Search Results (193)

The present study offers a systematic review of the current state of research on lattice structures manufactured by additive technologies for biomedical applications, with the aim of identifying common patterns, such as the use of triply periodic minimal surfaces (TPMS) for bone scaffolds, as well as technological gaps and future research opportunities. Employing the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology, the review process ensures methodological rigor and replicability across the identification, screening, eligibility, and inclusion phases. Additionally, PRISMA was tailored by prioritizing technical databases and engineering-specific inclusion criteria, thereby aligning the methodology with the scope of this field. In recent years, a substantial surge in interdisciplinary research has underscored the promise of architected porous structures in enhancing mechanical compatibility, fostering osseointegration, and facilitating personalized medicine. A growing body of literature has emerged that explores the optimization of geometric features to replicate the behavior of biological tissues, particularly bone. Additive manufacturing (AM) has played a pivotal role in enabling the fabrication of complex geometries that are otherwise unachievable by conventional methods. The applications of lattice structures range from permanent load-bearing implants, commonly manufactured through selective laser melting (SLM), to temporary scaffolds for tissue regeneration, often produced with extrusion-based processes such as fused filament fabrication (FFF) or direct ink writing (DIW). Notwithstanding these advances, challenges persist in areas such as long-term in vivo validation, standardization of mechanical and biological testing, such as ISO standards for fatigue testing, and integration into clinical workflows. Full article

Settlement on the Moon will require full exploitation of its resources if such settlements are to be permanent. Such in situ resource utilisation (ISRU) has primarily been focused on accessing water ice at the lunar poles and the use of raw lunar regolith as a compressive building material. Some work has also examined the extraction of metals, but there has been little consideration of the many useful ceramics that can be extracted from the Moon and how they may be fabricated. We introduce a strategy for full lunar industrialisation based on a circular lunar industrial ecology and examine the contribution of ceramics. We review ceramic fabrication methods but focus primarily on 3D printing approaches. The popular direct ink writing method is less suitable for the Moon and other methods require polymers which are scarce on the Moon. This turns out to be crucial, suggesting that full industrialisation of the Moon cannot be completed until the problem of ceramic fabrication is resolved, most likely in conjunction with polymer synthesis from potential carbon sources. Full article

In the healthcare industry, the selection of biocompatible materials suitable for 3D printing is markedly less extensive than what is typically available through conventional manufacturing processes. Liquid silicone rubber (LSR) is distinguished by its exceptional stability, excellent biocompatibility, and considerable flexibility, offering significant prospects for manufacturers of medical devices involved in 3D printing. The primary aim of this research is to examine the essential factors and their interconnections that affect the 3D printing process with a Direct Ink Writing (DIW) 3D printer, which is specifically tailored for the production of aortic heart valves made from UV-cured silicone. Additionally, this study aims to investigate how the size of the heart valve impacts cardiac performance. This study implements House of Quality (HOQ) and Interpretive Structural Modeling (ISM) techniques to evaluate the interrelations among the different factors identified in the 3D printing process. Liquid silicone is especially advantageous for Direct Ink Writing (DIW) due to its low-temperature curing properties and low viscosity, which enable precise printing for intricate designs. Two different sizes of aortic heart valves, namely 23 mm and 36 mm, will be manufactured using UV-cured silicone, with both sizes having the same leaflet thickness of 0.8 mm and 1.6 mm. An examination will be conducted to assess how the size of the valve influences its performance and functionality. A Mock Circulatory Loop experimental setup will be used to test the silicone-printed heart valves, focusing on their capacity to maintain unidirectional flow and inhibit backflow through the flexible leaflets that function in alignment with the cardiac cycle. Full article

A group of renewable, unsaturated resins from itaconic acid, 1,8-octanediol, and succinic anhydride were synthesized in a non-solvent and non-catalyst melt polycondensation reaction. The study addresses the need for sustainable polymeric materials suitable for additive manufacturing by investigating the influence of synthesis parameters—namely itaconic acid content, reaction time, and temperature—on the properties of poly(octamethylene itaconate-co-succinate) (POItcSc). The Box-Behnken mathematical planning method was applied to optimize the reaction conditions. The optimal synthesis conditions of POItcSc were achieved with an itaconic acid molar fraction = 0.50:0.50, reaction time t = 7 h, and reaction temperature T = 150 °C. The conversion of the carboxyl group (by titration) was 83.3%, and the maintenance of C=C bonds (by NMR) was 88.7%. Structural characterization confirmed the formation of the desired polymer through FTIR and ¹H NMR analyses. Molecular weight (M_n = 1001 g/mol for an optimal product), thermal behavior (DSC, TG, DTG), and rheological properties (η = 14.4 and 3.6 Pa∙s for an optimal product at 25 and 36.6 °C) were systematically evaluated. The synthesized POItcSc resins were transparent and exhibited physicochemical properties favorable for extrusion-based 3D printing techniques such as Direct Ink Writing, offering a promising alternative to conventional petrochemical-based inks. Full article

Direct ink writing (DIW) has emerged as a powerful technique for functional-structure fabrication. However, its application to materials with heterogeneous or time-dependent rheology remains limited. This study introduces dual-mode electropneumatic extrusion, supported by a real-time digital twin. This platform integrates a motorized pneumatic cylinder with an electropneumatic pressure regulator, enabling continuous blending of pressure and displacement control. System performance is evaluated across five material characteristics: homogeneity, heterogeneity, time-dependent rheology, self-curing ability, and thermoplasticity. The results demonstrate that feedback current control reduces the linewidth variability to ≈2% and settling time to <250 ms, even under four-fold increases in viscosity. Adaptive pressure ramps restore variability to ≤4% throughout material curing, while hybrid velocity–pressure operation maintains variability at ≤4% and a pore geometry error below 4% over 20 layers. These findings establish a robust framework for rheology-adaptive DIW and offer practical guidelines for implementing dual-mode control in high-throughput, multi-nozzle applications. Full article

This study provides a comprehensive comparison of two leading direct-write manufacturing technologies: Aerosol Jet Printing (AJP) and Micro Dispensing Technology (MDT). The investigation examines their capabilities, limitations, and performance characteristics for printing on both 2D and 3D substrates. The findings offer valuable insights into the suitability of each printing method for flexible electronics based on the morphology and electrical performance of the deposited inks. The results reveal distinct advantages for each technique: AJP excels in resolution, while nScrypt’s micro dispensing offers superior 3D conformality, greater material versatility, and higher throughput. Full article

Developing advanced nuclear fuel technologies is critical for high-performance applications such as nuclear thermal propulsion (NTP). This study explores the feasibility of direct ink writing (DIW) for fabricating ceramic pellets for potential nuclear applications. Zirconium carbide (ZrC) is used as a matrix material and vanadium carbide (VC) is used as a surrogate for uranium carbide (UC) in this study. A series of ink formulations were developed with varying concentrations of VC and nanocrystalline cellulose (NCC) to optimize the rheological properties for DIW processing. Post-sintering analysis revealed that conventionally sintered samples at 1750 °C exhibited high porosity (>60%), significantly reducing the compressive strength compared to dense ZrC ceramics. However, increasing VC content improved densification and mechanical properties, albeit at the cost of increased shrinkage and ink flow challenges. Spark plasma sintering (SPS) achieved near-theoretical density (~97%) but introduced geometric distortions and microcracking. Despite these challenges, this study demonstrates that DIW offers a viable route for fabricating ZrC-based ceramic structures, provided that sintering strategies and ink rheology are further optimized. These findings establish a baseline for DIW of ZrC-based materials and offer valuable insights into the porosity control, mechanical stability, and processing limitations of DIW for future nuclear fuel applications. Full article

Graphene is considered one of the most promising flexible transparent electrode materials as it has high charge carrier mobility, high electrical conductivity, low optical absorption, excellent mechanical strength, and good bendability. However, graphene-based flexible transparent electrodes face a critical challenge in balancing electrical conductivity and optical transmittance. Here, we present a green and scalable direct ink writing (DIW) strategy to fabricate graphene grid patterns by optimizing ink formulation with sodium dodecyl sulfate (SDS) and ethanol. SDS eliminates the coffee ring effect via Marangoni flow, while ethanol enhances graphene flake alignment during hot-pressing, achieving a high conductivity of 5.22 × 10⁵ S m⁻¹. The grid-patterned graphene-based flexible transparent electrodes exhibit a low sheet resistance of 21.3 Ω/sq with 68.5% transmittance as well as a high stability in high-temperature and corrosive environments, surpassing most metal/graphene composites. This method avoids toxic solvents and high-temperature treatments, demonstrating excellent stability in harsh environments. Full article

Solid-state electrolytes (SSEs) have emerged as a promising solution for next-generation lithium-ion batteries due to their excellent safety and high energy density. However, their practical application is still hindered by critical challenges such as their low ionic conductivity and high interfacial resistance at room temperature. The innovative application of 3D printing in the field of electrochemistry, particularly in solid-state electrolytes, endows energy storage devices with attractive characteristics. In this study, ceramic-in-gel polymer electrolytes (GPEs) based on PVDF-HFP/PAN@LLZTO were fabricated using a direct ink writing (DIW) 3D printing technique. Under the optimal printing conditions (printing speed of 40 mm/s and fill density of 70%), the printed electrolyte exhibited a uniform and dense sponge-like porous structure, achieving a high ionic conductivity of 5.77 × 10⁻⁴ S·cm⁻¹, which effectively facilitated lithium-ion transport. A structural analysis indicated that the LLZTO fillers were uniformly dispersed within the polymer matrix, significantly enhancing the electrochemical stability of the electrolyte. When applied in a LiFePO₄|GPEs|Li cell configuration, the electrolyte delivered excellent electrochemical performance, with high initial discharge capacities of 168 mAh·g⁻¹ at 0.1 C and 166 mAh·g⁻¹ at 0.2 C, and retained 92.8% of its capacity after 100 cycles at 0.2 C. This work demonstrates the great potential of 3D printing technology in fabricating high-performance GPEs. It provides a novel strategy for the structural design and industrial scalability of lithium-ion batteries. Full article

This study investigates the application of additive manufacturing (AM) in fabricating transverse thermoelectric (TTE) composites, demonstrating the feasibility of this methodology for TTE material synthesis. Zinc oxide (ZnO), a wide-bandgap semiconductor with moderate thermoelectric performance, and copper (Cu), a highly conductive metal, were selected as base materials. These were formulated into stable paste-like feedstocks for direct ink writing (DIW). A custom dual-nozzle 3D printer was developed to precisely deposit these materials in pre-designed architectures. The resulting structures exhibited measurable transverse Seebeck effects. Unlike prior TE research primarily focused on longitudinal configurations, this work demonstrates a novel AM-enabled strategy that integrates directional compositional anisotropy, embedded metal–semiconductor interfaces, and scalable multi-material printing to realize TTE behavior. The approach offers a cost-effective and programmable pathway toward next-generation energy harvesting and thermal management systems. Full article

Stimulus-responsive hydrogels have broad applications in the biomedical, sensing, and actuation fields. However, conventional fabrication methods are often limited to 2D structures, hindering the creation of complex, personalized 3D hydrogel architectures. Furthermore, hydrogels responding to only a single stimulus and delays in fabrication techniques restrict their practical utility in biomedicine. In this study, we developed two novel multi-stimuli-responsive hydrogels (based on Gelatin/Sodium Alginate and Tannic Acid/EDTA-FeNa complexes) specifically designed for direct ink writing (DIW) 3D printing. We systematically characterized the printed properties and optimized component ratio, revealing sufficient mechanical strength (e.g., tensile modulus: Gel/SA-TA ≥ 0.22854 ± 0.021 MPa and Gel/SA-TA@Fe³⁺ ≥ 0.35881 ± 0.021 MPa), high water content (e.g., water absorption rate Gel/SA-TA ≥ 70.21% ± 1.5% and Gel/SA-TA@Fe³⁺ ≥ 64.86% ± 1.28%), excellent biocompatibility (e.g., cell viability: Gel/SA-TA and Gel/SA-TA@Fe³⁺ ≥ 90%) and good shape memory performance (e.g., the highest shape recovery rate of Gel/SA-TA reaches 74.85% ± 4.776%). Furthermore, we explored electrical characteristics, showing that the impedance value of Gel/SA-TA@Fe³⁺ hydrogel changes significantly under finger bending and NIR irradiation. This investigation demonstrates the potential of these 3D-printed multi-stimuli hydrogels for applications such as wearable flexible strain sensors. Full article

Patient-specific scaffolds for tissue and organ regeneration are still limited by the difficulty of simultaneously shaping complex geometries, preserving hierarchical porosity, and guaranteeing sterility. Additive technologies represent a promising approach for addressing problems in tissue engineering, with the potential to develop personalized matrices for the growth of tissue and organ cells. The utilization of supercritical technologies, encompassing the processes of drying and sterilization within a supercritical fluid environment, has demonstrated significant opportunities for obtaining highly effective matrices for cell growth based on biocompatible materials. We present a comprehensive methodology for fabricating intricately structured, sterile aerogels based on alginate–chitosan polyelectrolyte complexes. The target three-dimensional macrostructure is achieved through (i) direct ink writing or (ii) heterophase printing, enabling the deposition of inks with diverse rheological profiles (viscosities ranging from 0.8 to 2500 Pa·s). A coupled supercritical carbon dioxide drying–sterilization regimen at 120 bar and 40 °C is employed to preserve the highly porous architecture of the printed constructs. The resulting aerogels exhibit 96 ± 2% porosity, a BET surface area of 108–238 m² g⁻¹, and complete sterility. The proposed integration of 3D printing and supercritical processing yields sterile, intricately structured aerogels with substantial potential for the fabrication of patient-specific scaffolds for tissue and organ regeneration. Full article

The development of biocompatible, conductive hydrogels via direct ink writing (DIW) has gained increasing attention for strain sensor applications. In this work, a hydrogel matrix composed of polyvinyl alcohol (PVA) and κ-carrageenan (KC) was formulated and enhanced with polyvinylidene fluoride (PVDF) and silver nanoparticles (AgNPs) to impart piezoelectric properties. The ink formulation was optimized to achieve shear-thinning and thixotropic recovery behavior, ensuring printability through extrusion-based 3D printing. The resulting hydrogels exhibited high water uptake (~280–300%) and retained mechanical integrity. Rheological assessments showed that increasing PVDF content improved stiffness without compromising printability. Electrical characterization demonstrated that AgNPs were essential for generating piezoelectric signals under mechanical stress, as PVDF alone was insufficient. While AgNPs did not significantly alter the crystalline phase distribution of PVDF, they enhanced conductivity and signal responsiveness. XRD and SEM-EDX analyses confirmed the presence and uneven distribution of AgNPs within the hydrogel. The optimized ink formulation (5% PVA, 0.94% KC, 6% PVDF) enabled the successful fabrication of functional sensors, highlighting the material’s strong potential for use in wearable or biomedical strain-sensing applications. Full article

Direct ink writing (DIW) is an attractive, extrusion-based, additive manufacturing method for fabricating scaffold structures with controlled porosity using custom composite inks. Polycaprolactone–bioactive glass (PCL-BG) inks have gained attention for bone applications, but optimizing the formulation and fabrication of PCL-BG-based inks for improved printability and desired mechano-biological properties remains a challenge. This study employs a two-step design to systematically evaluate the effect of three factors in terms of PCL-BG composite printability and mechano-biological properties: ink preparation (acetone or dichloromethane (DCM) as the solvent, and mechanical compounding), the extrusion temperature (90 °C, 110 °C, and 130 °C), and the BG content (0%, 10%, and 20% BG). Pure PCL was used as the control. Rheological, calorimetric, and thermo-gravimetric analyses were conducted before printing. Cylindrical scaffolds and solid wells were printed to evaluate the printability, mechanical properties, and cytocompatibility. The scaffold porosity and pore size were carefully examined. Mechanical tests demonstrated that composite formulations with added BG and higher printing temperatures increased the elastic modulus and yield strength. However, PCL-DCM-BG combinations exhibited increased brittleness with higher BG content. Despite concerns about the toxic solvent DCM, the cytocompatibility was comparable to pure PCL for all ink preparation methods. The results suggest that the interaction between the ink preparation solvent, the BG content, and the printing temperature is critical for material design and fabrication planning in bone tissue engineering applications, providing insights into optimizing PCL-BG composite ink formulations for 3D printing in bone tissue engineering. Full article

High-performance flexible sensors capable of direct integration with biological tissues are essential for personalized health monitoring, assistive rehabilitation, and human–machine interaction. However, conventional devices face significant challenges in achieving conformal integration with biological surfaces, along with sufficient biomechanical compatibility and biocompatibility. This research presents an in situ 3D biomanufacturing strategy utilizing Direct Ink Writing (DIW) technology to fabricate functional bioelectronic interfaces directly onto human skin, based on a novel annealing PEDOT:PSS/PVA composite bio-ink. Central to this strategy is the utilization of a novel annealing PEDOT:PSS/PVA composite material, subjected to specialized processing involving freeze-drying and subsequent thermal annealing, which is then formulated into a DIW ink exhibiting excellent printability. Owing to the enhanced network structure resulting from this unique fabrication process, films derived from this composite material exhibit favorable electrical conductivity (ca. 6 S/m in the dry state and 2 S/m when swollen) and excellent mechanical stretchability (maximum strain reaching 170%). The material also demonstrates good adhesion to biological interfaces and high-fidelity printability. Devices fabricated using this material achieved good conformal integration onto a finger joint and demonstrated strain-sensitive, repeatable responses during joint flexion and extension, capable of effectively transducing local strain into real-time electrical resistance signals. This study validates the feasibility of using the DIW biomanufacturing technique with this novel material for the direct on-body fabrication of functional sensors. It offers new material and manufacturing paradigms for developing highly customized and seamlessly integrated bioelectronic devices. Full article