Ink Viscosity Research Articles

An innovative 4D printing approach for fabrication of anisotropic collagen scaffolds

Collagen anisotropy is known to provide the essential topographical cues to guide tissue-specific cell function. Recent work has shown that extrusion-based printing using collagenous inks yield 3D scaffolds with high geometric precision and print fidelity. However, these scaffolds lack collagen anisotropy. In this study, extrusion-based 3D printing was combined with a magnetic alignment approach in an innovative 4D printing scheme to generate 3D collagen scaffolds with high degree of collagen anisotropy. Specifically, the 4D printing process parameters-collagen (Col):xanthan gum (XG) ratio (Col:XG; 1:1, 4:1, 9:1 v/v), streptavidin-coated magnetic particle concentration (SMP; 0, 0.2, 0.4 mg ml-1), and print flow speed (2, 3 mm s-1)-were modulated and the effects of these parameters on rheological properties, print fidelity, and collagen alignment were assessed. Further, the effects of collagen anisotropy on human mesenchymal stem cell (hMSC) morphology, orientation, metabolic activity, and ligamentous differentiation were investigated. Results showed that increasing the XG composition (Col:XG 1:1) enhanced ink viscosity and yielded scaffolds with good print fidelity but poor collagen alignment. On the other hand, use of inks with lower XG composition (Col:XG 4:1 and 9:1) together with 0.4 mg ml-1SMP concentration yielded scaffolds with high degree of collagen alignment albeit with suboptimal print fidelity. Modulating the print flow speed conditions (2 mm s-1) with 4:1 Col:XG inks and 0.4 mg ml-1SMP resulted in improved print fidelity of the collagen scaffolds while retaining high level of collagen anisotropy. Cell studies revealed hMSCs orient uniformly on aligned collagen scaffolds. More importantly, collagen anisotropy was found to trigger tendon or ligament-like differentiation of hMSCs. Together, these results suggest that 4D printing is a viable strategy to generate anisotropic collagen scaffolds with significant potential for use in tendon and ligament tissue engineering applications.

Dispense Printing of Silver Flake Inks on Hydrophilic and Hydrophobic Surfaces

In printed electronics, achieving precise deposition of conductive materials on challenging substrates like Teflon is critical. This study delves into dispense printing, a technique that offers precision and versatility for creating electronic patterns. The deposition of high‐viscosity silver flake inks on both hydrophobic surfaces is investigated, such as Teflon, and hydrophilic ones, highlighting the significant interplay between ink viscosity and substrate wettability. This interaction is key to controlling ink spreading, drying behavior, and, ultimately, printing success. Research explores the relationships between critical parameters such as nozzle height, dispense pressure, and print speed, aiming to enhance the quality and functionality of printed electronics. The printing process is analyzed through its distinct phases: extrusion from the nozzle, spreading on the substrate, and line shrinking during drying. This methodological approach allows one to pinpoint how each parameter specifically influences the printing outcome, particularly on challenging substrates like Teflon. By advancing the understanding of these dynamics, the study offers valuable theoretical insights and practical advancements for fabricating high‐quality, flexible electronics across diverse substrates. The findings underscore dispense printing's potential to meet the growing demand for flexible electronics.

Fabrication and characterization of blue nano ceramic-inks: Utilization of cobalt aluminate pigments prepared by solid state method

The current study focuses on the development and fabrication of ceramic nano inks with improved properties. Firstly, two types of pigments were prepared through a solid state process using fine gibbsite (Al(OH)3) or aluminum chloride (AlCl3) with cobalt chloride hexahydrate (CoCl2.6H2O). The stoichiometric precursors were well-mixed and fired at 1000oC; then milled by a high energy ball mill to obtain nano pigments. The prepared pigments were investigated for their phase composition and crystallite size by X-ray diffraction, and further confirmed by Fourier Transform Infrared (FTIR). The morphology and particle size were examined using a scanning electron microscope. The optical properties in terms of UV–Vis, photoluminence emission spectra and CIE chromaticity diagram were also tested. The chemical-state of cobalt and surface elemental composition of prepared Co-aluminate pigments were tested by X-ray photoelectron spectroscopy (XPS). Four groups of ceramic-inks (twelve formulations) were prepared using different percentages of cobalt aluminate pigments and additives. The fabricated inks were investigated for their morphology, rheology, contact-angle and sedimentation behavior. The results revealed that two cobalt aluminate pigments with spinel structure, nano sized particles and blue color, were successfully prepared by the proposed method. The results of optical properties indicated that the cobalt ions are located mainly in tetrahedral sites with a small amount in octahedral sites. The prepared pigments were successfully used in the fabrication of ceramic nano inks with improved properties. The viscosity of most fabricated inks was in the range needed for the industry (4–40 mPa s).

3D Bioprinting with Visible Light Cross-Linkable Mucin-Hyaluronic Acid Composite Bioink for Lung Tissue Engineering.

3D printing can revolutionize personalized medicine by allowing cost-effective, customized tissue-engineering constructs. However, the limited availability and diversity of biopolymeric hydrogels restrict the variety and applications of bioinks. In this study, we introduce a composite bioink for 3D bioprinting, combining a photo-cross-linkable derivative of Mucin (Mu) called Methacrylated Mucin (MuMA) and Hyaluronic acid (HA). The less explored Mucin is responsible for the hydrogel nature of mucus and holds the potential to be used as a bioink material because of its plethora of features. HA, a crucial extracellular matrix component, is mucoadhesive and enhances ink viscosity and printability. Photo-cross-linking with 405 nm light stabilizes the printed scaffolds without damaging cells. Rheological tests reveal shear-thinning behavior, aiding cell protection during printing and improved MuMA bioink viscosity by adding HA. The printed structures exhibited porous behavior conducive to nutrient transport and cell migration. After 4 weeks in phosphate-buffered saline, the scaffolds retain 70% of their mass, highlighting stability. Biocompatibility tests with lung epithelial cells (L-132) confirm cell attachment and growth, suggesting suitability for lung tissue engineering. It is envisioned that the versatility of bioink could lead to significant advancements in lung tissue engineering and various other biomedical applications.

Development of Efficient Ink Dispersion Process for Solid-State Electrolyte and Electrode Manufacturing

All-solid-state lithium batteries (ASSBs) have several advantages over lithium-ion batteries (LIBs) such as higher safety thresholds associated with solid electrolytes (SEs) and the possibility of using lithium metal or silicon anodes to achieve comparatively higher energy and power density. The SE can also prevent chemical interactions with dissolved active materials, and thus solve the issue of long-term instability of LIBs. However, there are also challenges associated with ASSBs manufacturing, such as local stress and contact-loss between SE and active materials in cathodes due to active material “breath”, poor contact and high ionic resistance at the SE-cathode interface, difficulty in fabricating thin SEs, and the absence of scalable and cost-effective manufacturing processes (J. Janek and W.G. Zeier, Nature Energy 8 (2023): 230-240). A key to tackling these issues begins with ink formulation for electrolyte and cathode coating, including ink compositions and rheological properties.In this study, we report the influence of ink preparation methods and conditions on the solid-state electrolyte and cathode coating qualities, where lithium lanthanum zirconium oxide (LLZO) and lithium nickel manganese cobalt oxide (NMC) are used as model systems. Various mixing methods, such as acoustic wave mixing, high-speed off-axis mixing, and thin film mixing, are compared. Their influence on ink viscosity and particle dispersion, coating thickness and microstructure uniformity, and electrolyte and electrode electrochemical properties will be discussed.

Effect of the Solvent Composition in Catalyst Inks on Viscosity, Catalyst Layer Morphology, and PEMFC Performance

The solvent composition in a catalyst ink is a key parameter in fabricating cathode catalyst layers (CCLs) to reach high-performance proton exchange membrane fuel cells (PEMFCs). In general, an optimized solvent composition in a catalyst ink (e.g., the H2O-to-alcohol ratio) can yield reasonably uniform and thin ionomer structures covering the catalyst surface, leading to better proton and oxygen transport resistances of the CCLs.1,2 While the impact of solvent composition on the morphology of ionomer or catalyst in both solvent dispersion and CCLs was widely investigated, those results could vary significantly and remain inconclusive in between different studies.3 This is likely due to complex interactions between the solvent system, the ionomer, and the catalyst, and additional experimental parameters (e.g., the solvent composition in the ionomer stock dispersion, or the ink mixing method) that were not controlled. Minor changes in the fabrication process can alter the final morphology of the components in a CCL and thus vary its PEMFC performance.4 To the best of our knowledge, there are only a few systematic studies correlating the effect of the solvent system on ionomer dispersions and catalyst inks to the CCL micromorphology and PEMFC performance.In this study, we systematically examined the impact of the ratio of two commonly used solvents, 1-propanol (1-PA) and H2O, on the viscosity of ionomer dispersions (without catalysts), on the viscosity of catalyst inks (using Pt supported on a Vulcan and a Ketjenblack carbon support), on the crack formation in CCLs, and on the single-cell PEMFC performance (using 5 cm2 active area single-cell testing under differential-flow conditions). The occurrence of cracks in the CCLs was rationalized based on the rheology of the catalyst inks, the surface tension of the solvent mixtures, and the change in solvent composition during the drying process. Moreover, the influence of the ionomer stock dispersion on the viscosity of catalyst inks was investigated. This analysis shows that catalyst inks with identical compositions can have significantly different viscosities and crack formation in CCLs, depending on the ionomer stock dispersion used in the catalyst ink preparation, which highlights the importance of the processing history of the ionomer. An exemplary result is given in Figure 1, comparing the photographs of two CCLs coated on a PTFE substrate prepared with catalyst inks of identical composition. Both CCLs were fabricated with 10/90 wt% 1-PA/H2O in the catalyst inks, but different ionomer stock dispersions were used: One stock dispersion was prepared with 100 wt% H2O (Fig. 1A), and the other with a 60/40 wt% 1-PA/H2O mixture (Fig. 1B). Furthermore, we show that the shear force due to the grinding media used during the mixing of catalyst inks can trigger a gelation process of the ionomer, which strongly affects the viscosity and processibility of the catalyst ink. Finally, the impact of the solvent composition of catalyst inks on the PEMFC performance (in H2/O2 and H2/air configuration), the proton conduction resistance, and the oxygen transport resistance of the CCL were compared. Based on those results, we highlight the importance of the processing history for the fabrication of CCLs. References T. van Cleve, S. Khandavalli, A. Chowdhury, S. Medina, S. Pylypenko, M. Wang, K. L. More, N. Kariuki, D. J. Myers, A. Z. Weber et al., ACS applied materials & interfaces 2019, 11, 46953.A. Orfanidi, P. J. Rheinländer, N. Schulte, H. A. Gasteiger, J. Electrochem. Soc. 2018, 165, F1254-F1263.S. A. Berlinger, S. Garg, A. Z. Weber, Current Opinion in Electrochemistry 2021, 29, 100744.S. Khandavalli, J. H. Park, N. N. Kariuki, D. J. Myers, J. J. Stickel, K. Hurst, K. C. Neyerlin, M. Ulsh, S. A. Mauger, ACS applied materials & interfaces 2018, 10, 43610. Acknowledgment This work has been supported by the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No. 826097 (GAIA). This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation program, Hydrogen Europe, and Hydrogen Europe Research. Figure 1

Dispersion Strategy improves the mechanical properties of 3D-Printed biopolymer nanocomposite

Homogenous dispersion of nanoparticles in polymer matrices is a technical challenge that if overcome can lead to improved mechanical properties of the resulting nanocomposites. In this work, we successfully refined commercially-available nanoscale, calcium deficient, and poorly crystalline hydroxyapatite (nHA) particles and composited them with acrylate and methacrylate functionalized soybean oil (mAESO) and triethylene glycol dimethacrylate (TEGDMA) producing inks for masked stereolithography (mSLA) -based 3D printing. First, we used shear mixing and ultrasonication on nHA/ethanol mixtures to break down agglomerates and then separated the finest nanoparticles from the remaining agglomerates using centrifugation. The refined nanoparticles (termed fine) were then mixed with the resins and UV-initiator to produce inks for 3D printing. Similarly, we prepared one ink using as-purchased nHA particles (termed raw) and another ink using leftover agglomerates after refinement (termed coarse). We compared the rheological properties of the nHA-resin inks. We used mSLA to fabricate nanocomposite specimens and tested them using flexural, and Mode-I fracture toughness testing following ASTM standards. The dispersion of nanoparticles in the polymer matrix was studied by analyzing backscattered mode scanning electron microscopy images. The nHA particle refinement improved the nanoparticle dispersion in the resin matrix while also increasing the viscosity and shear yield strength of the nanocomposite ink. The flexural fracture strength, flexural modulus, and Mode-I fracture toughness of refined nHA-based nanocomposites were increased by 11 %, 71 %, and 12 %, respectively compared to the raw nHA-based nanocomposites. However, the flexural fracture strain of refined nHA-based nanocomposites was lower by 40 % compared to the raw nHA-based nanocomposites. The nanocomposites became stiffer with the incorporation of refined nanoscale nHA. The separation of nanoscale nHA particles, excellent dispersion of these nanoparticles in polymer matrix, and improved flexural strength and modulus opens a new avenue towards the 3D printing of high-performance nHA-based nanocomposites.

The influence mechanism of ink viscosity on ink transfer rates and film defects of the roll-to-roll printed organic photoactive layers

The influence mechanism of ink viscosity on ink transfer rates and film defects of the roll-to-roll printed organic photoactive layers

The Effect of The Ink Coffee Grounds Material for Black Colour in Screen Printing

The carbon content in coffee grounds can be utilized as a base material or organic pigment in making ink. Organic pigments are made by refining and reducing the particle size of coffee grounds using a screen mesh, and mortar and pestle. The process of making ink is done by mixing coffee grounds with ink-making materials such as distilled water, gum arabic, and arrowroot flour. The process of making this ink is carried out with 4 variations of the composition of coffee grounds, which are 15, 20, 25, and 30 grams. The purpose of this study is to determine the effect of variations in the composition of coffee grounds on the physical properties of the ink, namely viscosity, and on print quality, such as density and L*a*b. The results showed that the addition of coffee grounds pigments affected the density, L*a*b, and viscosity values. The higher the composition of coffee grounds, the higher the density, L*a*b, and ink viscosity values.

Functionalization of calcium-deficient nanohydroxyapatite improves the mechanical properties of 3D printed biopolymer nanocomposites

Agglomerations of nanoparticles in a polymer matrix can drastically reduce the mechanical properties of a polymer nanocomposite, especially its strength. The grafting of nanoparticle surfaces with suitable functional groups can provide improved dispersion and stronger interfacial bonding, improving the fracture resistance of the nanocomposite. In this study, calcium-deficient nanohydroxyapatite (nHA) particles were functionalized with an amino acid-based urethane methacrylate (lysine urethane methacrylate, LUM) and subsequently reacted with hydroxyethyl methacrylate. We mixed these functionalized nHA particles with resin, composed of methacrylated acrylated epoxidized soybean oil, methacrylated isosorbide, and triethylene glycol dimethacrylate, and 3D-printed nanocomposites using masked stereolithography. We hypothesized that the functionalized nanoparticles would enhance the mechanical performance of the 3D-printed nanocomposites due to the greater dispersion and stronger interface. Flexural, tensile, compression and Mode-I fracture toughness test specimens were fabricated using a mSLA printer and tested following ASTM standards. The LUM functionalization of nHA improved the dispersion and increased the viscosity of the uncured nanocomposite ink. The flexural fracture strength, yield strength, and mode-I fracture toughness values were increased by 10 %, 30 %, and 11 %, respectively. The LUM improved the strength and fracture toughness by providing a stronger, more stable interface, resisting debonding between the matrix and particles, allowing for greater plastic deformation.

20‐2: High‐resolution Pixelated Quantum Dot Light Emitting Diodes via Electrohydrodynamic Printing Technology

In this study, we achieved high‐resolution pixelated QLED device with 500 pixels per inch (ppi) through electrohydrodynamic printing (EHD) technology. We optimize the EHD printing process by controlling ink viscosity and printing speed to obtain a uniform and flat emission layer film. Then, we prepared high‐resolution pixelated bottom‐emission and top‐emission PMQLED with maximum current efficiencies of 13.6 cd/A and 16.4 cd/A, respectively. Finally, we fabricated a 500 ppi red and green (R/G) dual‐color bottom‐emission QLED device using the EHD printing method. The successful preparation of these 500 ppi QLED devices with high efficiency indicated that the EHD printing method can provides a technical basis for developing the high‐resolution QLED display technology in the future.

3D Printed Architectured silicone composites containing a UV-curable rheological modifier with tailorable structural collapse

3D printed silicones, combining the unique physiochemical performances of silicones with the attractive design freedom of additive manufacturing, have aroused intensive interest from academia and industry owing to their attractive applications. Direct writing (DW) was the most used method to enable the 3D printing of silicones, but it was limited by its conflicting rheological requirements. Herein, we present novel design of an ultraviolet (UV)-thermal dual-cure ink for UV assisted DW of silicone composites. A UV curable rheological modifier was key to the ink design, which would not only increase the ink viscosity and yield stress substantially at low contents, but also further enhance its shape-retaining capability during printing by UV-assisted curing. As a result, challenging structures with good mechanical performances and isotropy were printable. Interestingly, the degree of structural collapse for the product could be controlled by tailoring the printing parameters, which proved to be a new design dimension for property manipulation of 3D-printed cellular architectures. Rheology of the inks and boundary conditions for structural collapse were discussed in detail. This work will open new opportunities for the development of 3D-printed silicones with customized architectures and tailored performances.

Polymer‐Regulating MXene@Dopamine Electroactive Gel‐Inks for Textile‐Based Multi‐Protective Wearables

Abstract2D transition metal carbide/nitride (MXene) show significant potential for fabricating flexible wearables due to its outstanding electroactive characteristic. However, the complex processes in rheology regulation and easy agglomeration of MXene nanosheets hinder their applications as inks for homogeneous printing and coating. Herein, an electroactive gel‐ink with a low concentration of MXene (20 mg mL−1) using poly(3,4‐ethylenedioxythiophene):poly(sodium 4‐styrenesulfonate) (PEDOT:PSS) as a dopant and conductive binder is developed. The dopamine‐involved modification and PEDOT:PSS doping together promote the formation of ordered lamellar structure of MXene nanosheets, and in turn the nanosheets can regulate the interconnected electronic structure of PEDOT:PSS, which enables the transition from micellar to linear structures. Through adjusting the combination ratio of dopamine‐modified MXene (MD) to PEDOT:PSS, the viscosity of MXene inks (MDP) is tunable within 1–104 Pa·s to realize scalable printing and other processing. Screen‐printing with MDP gel‐ink endows textiles with excellent conductive stability while retaining the inherent wearability of the original fabric. With high conductivity (109.6 S m−1) and low mid‐infrared emissivity (0.34), the decorated textiles exhibit remarkable multi‐protective abilities. This work provides a novel strategy for formulating versatile MXene inks that will facilitate the large‐scale fabrication of high‐performance personal wearable multi‐protective textiles.

Enzymatically gellable chitosan inks with enhanced printability by chitosan nanofibers for 3D printing of wound dressings

Chitosan-based hydrogels have received considerable attention as wound dressing materials. The utility of these materials can be further enhanced in combination with three-dimensional (3D) printing for the fabrication of dressings tailored to the specific needs of individual wounds. Here, we investigated the fabrication of wound dressings from hydrogel precursor inks containing phenolated chitosan (chitosan-Ph) and chitosan nanofibers (chitosan-NF) via 3D printing with horseradish peroxidase (HRP)-mediated hydrogelation. By adjusting the content of chitosan-Ph and chitosan-NFs, the ink viscosity, gelation time, and hydrogel stiffness could be controlled. The composite hydrogel exhibited antibacterial properties and cytocompatibility. In particular, hydrogels with 2% (w/w) chitosan-Ph and 1% (w/w) chitosan-NFs demonstrated superior design fidelity and promising wound healing properties compared to commercial dressings. These hydrogels promoted re-epithelialization, granulation tissue formation and extracellular matrix organization without exacerbating inflammation or foreign body reaction. These results underscore the efficacy of incorporating chitosan-NF into chitosan-Ph inks to produce patient-specific wound dressings by extrusion 3D printing, which represents a significant advancement in personalized wound care.

Effect of bioactive borate glass on printability and physical properties of hydrogels

Hydrogels are a key component in bioinks and biomaterial inks for bioprinting due to their biocompatibility and printability at room temperature. The research described in the present paper contributes to the advancement of bioprinting by studying the effect of bioactive borate glass (BBG) incorporated into hydrogels on printability and physical properties. In this study, we fabricated 3D-printed hydrogel scaffolds using gelatin and alginate hydrogel mixture incorporated with various amounts of BBG, a bioceramic rich in therapeutic ions including boron, calcium, copper, and zinc. We investigated the effect of incorporating BBG on the density, viscosity, physical interactions, chemical structure, and shear thinning behavior of gelatin-alginate hydrogel biomaterial ink at different temperatures. After 3D printing and crosslinking of scaffolds, we measured mechanical properties and printing outcomes. The near-optimal extrusion temperature and pressure for uniform extrusion of hydrogel filaments at various BBG contents were determined. We compared the printing outcomes by quantifying the uniformity of printed filaments and shape fidelity of printed scaffolds. The rheological analysis showed that the addition of BBG increased the viscosity of the biomaterial inks and Young’s modulus of the 3D-printed scaffolds. Biomaterial inks with a dynamic viscosity within the range of 4.5 – 6.5 Pa·s showed the best printability across all samples. In conclusion, the inclusion of BBG contributes to a substantial improvement in the physical properties and printability of 3D-printed gelatin-alginate hydrogels.

In situ Synthesis of Single Layered Metal-Organic Frameworks via Inkjet Printing on a Cellulose Nanofiber Film.

The inkjet printing is a simple method to develop pattern-controlled 2D metal-organic frameworks (MOFs) due to its cost-effectiveness and ease of operation. Despite the sophisticated structures of MOF crystals, the MOF surfaces are easily contaminated by the adsorption of an ink solution, and the printing nozzle can be clogged by the aggregates of MOFs during printing. Unlike the mixture inks of MOFs and a carrier medium, the surface-specific patterning by in situ synthesis provides the film surface with the controlled patterns of an MOF single layer having different morphologies of MOFs without changing the ink cartridges. It enables facile printing due to the low viscosity of inks and escapes the risk of nozzle clogging because MOFs are synthesized at the printed patterns on the substrates. The ion-exchanged cellulose nanofiber (CNF) films form strong coordination with metal ions enhancing the stability of the MOFs on the film surface. It also demonstrates the controlled coverage of the MOFs by the printing pass number and the carboxylate content of CNF and the tunable adsorption of the guest molecules for different loading capacities of the printed patterns.

Considering cell viability in 3D printing of structured inks: A comparative and equivalent analysis of fluid forces

In conventional extrusion-based three-dimensional (3D) printing (E3DP), smaller needles reduce cell viability due to increased fluid forces like pressure and shear stress. A novel E3DP approach has emerged, involving 3D printing with structured inks. Fluid forces in both conventional and structured ink-based methods were evaluated through computational fluid dynamics (CFD) simulations. By employing 18G needles, we showcased the advantages of structured inks, including 2-symmetric, 4-symmetric, vascular-like, and hepatic lobule analogue-like inks, which demonstrated consistently lower pressures and shear stress compared with conventional inks. Specifically, vascular-like inks with a 2:1:1 extruded fiber layer distance showed significantly lower shear stress (average 6.595e+0 Pa, maximum 2.069e+2 Pa) than conventional methods. Equivalent analyses explored commonly used symmetric and core–shell inks, examining fluid forces on cells. Particularly, in core–shell inks with a 2.8 mm core layer radius, cells in the flow domain of the shell layer experienced an equivalent viscosity of 3.70 Pa·s, while in the core layer, it was 1.72 Pa·s. The analyses revealed a positive correlation between equivalent homogeneous ink viscosity and shear stress. The proposed workflow, emphasizing cell viability, offers an efficient approach for structured ink design. Also, experiments that used vascular-like ink-based printing as an example indicated significantly higher cell viability when compared with conventional printing. This research provides valuable insights for enhancing cell viability in 3D printing and advancing printing material design.

The effect of triglycerol diacrylate on the printability and properties of UV curable, bio-based nanohydroxyapatite composites

3D printable biopolymer nanocomposites composed of hydroxyapatite nanoparticles and functionalized plant-based monomers demonstrate potential as sustainable and structural biomaterials. To increase this potential, their printability and performance must be improved. For extrusion-based 3D printing, such as Direct Ink Writing (DIW), printability is important for print fidelity. In this work, triglycerol diacrylate (TGDA) was added to an acrylated epoxidized soybean oil:polyethylene glycol diacrylate resin to increase hydrogen bonding. Greater hydrogen bonding was hypothesized to improve printability by increasing the ink's shear yield strength, and therefore shape holding after deposition. The effects of this additive on material and mechanical properties were quantified. Increased hydrogen bonding due to TGDA content increased the ink's shear yield stress and viscosity by 916% and 27.6%, respectively. This resulted in improved printability, with best performance at 3 vol% TGDA. This composition achieved an ultimate tensile strength (UTS) of 32.4 ± 2.1 MPa and elastic modulus of 1.15 ± 0.21 GPa. These were increased from the 0 vol% TGDA composite, which had an UTS of 24.8 ± 1.8 MPa and a modulus of 0.88 ± 0.06 GPa. This study demonstrates the development of bio-based additive manufacturing feedstocks for potential uses in sustainable manufacturing, rapid prototyping, and biomaterial applications.

Preparation of HNS-based sticks through 3D printing and its combustion performance

Microscale energetic materials have garnered considerable attention because they can be integrated in microelectromechanical systems for several potential applications. Hexanitrostilbene (HNS) has been widely utilized in ignition and initiation devices owing to its excellent thermal and shock stability and high sensitivity to short pulse shock waves. To meet the energy release requirements of micro-detonation devices, HNS sticks were prepared using direct ink writing and their reaction and flame propagation properties were studied. HNS particles sized 17.5 µm to 5 µm and ∼500 nm was prepared. Then, the viscosity of HNS-based inks prepared via acoustic resonance technology decreased when the particle size decreased or when the HNS content reduced from 97 wt.%, 95 wt.%, and 92 wt.%, to 90 wt.%. Additionally, the HNS-based inks with different binders exhibited different viscosity. The effect of the inner diameter of needle (0.4 mm, 0.6 mm, and 0.9 mm), printing rate (13 mm/s, 15 mm/s, 17 mm/s, 19 mm/s), and pressure (0.05 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa) on the width of HNS sticks was also elucidated. HNS-based sticks with a diameter of 0.9 mm underwent self-sustaining combustion reactions, and the burning rate increased from 5.1 mm/s to 6.8 mm/s as the particle size decreased from 17.5 µm to 500 nm. Overall, this work provides an effective approach to prepare microscale HNS for integration into micro-energetic devices.

Stabilization of permalloy nanoparticles for syringe printable inductors

Additive manufacturing has the potential to fabricate custom parts with complex shapes. For syringe printing, there is a possibility for printing filaments consisting of different materials on a single tool. Additively manufactured electronics is a major field of investigative research, where filaments contain nanoparticles to tailor properties, such as metal to improve magnetic permeability. This study investigates syringe printing parts with high magnetic permalloy (Ni80Fe20) nanoparticle content (>35 vol%) and the properties of inductors printed from these inks. Two different metal alloy particle sizes of 250 nm and 30 nm are synthesized to observe the effect of particle size on stability. Zeta potential and settling behavior are observed to discern how coating procedures enhance particle stability in water. Permalloy nanoparticle inks are concentrated with polyethylene glycol (PEG) to increase viscosity and glycerol to decrease evaporation rates while printing. It is found that PEG and glycerol stabilize 30 nm permalloy nanoparticles in addition to increasing ink viscosity. Permalloy nanoparticle inks are printed into toroid shapes demonstrating the feasibility of fabricating useful three-dimensional magnetic structures. These inductors exhibited an inductance of 180 nH at 30 MHz.