Search Results (4,986)

3D-printed hand exoskeletons are important because they enable the creation of affordable, lightweight, and highly customizable assistive and rehabilitation devices tailored to individual patient needs. Their rapid production and design flexibility accelerate innovation, improve access to therapies, and accelerate functional recovery for people with hand impairments. This article discusses the development of a hand exoskeleton using advanced additive manufacturing. It highlights how Industry 4.0 principles such as digital design, automation, and smart manufacturing enable precise prototyping and efficient use of materials. Moving on to Industry 5.0, the study highlights the role of human–machine collaboration, where customization and ergonomics are prioritized to ensure user comfort and rehabilitation effectiveness. The integration of AI-based generative design and digital twins (DTs) is explored as a path to Industry 6.0, where adaptive and self-optimizing systems support continuous improvement. The perspective of personal experience provides insight into practical challenges, including material selection, printing accuracy, and wearability. The results show how technological optimization can be used to reduce costs, improves efficiency and sustainability, and accelerates the personalization of medical devices. The article shows how evolving industrial paradigms are driving the design, manufacture, and refinement of 3D-printed hand exoskeletons, combining technological innovation with human-centered outcomes. Full article

Currently, the possibility for the high-value utilization of abandoned oyster shells in the Zhuhai–Macao region of Guangdong Province, China, lacks sufficient attention, leading to resource wastage. Most oyster shells are treated as kitchen waste or directly landfilled, and their potential cultural and material value is not fully realized. To address this issue, this study explores sustainable utilization pathways for local abandoned oyster shells from the dual perspectives of environmental and cultural sustainability. Our research develops a 3D printing material made of oyster shells and designs a series of incense holders inspired by the traditional marine culture of the Zhuhai–Macao area. Within the framework of systematic design, this study focuses on optimizing key aspects such as material regeneration, design transformation, and cultural empowerment, thereby validating the effectiveness of systematic design in material recycling and culturally sustainable innovation. The findings not only provide theoretical and practical support for local ecodesign but also lay a foundation for promoting the synergistic development of environmental and cultural sustainability. Full article

In Louisiana’s marsh creation projects designed to mitigate wetland loss, riverine sediments are hydraulically dredged and transported through pipelines. These dredged materials are extremely soft, with moisture contents well above 100%, resulting in significant consolidation settlements even under minimal self-weight loads. Conventional one-dimensional (1-D) oedometer consolidation tests are commonly used to assess consolidation behavior; however, they are limited to soils with much lower moisture contents. At higher moisture levels, the soft slurry tends to overflow due to the weight of the standard stainless-steel dial cap and porous stone, which together apply a seating pressure of 1.07 kPa (0.01 TSF). This study presents a modified oedometer setup utilizing 3D-printed dial caps made from lightweight materials such as polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS), reducing the seating pressure to 0.21 kPa (0.002 TSF). This modification enables the testing of dredged soils with moisture contents up to 100% without overflow. Settling column tests were also integrated with the modified oedometer tests, allowing for the development of void ratio–effective stress relationships spanning from 0.02 kPa (0.0002 TSF) to 107.25 kPa (1 TSF). The results demonstrate that combining settling column and modified oedometer tests provides an effective approach for evaluating the consolidation behavior of high-moisture slurry soils. Full article

This study introduces a novel enhanced voxel-by-voxel fused filament fabrication approach utilizing a custom 3D printer. The key innovation is the simultaneous, real-time manipulation of both filament flow and printing speed per voxel. By adjusting the printing speed proportionally to the extrusion rate, the method ensures sufficient time for precise material deposition, effectively countering under-extrusion effects and significantly improving the process’s responsiveness and accuracy. The method was validated through a calibration process and in the fabrication of a breast phantom derived from a patient’s MRI data. Calibration demonstrated a strong linear correlation between HUs, extrusion rate, and speed, with a coefficient of R = 0.99. CT scans of the phantom confirmed consistent replication of the expected HU distribution and anatomical features, visually demonstrating high correlation with the original patient images. The dual-parameter control strategy successfully enhances the fidelity of soft tissue phantoms fabrication. Future work will focus on adapting the method for high-speed printing and multi-material applications. Full article

Stimuli-responsive hydrogels are an emerging class of smart materials with immense potential across biomedical engineering, soft robotics, environmental systems, and advanced manufacturing. In this review, we present an in-depth exploration of their material design, classification, fabrication strategies, and real-world applications. We examine how a wide range of external stimuli—such as temperature, pH, moisture, ions, electricity, magnetism, redox conditions, and light—interact with polymer composition and crosslinking chemistry to shape the responsive behavior of hydrogels. Special attention is given to the growing field of 4D printing, where time-dependent shape and property changes enable dynamic, programmable systems. Unlike existing reviews that often treat materials, stimuli, or applications in isolation, this work introduces a multidimensional comparative framework that connects stimulus-response behavior with fabrication techniques and end-use domains. We also highlight key challenges that limit practical deployment—including mechanical fragility, slow actuation, and scale-up difficulties—and outline engineering solutions such as hybrid material design, anisotropic structuring, and multi-stimuli integration. Our aim is to offer a forward-looking perspective that bridges material innovation with functional design, serving as a resource for researchers and engineers working to develop next-generation adaptive systems. Full article

The increasing interest in sustainable materials has led to the development of bio-based composites for additive manufacturing applications. This study aimed to investigate the influence of key printing parameters and new-generation infill patterns together on the maximum compressive force of PLA–wood bio-composites produced by Material Extrusion. By optimizing this material, low-cost wood-like products can be produced. New-generation 3D infill patterns (octet, cubic-subdivision, and lightning which is a biomimetic infill pattern) infill densities, printing temperatures, and layer heights were selected as variables/factors, and the Taguchi method was applied for design of the experiment. The signal-to-noise ratio and Analysis of Variance were used to evaluate the statistical significance and contribution of each parameter to the mechanical response. The signal-to-noise ratio indicated that the optimal printing settings were as follows: printing temperature, 205 °C; infill density, 80%; infill pattern, octet; and layer height, 0.2 mm (7123.4 N). ANOVA results showed that infill density was the most significant factor affecting maximum compressive force at 60%, while infill pattern also exhibited a notable effect. According to these results, infill density and infill pattern are the most important factors for achieving high compressive strength. These findings suggest that optimizing infill architecture and density can improve the mechanical performance of PLA–wood composites, also they can offer assistive design guidelines for lightweight and eco-friendly components. Full article

This review synthetizes experimental evidence on collagen-related bioactivity and the biomaterial potential of plant species native to the Chihuahuan Desert, aiming to identify natural compounds that could enhance next-generation dermal bioinks for 3D bioprinting. A structured search across major databases included studies characterizing plant extracts or metabolites, with reported effects on collagen synthesis, fibroblast activity, inflammation, oxidative balance, or interactions with polymers commonly used in skin-engineering materials being developed. Evidence was organized thematically to reveal mechanistic patterns despite methodological heterogeneity. Several species, among them Larrea tridentata, Opuntia spp., Aloe spp., Matricaria chamomilla, Simmondsia chinensis, Prosopis glandulosa, and Artemisia ludoviciana, repeatedly demonstrated the presence of bioactive metabolites such as lignans, flavonoids, phenolic acids, terpenoids, and polysaccharides. These compounds support pathways central to extracellular matrix repair, including stimulation of fibroblast migration and collagen I/III expression, modulation of inflammatory cascades, antioxidant protection, and stabilization of ECM structures. Notably, several metabolites also influence viscoelastic and crosslinking behaviors, suggesting that they may enhance the printability, mechanical stability, and cell-supportive properties of collagen-, GelMA-, and hyaluronic acid-based bioinks. The review also reflects on the bioethical and sustainability considerations regarding endemic floral resources, highlighting the importance of responsible sourcing, conservation extraction practices, and alignment with international biodiversity and access to benefit/sharing frameworks. Taken together, these findings point to a promising, yet largely unexplored, opportunity: integrating regionally derived phytochemicals into bioinks to create biologically active, environmentally conscious, and clinically relevant materials capable of improving collagen remodeling and regenerative outcomes in 3D-printed skin. Full article

This study focuses on the design and control system of a rotating nozzle for 3D construction printers. The development of a rotating nozzle is motivated by the need to enhance control over extrusion direction and material alignment, thereby improving the mechanical performance of printed structures by the use of non-circular nozzles. The typical 3D construction printer is equipped only with a stationary circular nozzle, which prevents the use of a non-circular nozzle due to the printer’s lack of a rotational mechanical system. This, in turn, limits the opportunity to enhance mechanical properties such as tensile and compressive strengths effectively. The proposed design is developed through computer-aided design (CAD) software, and the printer’s configuration is adjusted for integration of the rotational mechanism’s control system. This design includes a full description of the rotational mechanism and integration steps for the 3D printer. Besides the main motor of the 3D printer, an additional motor is installed next to the nozzle and controlled by a new axis (parameter), which is added into the G-code. A new axis, called “U”, is responsible for the rotation of the nozzle itself. For the development of this axis design, the cosine law is applied. The calculation is based on the three consecutive points in the G-code to obtain an accurate degree of rotation for the nozzle. The effectiveness of the system was confirmed by evaluating the compressive strength depending on printhead type. Based on testing results, one trowel printhead had the highest flexural strength of 5 MPa, and a trapezoidal printhead with teeth had the highest compressive strength of 8 MPa, compared to a circular default nozzle head with 6 MPa and 2 MPa for compressive and flexural strengths, respectively. The new optimized nozzle design is implemented in existing 3D printers, which allows it not only to develop its capability in the printing process but also to make sustainable contributions in the 3D construction industry. Full article

Metal Material Extrusion (MEX/M) provides a rapid, low-cost additive manufacturing option for individual and batch productions; however, cast materials are not typically available in the material pool. White cast iron is subject to long casting lead times and high foundry costsThis research details a comparative sintering process study for MEX/M printed white cast iron, a novel addition to the metal additive manufacturing field. A mechanical properties and microscopic evaluation on MEX/M white cast iron samples was completed to compare the influence of three sintering parameters: peak sintering temperature, dwell time, and cooling process. It was observed that increasing the peak sintering temperature increased the sintered density by 23.2% and the volumetric shrinkage by 14.25%. A longer dwell time increased the sintered density by 30.1% and the volumetric shrinkage by 9.42% but decreased the microhardness of the sample. A change in the cooling process of the sample had no effect on the mechanical properties or the microstructure of the sample. The samples achieved a 79.9% increased average density after sintering to 5.75 g/cc, with 57.82% volumetric shrinkage and a 23.3% mass loss. Overall, the samples were 85.8% less dense than casted white cast iron but showed features of a white cast iron microstructure. Full article

4D printing, as an advanced evolution of 3D bioprinting, introduces time as an active design dimension, enabling printed constructs to undergo programmed morphological or functional transformations in response to external or endogenous stimuli. By integrating stimuli-responsive smart materials with precise additive manufacturing, 4D printing provides a bio-inspired strategy to overcome the inherent limitations of static scaffolds and to achieve spatiotemporal dynamic matching with the evolving biological microenvironment during tissue regeneration. Over the past decade, significant progress has been made in applying 4D printing to structurally and functionally complex tissues, including bone, muscle, vasculature, nerve repair, wound closure, and other emerging biomedical scenarios. Rather than emphasizing shape change alone, recent advances demonstrate that 4D-printed constructs can emulate key biological processes such as morphogenesis, contraction, directional guidance, electrophysiological signaling, and microenvironment-responsive regulation, thereby enhancing tissue integration and functional recovery. This review systematically summarizes materials, stimulus–response mechanisms, and representative applications of 4D printing from a bio-inspired perspective, while critically discussing current challenges related to material performance, mechanistic understanding, manufacturing precision, and clinical translation. Finally, future perspectives are outlined, highlighting the importance of interdisciplinary integration, intelligent manufacturing, and clinically oriented evaluation frameworks to advance 4D printing toward personalized and precision regenerative medicine. Full article

Additive manufacturing (AM) is a significant contributor to Industry 4.0. However, one considerable challenge is usually encountered by AM due to the bed size limitations of 3D printers, which prevent them from being adopted. An appropriate post-joining technique should be employed to address this issue properly. This study investigates the influence of key friction stir butt welding (FSBW) factors (FSBWFs), such as tool rotational speed (TRS), tool traverse speed (TTS), and pin profile (PP), on the weldability of 3D-printed PLA–Chromium (PC) composites (3PPCC). A filament containing 10% by weight of chromium reinforced in PLA was used to prepare samples. The material extrusion additive manufacturing process (MEX) was employed to prepare the 3D-printed PCC. A Taguchi-based design of experiments (DOE) (L9 orthogonal array) was employed to systematically assess weld hardness (WH), weld temperature (WT), weld strength (WS), and weld efficiency. As far as the 3D-printed samples were concerned, two distinct infill patterns (linear and tri-hexagonal) were also examined to evaluate their effect on joint performance; however, all other 3D printing factors were kept constant. Experimentally validated findings revealed that weld efficiency varied significantly with PP and infill pattern, with the square PP and tri-hexagonal infill pattern yielding the highest weld efficiency, i.e., 108%, with the corresponding highest WS of 30 MPa. The conical PP resulted in reduced WS. Hardness analysis demonstrated that tri-hexagonal infill patterns exhibited superior hardness retention, i.e., 46.1%, as compared to that of linear infill patterns, i.e., 34%. The highest WTs observed with conical PP were 132 °C and 118 °C for both linear and tri-hexagonal infill patterns, which were far below the melting point of PLA. The lowest WT was evaluated to be 65 °C with a tri-hexagonal infill, which is approximately equal to the glass transition temperature of PLA. Microscopic analysis using a coordinate measuring machine (CMM) indicated that optimal weld zones featured minimal void formation, directly contributing to improved weld performance. In addition, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were also performed on four deliberately selected samples to examine the microstructural features and elemental distribution in the weld zones, providing deeper insight into the correlation between morphology, chemical composition, and weld performance. Full article

Concrete 3D printing (3DCP) combines materials science with material processing technologies to enable automated, additive construction. This review summarizes findings from the literature and industrial practice on 3DCP mortar formulation with emphasis on the material processing chain. The workflow is examined from raw material storage through handling, mixing, and deposition. The roles of binders, aggregates, dispersed reinforcement, and chemical admixtures are discussed in relation to rheological behavior, buildability, and early-age mechanical performance. The analysis covers storage, dosing, and mixing strategies with respect to mix consistency and overall process reliability, while mortar pumping and extrusion are addressed alongside nozzle-injected additives and automation. Finally, limitations and scalability challenges are outlined with research directions such as continuous mixing, in-line monitoring, and adaptive mix formulation for on-site applications. Full article

Additive manufacturing of hydrogel-based scaffolds requires concurrent control of material rheology and extrusion dynamics, especially in multi-material architectures. In this work, we develop a modular multi-material extrusion-based 3D-printing platform that combines a filament-fed extruder for thermoplastic polymers with a piston-driven extruder for viscous gel inks, together with an empirical calibration procedure for gel dosing. The calibration algorithm optimizes the pre-extrusion and retraction displacement (E_Pr/R) based on stepwise extrusion experiments and reduces the discrepancy between theoretical and measured deposited mass for shear-thinning alginate gels to below the prescribed tolerance. The calibrated system is then used to fabricate two representative hybrid constructs: partially crosslinked sodium alginate scaffolds with an internal hollow channel supported by a removable polycaprolactone framework, and self-supporting structures based on a sodium alginate–chitosan polyelectrolyte complex obtained by sequential co-extrusion. The resulting constructs remain mechanically stable after ionic crosslinking and solvent treatment and can subsequently be converted into highly porous scaffolds by freeze- or supercritical drying. The proposed combination of hardware architecture and extrusion calibration enables reproducible multi-material 3D printing of hydrogel–thermoplastic hybrid scaffolds and can be readily adapted to other gel-based inks for tissue engineering applications. Full article

Overlay restorations offer a conservative solution for teeth with substantial loss of tooth structure, but their success depends largely on the preparation design, material type, and fabrication technique. This study aimed to assess the effects of two different preparation designs and fabrication techniques on the fracture resistance and marginal adaptation of overlays fabricated from zirconia-reinforced lithium silicate (ZLS) and 3D-printed resin. Forty extracted human molars were randomly divided into two preparation design groups: occlusal reduction (O) and occlusal reduction with a round shoulder (OS). Each group was subdivided based on the material type: ZLS or 3D-printed resin (n = 10 per subgroup). Restorations were designed using CAD and manufactured using milling (ZLS) or additive manufacturing (3D-Printed). After cementation and thermomechanical aging (5500 cycles, 5–50 °C), marginal gaps were measured at 20 predefined points using scanning electron microscopy (SEM). The fracture resistance was tested using a universal testing machine. Data were analyzed using two-way ANOVA and post hoc tests (α = 0.05). The preparation design had a significant effect on both fracture resistance and marginal adaptation (p < 0.05). Group O showed significantly smaller marginal gaps than Group OS for both materials. The ZLS overlays exhibited a significantly higher fracture resistance than the 3D-printed resin overlays. All groups demonstrated marginal gaps within the clinically acceptable range (<120 μm). The fracture resistance and marginal adaptation of overlay restorations are significantly influenced by the preparation design and material type. A simpler occlusal reduction design results in better marginal adaptation, whereas round shoulder preparations provide a higher fracture resistance. Although the 3D-printed resin showed lower fracture resistance, its marginal adaptation was comparable to that of milled restorations, suggesting its potential as a conservative and cost-effective polymer composite alternative for digitally fabricated overlay restorations. Full article

In additive manufacturing technologies, the use of pastes and inks based on materials such as clay to create three-dimensional objects layer by layer has opened new possibilities in fields such as engineering and biomedicine. This review article aims to provide a comprehensive understanding of 3D printing of ceramic pastes through Direct Ink Writing (DIW), also referred to as Robocasting. DIW offers specific advantages for ceramic 3D printing, including the ability to extrude highly loaded pastes with customized rheological properties to accommodate a broad spectrum of ceramic compositions, varying from conventional clays to advanced ceramics. It is characterized by filament deposition control, which facilitates the fabrication of complex, porous, or customized architectures while simultaneously minimizing material waste. Through a bibliometric analysis of the literature published between 2020 and 2024, the most relevant studies regarding printing system architectures, ceramic paste formulations, and adjustment of parameters to obtain high-quality parts were identified. This work presents relevant and accurate explanations of the DIW technology, supporting researchers and industry professionals seeking to initiate or improve ceramic 3D printing processes for a wide range of applications. Full article