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The growing demand for efficient energy storage systems, particularly in portable electronics and electric vehicles, has led to increased interest in supercapacitors, which offer high power density, rapid charge/discharge rates, and long cycle life. However, improving their energy density without compromising performance remains a challenge. In this study, we developed novel 3D-printed reduced graphene oxide (rGO) electrodes coated with polyaniline (PANI) to enhance their electrochemical properties. The rGO 3D-printed electrodes were fabricated using direct ink writing (DIW), which allowed precise control over thickness, ranging from 4 to 24 layers. A unique ink formulation was optimized for the printing process, consisting of rGO, cellulose acetate (CA) as a binder, and acetone as a solvent. The PANI coating was applied via chemical oxidative polymerization (COP) with up to five deposition cycles. Electrochemical testing, including cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS), revealed that 12-layer electrodes with three PANI deposition cycles achieved the highest areal capacitance of 84.32 mF/cm2. While thicker electrodes (16 layers and beyond) experienced diminished performance due to ion diffusion limitations, the composite electrodes demonstrated excellent cycling stability, retaining over 80% of their initial capacitance after 1500 cycles. This work demonstrates the potential of 3D-printed PANI/rGO electrodes for scalable, high-performance supercapacitors with customizable architectures. [ABSTRACT FROM AUTHOR]

This research aims to use energy harvested from conductive materials to power microelectronic components. The proposed method involves using vibration-based energy harvesting to increase the natural vibration frequency, reduce the need for battery replacement, and minimise chemical waste. Piezoelectric transduction, known for its high-power density and ease of application, has garnered significant attention. Additionally, graphene, a non-piezoelectric material, exhibits good piezoelectric properties. The research explores a novel method of printing graphene material using 3D printing, specifically Direct Ink Writing (DIW) and fused deposition modelling (FDM). Both simulation and experimental techniques were used to analyse energy harvesting. The experimental technique involved using the cantilever beam-based vibration energy harvesting method. The results showed that the DIW-derived 3D-printed prototype achieved a peak power output of 12.2 µW, surpassing the 6.4 µW output of the FDM-derived 3D-printed prototype. Furthermore, the simulation using COMSOL Multiphysics yielded a harvested output of 0.69 µV. [ABSTRACT FROM AUTHOR]

Progressing towards a sustainable energy model, safer new generation high-performance energy storage devices with large energy density and power are needed. In this sense, the improvement in terms of efficiency and sustainability has led to the interest in solid-state batteries (SSBs). Lately, sodium-ion batteries (SIBs) have become an emerging alternative due to the abundance of raw materials, low cost, and improvements in terms of fast sodium-ion conductor solid electrolytes (SCSEs). Among all the SCSEs, the sodium superionic conductor (NASICON) type electrolyte is one of the most well-known electrolytes, being widely developed in terms of synthesis and materials. However, the processing and manufacturing of these electrolytes have gone almost unnoticed, without considering that well-designed structures of electrodes/electrolytes are the bridge toward turning advanced energy materials into high-performance devices. This work presents the fabrication of 3D complex structures based on NASICON sodium solid electrolytes, obtained for the first time by direct ink writing (DIW). Through a colloidal route, fine NASICON phase powder with high pureness was prepared, enabling the manufacturing of intricate NASICON-printed electrolytes in a one-step fabrication process. By optimizing the ink, a dense electrolyte layer, acting as an ionic conductor and separator, was inserted between two complex porous pattern layers obtaining a device with a total height below 1.15 mm. Further, the densification of the 3D electrolyte was enhanced, reaching high ionic conductivities at room temperature (3.10−4 S cm−1). Thus, a high-performance sodium ion conductor NASICON solid electrolyte with shorter diffusion pathways and larger interfacial surface areas between electrode/electrolyte was obtained, improving the overall electrochemical performance of the device by a 3D layer-by-layer design.

The direct ink writing (DIW) technique utilizing a single-screw mixing exhibits the capability of fabricating functionally graded materials (FGMs) featuring continuous gradients. Nevertheless, the vast array of parameters involved in the printing process and the absence of standard values and suitable matching relationships between individual parameters are factors that negatively impact print quality. This, in turn, hampers the potential application of FGMs across a multitude of fields. Thus, the primary objective of this study was to devise a process parameter model that can facilitate the setup of additional control parameters. To this end, the parametric model was constructed on the basis of the correlation between volumetric flow and pressure in each zone, and took into consideration all structural parameters of the prototype and material property parameters. Moreover, the digital image processing was employed to analyze and compare the printing results of FGM samples fabricated using different screw speeds across three groups. The analysis revealed that for stacking quality, deviations from the optimal screw speed resulted in understacking or overstacking. Furthermore, unsuitable screw speeds led to inconsistencies between the printed material information and the expected results. [ABSTRACT FROM AUTHOR]

We offer the possibility of implementing a lab-made extruder for direct ink writing (DIW) into a conventional fused deposition modelling (FDM) 3D printer. The ink extruder was designed to comply with various requirements including the possibility of using multiple syringe volumes, ease of assembly, compatibility with numerous commercial FDM printers, ink retraction and ink flow control and the ability to extrude inks with a wide range of viscosities (ink yield stresses from 135 to 1100 Pa). The load in the extruder was attained by combining a stepper motor and a gear reduction system. The reduction system was connected to a trapezoidal threaded spindle through a rigid coupler. The movement of the spindle was transmitted to the plunger of a syringe that contained the ink (with volumes ranging from 3 to 30 mL), by means of a linear guide system. Most of the extruder parts were printed with the same FDM printer to which the DIW extruder ended attached to. The DIW extruder wiring connections were simply made by using the E-axis connectors available in the FDM printer. Modifications of the FDM printer software required for the correct control of the DIW extruder were also relatively simple, avoiding firmware modification. This simplicity made the two DIW and FDM heads easily interchangeable, thus amplifying the functionality of a conventional FDM printer. The cost of this new DIW extruder is approx. 100€. [ABSTRACT FROM AUTHOR]

Embedded sensors (ESs) are used in smart materials to enable continuous and permanent measurements of their structural integrity, while sensing technology involves developing sensors, sensory systems, or smart materials that monitor a wide range of properties of materials. Incorporating 3D-printed sensors into hosting structures has grown in popularity because of improved assembly processes, reduced system complexity, and lower fabrication costs. 3D-printed sensors can be embedded into structures and attached to surfaces through two methods: attaching to surfaces or embedding in 3D-printed sensors. We discussed various additive manufacturing techniques for fabricating sensors in this review. We also discussed the many strategies for manufacturing sensors using additive manufacturing, as well as how sensors are integrated into the manufacturing process. The review also explained the fundamental mechanisms used in sensors and their applications. The study demonstrated that embedded 3D printing sensors facilitate the development of additive sensor materials for smart goods and the Internet of Things. [ABSTRACT FROM AUTHOR]

Boron/potassium nitrate (B/KNO3) is a type of critical energetic composite material (ECM). However, the inert oxide layer on the B surface of B/KNO3 hinders the contact between pure fuel and oxidant, thus limiting energy release This limitation could be eliminated by adding highly reactive Al powder. To discern the effects of Al powder size on the reaction process and reactivity of B/KNO3, this study prepared Al/B/KNO3/polyvinylidene fluoride (PVDF) energetic sticks using the direct ink writing (DIW) technology. This study characterized the macroscopic morphology and structure of the energetic sticks using a laser scanning microscope and a scanning electron microscope, examined the reaction process of the composites using a differential scanning calorimeter and a thermogravimetric analyzer, and observed the flame propagation behavior of energetic sticks and energetic architectures using a high-speed camera. Furthermore, it tested the pressure output characteristics of the energetic composites using a closed volume tank. The results show that adding Al powder can improve the combustion efficiency of B/Al composite fuels and reduce the agglomeration of the combustion products. The Al powder with various particle sizes affects various reaction stages of the composite. The combustion and pressure output tests suggest that adding Al powder with a particle size of 1 μm yielded high reactivity and that flame jump propagation appeared in energetic architectures when the channel spacing was below 10 mm. These findings provide a guide for modifying the B/KNO3 energetic composites and regulating the reactivity of energetic sticks.

Boron/potassium nitrate (B/KNO3) is a type of critical energetic composite material (ECM). However, the inert oxide layer on the B surface of B/KNO3 hinders the contact between pure fuel and oxidant, thus limiting energy release This limitation could be eliminated by adding highly reactive Al powder. To discern the effects of Al powder size on the reaction process and reactivity of B/KNO3, this study prepared Al/B/KNO3/polyvinylidene fluoride (PVDF) energetic sticks using the direct ink writing (DIW) technology. This study characterized the macroscopic morphology and structure of the energetic sticks using a laser scanning microscope and a scanning electron microscope, examined the reaction process of the composites using a differential scanning calorimeter and a thermogravimetric analyzer, and observed the flame propagation behavior of energetic sticks and energetic architectures using a high-speed camera. Furthermore, it tested the pressure output characteristics of the energetic composites using a closed volume tank. The results show that adding Al powder can improve the combustion efficiency of B/Al composite fuels and reduce the agglomeration of the combustion products. The Al powder with various particle sizes affects various reaction stages of the composite. The combustion and pressure output tests suggest that adding Al powder with a particle size of 1 µm yielded high reactivity and that flame jump propagation appeared in energetic architectures when the channel spacing was below 10 mm. These findings provide a guide for modifying the B/KNO3 energetic composites and regulating the reactivity of energetic sticks. [ABSTRACT FROM AUTHOR]

Additive manufactured bimetallic structures provide site-specific functions by joining two metallic materials in the designed area, offering customized solutions for biomedical and engineering applications. However, cracking, delamination, or cross-contamination frequently occurs at the joint between two dissimilar metallic materials due to their different thermal properties. In the paper, porous bimetallic structures made of biomedical materials (Fe, Ti6Al4V, and Inconel 718) for bone implants are fabricated via direct ink writing (DIW) with a dual syringe system. After subsequent heat treatment, the original shapes of the bimetallic structures are well-preserved, and the shrinkages of the two materials are equalized by adjusting the sintering temperature. All joints are free of cracks and delamination, and the material deposition sequence has no impact on them, according to microstructural analyses of the interface. The pores created by binder pyrolysis and metallic powder sintering are necessary for bone growth, cell migration, body fluid flow, etc. The Fe–Ti6Al4V and Fe-Inconel 718 bimetallic structures have better mechanical properties than the Fe structures and can perform multiple functions that are challenging for monometallic implants.

In this study, a novel hydrogel ink made from gelatin and tragacanth gum was prepared. Two additives and a crosslinking agent were added to improve the viscoelastic properties of the material during gelation and its printability. Alginic acid was introduced as a crosslinking agent along with additives such as rice starch and halloysite nanotubes (HNT). Two rheological measurement modes, rotational and oscillatory, were utilized to measure the steady state viscosity and complex moduli, respectively. Auxiliary measurements such as Fourier‐transform spectroscopy infrared and gel permeation chromatography were implemented to determine the bonds formed and the molecular weight of gelatin and tragacanth gum, respectively. We have demonstrated how these additives can affect fluid uptake by examining them in water at ambient temperature and also in 1× PBS at both ambient and normal body temperatures. The printability was analyzed by the grid pattern dispensed by interconnected filaments. It was observed that the sample containing HNT and rice starch show the best properties. The hydrogel nanocomposite, unlike the pure gelatin films, retains water and buffer solution for 72 h with minimum changes. Moreover, the printability criterion (Pr) was improved from 0.3 for pure gelatin to about 1 for the sample containing alginate, HNT, and rice starch. [ABSTRACT FROM AUTHOR]

This study investigated a new colloidal ink, containing Laponite® nanoclay as additive, to develop ZrO 2 -based ceramic prototypes by Direct Ink Writing (DIW). The ink developed contained 31 vol% 3Y-TZP as solid load and 69% v/v of gel containing 7.5% (w/w) Laponite®, polyethylene glycol (PEG), and dibutyl phthalate. The rheologyical behavior of this ceramic ink was analyzed and its extrudability was optimized. The samples were DIW 3D-printed at a speed of 10 mm/s with nozzle diameter of 0.41 mm. After drying for 24 h, the zirconia samples underwent debinding and were pre-sintered at 1100 °C under a heating rate of 1 °C/min. After pre-sintering, the samples were sintered at 1550 °C for 2 h. Subsequently, the sintered samples were characterized by Scanning Electron Microscopy and X-ray diffractometry. Fracture toughness was measured by Vickers indentation, whereas nano-hardness and Young's modulus were assessed by dynamic Vickers nanoindentation (250–1960 mN loads). A relative density of 89.3 ± 0.5% was found. The following crystalline phases were observed: monoclinic-ZrO 2 (34%), tetragonal-ZrO 2 (31%), and cubic-ZrO 2 (35%). This behavior is probably due to the segregation of Y+3 between the zirconia grains, favored by the presence of Laponite® nanoclay during the sintering process. The microstructure of the prototypes showed two distinct populations of ZrO 2 grains with average particle sizes of 1 μm (monoclinic and tetragonal phases) and >5 μm (cubic phase). Vickers hardness (HV 1000gF) was 952 ± 40 HV and fracture toughness was 4.6 ± 1.1 MPa m1/2. A Young's modulus of ∼200 GPa and hardness values of 1837.9 and 1943.3 HV were found for loads of 250 and 1960 mN, respectively. [ABSTRACT FROM AUTHOR]

In order to solve the short stabilization time of the water‐in‐oil emulsion binder system and the shortcomings of the critical blast size of the explosive ink molding sample, a water‐in‐oil emulsion binder was designed with polyvinyl alcohol (PVA) aqueous solution as the aqueous phase, fluorocarbon resin (FEVE) ethyl acetate solution as the oil phase, and toluene diisocyanate (TDI) added to modify the water‐in‐oil emulsion binder. The hexanitrohexaazaisowurtzitane(CL‐20)based explosive ink was made by incorporating submicron CL‐20 into the binder system, and the print‐formed samples were tested for microscopic morphology, crystallographic analysis, mechanical susceptibility, and detonation transmission performance. The results showed that the explosive ink's viscosity was moderate and suitable for direct printing, and the formed sample's surface particles were uniformly dispersed and had a honeycomb structure. The crystal form of CL‐20 explosive in the explosive ink did not change, the molded sample's impact and frictional sensitivities were 1 J and 32 N lower than those of submicron CL‐20, respectively, and the detonation velocity of the molded sample was 6655 m/s. The critical detonation size and critical detonation thickness were 1×0.0078 mm and 0.1 mm, respectively, and a critical detonation corner turning of 90°–160° could be achieved. The results show that the prepared binder system is stable for a long time, and the explosive ink molding samples have excellent blast transmission performance. [ABSTRACT FROM AUTHOR]

The direct ink writing (DIW) technology of slurry is a 3D printing technology based on slurry extrusion. It has the advantages of low energy consumption, low cost, fast printing speed and no structural design restrictions. On the basis of summarizing the advantages of the application of DIW technology to ceramic-based diamond tools, key steps in the application process, such as the raw material selection, the slurry preparation, the printing suitability, the degreasing and the sintering process, are discussed and the powder agglomeration problem that needs to be given attention to in the slurry preparation process is pointed out. At the same time, some research examples of DIW manufacturing process are analyzed. Finally, it points out the key problems that should be solved in DIW manufacturing ceramic-based diamond tools.

An exhaustive and integrative overview of recent developments in 3D and 4D textiles based on Additive Manufacturing (AM) were provided in order to identify the current state‐of‐the‐art. Despite all scientific progress, AM applied on textiles is a challenging technique and is still at an embryonic stage of research and technological development (R&TD), mainly due to the technological gap between featured prototypes and scalability in manufacturing. Despite its full potential across a range of different applications, such as development of functional filament fibres/wires, 3D printing on textiles, 3D printing completed garments and 4D textiles, needs future developments. Although, AM applied on textiles, enables cost and resource efficiency for small scale production through localised production, shorten supply chain and demand driven manufacture, both customisable and scalable, embracing cost and environmental sustainability. The opportunities and limits of 3D and 4D printing textiles are also discussed. Finally, the conclusion highlights the potential future development and application of the convergence of advanced computational design techniques, product customization, mathematical modelling, simulation, and digital modelling within multifunctional textiles. [ABSTRACT FROM AUTHOR]

Reticulated åkermanite (Ca2MgSi2O7) 3D scaffolds were fabricated by direct ink writing of pastes based on a commercial silicone resin and fillers, such as calcium carbonate (CaCO3) and magnesium hydroxide (Mg(OH)2) microparticles, followed by heat treatment at 1100 °C in air. To form liquid phase upon firing and thus promote the ionic interdiffusion, borax (Na2B4O7·10H2O) or hydrated sodium phosphate (Na2HPO4·12H2O) were considered as alternative additives. Although leading to scaffolds with different strength-to-density ratio, the two additives did not lead to substantial differences in terms of biological response. All fabricated ceramics exhibited acellular in-vitro bioactivity upon immersion in simulated-body-fluid (SBF) as well as antibacterial activity against S. aureus and E. coli. Direct contact cell viability test, performed with a stromal-cell line from mouse bone marrow (ST-2 cells), indicated no cytotoxicity of both samples determined by the WST-8 assay.

Significant advances have been made in recent years in the materials development of liquid-based 4D printing. Nevertheless, employing additive materials such as nanoparticles for enhancing printability and shape memory characteristics is still challenging. Herein, we provide an overview of recent developments in liquid-based 4D printing and highlights of novel 4D-printable polymeric resins and their nanocomposite components. Recent advances in additive manufacturing technologies that utilise liquid resins, such as stereolithography, digital light processing, material jetting and direct ink writing, are considered in this review. The effects of nanoparticle inclusion within liquid-based resins on the shape memory and mechanical characteristics of 3D-printed nanocomposite components are comprehensively discussed. Employing various filler-modified mixture resins, such as nanosilica, nanoclay and nanographene, as well as fibrous materials to support various properties of 3D printing components is considered. Overall, this review paper provides an outline of liquid-based 4D-printed nanocomposites in terms of cutting-edge research, including shape memory and mechanical properties. [ABSTRACT FROM AUTHOR]

The in situ strain/stress detection of hot components in harsh environments remains a challenging task. In this study, graphene/SiCN (G-SiCN) thin-film strain gauges (TFSGs) were fabricated on alumina substrates by direct ink writing (DIW). The percolation model and the piezoresistive effect of G-SiCN composites were systematically studied. On this basis, a TFSG with high conductivity (0.1 S/cm) and high sensitivity (gauge factor (GF) 9.9) of ceramic matrix conductive composites was fabricated. The graphene/SiCN TFSG has excellent static and dynamic strain response at room temperature. Subsequently, the strain dynamic test was conducted at 400 °C, and there was no attenuation of the GF, so as to verify the high-temperature performance of the G-SiCN TFSG. Therefore, G-SiCN TFSGs provide an effective approach for the measurement of the in situ static and dynamic strain of hot components in high-temperature environments. [ABSTRACT FROM AUTHOR]

Over the past ten years, the use of additive manufacturing techniques, also known as "3D printing", has steadily increased in a variety of scientific fields. There are a number of inherent advantages to these fabrication methods over conventional manufacturing due to the way that they work, which is based on the layer-by-layer material-deposition principle. These benefits include the accurate attribution of complex, pre-designed shapes, as well as the use of a variety of innovative raw materials. Its main advantage is the ability to fabricate custom shapes with an interior lattice network connecting them and a porous surface that traditional manufacturing techniques cannot adequately attribute. Such structures are being used for direct implantation into the human body in the biomedical field in areas such as bio-printing, where this potential is being heavily utilized. The fabricated items must be made of biomaterials with the proper mechanical properties, as well as biomaterials that exhibit characteristics such as biocompatibility, bioresorbability, and biodegradability, in order to meet the strict requirements that such procedures impose. The most significant biomaterials used in these techniques are listed in this work, but their advantages and disadvantages are also discussed in relation to the aforementioned properties that are crucial to their use. [ABSTRACT FROM AUTHOR]

In-situ strain detection of complex structures at high temperatures remains a challenging task. In this article, the feasibility and performance of silver-palladium (AgPd) high-temperature thin-film strain gauge (TFSG) fabricated by direct ink writing (DIW) based on the Weissenberg effect is investigated, providing an in-situ strain detection method for structures working at high temperatures. The micrometer-thick AgPd film was directly written on a planar alumina substrate, and its surface topography and electrical were characterized. The four-wire resistance measurement method was adopted to eliminate the wire resistance and the contact resistance at the solder joint, thereby improving the accuracy of detection. The strain test at room temperature showed that the gauge factor (GF) of AgPd TFSGs under both tension and compression was about 1.25. They also possessed excellent linearity (${R}$ 2 = 0.998), good static and dynamic responses, and extremely low mechanical hysteresis. To verify the high-temperature performance of the AgPd TFSG, the strain dynamic test was carried out at 600 °C. And there was no severe attenuation of the GF. AgPd TFSG fabricated by DIW provides an efficient method for in-situ static and dynamic strain detection of complex structures at high temperatures. [ABSTRACT FROM AUTHOR]

The main goal of this work was to obtain dense Al2O3–Y3Al5O12 ceramic composites by reactive sintering of three-dimensional samples, built by direct ink writing from a paste containing a mixture of Al2O3 and Y2O3 powders. To obtain a ceramic ink with proper rheological properties for extrusion-based printing, highly pure Al2O3 and Y2O3 powders in a percentage–weight ratio of 64:36 was mixed with 0.2 wt% MgO in a total solid loading of 42 vol% in aqueous media, adding carboxymethyl cellulose and polyethyleneimine solution as additives. The dried printed samples were sintered at final temperatures in the range of 1550 °C and 1650 °C; thus, relative densities of 83.7 ± 0.8%, 95.4 ± 0.4%, and 96.5 ± 0.5% were obtained for 1550 °C, 1600 °C, and 1650 °C, respectively. Rietveld refinement performed on the X-ray diffraction patterns indicated the presence of Al2O3 (42 to 47%) and Y3Al15O12 (58 to 61%) as crystalline phases, while micrographs showed the presence of equiaxial micrometric grains with average sizes of 1.8 ± 0.6 μm, for both phases and all sintering conditions. Samples sintered at 1600 °C and 1650 °C presented similar average Vickers hardness values of 14.2 ± 0.27 GPa and 14.5 ± 0.25 GPa, respectively. A slight increase in fracture toughness as sintering temperature increases was also stated, consistent with the densification.

The porosity and degradation rate are critical properties of biodegradable bone implants, as they facilitate the regeneration of bone tissues and ensure a gradual load transfer. Herein, porous iron-hydroxyapatite (Fe-HA) metal-matrix composites (MMCs) with independently adjustable porosity and degradation rate are fabricated through a 3D printing technique, i.e., direct ink writing (DIW). HA micro powders exhibit a significant acceleration effect on the degradation rate, which act as a variable that is independent of the porosity to regulate the degradation rate. The mass losses of Fe-HA MMCs with the porosities of 30%, 50%, and 70% after 21d in-vitro immersion increased by 26%, 38%, and 93%, respectively, with the rising of HA content from 0 to 7.5 wt%. The novel porous Fe-HA MMCs have an adjustable and wide porosity-degradation rate range, yielding great potential to match with varied porosity and regeneration rate among various bones of different people.

Multilayer circuits, especially in stretchable electronic devices, are considered to be an effective way to integrate various components and modules for complex functions. However, the existing manufacturing methods for multilayer flexible and stretchable electronics have problems such as complex technology, expensive equipment, and low production efficiency. Here, a direct ink writing 3D printing method is proposed to fabricate multilayer stretchable electronic devices by using high‐viscosity stretchable silver paste as the material for interconnecting wires, and stretchable polydimethylsiloxane as the dielectric layer. The optimal range of printing parameters is explored to realize the stable and repeatable manufacturing of wires. A protective layer is printed on the interconnection wires and rigid components to connect the soft substrate and the rigid electronic components. The results show that stress concentration is reduced and stable electrical response of the device is achieved under more than 49% tensile deformation. Vertical interconnect accesses and arc‐shaped wires are applied to a multilayer flexible thermal imaging display device and a NE555 timer device, and the outcomes prove that the direct ink writing 3D printing method provides an efficient, simple, and low‐cost manufacturing method for fabricating multilayer stretchable electronics. [ABSTRACT FROM AUTHOR]

A new explosive ink based on 2,6‐diamino‐3,5‐dinitropyrazine‐1‐oxide (LLM‐105) was designed and prepared. The explosive ink was deposited into micro‐size grooves by using direct ink writing (DIW) technology and its detonation properties in an explosive network were explored. The properties of impact sensitivity, detonation velocity and critical size of detonation were determined and analyzed. The results show that this explosive has a good impact safety. When the LLM‐105 content is 88 % and the density is 95 % TMD, the detonation velocity and critical size of detonation values are 7,771 m/s and 0.5×0.5 mm respectively. Moreover detonation velocity results indicated the explosive ink in micro‐size grooves loaded by DIW was uniform. [ABSTRACT FROM AUTHOR]

A significant challenge in the photocatalysis field is getting self-supporting three-dimensional (3D)-printable photocatalysts that preserve their photocatalytic activity. Herein, we disclose reusable 3D-printable photocatalysts based on binder-free TiO2 nanoparticles (3DM-TiO2) under an eco-friendly, affordable, and reliable methodology for the first time. Strong and mechanically stable 3DM-TiO2 structures (compression strength = 16 MPa) were obtained under soft sintered conditions (∼400 °C), exhibiting an anatase/rutile ratio of 85/15% by the Rietveld refinement, a mesoporous structure with a surface area (SBET) of 45.2 m2/g, and outstanding photocatalytic activity. 3DM-TiO2 successfully demonstrated high recyclability and adaptability in the dust-free photodegradation experiments of emerging contaminants in the liquid phase (triclosan, TCS) and gas phase (liquefied petroleum gas, LPG). A TCS mineralization of ∼95% was obtained at 6 h of photodegradation. The reusability from the 3DM-TiO2 was assessed during 12 cycles of TCS degradation, recovering its photocatalytic activity by 100% after reactivation at 400 °C. In the gas phase, the maximum conversion of LPG to CO2 was 95.3% for n-butane, 93.7% for isobutane, and 52.9% for propane after 15 h of photodegradation. All photodegradation experiments were fitted to the Langmuir–Hinshelwood kinetic model. We believe that the technology proposed here could trigger applications of nanomaterial-based photocatalysts, replacing the powdered materials to achieve new reactor designs and process configurations on a large scale. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new mechanical isolation design of pressure/shear sensor is proposed for direct multi-directional stimuli recognition. • The new tactile sensor system with island-bridge-form sensing units is verified by object manipulation and motion detection. • The new sensor array layout with scalable and adaptable circuit design is suitable for large-area smart applications. Multiple mechanical stimuli recognition ability with direction discrimination function is of importance for a tactile sensor. However, typical multi-directional tactile sensor needs complex analysis to classify ambiguous output signals because of the nonspecific response. Besides, conventional sensor array layout with separate output ports for each sensor unit limits the integration and adaptability of the sensor system. This work proposes a novel sensor array configuration with island-bridge-form sensing units to isolate pressure and shear loading. Meanwhile, the reasonable integration scheme with specially-designed circuit effectively reduces the total output ports and data acquisition cost, capable of scaling up the sensor array according to application scenarios easily. A series of experiments and analysis from the characterization of sensing units to real-time recording of multiple mechanical stimuli are conducted, showing the independent, timely and high-sensitivity response of the tactile sensor array, exhibiting the application potential in human–machine interaction, wearable electronics and soft robotics. [ABSTRACT FROM AUTHOR]

Traditional film initiator fabrication techniques were limited by material and process constraints, resulting in restricted ignition capability, durability issues, and complexity in manufacturing. In this study, Metal/polymer composite materials were applied in film initiators in order to enhance the mechanical properties, longevity, and thermal attributes. Silver/polyvinylpyrrolidone composite film bridge (SPB) initiators were fabricated by direct ink writing (DIW). By adjusting the silver loading level and sintering temperature in the Ag nanoparticles/polyvinylpyrrolidone (Ag NPs/PVP) ink formulation, precise control over the structure and resistivity of the SPB was achieved. Compared to single silver film bridge (SFB) initiators prepared by magnetron sputtering (MS), SPBs demonstrated superior heating performance, higher current carrying capacity, and energy utilization under constant current excitation. In capacitor discharge tests, SPBs exhibited superior electric explosion characteristics and plasma properties, with a 25.53 % higher energy utilization efficiency compared to SFBs. The peak plasma electron temperature of SPBs reached 7610 K, which was 1065 K higher than that of SFBs. This makes Silver/polyvinylpyrrolidone composite highly promising practical alternatives for high-efficiency, stable, and reliable ignition processes, with potential widespread applications in the aerospace field. [Display omitted] • Silver/polyvinylpyrrolidone film bridge (SPB) and single film bridge (SFB) initiators were fabricated. • The performance of SPBs can be enhanced by adjusting the sintering temperature and silver loading. • SPBs have remarkable advantages in heating capabilities electrical explosive characteristics, and plasma properties compare to SFBs. [ABSTRACT FROM AUTHOR]

Rheological modifiers enable direct ink writing of polymers with low viscosity such as epoxy without requiring light or heat. Modifiers that conduct electrons and phonons impart multifunctional properties to 3D printed polymers. Here, we report the development of printable nanocomposite inks comprised of epoxy, carbon fibers (CFs), and carbon nanotubes (CNTs) to achieve excellent mechanical properties and multifunctionality via high electrical conductivity required for next-generation light weight aerospace, electronics, and energy applications. CF and CNT concentrations of 8.5 and 1.7 wt%, respectively, render the material shear-thinning with a high yield stress, hence printable and self-supporting after being printed. An average electrical conductivity of 10−2 S/cm and thermal conductivity of 0.3 W/m.K were measured for the 3D-printed multi-layer structures. Furthermore, tensile modulus, tensile strength, flexural modulus, and flexural strength were measured to be 5.8, 0.08, 6.0, and 0.1 GPa, respectively. Compared with other 3D printed conductive polymer nanocomposites with reported electrical conductivity and elastic modulus, the structures here have the highest specific elastic modulus. They also possess the highest electrical conductivity among the 3D printed polymeric composites of carbon nanomaterials with an elastic modulus above 1 GPa. This is due to the outstanding combination of CNTs, CFs, and epoxy. The results expand the range of polymer properties for multifunctional applications. [ABSTRACT FROM AUTHOR]

The main goal of this work was to obtain dense Al2O3–Y3Al5O12 ceramic composites by reactive sintering of three-dimensional samples, built by direct ink writing from a paste containing a mixture of Al2O3 and Y2O3 powders. To obtain a ceramic ink with proper rheological properties for extrusion-based printing, highly pure Al2O3 and Y2O3 powders in a percentage–weight ratio of 64:36 was mixed with 0.2 wt% MgO in a total solid loading of 42 vol% in aqueous media, adding carboxymethyl cellulose and polyethyleneimine solution as additives. The dried printed samples were sintered at final temperatures in the range of 1550 °C and 1650 °C; thus, relative densities of 83.7 ± 0.8%, 95.4 ± 0.4%, and 96.5 ± 0.5% were obtained for 1550 °C, 1600 °C, and 1650 °C, respectively. Rietveld refinement performed on the X-ray diffraction patterns indicated the presence of Al2O3 (42 to 47%) and Y3Al15O12 (58 to 61%) as crystalline phases, while micrographs showed the presence of equiaxial micrometric grains with average sizes of 1.8 ± 0.6 μm, for both phases and all sintering conditions. Samples sintered at 1600 °C and 1650 °C presented similar average Vickers hardness values of 14.2 ± 0.27 GPa and 14.5 ± 0.25 GPa, respectively. A slight increase in fracture toughness as sintering temperature increases was also stated, consistent with the densification. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) and multiwalled carbon nanotubes (MWCNTs) have been extensively investigated in recent decades as electrical double-layer capacitor (EDLC) electrode materials for supercapacitors, owing to their superior capacitive properties and cycling stability performance. However, in the modern electronics industry, ternary electrode materials have been designed to develop high-performance and efficient energy storage devices. EDLC-based ternary materials are of great importance, where all the present components participate both individually and as a multicomponent electrode system to promote high-electrochemical performance electrode materials. In this study, we have incorporated an optimized content of boron nitride nanotube (BNNT) powder into a binary material composed of AC and MWCNTs to enhance their electrochemical performance using a pneumatic printer. The printed MWCNTs/AC/BNNTs ternary composite electrode material has shown a maximum specific capacitance of 262 F g−1 at a minimum current density of 1 A g−1, with a capacitance retention of 49.61% at a maximum current density of 10 A g−1. These results demonstrate that the printable MWCNTs/AC/BNNTs ternary composite electrode material is a potential candidate for the development of high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

• Zr/B/KNO 3 energetic sticks were prepared by direct ink writing method. • Zr/KNO 3 greatly improves the reactivity of B/KNO 3 energetic composites. • Energetic powders and energetic sticks differ in energy release behavior. • The burning rate curves of energetic sticks appear platform phenomenon. To enhance the reactivity of B/KNO 3 (BPN) energetic composites and study the energy release behavior of energetic sticks, Zr/KNO 3 (ZPN) was added to the BPN energetic system, and the energetic sticks with different ZPN/BPN ratios and different thicknesses were prepared by direct ink writing (DIW). In addition, the pore-size distribution, thermal decomposition characteristics, combustion characteristics, and pressure release characteristics of the different energetic sticks were studied. Considering this, the flame propagation behavior of the energetic powders and sticks was examined. The results demonstrate that energetic sticks with different ZPN/BPN ratios and thicknesses exhibit a consistent pore-size distribution. With increasing ZPN content, the peak temperature of the condensed phase reaction of the composite decreased from 479.9 °C to 362.1 °C, the reaction enthalpy increased from 879.5 to 3200.4 J·g−1, and the burning rate of the energetic sticks increased from 62.1 to 136.8 mm·s−1, indicating that the addition of ZPN improved the reaction characteristics of the composite. In addition, the reactivity of the energetic sticks can be regulated by adjusting their thickness With the increase of layers, the burning rate of energetic sticks increases from 58.6 mm·s−1 to 113 mm·s−1. The burning rate–time curves of all energetic sticks show different numbers and ranges of platforms. In comparison to energetic powder, energetic sticks exhibit lower pressure release and pressurization rates but a longer reaction time. This study provides valuable insights into the microscale reactivity regulation of BPN energetic composites and their application in microenergy devices. [ABSTRACT FROM AUTHOR]

Abstract There is increasing demand for synthetic bone scaffolds for bone tissue engineering as they can counter issues such as potential harvesting morbidity and restrictions in donor sites which hamper autologous bone grafts and address the potential for disease transmission in the case of allografts. Due to their excellent biocompatibility, titanium scaffolds have great potential as bone graft substitutes as they mimic the structure and properties of human cancellous bone. Here we report on a new thermoset bio-polymer which can act as a binder for Direct Ink Writing (DIW) of titanium artificial bone scaffolds. We demonstrate the use of the binder to manufacture porous titanium scaffolds with evenly distributed and highly interconnected porosity ideal for orthopaedic applications. Due to their porous structure, the scaffolds exhibit an effective Young's modulus similar to human cortical bone, alleviating undesirable stress-shielding effects, and possess superior strength. The biocompatibility of the scaffolds was investigated in vitro by cell viability and proliferation assays using human bone-marrow-derived Mesenchymal stem cells (hMSCs). The hMSCs displayed well-spread morphologies, well-organized F-actin and large vinculin complexes confirming their excellent biocompatibility. The vinculin regions had significantly larger Focal Adhesion (FA) area and equivalent FA numbers compared to that of tissue culture plate controls, showing that the scaffolds support cell viability and promote attachment. In conclusion, we have demonstrated the excellent potential of the thermoset bio-polymer as a Direct Ink Writing ready binder for manufacture of porous titanium scaffolds for hard tissue engineering. Graphical abstract Unlabelled Image Highlights • A thermoset biopolymer is introduced as a binder for Direct Ink Writing of titanium. • Manufactured scaffolds mimic the mechanical performance of cancellous bone. • The scaffolds provide ideal conditions for cells adhesion and proliferation. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) and multiwalled carbon nanotubes (MWCNTs) have been extensively investigated in recent decades as electrical double-layer capacitor (EDLC) electrode materials for supercapacitors, owing to their superior capacitive properties and cycling stability performance. However, in the modern electronics industry, ternary electrode materials have been designed to develop high-performance and efficient energy storage devices. EDLC-based ternary materials are of great importance, where all the present components participate both individually and as a multicomponent electrode system to promote high-electrochemical performance electrode materials. In this study, we have incorporated an optimized content of boron nitride nanotube (BNNT) powder into a binary material composed of AC and MWCNTs to enhance their electrochemical performance using a pneumatic printer. The printed MWCNTs/AC/BNNTs ternary composite electrode material has shown a maximum specific capacitance of 262 F g−1 at a minimum current density of 1 A g−1, with a capacitance retention of 49.61% at a maximum current density of 10 A g−1. These results demonstrate that the printable MWCNTs/AC/BNNTs ternary composite electrode material is a potential candidate for the development of high-performance supercapacitors.

In the present work, direct ink writing (DIW) technology was utilized to fabricate geopolymer-based anisotropic membranes from metakaolin precursors. For evaluation of filtration performance in water treatment, the 3D-printed membranes were characterized, tested systematically, compared with a molded membrane and benchmarked against other geopolymer and ceramic membranes reported in the literature. With a novel approach, geopolymer-yttria stabilized zirconia (YSZ) ultrafiltration (UF) membrane with configuration of relatively dense rejection layer and gradient macroporous support was obtained via a one-step process of alkaline activation, DIW and curing, starting from a computer aided design (CAD) figure of an isotropic solid plate. The achievement of such structure resulted from the printing procedure leveraging both rheological properties of geopolymer ink and printing principle of DIW. The printed membrane displayed very high permeances (1453 L/(m2hbar) for pure water and 1311 L/(m2hbar) for suspension of 80-nm alumina particles), high rejection efficiency (98.4% for suspension of 80-nm alumina particles) and good chemical stability in alkaline solution. The present work provided the first-time report on additive manufacturing of geopolymer-based asymmetric UF membranes with superb performance for water treatment. [Display omitted] • Geopolymer-based membranes with anisotropic structures were fabricated from a process mainly comprising direct ink writing. • Ink rheological property and printing process were leveraged to achieve such configuration. • The produced membrane displayed high permeance and rejection efficiency in water treatment. • The first-time report on 3D printing of geopolymer-based asymmetric membranes was provided in this work. [ABSTRACT FROM AUTHOR]

Direct ink writing (DIW), a promising technology for manufacturing energetic materials, has been a hot topic in the micro‐scale charge of explosives. Herein, three kinds of pentaerythrite tetranitrate (PETN)‐based all‐liquid explosive inks were engineered and patterned using DIW. Scanning electron microscopy, energy‐dispersive x‐ray spectroscopy, X‐ray diffraction, differential scanning calorimetry, and nanoindentation were used to characterize the printed samples. The density, thickness of single layer, impact sensitivity and critical size of detonation were measured and analyzed. Results show that PETN/EC/Viton exhibits excellent properties, specifically greater activation energy (148.09 KJ mol−1), elastic modulus (2.808 GPa), and characteristic height (49.9 cm, 2.5 kg), over the two other samples. Moreover, a directly deposited sample in small grooves can provide steady detonation above the size of 1×0.101 mm. These features all contribute to the application of micro‐size detonation to a certain degree. [ABSTRACT FROM AUTHOR]

Abstract: Direct ink writing (DIW) of energetic materials has been an area of interest for micro size charge. In this work, 3, 4‐dinitrofurazanofuroxan (DNTF) based composite was prepared with nitrocotton (NC) and Viton as binders by DIW. Scanning Electro Microscope (SEM) and X‐ray diffraction were employed to characterize the composite samples. The impact sensitivity and thermal decomposition of the composites were also tested and analyzed. In addition, the critical size of detonation and detonation velocity were measured. The results show that DNTF based composite has a high density with whose value is 1.785 g cm−3, reaching 93.16 % of theoretical maximum density (TMD). The particles in composites are spheroidal with size ranging from 1 to 2 μm. Compared with raw DNTF, the obtained composite has a lower impact sensitivity and higher thermal stability. Moreover, the composites exhibit excellent detonation properties, whose critical size of detonation is around 0.01 mm and the mean detonation velocity is 8580 m s−1 at the charging width of 1 mm. Furthermore, part performances of this composite are contrasted with previous reported CL‐20 based composite and show better characters. [ABSTRACT FROM AUTHOR]

In this research, kaolinite clay from Colombia is employed as a raw material for the additive manufacturing of diverse samples using the Direct Ink Writing (DIW) technique in which a filament of the printing material is extruded from a nozzle. DIW is a simple and inexpensive technology suitable for adaption to large-scale production. Different samples fabricated from clays were manufactured with water to clay ratios (W/C) of between 0.65 and 0.69. Cylinders for compression tests were printed and tested after being cured for one day at room temperature and then exposed to 1100 °C for 1 h. Compression, thermal stability, density tests and Weibull analysis are presented. Scanning electron microscopy images showed no significant macro or micro defects after manufacturing, and x-ray diffraction and Rietveld quantitative analysis revealed different phases. Rheological behavior and several process parameters are also shown. [ABSTRACT FROM AUTHOR]

We introduce a strategy to disintegrate cellulose microfibrils present in the cell walls of plant fibers. The process includes impregnation and mild oxidation followed by ultrasonication, which loosens the hydrophilic planes of crystalline cellulose while preserving the hydrophobic ones. The resultant molecularly-sized cellulose structures (cellulose ribbons, CR) retain a length of the order of a micron (1.47 ± 0.48 μm, AFM). A very high axial aspect ratio is determined (at least 190), considering the CR height (0.62 ± 0.38 nm, AFM), corresponding to 1–2 cellulose chains, and width (7.64 ± 1.82 nm, TEM). The new molecularly-thin cellulose proposes excellent hydrophilicity and flexibility, enabling a remarkable viscosifying effect when dispersed in aqueous media (shear-thinning, zero shear viscosity of 6.3 × 105 mPa·s). As such, CR suspensions readily develop into gel-like Pickering emulsions in the absence of crosslinking, suitable for direct ink writing at ultra-low solids content. [Display omitted] [ABSTRACT FROM AUTHOR]

Direct ink writing (DIW) is a new trend in the micro-scale charging of energetic materials. In this study, a CL-20 based composite was prepared using DIW, and its properties were characterized. Results indicated that the particles of the composite are found at the sub-micron level, and a single layer measures at 2.4 μm. The composite has high density and low impact sensitivity, and its critical detonation size is around 1×0.4 mm. This feature will contribute to the detonation at the micro levelto a certain degree. [ABSTRACT FROM AUTHOR]

• The powder integration of B/KNO 3 was realized using DIW. • The reactivity of B/KNO 3 micro-energetic stick has a size effect. • The reactivity of energetic stick can be significantly enhanced using architectures. Boron/potassium nitrate (B/KNO 3 , BPN) is a promising intermolecular energetic complex with a high calorific value. The powder integration and reactivity regulation mechanism of BPN-based composite on the integrated state have not been revealed. In this study, the BPN/PVDF energetic sticks with good forming performance were prepared through a direct ink writing (DIW) device with polyvinylidene fluoride (PVDF) as the polymer skeleton. Furthermore, the energetic sticks were ignited by a Joule-heated Ni-Cr wire, and the flame propagation behaviors of energetic sticks with different BPN loading, fuel/oxidant ratios, and physical sizes were tracked using a high-speed camera. Additionally, the energy coupling behavior of architectures with different channel widths was studied. The results show that when BPN loading decreases, the linear burning rate of energetic sticks shows a trend of first rapid and then slow decrease, and the burning rates reduce from 125.59 to 28.36 mm/s. When the BPN loading is certain, the slightly fuel-rich formulation (20–30 wt% B content) has the highest burning rate. The energetic sticks have an obvious size effect: when the thickness is less than 110 μm, the combustion cannot propagate stably, and when the thickness is between 750 and 1400 μm, the burning rate–thickness curve shows a plateau. For simple architectures, the burning rate is related to the channel width. When the channel width of the structure reaches 0.2–0.5 times the width of the stick, the burning rate (∼240 mm/s) is about 3 times that of the architecture without channels (∼80 mm/s). Through these studies, we realized the powder integration of the BPN combination and provided a reference for the chemical reaction regulation and the multifunctional applications of BPN sticks. [ABSTRACT FROM AUTHOR]

The layer flatness and interfacial strength for the direct ink writing (DIW)-fabricated multilayer sensors are two significant factors in dominating the printing precision and the structural integrity of the sensors, respectively. However, it is still a challenge to control the interfacial strength and layer flatness of the multilayer sensors due to the multiplicity of materials and inherent lines-to-plane forming process of DIW technology. Here we probe a set of DIW fabrication parameters to optimize the layer flatness and design the interfacial strength of the multilayer sensors. The nonlinear thickness-dependent interfacial strength is then measured by single-lap joints experiments, which can be further predicted by an analytical model and finite element simulations. Finally, the high precision and stability of the printed strain sensors with considerably flat layers and high interfacial strength are further tested under static and cyclic tensile loadings. This study provides a feasible approach for parametrically designing and precisely manufacturing multilayer sensors based on the widely used DIW technology. Image 1 [ABSTRACT FROM AUTHOR]

Highly porous bioceramics, based on a complex hardystonite solid solution, were developed from silicone resins and micro-sized oxide fillers fired in air at 950 °C. Besides CaO, SrO, MgO, and ZnO precursors, and the commercial embedded silicone resins, calcium borate was essential in providing the liquid phase upon firing and favouring the formation of an unprecedented hardystonite solid solution, corresponding to the formula (Ca0.70Sr0.30)2(Zn0.72Mg0.15Si0.13) (Si0.85B0.15)2O7. Silicone-filler mixtures could be used in the form of thick pastes for direct ink writing of reticulated scaffolds or for direct foaming. The latter shaping option benefited from the use of hydrated calcium borate, which underwent dehydration, with water vapour release, at a low temperature (420 °C). Both scaffolds and foams confirmed the already-obtained phase assemblage, after firing, and exhibited remarkable strength-to-density ratios. Finally, preliminary cell tests excluded any cytotoxicity that could be derived from the formation of a boro-silicate glassy phase. [ABSTRACT FROM AUTHOR]