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High-performance biocompatible flame-retardant polymer composites are considered one of the most promising candidates for next-generation biomedical engineering material. However, the practical applications are thought to appropriately contain flame retardancy and structural mechanical properties. In this study, the carbon nanotube (CNT), ZIF-67, and PVP have synergistically boosted polyvinyl alcohol (PVA)/sodium alginate (SA) composite with both excellent fire safety and mechanical properties, which first prepared with aqueous-phase mixed and freeze-drying method. As the addition of nano-fillers significantly improved the fire protection capability of PS nanocomposites, char residues were produced by aerogels at high temperatures. And the inorganic phase serves as a thermal barrier to prevent heat from spreading. The incorporation of CNTm/ZIF-67/PVP reduced the peak smoke release rate and peak heat release rate by 50% and 20.36%, respectively. In addition, the incorporation of nano-fillers also improved the compressive strength of the PS composites significantly, from 1.34 MPa to 2.45 MPa (Increased 82.8%). ZIFs heterogeneous nanoparticles synthesized with a high concentration of reactive groups provide a workable perspective on the future development of designing nano-filling flame-retardant polymer composites.

Customisation of bioactivity and degradability of porous bioceramic scaffolds is a formidable challenge in the field of regenerative medicine. In this study, we developed gyroid-structured ternary composite scaffolds (biphasic calcium phosphate (BCP) and 45S5 bioglass® (BG)) using digital light processing 3D printing technology based on material and structural design. Additionally, the mechanical strength, bioactivity, degradability, and biocompatibility of the composite ceramic scaffolds were evaluated. The results revealed that BG reacted with BCP to generate major active crystalline phases of CaSiO3and Na3Ca6(PO4)5. These active crystalline phases accelerated the exchange rate of Si4+, Ca2+, and PO43−with HCO3−in simulated body fluids and resulted in the rapid formation of carbonated hydroxyapatite (CHA), analogous to the formation of natural bone tissue. Interestingly, the precipitated CHA showed petal- and needle-like morphologies, which provided a large surface area to promote cell adhesion and proliferation. Furthermore, an increase in the BG content improved the degradability of ternary composite scaffolds after soaking in Tris-HCl solution. The tuneable degradability increased by three times at 30 wt% BG and sharply increased by 6.8 times at 40 wt% BG. This study provides a promising strategy to design scaffolds with improved bioactivity and tuneable degradability to assist a diverse population suffering from orthopedic conditions.

Additive manufacturing (AM) technology enables the creation of a wide variety of assemblies and complex shapes from three-dimensional model data in a bottom-up, layer-by-layer manner. Therefore, AM has revolutionized the modern manufacturing industry, attracting increasing interest from both academic and industrial fields. The Rapid Manufacturing Center (RMC) of the School of Materials Science and Engineering at the Huazhong University of Science and Technology (HUST), one of the earliest and most powerful AM research teams in China, has been engaged in AM research since 1991. Aiming to address the “stuck neck” problems of specific high-strength products for AM, the RMC has conducted full-chain research in the aspects of special materials, processes, equipment, and applications for AM. Moreover, it has formed a multi-disciplinary research team over the past three decades. Relevant research achievements in the AM field include winning five national awards, more than ten first prizes, and more than ten second prizes at the provincial and ministerial levels. The RMC was complimented as “the world's most influential organization in the laser AM field in 2018” by Virtual and Physical Prototyping (an international authoritative magazine of AM). Moreover, their industrialization achievements were evaluated as “having affected countries such as Singapore, South Korea, and the United States” by an international authoritative Wohlers Report on AM. In this study, we first summarize the representative research achievements of the RMC in the AM field. These include the preparation and processing technology of high-performance polymeric, metallic, and ceramic materials for AM; advanced processing technology and software/equipment for AM; and typical AM-fabricated products and their applications. Further, we discuss the latest research achievements in cutting-edge 4D printing in terms of feedstock selection, printing processes, induction strategies, and potential applications. Finally, we provide insights into the future directions of AM technology development: (ⅰ) Evolving from three-dimensional printing to multi-dimensional printing, (ⅱ) transitioning from plane slicing to curved surface slicing to woven slicing, (ⅲ) enhancing efficient formation from dot-line-sheet-volume printing, (ⅳ) shifting from single material to multi-materials AM, (ⅴ) advancing from the multiscale direction of macroscopic–mesoscopic–microscopic structures, (ⅵ) integrating material preparation with forming integration, (ⅶ) expanding from small batch to large batch.

Magnetic soft materials (MSMs) have a rising requirement in self-powered stress sensors and energy harvesters due to the considerable flexibility and force-driven variable magnetic strengths. Structural designs aided by additive manufacturing for MSMs can regulate their mechanoelectrical conversion capability. Here we report that porous MSMs with negative, zero and positive Poisson’s ratios (NPR, ZRP and PPR, respectively) composed of Nd2Fe14B and thermoplastic urethane can be one-step fabricated by selective laser sintering. The mechanoelectrical conversion performances of MSMs with three different kinds of Poisson’s ratios are investigated under vertical deformations. The results show that the lateral contraction of NPR MSMs concentrates the magnetic field distribution, leading to the maximum electrical output (7.42 mV at the strain of 40 % and compression velocity of 40 mm/s), which is 1.80 and 2.07 times that of ZPR and PPR MSMs, respectively. The experimental results have been confirmed by finite element analysis including ABAQUS/CAE and Ansys Maxwell. In addition, the electrical output of as-printed magnetoelectric devices can be adjusted by altering cells’ parameters and their array permutations. In summary, the study for improving the electrical outputs of MSMs by structural design will offer a high-efficiency and promising route for self-powered sensors and other mechanoelectrical conversion devices.

As metal additive manufacturing (MAM) becomes more widely used in engineering, an increasing number of novel lattice structures are being developed. However, most recently developed lattice structures do not match the requirement of MAM efficiently. Based on the Design for Additive Manufacturing (DfAM), comparing the mainstream implicit and explicit modelling methods, it is proposed to introduce a Subdivisional (Sub-D) modelling method to model lattice structures with better modelling versatility, 3D printability, and mechanical properties. To this end, a novel negative Poisson's ratio (NPR) structure is developed as an example to demonstrate the efficient and wide applicability of the Sub-D modelling method. The structure is a lattice structure that is complex to model, difficult to print, and has specific mechanical properties. The results show that the Sub-D modelling method allows for the intuitive design, flexible adjustment, efficient G2 surface generation, and robust model output of truss-based and sheet-based NPR structures (modelling versatility); the generated G2 curvature continuum surface can mitigate manufacturing difficulties and form lightweight structures. In comparison to NURBS modelling methods, it can generate cantilever truss structures with a 1.33 times greater span and 55% higher geometric fidelity (3D printability); its Young's modulus, yield strength, compressive strength, and specific energy absorption are 186%, 60%, 66% and 50% higher, respectively (mechanical properties). In addition, the use of highly ductile silver as a material has provided new insights into the structural mechanics of MAM lattice structures with high ductility.

The preparation of poly-ether-ether-ketone/bioactive glass (PEEK/BG) composite scaffolds using laser powder bed fusion (LPBF) has enormous clinical potential. However, ensuring the desired accuracy and reproducibility of composite scaffolds during the LPBF process remains a significant challenge. Therefore, a thorough understanding of the relationship between the crystallization behaviors and the scaffold warpage during the LPBF process is crucial. To address this challenge, this study systematically investigates the isothermal crystallization kinetics of PEEK/BG composites and their relationship with scaffold warpage. The results reveal that the crystallization rates of pure PEEK and PEEK/BG composites decrease as isothermal crystallization temperature increases. Additionally, BG significantly suppresses the isothermal crystallization kinetics of PEEK, resulting in a 250% increase in the half-crystallization time (t1/2) of PEEK/25wt% BG at 316 °C relative to pure PEEK. Extrapolating the t1/2using the Hoffman-Lauritzen model can obtain the optimal powder bed temperature (Tb) for each powder in LPBF. Pure PEEK and PEEK/25wt% BG Diamond scaffolds are printed at the respective inferred Tb(330 °C and 323 °C) and their warpage degrees are compared to that of the pure PEEK scaffold printed at 323 °C. The results demonstrate that raising Tbfrom 323 °C to 330 °C and adding 25wt% BG are both effective methods to reduce the scaffold warpage by slowing down the crystallization kinetics of PEEK, resulting in reductions of 57.8% and 50.6% in warpage degree respectively. Furthermore, the incorporation of BG successfully tackles the challenge of simultaneously preventing warpage and secondary sintering in pure PEEK printing. Overall, this study offers a deep comprehension regarding the relationship between crystallization kinetics and scaffold warpage, which is crucial for achieving the reproducibility with desired accuracy of LPBF-printed biological scaffolds for clinical applications.

Laser powder bed fusion (LPBF) combined with reaction bonding (RB) of Al particles is an effective method for preparing high-performance 3D Al2O3ceramic foams. However, the indistinct microstructure evolution hinders the regulation of pore features and the improvement of synthetic properties. Herein, the microstructure evolution of the Al2O3ceramic foams during the LPBF/RB process is clarified by various characterization methods, and the corresponding mechanical property modulation is realized by optimizing LPBF parameters, organic binder (E12 epoxy resin) content, heating rate, sintering time, and coral-like Al2O3content. The expansion from Al2O3outward growth and Al granule precipitation counteracts the shrinkage from E12 decomposition and Al2O3sintering, resulting in an ultra-low shrinkage of 0.94%–3.01%. The pore structures of particle packing pores, hollow spheres, and microporous structures allow a tunable porosity of 52.6%–73.7%. The in-situformation of multi-scale features including hollow spheres, flaky grains, whiskers, nanofibers, and bond bridges brings about a remarkably high bending strength of 6.5–38.3 MPa. Our findings reveal the relationship between microstructure evolution and property optimization of high-performance ceramic foams, with potential significance for microstructure design and practical application.

Bone regeneration remains a great clinical challenge. Low intensity near-infrared (NIR) light showed strong potential to promote tissue regeneration, offering a promising strategy for bone defect regeneration. However, the effect and underlying mechanism of NIR on bone regeneration remain unclear. We demonstrated that bone regeneration in the rat skull defect model was significantly accelerated with low-intensity NIR stimulation. In vitro studies showed that NIR stimulation could promote the osteoblast differentiation in bone mesenchymal stem cells (BMSCs) and MC3T3-E1 cells, which was associated with increased ubiquitination of the core circadian clock protein Cryptochrome 1 (CRY1) in the nucleus. We found that the reduction of CRY1 induced by NIR light activated the bone morphogenetic protein (BMP) signaling pathways, promoting SMAD1/5/9 phosphorylation and increasing the expression levels of Runx2and Osterix. NIR light treatment may act through sodium voltage-gated channel Scn4a, which may be a potential responder of NIR light to accelerate bone regeneration. Together, these findings suggest that low-intensity NIR light may promote in situ bone regeneration in a CRY1-dependent manner, providing a novel, efficient and non-invasive strategy to promote bone regeneration for clinical bone defects.

A comparative study on the influence of different manufacturing methods (selective laser melting and hot rolling) on the microstructure, mechanical and thermal behaviours of tungsten (W) was presented for the first time. The results indicated that the selective laser melting (SLM) W exhibited a finer grain sizes, a lower strength ductility, hardness and thermal conductivity compared to hot-rolled W. The main reason for this result was that the laser underwent rapid heating and cooling when it was used to melt W powder with high energy density, resulting in large internal stress in the sample after manufacturing. Subsequently, the internal stress was released, leading to the generation of micro-cracks at the grain boundaries, thereby affecting the performance of SLM W samples. In addition, the higher fraction of high-angle grain boundaries (HAGBs) of SLM W was found to be the key factor for intrinsic brittleness. Because the HAGBs are the preferred crack paths, which could promote crack propagation and decrease fracture energy.

Alumina-based ceramic molds are extensively applied in investment casting processes of hollow turbine blade due to their outstanding high-temperature chemical stability and creep resistance. Herein, laser powder bed fusion (L-PBF) method was utilized to fabricate an alumina-based ceramic mold with integral core and shell (CMCS). The influences of the component contents in the composite powder on fluidity and packing density were comprehensivley studied, and the optimized formulation for the composite powder was consequently determined as 88 wt% mixed spherical alumina (coarse: fine = 9:1), 12 wt% epoxy resin E12, and 0.1 wt% fumed silica. The vacuum infiltration process was adopted to improve mechanical properties of alumina ceramic after the sintering, where the solid loading of ceramic slurry was investigated. The CMCS was divided into two parts for fabrication, i.e., the core&shell and the base with a spiral grain selector, which could facilitate convenient of cleaning residual powder due to enlarged openings. After the first infiltration and pre-sintering, the separated two parts were bonded by a ceramic binder and then underwent second infiltration and final-sintering to obtain a complete CMCS. The alumina-based ceramic fabricated through L-PBF and post-treatment possessed low sintering shrinkage (1.51–2.03%), adequate apparent porosity (30.82 ± 0.01%), and room-temperature strength (13.03 ± 2.90 MPa for unbonded specimen, 9.72 ± 1.34 MPa for bonded specimen). Strikingly, the subsequent casting experiment has proved that the method proposed in this paper is promising to fabricate superior alumina-based CMCSs.

Porous poly-ether-ether-ketone (PEEK) scaffolds have a good application prospect in orthopedics because of their excellent biocompatibility, chemical stability, and permeability. However, the porous PEEK scaffolds fabricated by conventional manufacturing methods are restricted to the uncontrollable and weak mechanical properties. In this work, porous PEEK scaffolds with highly-tunable elastic modulus are designed using typical triply periodic minimal surface (TPMS) structures, Gyroid, Diamond, I-WP, and then printed by laser powder bed fusion (LPBF). The effects of unit cell type and volume fraction on the manufacturing deviation, stress distribution, and mechanical properties of LPBF-printed PEEK scaffolds are investigated. The results illustrate that the Gyroid scaffolds present the lowest volume fraction deviation, followed by the I-WP scaffolds. By adjusting the volume fraction, the elastic modulus of the TPMS scaffolds is in the range of 42.17–512.12 MPa, which is comparable with those of human trabecular bones. Using the finite element (FE) simulation method, the experimental mechanical properties of the TPMS scaffolds can be predicted. In summary, the Gyroid structure is the optimal choice for the design and LPBF fabrication of porous PEEK scaffolds due to the best manufacturing fidelity and relatively good mechanical properties.