Search Results (1,163)

The automation of concrete constructions through 3D printing (3DP) has been increasingly developed and adopted in civil engineering due to its promising advantages over traditional construction methods. However, widespread implementation is hindered by uncertainties in quality control, homogeneity, and interlayer bonding, as well as the uniqueness of each printed component. Building upon our prior work in developing 3D-printable self-sensing cementitious materials by incorporating graphite powder and carbon microfibers into a cementitious matrix to enhance its piezoresistive properties, this study aims at enabling condition assessment of cementitious 3DP by integrating the self-sensing materials as sensing nodes within conventional components. Three different 3D-printed strip patterns, consisting of one, two, and three strip lines that mimic the pattern used in fabricating foil strain gauges were investigated as conductive electrode designs to impart strain sensing capabilities, and characterized from a series of quasi-static and dynamic tests. Results demonstrate that the three-strip design yielded the highest sensitivity (${\lambda }_{\mathrm{stat}}$ of 669, ${\lambda }_{\mathrm{dyn}}$ of 630), whereas the two-strip design produced the highest signal quality (SNR_stat = 9.5 dB, SNR_dyn = 10.8 dB). These findings confirm the feasibility of integrating 3D-printed self-sensing cementitious materials through hybrid manufacturing, enabling monitoring of print quality, detection of load path changes, and identification of potential defects. Full article

Edible hydrogels are the central material class in 3D food printing because they reconcile two competing needs: (i) low resistance to flow under nozzle shear and (ii) fast recovery of elastic structure after deposition to preserve geometry. This review consolidates the recent years of progress on hydrogel formulations—gelatin, alginate, pectin, carrageenan, agar, starch-based gels, gellan, and cellulose derivatives, xanthan/konjac blends, protein–polysaccharide composites, and emulsion gels alongside a critical analysis of printing technologies relevant to food: extrusion, inkjet, binder jetting, and laser-based approaches. For each material, this review connects gelation triggers and compositional variables to rheology signatures that govern printability and then maps these to process windows and post-processing routes. This review consolidates a decision-oriented workflow for edible-hydrogel printability that links formulation variables, process parameters, and geometric fidelity through standardized test constructs (single line, bridge, thin wall) and rheology-anchored gates (e.g., yield stress and recovery). Building on these elements, a “printability map/window” is formalized to position inks within actionable operating regions, enabling recipe screening and process transfer. Compared with prior reviews, the emphasis is on decisions: what to measure, how to interpret it, and how to adjust inks and post-set enablers to meet target fidelity and texture. Reporting minima and a stability checklist are identified to close the loop from design to shelf. Full article

Rapid population growth and accelerating urbanization are intensifying the demand for construction materials, particularly concrete, which is predominantly produced with Portland cement and natural aggregates. This reliance imposes substantial environmental burdens through resource depletion and greenhouse gas emissions. Within the framework of sustainable construction, recycled aggregates and industrial by-products such as fly ash, slags, crushed glass, and other secondary raw materials have emerged as viable substitutes in concrete production. At the same time, three-dimensional concrete printing (3DCP) offers opportunities to optimize material use and minimize waste, yet it requires tailored mix designs with controlled rheological and mechanical performance. This review synthesizes current knowledge on the use of recycled construction and demolition waste, industrial by-products, and geopolymers in concrete mixtures for 3D printing applications. Particular attention is given to pozzolanic activity, particle size effects, mechanical strength, rheology, thermal conductivity, and fire resistance of recycled-based composites. The environmental assessment is considered through life-cycle analysis (LCA), emphasizing carbon footprint reduction strategies enabled by recycled constituents and low-clinker formulations. The analysis demonstrates that recycled-based 3D printable concretes can maintain or enhance structural performance while mix-level (cradle-to-gate, A1–A3) LCAs of printable mixes report CO₂ reductions typically in the range of ~20–50% depending on clinker substitution and recycled constituents—with up to ~48% for fine recycled aggregates when accompanied by cement reduction and up to ~62% for mixes with recycled concrete powder, subject to preserved printability. This work highlights both opportunities and challenges, outlining pathways for advancing durable, energy-efficient, and environmentally responsible 3D-printed construction materials. Full article

Three-dimensional (3D) bioprinting has become one of the most advanced and useful innovations that allows the creation of personalized macroscopic and microscopic constructs at different scales that match a patient’s anatomy. Intensive research efforts are currently underway to develop highly printable and biocompatible materials. Among the variety of bioprinting materials (i.e., biomaterial inks), naturally derived hydrogels have attracted great interest due to their beneficial properties in terms of biocompatibility, cost-effectiveness, and biodegradability. In this proceeding paper, we provide an overview of the formulation and use of three functional polysaccharides as ink-based hydrogels. First, 3D bioprinting is summarized as revolutionary technology that is able to create cell-laden structures layer by layer in a specific pattern that mimics native tissue and organs. Cellulose, chitosan, and lignin are presented below, followed by an overview of their applicability in 3D bioprinting, focusing on printability and the resulting printed 3D structures as illustrated in various published figures. In the same way, a comparative overview of 3D bioprinting applications is summarized. Finally, a section dedicated to comparisons, limitations, and crosslinking strategies is provided. It is worth noting that this proceedings paper provides a brief overview rather than a comprehensive review, as it is limited by page constraints and is based on the content of our poster presented at the 1st International Online Conference on Bioengineering. Full article

Three-dimensional printing (3DP) represents a significant innovation in the construction sector, offering substantial benefits in terms of efficiency, customisation, and sustainability. In the context of built heritage rehabilitation, it is capable of accurately reproducing architectural elements, facilitating conservation efforts, while minimising waste and resource consumption. However, in this field, ensuring material compatibility with original structures is essential. This study explores the development and optimisation of lime and cement-based mortars for 3DP applications, focusing on their physical and mechanical performances (on moulded specimens) for use in replicating elements of a renowned Portuguese theatre. Laboratory testing supports the selection of suitable mortar compositions, aiming to balance performance and fidelity to historical construction practices. This research seeks to contribute to explore the potential of 3DP for heritage conservation, promoting innovative, durable, and culturally sensitive restoration strategies. Full article

Three-dimensional concrete printing (3DCP) is rapidly emerging as a transformative construction technology, enabling formwork-free fabrication, geometric flexibility, and reduced labour. However, the lack of conventional reinforcement and the strict requirements for fresh and hardened properties present significant challenges. Fibre reinforcement and supplementary cementitious materials (SCMs), such as ground granulated blast furnace slag (GGBS), offer pathways to enhance printability while mitigating environmental impact. This study investigates the combined effect of natural cellulose microfibres and silica fume on the rheological, mechanical, and sustainability performance of 3D-printable mortars. Six mixes were prepared with 50% GGBS, 45% cement, and 5% silica fume, incorporating fibre dosages from 0% to 1%. Results showed that a 0.5% fibre dosage provided the most favourable balance. At this dosage, static yield stress increased to 9.35 Pa and thixotropy reached 8623 mPa·s, enhancing structuration for shape retention. Plastic viscosity remained stable at 4–5 Pa·s, ensuring adequate extrusion performance. Higher fibre dosages (≥0.75%) caused a significant increase in rheological resistance, with static yield stress reaching 208 Pa and thixotropy 135,342 mPa·s. This resulted in excessive structuration, fibre clustering, and poor extrudability. Compressive strength was achieved at 109.10 MPa (92% of silica fume-only mix) with 0.5% fibre. In comparison, flexural strength was 13.20 MPa at 0.5% fibre content and reduced gradually to 12.29 MPa at 1% fibre due to weak fibre–matrix bonding and porosity. Sustainability analysis confirmed that using 50% GGBS and 5% silica fume reduced embodied carbon compared to a 100% cement mix. This study also demonstrated that cellulose microfibres at 0.25–0.5% are optimal for balancing fresh properties, mechanical strength, and sustainability in 3D-printed mortars. Full article

This study introduces the Gyroid structure, a type of triply periodic minimal surface (TPMS), for enhanced effusion cooling performance. Conjugate heat transfer simulations are used to compare the flow behavior, pressure loss, and overall cooling effectiveness of single- and double-wall Gyroid configurations against a baseline film hole model at blowing ratios of 0.5–2.0. Results show that the Gyroid design eliminates jet lift-off and counter-rotating vortex pairs, ensuring full coolant coverage and a thicker coolant layer than the baseline. The double-wall configuration further improves cooling with jet impingement, yielding higher average Nusselt numbers than the single-wall design. At equal pressure loss, the impingement/Gyroid model outperforms the baseline by 102.7% in cooling effectiveness. To assess manufacturability, a high-resolution CT scan is used to validate a laser powder bed fusion-printed Gyroid sample at gas turbine blade scale, confirming feasibility for industrial application. These findings highlight the superior thermal performance and manufacturability of the 3D-printed Gyroid structure, offering a promising cooling solution for next-generation turbine blades. Full article

Copper is a critical material for energy transition and green technologies, making its sustainable use increasingly important. Its superior thermal and electrical conductivity make it highly well-suited for additive manufacturing (AM). In this study, copper sourced from offshore electrical cables was upcycled to produce high-quality metal powder for AM. The scrap was processed to separate the metal from plastic and rubber, then refined through ultrasonic atomization, achieving a purity of ~99.5% wt.% with minimal impurities. Characterization demonstrated good flowability, apparent and tap densities, and a well-distributed particle size. To assess its performance in AM, the powder was printed using Directed Energy Deposition (DED) with a laser beam, confirming its high printability and compatibility with the base material. Finally, a comparative Life Cycle Assessment (LCA) revealed a significant environmental advantage of the recycling-based process over conventional mining, reducing global warming potential by more than 70%. These findings highlight the importance of feedstock origin in AM sustainability and support the adoption of circular economy strategies to lower the environmental footprint of advanced manufacturing. Full article

Three-dimensional concrete printing (3DCP) is advancing rapidly, yet its sustainable adoption requires alignment with circular-economy principles. This study evaluates the substitution of natural aggregates with recycled constituents, 3DCP waste, brick debris, glass cullet, mixed rubble, fly ash, and slag, and the use of lightweight fillers (expanded perlite, lightweight expanded clay aggregate (LECA), and expanded polystyrene (EPS)) to reduce density and improve insulation. Key properties, such as particle-size distribution, printability, mechanical performance, thermal conductivity, and water absorption, were determined. Results indicate that grading strongly affected mixture behavior. Narrow distributions (fly ash, milled 3DCP waste) enhanced extrudability, while broader gradings (glass, rubble, slag) increased water demand and extrusion risks. Despite these differences, all systems remained within the printable window: flow spread decreased with most recycled additions (lowest for brick) and increased with glass. Mechanical responses were composition-dependent. Flexural strength typically decreased. Compressive strength benefited from broader gradings, with replacement levels up to ~6% enhancing strength due to improved packing. Loading anisotropy typical of 3DCP was observed, with perpendicular compressive strength reaching up to 13% higher values than parallel loading. Lightweight fillers significantly reduced thermal conductivity. LECA provided the best compromise between strength and insulation, perlite showed intermediate behavior, and EPS achieved the lowest thermal conductivity but induced significant strength penalties due to weak matrix-EPS interfaces. Water absorption decreased in recycled-aggregate mixes, whereas lightweight systems, particularly with perlite, retained higher uptake. The results demonstrate that non-reactive recycled aggregates and lightweight insulating fillers can be successfully integrated into extrusion-based 3DCP without compromising printability. Full article

3D-printable concretes often require high binder content. This study evaluates the use of industrial gypsum by-products, phosphogypsum (PG) and borogypsum (BG), as partial cement replacements to enhance sustainability without compromising printability. PG and BG were incorporated at 2.5–10 wt% to replace the gypsum fraction in cement-based mortars containing fly ash (FA) or ground granulated blast-furnace slag (GGBS), with and without fibers. The fresh properties (spread flow diameter, open time, air content, density, and pH) and compressive strength were measured. At 28 days, the highest strength was achieved with a 7.5% PG addition to the GGBS system (~51 MPa), which exceeded the strength of the GGBS control C1 (~47.6 MPa). In the FA system, 2.5% PG reached 42.5 MPa, comparable to the FA control C2 (41.2 MPa). BG caused pronounced strength penalties at ≥7.5% across both binder systems, indicating a practical BG ceiling of ≤5%. Open time increased from ~0.75 h in the controls to ~2–2.5 h in BG-FA mixes with fibers, whereas PG mixes generally maintained a stable, printable window close to control levels. Overall, adding 5–7.5% PG, particularly in the presence of GGBS, improved mechanical performance without compromising workability. However, BG should be limited to ≤5% unless extended open time is the primary objective. These findings provide quantitative guidance on selecting PG/BG dosages and FA/GGBS systems to balance strength and printability in cement-based, 3D-printable concretes. Full article

Additive manufacturing using fused deposition modelling (FDM) is increasingly explored for personalised drug delivery, but the lack of suitable biodegradable and printable filaments limits its pharmaceutical application. In this study, we investigated the influence of formulation and structural design on the performance of polyvinyl alcohol (PVA)-based filaments doped with theophylline anhydrous for 3D printing. To address the intrinsic brittleness and poor printability of PVA, cassava pulp-derived fibres—a sustainable and underutilised agricultural by-product—were incorporated together with polyethylene glycol (PEG 400), Eudragit^® NE 30 D, and calcium stearate. The addition of fibres modified the mechanical properties of PVA filaments through hydrogen bonding, improving flexibility but increasing surface roughness. This drawback was mitigated by Eudragit^® NE 30 D, which enhanced surface smoothness and drug distribution uniformity. The optimised composite formulation (P₁₀F₅E₅T₅) was successfully extruded and used to fabricate 3D-printed constructs. Release studies demonstrated that drug release could be modulated by pore geometry and construct thickness: wider pores enabled rapid Fickian diffusion, while narrower pores and thicker constructs shifted release kinetics toward anomalous transport governed by polymer swelling. These findings demonstrate, for the first time, the potential of cassava fibre as a functional additive in pharmaceutical FDM and provide a rational formulation–structure–performance framework for developing sustainable, geometry-tuneable drug delivery systems. Full article

Collagen is a versatile material, and collagen in the human body strengthens the muscles and related organs, allowing good substances to be absorbed into the bloodstream while preventing the absorption of toxic substances. Thus, collagen has been broadly applied in regenerative medicine and tissue engineering. A comprehensive framework for various collagen products has been created by integrating collagen resources with additive components. The application of 3D-bioprinting technologies for designing physiological models further allows for the introduction of enhanced preclinical testing tools that can contribute to successful elucidation of the mechanisms behind host–pathogen interactions, and subsequent prevention and treatment of various diseases. In this review, novel strategies for the 3D-printing production of collagen-sourced biomedical devices, as well as diverse applications customized with advanced artificial intelligence (AI) technologies, were thoroughly examined. Ongoing challenges, including the inherent limitations in the mechanical weakness of collagen-based bioinks, such as printability and stability, along with cell viability and bioavailability, and advanced strategies addressing those challenges, were also reviewed. An integration of 3D printing with collagen as a bioink is enormously efficient in biomedical applications, demonstrating its great potential for clinical translation against infectious diseases, including cardiovascular diseases. Full article

In this study, multilayer biopolymer films composed of furcellaran, chitosan, and gelatin were incorporated with aqueous extracts of Lavandula angustifolia and Clitoria ternatea. These materials were engineered as sustainable, biodegradable substrates suitable for screen-printing applications. The primary objective was to enhance the films’ functional properties, including their mechanical integrity, barrier performance, and printability, thereby broadening their potential utility in environmentally responsible technological applications. FTIR and UV–Vis analyses confirmed the presence of functional groups associated with the contained plant extracts and showed significantly improved UV-blocking properties. Thermal and mechanical tests showed that the films maintained good structural integrity, and only high extract concentrations slightly affected tensile strength. Importantly, the materials exhibited gradual but limited thermal shrinkage (<3.7%) up to 130 °C, while maintaining their multilayer structure. Water-related evaluations, including WCA, solubility, pH, and conductivity, confirmed their biodegradability in aqueous environments without exceeding ecotoxicological thresholds. Microbiological tests demonstrated selective antimicrobial activity. The key novelty of this work is the evaluation of these active multilayer biopolymer films as screen-printing substrates. This is the first report in which screen-printing compatibility with active multilayer biopolymer systems is presented, highlighting their potential in sustainable packaging that integrates biodegradable matrices with printed sensor layers. Full article

Background: Functional Neurological Disorders (FNDs) encompass a spectrum of disabling conditions, including functional limb weakness, tremor, gait disorders, seizures, and cognitive impairments. While previously diagnosed by exclusion, a growing consensus now supports the use of positive clinical signs as a basis for diagnosis. Despite this paradigm shift, frontline clinicians lack an integrated, accessible clinical tool for guiding diagnostic reasoning across FND subtypes. Objectives: This study aims to (1) synthesize the contemporary evidence on positive clinical signs across major FND subtypes and (2) develop a structured Clinical Decision Tool to support early and confident diagnosis in routine clinical settings. Methods: A focused narrative review was conducted using peer-reviewed publications and neurology reference texts, identifying reproducible positive clinical signs relevant to FND diagnosis. Signs were extracted, tabulated by subtype, and integrated into a modular decision-making framework designed for usability across outpatient, emergency, and specialist contexts. Results: The review identified 60+ positive signs across seven FND subtypes. These include Hoover’s sign for limb weakness, entrainment for tremor, variable responsiveness in NESs, and paradoxical memory performance in Functional Cognitive Disorder. A Clinical Decision Tool was developed, featuring subtype-specific checklists, diagnostic confidence indicators, and red flag alerts, and it is currently available in printable format. Conclusions: This study offers a novel, evidence-based decision tool to facilitate the positive diagnosis of FND. By consolidating observable signs into a practical format, it aims to reduce diagnostic delays, avoid unnecessary investigations, and enhance patient–clinician communication. Future efforts will focus on clinical validation and digital implementation. Full article

Object detection is used to automatically identify and locate specific objects within images or videos for applications like autonomous driving, security surveillance, and medical imaging. Protecting object detection models against adversarial attacks, particularly malicious patches, is crucial to ensure reliable and safe performance in safety-critical applications, where misdetections can lead to severe consequences. Existing defenses against patch attacks are primarily designed for stationary scenes and struggle against adversarial image patches that vary in scale, position, and orientation in dynamic environments.In this paper, we introduce SAR, a patch-agnostic defense scheme based on image preprocessing that does not require additional model training. By integration of the patch-agnostic detection frontend with an additional broken pixel restoration backend, Segment and Recover (SAR) is developed for the large-mask-covered object-hiding attack. Our approach breaks the limitation of the patch scale, shape, and location, accurately localizes the adversarial patch on the frontend, and restores the broken pixel on the backend. Our evaluations of the clean performance demonstrate that SAR is compatible with a variety of pretrained object detectors. Moreover, SAR exhibits notable resilience improvements over state-of-the-art methods evaluated in this paper. Our comprehensive evaluation studies involve diverse patch types, such as localized-noise, printable, visible, and adaptive adversarial patches. Full article