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Bioprinting three‐dimensional (3D) tissue equivalents have progressed tremendously over the last decade. 3D bioprinting is currently being employed to develop larger and more physiologic tissues, and it is of particular interest to generate vasculature in biofabricated tissues to aid better perfusion and transport of nutrition. Having an advantage over manual culture systems by bringing together biological scaffold materials and cells in precise 3D spatial orientation, bioprinting could assist in placing endothelial cells in specific spatial locations within a 3D matrix to promote vessel formation at these predefined areas. Hence, in the present study, we investigated the use of bioprinting to generate tissue‐level capillary‐like networks in biofabricated tissue constructs. First, we developed a bioink using collagen type‐1 supplemented with xanthan gum (XG) as a thickening agent. Using a commercial extrusion‐based multi‐head bioprinter and collagen‐XG bioink, the component cells were spatially assembled, wherein the endothelial cells were bioprinted in a lattice pattern and sandwiched between bioprinted fibroblasts layers. 3D bioprinted constructs thus generated were stable, and maintained structural shape and form. Post‐print culture of the bioprinted tissues resulted in endothelial sprouting and formation of interconnected capillary‐like networks within the lattice pattern and between the fibroblast layers. Bioprinter‐assisted spatial placement of endothelial cells resulted in fabrication of patterned prevascularized constructs that enable potential regenerative applications in the future. [ABSTRACT FROM AUTHOR]

The development of the Internet of things has prompted an exponential increase in the demand for flexible, wearable devices, thereby posing new challenges to their integration and conformalization. Additive manufacturing facilitates the fabrication of complex parts via a single integrated process. Herein, the development of a multinozzle, multimaterial printing device is reported. This device accommodates the various characteristics of printing materials, ensures high‐capacity printing, and can accommodate a wide range of material viscosities from 0 to 1000 Cp. Complete capacitors, inclusive of the current collector, electrode, and electrolyte, can be printed without repeated clamping to complete the preheating, printing, and sintering processes. This method addresses the poor stability issue associated with printed electrode materials. Furthermore, after the intercalation of LiFePO4 with Na ions, X‐ray photoelectron spectroscopy and X‐ray diffraction results reveal that the Na ions permeate the interlayer structure of LiFePO4, enhancing the ion migration channels by increasing the ion transmission rate. A current rate of 2.5 mAh ensures >2000 charge/discharge cycles, while retaining a charge/discharge efficiency of 96% and a discharge capacity of 91.3 mAh g−1. This manufacturing process can provide conformal power modules for a diverse range of portable devices with various shapes, improving space utilization. [ABSTRACT FROM AUTHOR]

Metallic lattice structures are well known for having high specific elastic moduli and strength. However, very little is understood about their resistance to fracture. In this work Ti–6Al–4V lattice structures are additively manufactured by selective laser melting and their fracture toughness characteristics are investigated. Resistance to fracture was determined under Mode-I loading at static rates using an extended compact tension (EC(T)) specimen, modified to contain lattice cells. The lattices consist of octet cells with a 3.5 mm edge length and relative densities ranging from 25% to 56%. Toughness is shown to increase by a power law with relative density and this trend was also obtained with finite element models. A new functional grading optimisation methodology is also presented for increasing fracture toughness. The size optimisation results in a functionally graded lattice whereby lattice truss diameters become the design variables. After size optimisation, initiation fracture toughness increases by up to 37%. Image 1 • Novel optimisation method for generating lattices with high fracture toughness. • Crack size effect on toughness is suppressed by tailoring lattice truss diameters. • Additively manufactured lattices validate FE models with good agreement. [ABSTRACT FROM AUTHOR]

Additive manufacturing enables the fabrication of periodic ceramic lattices with controllable micro-architectures. Many studies reported their catastrophic brittle fracture behaviour. However, ceramic lattices may fail by a layer-by-layer pseudo-ductile fracture mode, by controlling micro-architectures and porosities. Moreover, their fracture behaviour can be optimised by introducing strut/wall thickness gradients. This paper investigates the fracture behaviour and the fracture mode transition of ceramic triply periodic minimal surface (TPMS) structures. Alumina TPMS structures with relative densities of 0.14-0.37 are fabricated by ceramic stereolithography. Quasi-static compression tests validate a transition density range for non-graded samples: low (<0.21) and moderate (>0.25) relative density samples show layer-by-layer pseudo-ductile and catastrophic brittle fracture modes, respectively. The pseudo-ductile failure mode increases the energy absorption performance, enabling load-bearing capacity for a compressive strain up to 50%. With appropriate thickness gradients, graded structures exhibit significant increase of energy absorption without a decrease of fracture strength compared to their non-graded counterparts. [ABSTRACT FROM AUTHOR]

Lightweight lattice structures are an important class of cellular structures with high potentials for multi-functional applications. Considering load-bearing requirements, truss buckling is one of the main failure mechanisms for low density and slender lattice structures. Critical buckling loads can be increased by modifying the profile of a truss. In this paper, we present a shape design method to optimize the critical buckling loads for lattice cores with free-form trusses. The free-form truss is represented by Fourier series and implicit surfaces, having smooth truss diameter variations and truss joints. The optimized truss profile is obtained by solving a parametric shape optimization problem with Fourier series coefficients as design variables. The method is used for designing optimized 1D columns and 3D Kagome lattice cores for sandwich panels. The numerical results predict 26.8% and 20.4% improvements of the critical buckling loads for 1D columns and 3D Kagome lattice cores compared to their uniform counterparts of the same mass, respectively. The optimized structures include complex smooth and curved geometries that are well suited for additive manufacturing because of the greater design freedom. Finally, the initial and optimized lattice cores are additively manufactured and tested. The experimental results validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Ensuring the removability of support structure and improving the surface quality of assembly interface are two key requirements to guarantee a model a valid fabrication and promote its kinematic performance in a product. Generally, determining a suitable fabrication orientation for the model is an effective way to meet those requirements. Accordingly, a novel validity- and kinematics-aware approach for optimizing fabrication orientation is proposed in this work. Viewing that it is effective and efficient (in an optimizing process) to evaluate whether a fabrication orientation will take unremovable support structures to a model by checking whether they contact the model on its inaccessible surface regions, a new voxel-based surface-accessibility analysis method is proposed. In detail, to analyze the accessibility (by a cleaning tool) of each surface region accurately, the input model and its bounding box are voxelized together first and represented by using a new voxel-adjacency graph. Then, integrating rapid individual-single-accessibility analysis, voxel-layer-scan analysis, and accessible direction reuse, a parallelable variable-neighborhood-search method is put forward based on the above graph. With this method, all inaccessible surface regions (if any) of the model can be effectively and efficiently identified at once. Moreover, the above-mentioned key requirements are usually two conflicting goals (especially for a model having two or more assembly interfaces) in determining suitable fabrication orientations. To make those goals reconcile with each other, a multi-objective optimization problem is first formulated to explore a set of pareto-optimized fabrication orientations. Here, two new functions are elaborately designed to evaluate the removability of support structures (by counting the number of inaccessible surface regions that appear support structures) and the surface quality of assembly interfaces, respectively. Finally, a greedy method is adopted to recommend one from these compromising fabrication orientations to the uses as the best-suitable fabrication orientation. Experiments are presented to demonstrate the characteristics, effectiveness, and efficiency of the approach. The methodological comparisons also show that the approach has several advantages in AM applications where support structures are mainly removed manually and the models are fabricated for mechanisms. • Optimizing fabrication orientation by reconciling validity with kinematics. • Smart and efficient accessible analysis by parallelable variable neighborhood search. • Rapid finding accessible surface regions by voxel-layer scan in voxel-adjacency graph. [ABSTRACT FROM AUTHOR]

The effects of trace MoSi 2 addition on the microstructure evolution, mechanical properties and fracture behavior of Ti–6Al–4V wall via cold metal transfer additive manufacturing (CMTAM) were investigated. After the addition of trace MoSi 2 powder, trace (β-Ti, Mo) phase and SiO 2 particles were obtained and partly prior-β→α' phase transformation was suppressed. Compared with the as-built Ti–6Al–4V wall, the prior-β grains changed from columnar to the equiaxed or near-equiaxed after the addition of trace MoSi 2. The tensile analysis result revealed that the addition of trace MoSi 2 could improve the average strain while reduce anisotropy. All specimens showed dimples corresponding to ductile failure mode. The possible thermal cycles for the trace-MoSi 2 -addition specimens during the CMTAM process were analyzed. • Ti–6Al–4V walls with trace MoSi 2 addition were manufactured via CMTAM. • The prior-β grains changed from columnar to the (near-)equiaxed and refined by MoSi 2. • The prior-β.→ α′ phase transformation was suppressed by MoSi 2 several times during CMTAM. • Elongation can be improved owing to grain refinement of prior-β and reduction in acicular α′ martensite. • Anisotropy can be reduced due to grain refinement of prior-β. [ABSTRACT FROM AUTHOR]