材料テクトニクス工学と光造形アディティブ・マニュファクチャリング

Mechanical properties of Al2O3 and Al2O3/Al with Gyroid structure obtained by stereolithographic additive manufacturing and melt infiltration

Quantitative characterization of defects in stereolithographic additive manufactured ceramic using X-ray computed tomography

Impact performance enhancement of honeycombs through additive manufacturing-enabled geometrical tailoring

The aim of the present study was to evaluate the effect of the build angle and the support configuration (thick versus thin support) on the dimensional accuracy of 3D-printed full-coverage dental restorations. A full-coverage dental crown was digitally designed and 3D-printed using stereolithography-additive manufacturing (SLA-AM) technology. Nine different angles were used during the build process: 90, 120, 135, 150, 180, 210, 225, 240, and 270 degrees. In each angle, the crown was printed using a thin and a thick support type, resulting in 18 specimens. The specimens were digitally scanned using a high resolution optical surface scanner (IScan D104i; Imetric 3D). The dimensional accuracy was evaluated by digital subtraction technique. The 3D digital files of the scanned printed crowns (test model), exported in standard tessellation language (STL) format, were superimposed with the STL file of the designed crown (reference model) using Geomagic Studio 2014 (3D Systems). The root mean square estimate value and color map results suggest that the build angle and support structure configuration have an influence on the dimensional accuracy of 3D-printed crown restorations. Among the tested angles, the 120-degree build angle showed a minimal deviation of 0.029 mm for thin support and 0.031 mm for thick support, indicating an accurate fit between the test and reference models. Furthermore, the deviation pattern observed in the color map was homogenously distributed and located further away from the critical marginal area. Within the limitations of this study, the selection of build angle should offer the crown the highest dimensional accuracy and self-supported geometry. This allows for the smallest necessary support surface area and decreases the time needed for finishing and polishing. These properties were mostly observed with a build angle of 120 degrees combined with a thin support type.

光造形アディティブ・マニュファクチャリングによる空間格子の配位数制御

Superparamagnetic iron oxide nanoparticles (SPIONs) represent an emerging class of nanoparticles that face increasing applications in medicine, in particular in nanoparticle-based oncology. Their superparamagnetic properties allow for the magnetic steering and the interlinked targeted and localized delivery of pharmaceuticals. The development of nanoparticle-based therapies requires a deep understanding of geometry-hydrodynamics-adhesion interactions, motivating the generation of blood vessel models. The present work addresses the geometry-dependent propagation of SPIONs under magnetic steering through generalized, transferable geometries. Such geometries were derived based on generalized, statistical considerations of branch-dependent vessel diameters, yielding a reproducible and transferable testing environment independent of individual angiographic data. Based on stereolithographic additive manufacturing, fluidic models with varied blood vessel diameters and branching orders were manufactured and tested under varying magnetic steering conditions, injected SPION concentration, and flow rate. Through optical in situ measurements and complementary ex situ scanning electron microscopy, a significant influence of flow-regime-dependent hydrodynamic effects on magnetic steerability could be identified. Experimental findings suggest that while reduced flow rates were associated with locally laminar flows that promoted sedimentation and enabled limited magnetic redistribution of SPION-containing colloidal solutions at a magnetic flux density of B = 0.35 T, increased flow rates and interlinked unsteady flows were shown to impair the magnetically controlled, local SPION deposition. Hence, flow conditions present in larger arteries and bifurcations during SPION injection can be shown to significantly influence the quantitative magnetic steering of SPIONs in vascular-inspired fluidic channel structures, displaying enhanced local particle residence times and redistribution of SPIONs under low-flow conditions.

Three dimensional micro photonic crystals with a diamond structure made of a dense titania and alumina were fabricated successfully by using stereolithographic additive manufacturing. Photonic band gap properties were investigated in gigahertz and terahertz wave frequency ranges. Acrylic diamond lattice structures with nanometer sized particles of titania and alumina dispersion at 40 vol. % were fabricated by the stereolithography. The forming accuracy was 10 μm. After dewaxing and sintering process, the titania and alumina diamond lattice structures were obtained. The relative density reached above 98 %. Electromagnetic wave transmittances were measured by using a W-band millimeter waveguide connected with a network analyzer and a terahertz wave time domain spectroscopy. In the transmission spectra for the Γ-X <100> direction, a forbidden band was observed at 90 – 110 GHz and 0.4 – 0.6 THz. The band gap frequencies well agreed with calculated results by plane wave expansion (PWE) method. Additionally, simulated results by transmission line modeling (TLM) method indicated that a localized mode can be obtained by introducing a plane defect between twinned diamond lattice structures.

This paper presents a novel over-the-air (OTA) gesture recognition system using a single antenna, 3D-printed using liquid metals infills, and utilizing magnitude-only RF transmission data, unlike previous approaches that rely on phase or complex-valued data. The antenna is fabricated via stereolithographic additive manufacturing with liquid metal microchannels, enabling a wearable and deformable sensing platform. Gestureinduced variations in antenna gain are detected in the farfield through received power measurements, eliminating the need for multiple antennas or phase calibration. The antenna's <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\left\vert S_{21}\right\vert$</tex> response was measured at -45 dB at 3.64 m and a frequency bandwidth in the MHz range, with gesture capture performed using a vector network analyzer (VNA) over a bandwidth of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$150-300 \text{MHz}$</tex>. A dataset of 10 British Sign Language gestures was collected at a distance exceeding 3.5 m and classified using machine learning (ML) techniques. The results show a high accuracy of 92%, validating magnitude-based OTA sensing relying on uncalibrated S-parameter magnitudes.

For ceramic stereolithographic (SL) additive manufacturing, the solid loading of ceramic photosensitive slurry plays an important role during the SL process. In this study, Al 2 O 3 ceramics were fabricated by SL additive manufacturing from photosensitive Al 2 O 3 slurries with various solid loadings, and the solid loading-property relationships of Al 2 O 3 ceramic were performed. The effects of solid loading on not only the rheological behavior and curing property of the photosensitive Al 2 O 3 slurry but also the microstructure and mechanical properties of the Al 2 O 3 ceramic were investigated. The results showed that both the viscosity and shear stress increased with the increase of the solid loading. High viscosity was greater than the critical value for self-leveling during the SL process. The curing properties of photosensitive Al 2 O 3 slurries were highly depended on the sold loading. Moreover, clear effects on the defect characteristics of Al 2 O 3 ceramics manufactured from various photosensitive slurries were observed. These manufactured defects are critical for the mechanical behavior of Al 2 O 3 ceramic. In addition, the relationship between rheological behavior and curing property of photosensitive Al 2 O 3 slurry. Meanwhile, the resulting microstructure and mechanical properties of the Al 2 O 3 ceramic were also illustrated. Inhomogeneous structure caused by high viscosity can lead to a sintered ceramic with poor strength. These findings provide fundamental understanding for SL additive manufacturing of ceramics.

In this paper we demonstrate that it is possible to produce low cost neutron-sensitive detectors using stereo-lithography additive manufacturing. A curable scintillating resin is made by mixing BN/ZnS with a commercially available UV resin. This resin is used to print several small area neutron detectors made of arrays of BN/ZnS cones that can be directly coupled to a photo-multiplier tube.

Octet-truss lattice structures can be used for lightweight structural applications due to their high strength-to-density ratio. In this research, octet-truss lattice specimens were fabricated by stereolithography additive manufacturing with a photopolymer resin. The mechanical properties of this structure have been examined in three orthogonal orientations under the compressive load. Detailed comparison and description were carried out on deformation mechanisms and failure modes in different lattice orientations. Finite element models using both beam elements and three-dimensional solid elements were used to simulate the compressive response of this structure. Both the load reaction and collapse modes obtained in simulations were compared with test results. Our results indicate that three-dimensional continuum element models are required to accurately capture the behaviour of real trusses, taking into account the effects of finite-sized beams and joints.

Strain rate sensitivity of rotating-square auxetic metamaterials

Chapter 1 - Overview of additive manufacturing technology and materials

Irregular 3D biological scaffolds have been widely observed in nature. Therefore, in the current work, new designs are proposed for lightweight 3D scaffolds based on Voronoi tessellation with high porosity. The proposed designs are inspired by nature, which has undoubtedly proven to be the best designer. Thus, the Rhinoceros 7/Grasshopper software was used to design three geometric models for both normal and elongated Voronoi structures: homogeneous, gradient I, and gradient II. Then, stereolithography (SLA) additive manufacturing was utilized to fabricate biopolymeric materials. Finally, a compression test was carried out to study and compare the mechanical properties of the designed samples. The gradient I cylinder show the highest Young's modulus. For the Homogeneous and gradient II cylinders, elongated Voronoi structures show superior mechanical properties and energy absorption compared to normal Voronoi designs. Hence, these designs are promising topologies for future applications.

Purpose Manufacturing companies still struggle to integrate additive manufacturing (AM) technologies with existing traditional manufacturing technologies. This paper explores AM technology integration into a global manufacturing company from an operational capability perspective. Design/methodology/approach The research was conducted using a single case study in collaboration with a global heavy-duty vehicle manufacturer. Data were collected through a focus group and interviews representing management and engineering roles. Additional data were collected from meetings, company documents, field notes and observations. Subsequently, the collected data were analyzed thematically. Findings The findings reveal that, despite the company embarking on its AM technology integration journey, it encountered challenges, including cognitive fixation, manufacturing fixation, situational awareness, ambiguous ownership and the make-or-buy dilemma. Furthermore, the findings showed that the company developed operational capabilities – such as developing proficiency in AM know-how, continuous use of AM technology, operational practices for AM technology, cross-collaboration for AM initiatives and business cases for AM technology – to address these challenges. A facilitation model was developed, outlining essential actions prioritized for the short-term, mid-term and long-term. These actions leverage the operational capabilities to address challenges in AM technology integration. Originality/value This paper offers an in-depth exploration of AM technology integration in a global heavy-duty vehicle manufacturer. It introduces a novel application of operational capability theory and proposes a facilitation model for managers and academics in pursuit of achieving AM technology integration.