3D photonic crystals with a hierarchical pore structure

Perfect 3D film photonic crystals are synthesized from submicron spherical silica particles consisting of a nonporous core and a mesoporous shell. The obtained photonic crystals with a hierarchical pore arrangement—transport macropores between particles and mesopores inside the shell—are promising for application in optical gas sensors.     

Mechanical properties of rock specimens containing pre‐existing flaws with 3D printed materials

Three‐dimensional printing (3DP) technology has undergone a rapid development in the last few years and become a useful tool in many research fields. This study applied 3DP technology to prepare solid specimens simulating rock‐type materials combined with computed tomography scanning and 3D image processing. 3DP specimens with pre‐existing flaws in different inclination angles were fabricated and then conducted a series of mechanical experiments to study the influence of number and inclination angle of pre‐existing flaw on strength and failure patterns under uniaxial compression. The experimental results indicated that 3DP specimens had similar mechanical properties with rock‐type materials. The 3DP specimens with 2 pre‐existing flaws had lower compressive strength with an average of 4.26 MPa, whereas compressive strength of specimens with one flaw was no less than 5.08 MPa. Different inclination angles led to various failure patterns and compressive strengths, which took on a V‐shaped curve with the increase of inclination angles. This study demonstrated that 3DP technology provided a new perspective for conducting laboratory experimental research of rock mechanics.     

Mechanical properties of 3D printed interpenetrating phase composites with novel architectured 3D solid-sheet reinforcements

Interpenetrating phase composites (IPCs) are novel types of multifunctional composite materials. This work focuses on investigating experimentally and computationally the mechanical behavior of novel types of three-dimensional (3D) architectured two-phase IPCs. The current IPCs are architectured using several morphologies of the fascinating and mathematically-known triply periodic minimal surfaces (TPMS) that promote several multifunctional attributes. Specifically, the second hard reinforcing phase takes the architecture of one of the 3D non-intersecting and continuous TPMS-based solid sheets. The mechanical response of the 3D printed polymer-based IPCs is measured under uniaxial compression where the effect of varying the second-phase architecture and volume fraction is explored. Anisotropy induced by the 3D printing is also investigated. 3D finite element analysis has been performed and validated for predicting elastic properties of the various types of TPMS-based IPCs. The most effective TPMS architecture in enhancing the mechanical properties and damage-tolerance has been identified.     

3D Metal printed heat sinks with longitudinally varying lattice structure sizes using direct metal laser sintering

This research relates to the design, modelling and fabrication of 3D metal printed heat sinks. The heat sinks presented in the research are the commonly used longitudinal fin solid heat sink (LFSHS) and three LFSHS lattice structure designs, differing only in their lattice sizes, fabricated using the Direct Metal Laser Sintering (DMLS) technique in Maraging Steel (MS1), on an EOSINT M280 system. In order to increase the heat sink surface area, the heat sinks are manufactured with mesh lattices along the length of the fins, while keeping the overall heat sink volume constant. The research is focused on pushing the limitations of the DMLS technique for the development of repeating unit, lattice structures heat sinks, and to examine the effect of incrementally varying the lattice sizes with regards to the resultant surface area of the heat sink and the thermal performance of the system. The results obtained under natural convection show that the thermal performance of the LFSHS outperformed all lattice structure heat sinks. This is due to the fact that, the pressure drop across the lattice heat sinks were so high, due to lattice meshes that it negated the positive effect of the greater surface area.     

Nanostructured Superhydrophobic Substrates Trigger the Development of 3D Neuronal Networks

The generation of 3D networks of primary neurons is a big challenge in neuroscience. Here, a novel method is presented for a 3D neuronal culture on superhydrophobic (SH) substrates. How nano‐patterned SH devices stimulate neurons to build 3D networks is investigated. Scanning electron microscopy and confocal imaging show that soon after plating neurites adhere to the nanopatterned pillar sidewalls and they are subsequently pulled between pillars in a suspended position. These neurons display an enhanced survival rate compared to standard cultures and develop mature networks with physiological excitability. These findings underline the importance of using nanostructured SH surfaces for directing 3D neuronal growth, as well as for the design of biomaterials for neuronal regeneration.     

Design of a 3D printed concrete bridge by testing*

The current state of research and development into the additive manufacturing of concrete is poised to become a disruptive technology in the construction industry. Although many academic and industrial institutions have successfully realised full-scale structures, the limitations in the current codes of practice to evaluate their structural integrity have resulted in most of these structures still not being certified as safe for public utilisation and thus deemed as test prototypes for display purpose only. To realise a 3D concrete printed (3DCP) structure which could be certified safe for public use, a bridge was realised using the print facility of the Eindhoven University of Technology (TU/e) based on the concept of ‘Design by Testing’. This paper holistically discusses the complications encountered while realising a reinforced 3DCP bridge in a public traffic network and decisions taken to find solutions for overcoming them.     

High performance natural rubber composites with a hierarchical reinforcement structure of carbon nanotube modified natural fibers

A simple and facile method for depositing multiwall carbon nanotubes (MWCNTs) onto the surface of naturally occurring short jute fibers (JFs) is reported. Hierarchical multi-scale structures were formed with CNT-networks uniformly distributed and fully covering the JFs (JF–CNT), as depicted by the scanning electron microscopy (SEM) micrographs. The impact of these hybrid fillers on the mechanical properties of a natural rubber (NR) matrix was systematically investigated. Pristine JFs were cut initially to an average length of 2.0 mm and exposed to an alkali treatment (a-JFs) to remove impurities existing in the raw jute. MWCNTs were treated under mild acidic conditions to generate carboxylic acid moieties. Afterward, MWCNTs were dispersed in an aqueous media and short a-JFs were allowed to react with them. Raman spectroscopy confirmed the chemical interaction between CNTs and JFs. The JF–CNT exposed quite hydrophobic behavior as revealed by the water contact angle measurements, improving the wettability of the non-polar NR. Consequently, the composite interfacial adhesion strength was significantly enhanced while a micro-scale “mechanical interlocking” mechanism was observed from the interphase-section transmission electron microscopy (TEM) images. SEM analysis of the composite fracture surfaces demonstrated the interfacial strength of NR/a-JF and NR/JF–CNT composites, at different fiber loadings. It can be presumed that the CNT-coating effectively compatibillized the composite structure acting as a macromolecular coupling agent. A detailed analysis of stress-strain and dynamic mechanical spectra confirmed the high mechanical performance of the hierarchical composites, consisting mainly of materials arising from natural resources.     

Ductility of 3D printed concrete reinforced with short straight steel fibers

ABSTRACT

With the number of 3D printed concrete structures rapidly increasing, the demand for concepts that allow for robust and ductile printed objects becomes increasingly pressing. An obvious solution strategy is the inclusion of fibers in the printed material. In this study, the effect of adding short straight steel fibers on the failure behaviour of Weber 3D 115-1 print mortar has been studied through several CMOD tests on cast and printed concrete, on different scales. The experiments have also been simulated numerically. The research has shown that the fibers cause an important increase in flexural strength, and eliminate the strength difference between cast and printed concrete that exists without fibers. The post-peak behaviour, nevertheless, has to be characterised as strongly strain-softening. In the printed specimens, a strong fiber orientation in the direction of the filament occurs. However, this has no notable effect on the performance in the tested direction: cast and printed concrete with fibers behave similarly in the CMOD test. For the key parameters, no scale effect was found for the specimens with fibers, contrary to the ones without. Numerical modelling of the test by using the Concrete Damage Plasticity material model of Abaqus, with a Thorenfeldt-based constitutive law in compression and a customised constitutive law in tension, results in a reasonable fit with the experimental results.     

Quick high-temperature hydrothermal synthesis of mesoporous materials with 3D cubic structure for the adsorption of lysozyme

Abstract

Three-dimensional cage-like mesoporous FDU-12 materials with large tuneable pore sizes ranging from 9.9 to 15.6 nm were prepared by varying the synthesis temperature from 100 to 200 °C for the aging time of just 2 h using a tri-block copolymer F-127(EO₁₀₆PO₇₀EO₁₀₆) as the surfactant and 1,3,5-trimethyl benzene as the swelling agent in an acidic condition. The mesoporous structure and textural features of FDU-12-HX (where H denotes the hydrothermal method and X denotes the synthesis temperature) samples were elucidated and probed using x-ray diffraction, N₂ adsorption, ²⁹Si magic angle spinning nuclear magnetic resonance, scanning electron microscopy and transmission electron microscopy. It has been demonstrated that the aging time can be significantly reduced from 72 to 2 h without affecting the structural order of the FDU-12 materials with a simple adjustment of the synthesis temperature from 100 to 200 °C. Among the materials prepared, the samples prepared at 200 °C had the highest pore volume and the largest pore diameter. Lysozyme adsorption experiments were conducted over FDU-12 samples prepared at different temperatures in order to understand their biomolecule adsorption capacity, where the FDU-12-HX samples displayed high adsorption performance of 29 μmol g^?1 in spite of shortening the actual synthesis time from 72 to 2 h. Further, the influence of surface area, pore volume and pore diameter on the adsorption capacity of FDU-12-HX samples has been investigated and results are discussed in correlation with the textural parameters of the FDU-12-HX and other mesoporous adsorbents including SBA-15, MCM-41, KIT-5, KIT-6 and CMK-3.     

Applications of excipients in the field of 3D printed pharmaceuticals

The aim of this study was to determine the effect of varying excipient content on the formation and physical properties of 3?D printed tablets. Fifteen different excipient preparations were formed into tablets with radii of 5?mm and thickness of 2?mm, using binder jetting (BJ). The tablets were analyzed by assessing visual and microstructural appearance, friability, hardness, and disintegration time. We found that filling agents with high water solubility (e.g. D-sucrose), binding agents with a high viscosity in solution (e.g. polyethylene glycol 4000) and moistening agent with higher water content can increase the bonding strength and hardness of the 3?D printed tablets and prolonged their disintegration time. This work has demonstrated that the type of excipient and its concentration affects the properties of the 3?D printed tablet. This article may be used as a guide for elucidation of the effects of using conventional tablet excipients in the field of 3?D printed pharmaceuticals. The present work should enable the identification of excipients that satisfy requirements, reduce analysis time, and improve efficiency.     

Quick high-temperature hydrothermal synthesis of mesoporous materials with 3D cubic structure for the adsorption of lysozyme

Three-dimensional cage-like mesoporous FDU-12 materials with large tuneable pore sizes ranging from 9.9 to 15.6 nm were prepared by varying the synthesis temperature from 100 to 200 °C for the aging time of just 2 h using a tri-block copolymer F-127(EO₁₀₆PO₇₀EO₁₀₆) as the surfactant and 1,3,5-trimethyl benzene as the swelling agent in an acidic condition. The mesoporous structure and textural features of FDU-12-HX (where H denotes the hydrothermal method and X denotes the synthesis temperature) samples were elucidated and probed using x-ray diffraction, N₂ adsorption, ²⁹Si magic angle spinning nuclear magnetic resonance, scanning electron microscopy and transmission electron microscopy. It has been demonstrated that the aging time can be significantly reduced from 72 to 2 h without affecting the structural order of the FDU-12 materials with a simple adjustment of the synthesis temperature from 100 to 200 °C. Among the materials prepared, the samples prepared at 200 °C had the highest pore volume and the largest pore diameter. Lysozyme adsorption experiments were conducted over FDU-12 samples prepared at different temperatures in order to understand their biomolecule adsorption capacity, where the FDU-12-HX samples displayed high adsorption performance of 29 μmol g⁻¹ in spite of shortening the actual synthesis time from 72 to 2 h. Further, the influence of surface area, pore volume and pore diameter on the adsorption capacity of FDU-12-HX samples has been investigated and results are discussed in correlation with the textural parameters of the FDU-12-HX and other mesoporous adsorbents including SBA-15, MCM-41, KIT-5, KIT-6 and CMK-3.     

Preparation and characterization of a novel porous titanium scaffold with 3D hierarchical porous structures

This study aims to prepare a novel porous titanium (Ti) scaffold in order to improve the biocompatibility of the metallic implants. Porous Ti was produced by a Liquid foaming method and subsequent chemical treatments. It was found that the scaffold had three-dimensionally hierarchical porous structures with pore size ranging from nanometer to micrometer scale, and it also had activated surface. Mechanical test results showed that the scaffold also has sufficient compressive strength to meet the requirements of implantation. Protein adsorption results indicated that the novel scaffolds significantly enhanced the protein adsorption.     

The chemical,mechanical, and physical properties of 3D printed materials composed of TiO2-ABS nanocomposites

To expand the chemical capabilities of 3D printed structures generated from commercial thermoplastic printers, we have produced and printed polymer filaments that contain inorganic nanoparticles. TiO₂ was dispersed into acrylonitrile butadiene styrene (ABS) and extruded into filaments with 1.75 mm diameters. We produced filaments with TiO₂ compositions of 1, 5, and 10% (kg/kg) and printed structures using a commercial 3D printer. Our experiments suggest that ABS undergoes minor degradation in the presence of TiO₂ during the different processing steps. The measured mechanical properties (strain and Young’s modulus) for all of the composites are similar to those of structures printed from the pure polymer. TiO₂ incorporation at 1% negatively affects the stress at breaking point and the flexural stress. Structures produced from the 5 and 10% nanocomposites display a higher breaking point stress than those printed from the pure polymer. TiO₂ within the printed matrix was able to quench the intrinsic fluorescence of the polymer. TiO₂ was also able to photocatalyze the degradation of a rhodamine 6G in solution. These experiments display chemical reactivity in nanocomposites that are printed using commercial 3D printers, and we expect that our methodology will help to inform others who seek to incorporate catalytic nanoparticles in 3D printed structures.     

蘑菇状多孔分级结构ZnTiO3/TiO2复合光催化剂的制备

以碱式醋酸锌和钛酸四正丁酯分别为锌源和钛源,采用溶胶-凝胶过程合成了具有蘑菇形状分级结构的ZnTiO3/TiO2复合光催化剂,并应用XRD、FT-IR、FESEM和光电流等分析技术,考察了锌-钛比例、煅烧温度对所合成光催化剂的形貌、微结构及光电特性的影响.当样品锌-钛物质的量比为1∶3,煅烧温度为500℃时,催化剂粒子...     

A preliminary study of cushion properties of a 3D printed thermoplastic polyurethane Kelvin foam

The cells in conventional packaging foams have random size and orientation, and the energy‐absorbing behaviour of these foams is determined by the collective contribution of different sizes of cells. In contrast to the random nature of stochastic foams, 3D printing technologies allow engineers to design and produce foams having engineered cellular structures. In this study, engineered cellular structures based on the classic Kelvin 1887 model were 3D printed in 30 × 30 × 30 mm thermoplastic polyurethane cubes with a repeating size of 216 unit cells. One hundred consecutive cyclic compression tests were performed to assess the 3D printed foam's resilience and energy absorption characteristics. The stress‐strain curve of the 3D printed thermoplastic polyurethane foam indicated viscoelastic behaviour and a Mullins effect indicative of resilient rubber. A long wave buckling mode was observed during cyclic compression cycles due to the Kelvin structure. The cushion factor computed from the stress‐strain curve was close to that of a metal spring with linear elasticity. The combination of the 3D printed foam's resilience, its much lower density than rubber, and the complete geometric freedom of the engineered cellular structures offer designers the potential to create high‐performance cushion materials tailored for packaging applications.     

Combinatorial On‐Chip Study of Miniaturized 3D Porous Scaffolds Using a Patterned Superhydrophobic Platform

One of the main challenges in tissue engineering (TE) is to obtain optimized products, combining biomaterials, cells and soluble factors able to stimulate tissue regeneration. Multiple combinations may be considered by changing the conditions among these three factors. The unpredictable response of each combination requires time‐consuming tests. High‐throughput methodologies have been proposed to master such complex analyses in TE. Usually, these tests are performed using cells cultured into 2D biomaterials or by dispensing arrays of cell‐loaded hydrogels. For the first time an on‐chip combinatorial study of 3D miniaturized porous scaffolds is proposed, using a patterned bioinspired superhydrophobic platform. Arrays of biomaterials are dispensed and processed in situ as porous scaffolds with distinct composition, surface characteristics, porosity/pore size, and mechanical properties. On‐chip porosity, pore size, and mechanical properties of scaffolds based on chitosan and alginate are assessed by adapting microcomputed tomography equipment and a dynamic mechanical analyzer, as well as cell response after 24 hours. The interactions between cell types of two distinct origins—osteoblast‐like and fibroblasts—and the scaffolds modified with fibronectin are studied and validated by comparison with conventional destructive methods (dsDNA quantification and MTS tests). Physical and biological on‐chip analyses are coherent with the conventional measures, and conclusions about the most favorable conditions for each cell type are taken.     

Transfer printing of 3D hierarchical gold structures using a sequentially imprinted polymer stamp

Complex three-dimensional (3D) hierarchical structures on polymeric materials are fabricated through a process referred to as sequential imprinting. In this work, the sequentially imprinted polystyrene film is used as a soft stamp to replicate hierarchical structures onto gold (Au) films, and the Au structures are then transferred to a substrate by transfer printing at an elevated temperature and pressure. Continuous and isolated 3D structures can be selectively fabricated with the assistance of thermo-mechanical deformation of the polymer stamp. Hierarchical Au structures are achieved without the need for a corresponding three-dimensionally patterned mold.     

Vorticity field structure associated with the 3D Tollmien-Schlichting waves

Details of the vorticity field structure associated with the 3D Tollmien-Schlichting waves have been examined based upon the recent numerical studies of the subject. First, a single obliquet-s wave has been found to have the velocity component parallel to the wave front playing an overall dominant role, in particular, to create the longitudinal vorticity. The so-called Benney-Lin longitudinal vortices are then demonstrated to be, in fact, a minor consequence compared with the localized longitudinal vorticity field and its periodic pumping. Finally, the formation of the longitudinal vorticity field in the fundamental- and subharmonic-mode interactions is explained. The research reported in this paper has been supported in part by Bundesministerium für Forschung und Technologie and by Deutsche Forschungsgemeinschaft. The major part of the paper has been presented at the Third Asian Congress of Fluid Mechanics, 1–5 September 1986, in Tokyo, as a General Lecture by the senior author, FRH.