electrode with 1.0 mm width showed significantly high electrical conductivity of 2.47 × 106 S/m, outstanding mechanical durability and satisfactory washability. The high-performance of electrodes screen-printed on different fabrics proved the feasibility and utility of UV curable nano-silver ink. In addition, the application potential of the conductive ink in fabricating electronic textiles (e-textiles) was confirmed by using the textile-based electrodes as the cathodes of silver-zinc batteries. We anticipate the developed UV curable conductive ink for screen-printing on textiles can provide a novel design opportunity for flexible and wearable e-textile applications.

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.

The ability of thermoelectric (TE) materials to convert thermal energy to electricity and vice versa highlights them as a promising candidate for sustainable energy applications. Despite considerable increases in the figure of merit zT of thermoelectric materials in the past two decades, there is still a prominent need to develop scalable synthesis and flexible manufacturing processes to convert high-efficiency materials into high-performance devices. Scalable printing techniques provide a versatile solution to not only fabricate both inorganic and organic TE materials with fine control over the compositions and microstructures, but also manufacture thermoelectric devices with optimized geometric and structural designs that lead to improved efficiency and system-level performances. In this review, we aim to provide a comprehensive framework of printing thermoelectric materials and devices by including recent breakthroughs and relevant discussions on TE materials chemistry, ink formulation, flexible or conformable device design, and processing strategies, with an emphasis on additive manufacturing techniques. In addition, we review recent innovations in the flexible, conformal, and stretchable device architectures and highlight state-of-the-art applications of these TE devices in energy harvesting and thermal management. Perspectives of emerging research opportunities and future directions are also discussed. While this review centers on thermoelectrics, the fundamental ink chemistry and printing processes possess the potential for applications to a broad range of energy, thermal and electronic devices.

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

Screen printing is regarded as a highly competitive manufacture technology for scalable and fast fabrication of printed microelectronics, owing to its advanced merits of low-cost, facile operability and scalability. However, its large-scale application in printed microelectronics is still limited by screen printing functional ink. In this review, we summarize the recent advances of ink formation, typical scalable applications, and challenging perspectives of screen printing for emerging printed microelectronics. Firstly, we introduce the major mechanism of screen printing and the formation of different organic- and aqueous-based inks by various solvents and binders. Next, we review the most widely used applications of screen printing technique in micro-batteries, micro-supercapacitors and micro-sensors, demonstrative of wide applicability. Finally, the perspectives and future challenges in the sight of screen printing are briefly discussed.

With the rapid development of the electronics industry, electronic products based on silicon and glass substrates electronic products will gradually be unable to meet the rising demand. Flexibility, environmental protection, and low costs are important for the development of electronic products. In this study, an efficient and low-cost method for preparing silver electrode structures by direct writing on paper has been demonstrated. Based on this method, a flexible paper-based sensor was prepared. The liquid printing ink used mainly comprises a precursor liquid without pre-prepared nanomaterials. The precursor liquid is transparent with good fluidity. Simple direct writing technology was used to write on the paper substrate using the precursor ink. When the direct-writing paper substrate was subsequently heated, silver nanostructures precipitated from the precursor liquid ink onto the paper substrate. The effect of different temperatures on the formation of the silver nanostructures and the influence of different direct writing processes on the structures were studied. Finally, a paper-based flexible sensor was prepared for finger-bending signal detection. The method is simple to operate and low in cost and can be used for the preparation of environment-friendly paper-based devices.

Purpose The surface energy of the printing material can be increased to desired levels with different chemicals or methods. However, the important thing is that the surface properties of printing material are not affected negatively. In this way the aim of this paper provide that the surface properties of matte and glossy coated paper is improved by the argon containing atmospheric pressure plasma device because the plasma treatment method does not occur surface damaging on the papers. Design/methodology/approach In experimental studies, test samples cut from 160 mm × 30 mm in size from 115 g/m2 gloss- and matt-coated papers were used. The plasma treatments of paper samples were carried out with an argon containing atmospheric pressure plasma device of laboratory scale that produces plasma of the corona discharge type at radio frequency. The optimized plasma parameters were at a frequency of 20 kHz and plasma power 200 W. A copper electrode of length 12 cm and diameter 2.5 mm was placed in the centre of the nozzle. Findings Research findings showed that the surface energies of the papers increased with the increase in plasma application time. While the contact angle of the untreated glossy paper is 82.2, 8 second plasma applied G3 sample showed 54 contact angle value. Similarly, the contact angle of the base paper of matt coated is 91.1, while M3 is reduced to 60.4 contact angles by the increasing plasma time. Originality/value Plasma treatment has shown that no chemical coating is needed to increase the wettability of the paper surface by reducing the contact angle between the paper and the water droplet. In addition, the surface energies of all papers treated by argon gas containing atmospheric pressure plasma, increased. Plasma treatment provides to improve both the wettability of the paper and the adhesion property required for the ink, with an environmentally friendly approach.

Surface texture is a valid way of improving hydrodynamic lubrication performance and reducing friction. In this work, a novel micro-additive manufacturing technique, selective laser melting ink-pri...

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.

Piezoelectric nanofibers sensors cannot be mass-produced due to the limitation of electrode technology. Herein, we proposed a parallel-stripes electrode pattern for the first time, which enables using the screen-printing technology to print electrodes on piezoelectric nanofibers mats to prepare piezoelectric nanofibers sensors. Firstly, combining PVDF-TrFE nanofibers with different electrodes to prepare piezoelectric sensors and comparing their sensitivity, we prove that PVDF-TrFE nanofibers sensor based on parallel-stripes electrode has piezoelectric output. What is more, the sensor has the highest sensitivity when the parallel-stripes electrode is parallel to the oriented piezoelectric nanofibers. And then, we directly printed parallel-stripes electrode on oriented PVDF-TrFE nanofibers mat, and the vibration test of 50,000 cycles verifies that the PVDF-TrFE nanofibers sensor prepared by this way possess satisfactory stability. Our research provides a new electrode pattern for preparing stable and reliable electrodes for piezoelectric nanofibers sensors via screen printing. Moreover, this electrode further increases the sensitivity of the piezoelectric nanofibers sensor.

Purpose Paper aims to preparation of new acid disperse dyes based on thiadiazol derivatives and evaluation of their use as antimicrobial colorants in digital transfer-printing ink formulations for printing onto polyester fabric substrates. Design/methodology/approach New disperse dyes based on 1,3,4 - thiadiazol derivative (dyes 1–3) were prepared and evaluated by different analysis then formulated as colored materials in the ink formulations. The viscosity, dynamic surface tension and particle size distribution of the prepared inks were measured. The printed polyester fabric substrates were tested using a variety of tests, including light fastness, washing, alkali perspiration and Crock fastness, as well as depth of penetration. Density-functional theory (DFT) calculations were carried out at the Becke3-Lee-Yang-parr (B3LYP) level using the 6–311** basis set, and the biological activity of the prepared disperse dyes was investigated. Findings The obtained results of the physical of the prepared ink revealed that thiadiazol disperse ink is a promising ink formulation for polyester printing and agrees with the quality of the printed polyester fabric. The optimization geometry for molecular structures agreed with the analysis of these compounds. The HOMO/LUMO and energy gap of the studied system were discussed. The molecular docking analysis showed strong interaction with DNA Gyrase and demonstrated to us the high ability of these inks to act as antimicrobial agents. Practical implications The prepared inks containing the prepared thiadiazol disperse dye were high-performance and suitable for this type of printing technique, according to the results. The prepared inks resist the growth of microorganisms and thus increase the ink's storage stability. Originality/value The prepared disperse dyes based on 1,3,4 - thiadiazol derivative (dyes 1–3) can be a promising colorant in different applications, like some types of paint formulations and as a colorant in printing of different fabric substrates.

We successfully offer a quantitative and qualitative analysis of the micro-toxic elements that are found in various brands of commercial ink powders (CIPs) available in Saudi Arabia employing short...

The technique of laser breakdown spectroscopy (LIBS) was employed for samples of writing inks under the influence of a Nd:YAG laser pulse 1064 nm with a pulse duration of 10 ns on different targets of writing ink models. The plasma parameters were also calculated, which are the temperature and density of electrons, assuming local thermodynamic equilibrium conditions (LTE) and using a spectral detector model (View spectra 2100) for the spectral range (200nm - 900nm). The results showed differences in the values of the pairing coefficient of electrons in the plasma. Produced due to the laser pulse used as well as in the plasma parameters mentioned, which can be applied in plasma spectroscopy for forensic sciences in detecting forgery in documents and tracking the performance and phenomena of the plasma formed due to the laser pulse.

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.

Flexible batteries have gained significant attention in recent years, owing to their huge demand for portable wearable electronics and smart fabrics. However, conventional Li-ion batteries (LIBs) have limited device adaptability because of their planar architecture. To address this issue, the LIBs are shrunk to a one-dimensional fiber shape, which provides the freedom and flexibility needed for their integration with wearable electronics and smart fabrics. Herein, we demonstrate a method to fabricate twisted yarn-type (TYT) LIBs by a direct ink writing-based three-dimensional printing technology, using natural graphite and LiNi0.6Co0.2Mn0.2O2 as anode and cathode active materials, respectively, along with vapor-grown carbon fibers as an integrated conductive matrix. The printed electrode fibers are twisted together to create anode and cathode yarns, which are then assembled together to obtain a prototype TYT LIB device. The fabricated device performs significantly better in terms of both electrochemical performance and flexibility. The proposed method thus enables the direct integration of batteries into commercial fabrics either in the form of individual electrodes or full devices, which opens up a new route for developing next-generation energy storage devices for smart fabrics.

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.

Recently, the three-dimensional (3D) printing of solid-state electrochemical energy storage (EES) devices has attracted extensive interests. By enabling the fabrication of well-designed EES device architectures, enhanced electrochemical performances with fewer safety risks can be achieved. In this review article, we summarize the 3D-printed solid-state rechargeable batteries and supercapacitors and discuss various types of printable polymer composite materials for the solid-state electrolyte. The architectures of the printed EES devices and their performances are analyzed. Three 3D printing techniques, namely direct ink writing, fused deposition modeling, and stereolithography are reviewed. The 3D printing techniques have enabled the EES devices to be fabricated into novel lightweight, flexible, and wearable constructions. The development of printable materials, together with the production efficiency of current main 3D printing techniques are discussed. Lastly, the challenges and outlooks for future 3D printing of EES devices are outlined.

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.

Next-generation devices and systems require the development and integration of advanced materials, the realization of which inevitably requires two separate processes: property engineering and patterning. Here, we report a one-step, ink-lithography technique to pattern and engineer the properties of thin films of colloidal nanocrystals that exploits their chemically addressable surface. Colloidal nanocrystals are deposited by solution-based methods to form thin films and a local chemical treatment is applied using an ink-printing technique to simultaneously modify (i) the chemical nature of the nanocrystal surface to allow thin-film patterning and (ii) the physical electronic, optical, thermal, and mechanical properties of the nanocrystal thin films. The ink-lithography technique is applied to the library of colloidal nanocrystals to engineer thin films of metals, semiconductors, and insulators on both rigid and flexible substrates and demonstrate their application in high-resolution image replications, anticounterfeit devices, multicolor filters, thin-film transistors and circuits, photoconductors, and wearable multisensors.

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.

Although there has been extensive development and exploration of small-scale robots, the technological challenges associated with their complicated and high-cost fabrication processes remain unresolved. Here, we report a one-step, bi-material, high-resolution three-dimensional (3D) printing method for the fabrication of multi-stimuli-responsive microactuators. This method exploits a two-phase femtoliter ink meniscus formed on a double-barreled theta micropipette to continuously print a freestanding bilayer microstructure, which undergoes an asymmetric volume change upon the adsorption or desorption of water. We show that the 3D-printed bilayer microstructures exhibit reversible, reproducible actuation in ambient humidity or under illumination with infrared light. Our 3D printing approach can assemble bilayer segments for programming microscale actuation, as demonstrated by proof-of-concept experiments. We expect that this method will serve as the basis for flexible, programmable, one-step routes for the assembly of small-scale intelligent actuators.

In conventional direct ink writing (DIW) process, low-viscosity liquids are usually nonprintable, which greatly limits the choices of inks and the potential applications of DIW. To address this challenge, the present work reports a novel electric-field-assisted method to enable DIW of low-viscosity liquids. An external electric field is applied between the dispensing nozzle and the substrate, to vertically pull the printed filament for decreasing the internal pressure along the printing direction. Our proposed method overcomes the common capillary instability characteristic of continuous extrusion of low-viscosity materials. Compared with conventional approaches, the electric-field-assisted DIW process significantly widens the available range of process parameters, increases the throughput by over 150%, and improves the printing accuracy by more than four-fold. These findings indicate an innovative approach for the fabrication of next-generation functional devices using low-viscosity liquids, which used to be difficult or even impossible to print.

Direct-ink-writing type additive manufacturing with water-based inks such as hydrogels or polymer solutions is broadly utilized for bioprinting applications. However, the resolution of this implementation is limited due to the rapid ink drying experienced at small size scales leading to nozzle clogging and low fidelity prints. To address this issue, a humidity-controlled direct-ink-writing (HCDIW) approach is presented, where the microenvironment around the printing nozzle is controlled through introduction of aerosolized water. Using this approach, the nozzle microenvironment can be varied between undersaturated yet high relative humidity (ambient to 100% RH) to oversaturated conditions where condensing droplets are deposited on the already printed ink filaments. The influence of the aerosolized water and the resultant micro-environment on the printing process was studied using water dissolved sodium carboxymethyl cellulose (NaCMC) ink, specifically focusing on nozzle clogging, printed filament geometry, surface quality and layer by layer stacking. These studies showed that the ink drying induced nozzle clogging issues can be mitigated through increased relative humidity at the nozzle exit and is virtually eliminated for ~100 μm nozzles in oversaturated conditions. The decelerated ink drying under the effect of aerosolized water leads to reduced solute advection and skin formation. This in turn improves surface roughness while reducing adverse effects such as coffee-ring and void formation during additive manufacturing of micro-scale structures. Furthermore, layer-to-layer fusion and associated side-surface quality were improved specifically in undersaturated conditions. Reduction of deposited ink filament concentration in oversaturated conditions leads to excessive spreading of the deposited inks leading to geometric distortions. These results indicate that the humidity control approach can significantly improve the resolution of the direct-ink-writing approaches, enabling processing of water-based inks at micro-scales.

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.

Gelatin-based inks have a broad range of applications in bioprinting for tissue engineering and regenerative medicine due to their biocompatibility, ease of modification, degradability, and rapid gelation induced by low temperature. However, gelatin-derived inks prepared through low-temperature treatment have poor mechanical properties that limit their applications. To solve this problem, we designed polyacrylamide/gelatin/silver nanoparticle (PAAm-GelatinAgNPs) ink to improve gelatin-based hydrogels. The ink is based on double networks, in which the physically cross-linked gelatin as the first network and covalently cross-linked PAAm as the second network. It was found that the presence of PAAm increased the tensile and compression strength of the gelatin-based ink. Moreover, silver nanoparticles endowed the antibacterial properties to the gelatin-based ink and were able to shield the UV irradiation and damages to rat skin. In addition, this ink showed the shear thinning property; Consequently it succeeded in printing complex 3D scaffolds such as the cube, five-pointed star, flower, and university logo of "SEU". In summary, this ink presents a new strategy for the modification of gelatin and offers new potential applications for customized therapy of antimicrobial and anti-UV damage to tissues.

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.