Showing papers in "Materials today communications in 2018"
TL;DR: The effect of wood content in 3D printing materials on the properties of 3D printed parts was investigated in this paper, where six filaments using polylactic acid (PLA) with varying loading levels of wood particles from 0% to 50% by weight were produced and used for 3D printings and the results showed that the surface of the parts printed from the filament without the addition of wood was smoother and the printed part had no voids within the structure.
Abstract: The effect of wood content in 3D printing materials on the properties of 3D printed parts was investigated. Six filaments using polylactic acid (PLA) with varying loading levels of wood particles from 0% to 50% by weight were produced and used for 3D printing. The density of the filaments and 3D printed parts used in this study slightly decreased with increasing wood content. The tensile strength of the filaments increased from 55 MPa to 57 MPa with an addition of 10% wood, but decreased with higher levels of wood content to 30 MPa for filaments with 50% wood content. The surface of the parts printed from the filament without the addition of wood was smoother and the printed part had no voids within the structure. With increasing wood content the surface becomes rougher, more voids were present, and had visible clusters of wood particles (due to wood particle clustering and clogging in the printer nozzle). Higher wood content in 3D printed parts decreased the storage modulus. measured with torsional loading on a rheometer, but did not change the glass transition temperature.
181 citations
TL;DR: A rapid continuous3D-printing platform was developed to print customizable NGCs with unprecedented resolution, speed, flexibility, and scalability and showed promising recovery of motor function and sensation in the ipsilateral limbs grafted with the 3D-printed N GCs.
Abstract: Engineered nerve guidance conduits (NGCs) have been demonstrated for repairing peripheral nerve injuries. However, there remains a need for an advanced biofabrication system to build NGCs with complex architectures, tunable material properties, and customizable geometrical control. Here, a rapid continuous 3D-printing platform was developed to print customizable NGCs with unprecedented resolution, speed, flexibility, and scalability. A variety of NGC designs varying in complexity and size were created including a life-size biomimetic branched human facial NGC. In vivo implantation of NGCs with microchannels into complete sciatic nerve transections of mouse models demonstrated the effective directional guidance of regenerating sciatic nerves via branching into the microchannels and extending toward the distal end of the injury site. Histological staining and immunostaining further confirmed the progressive directional nerve regeneration and branching behavior across the entire NGC length. Observational and functional tests, including the von Frey threshold test and thermal test, showed promising recovery of motor function and sensation in the ipsilateral limbs grafted with the 3D-printed NGCs.
164 citations
TL;DR: In this article, the authors summarized the methods used for (nano)material deposition onto an electrode surface for efficient biosensor fabrication and discussed the problems faced during biosensor application as well as the present challenges and prospects for superior deposition methods.
Abstract: Biosensor development includes the deposition of (nano)materials onto a conductive electrode surface, which is a crucial step for obtaining improved performance from the constructed biosensors. Various methods have been used to create a successful matrix of (nano)materials that ensures proper contact between the material and electrode surface. The purpose of (nano)material deposition is to provide a high surface area to improve the electroanalytical performance of biosensors by supporting the stable immobilization of enzymes in a more significant quantity as well as enhancing the catalytic or bioaffinity features. For decades, researchers have been using increasingly advanced methods not only for improving sensing performance, but also for improving stability, reproducibility, and mass production. In this review, we summarized the methods used for (nano)material deposition onto an electrode surface for efficient biosensor fabrication. An enhanced and optimized (nano)material deposition method is crucial for the mechanical stability and fabrication reproducibility of electrodes when designing a suitable biosensing device. In addition, we discussed the problems faced during biosensor application as well as the present challenges and prospects for superior deposition methods.
135 citations
TL;DR: In this article, the authors reviewed the new dimensions in enhancement of properties and their potential applications made by employing a range of metal and carbon based nanofiller into biodegradable polymers in detail.
Abstract: Innovation in the field of polymer nanocomposites leads to diverse applications in drug delivery, biosensors, bone regeneration, solar cells, super capacitors etc. A step towards sustainable development, biomimetic approach has been taken into consideration in which vital role is played by the integration of nanofiller in biopolymers. In the present scenario the utilization of biopolymers facilitated by the functionalization of nanofiller by different types of methods which can eradicate agglomeration and enhance thermal, mechanical and electrical properties. This paper reviews the new dimensions in enhancement of properties and their potential applications made by employing a range of metal and carbon based nanofiller into biodegradable polymers in detail. The key factors to incorporate nanofiller are to increase the efficiency of biopolymers due to their high aspect ratio, biocompatibility, low density and high mechanical strength. The observations have been summarized to convey the mechanism and structural changes involved into the biopolymer to the researchers.
128 citations
TL;DR: In this paper, the effect of electrospinning processing parameters and solvent selection on the morphology and diameter of polyimide (PI) fibers was studied, where 11 different solvents and 22 solvent systems were located in a Teas graph with the aim of building the solubility-electrospinnability map for this material.
Abstract: Polyimide (PI) fibers display excellent thermal and mechanical performance; they have been recently investigated to fabricate hydrophobic membranes (mats) for high-performance applications. We studied the effect of electrospinning processing parameters and solvent selection on the morphology and the diameter of PI fibers. 11 different solvents and 22 solvent systems able to dissolve PI were located in a Teas graph with the aim of building the solubility-electrospinnability map for this material. PI solutions prepared with various solvents were electrospun at different electrospinning process parameters according to a 34–1 fractional factorial design of experiments. Polymer concentration and applied voltage were the most significant factors to create thin and uniform fibers. More homogeneous fibers and reproducible electrospinning process were obtained by using polymer concentrations above 15 wt%. However, all solutions showed different morphological evolution according to the solvents used. Based on the solubility–spinnability region settled for this PI, non-woven mats were obtained with rough surface fiber morphology and high water contact angle, suitable for applications such as hydrophobic membranes for oil-water separation.
104 citations
TL;DR: In this article, the stiffness and strength of lightweight cellular PLA parts were investigated under uniaxial tensile loading and flexural loading both edgewise and flatwise, and the results showed that the stiffness increased by up to a factor of 2 and the strength increased by 82% at the same density simply by using a different type of infill pattern for the same number of perimeter shells.
Abstract: The use of cellular structures is an approach commonly employed to design lightweight high-performance components for diverse applications. 3D printing via the Fused Filament Fabrication (FFF) provides a higher geometric flexibility than conventional methods to generate thermoplastic cellular structures. Previous studies have mainly focused on the characterization and optimization of FFF process parameters for fully dense polylactide (PLA) parts. This study investigated the stiffness and strength of lightweight cellular PLA parts under uniaxial tensile loading and flexural loading both edgewise and flatwise. The cellular parts were fabricated with one and three perimeter shells by using five types of infill patterns at three different infill density levels. The stiffness and strength scaled with the part density. At the same density however, the mechanical response varied widely depending on the infill patterns and number of perimeter shells. The results showed that the stiffness was increased by up to a factor of 2 and the strength was increased by up to 82% at the same density simply by using a different type of infill pattern for the same number of perimeter shells. Likewise, the use of a higher number of perimeter shells for the same infill pattern improved the stiffness and the strength by up to a factor of 2 and up to 84%, respectively, at the same density. The scaling factors and rupture modes were examined and guidelines for part design were drawn.
100 citations
TL;DR: In this paper, the constitutive material models of 3D printed parts via fused deposition modeling were developed to capture the influence of build orientation, printing direction and layer thickness on the material behavior of the printed parts.
Abstract: The present paper develops the constitutive material models of the 3D printed parts via fused deposition modeling. Additive manufacturing of a part results in a complex microstructure which depends on the process parameters and build orientation. Consequently, anisotropy is introduced into the material properties. The mechanical behavior of the printed parts is governed by the constitutive behavior of the material. Therefore, the stiffness matrix of the material of the final printed part needs to be estimated for accurately capturing their behavior. The constitutive material modeling of the printed parts using numerical homogenization procedure is emphasized in this work. The present simulation models can capture the influence of build orientation, printing direction and layer thickness on the material behavior of the printed parts. Then, the influence of layer deposition in printing of differently oriented parts of the structure on the material behavior is investigated. It is revealed that the material behavior of different parts of the structure is not same and is dependent on the build orientation of the parts and also their thickness. This work aids the computation of elastic moduli and also selecting of the correct constitutive material model of the printed parts for stress analysis.
83 citations
TL;DR: In this article, 3-D printed samples based on acrylonitrile-butadiene-styrene (ABS) loaded with multi-walled carbon nanotubes (CNT), carbon black (CB) and a 50:50 hybrid combination (cNT/CB) were manufactured via fused deposition modelling (FDM).
Abstract: 3-D printed samples based on acrylonitrile-butadiene-styrene (ABS) loaded with multi-walled carbon nanotubes (CNT), carbon black (CB) and a 50:50 hybrid combination (CNT/CB) were manufactured via fused deposition modelling (FDM). The electromagnetic interference shielding efficiency (EMI SE) of resulting FDM specimens was assessed. Different amounts of CNT, CB and CNT/CB were dispersed in an ABS matrix by melt compounding using an internal mixer. On the basis of the rheological behavior a weight fraction of 3% was selected for the filaments production. The filaments were prepared using a twin-screw extruder and used to feed a commercial FDM machine for 3-D printed specimen's preparation along three different growing directions. The electrical conductivity, the EMI SE and the mechanical properties of the resulting extruded filaments, as well as the 3-D printed specimens, were measured and, they are discussed in terms of the type of filler and growing directions. In general, the conductivity, EMI SE and mechanical properties of 3D printed parts were markedly dependent on the growing direction. Through the experimental findings of this work, an appropriate choice of a polymer nanocomposite formulation alongside the 3-D printing parameters could lead to components manufactured via FDM with optimized EMI SE and mechanical properties.
80 citations
TL;DR: The role of adsorbed proteins, as important players in the initiation of interactions between cells and polymers, will be discussed in detail, and the critical physicochemical properties of the polymer’s surface which significantly impact on the functions of proteins and cells will be given.
Abstract: Although a promising progress has been recently accomplished in polymer science, cell biology, immunology and biotechnology, the biocompatibility of biomaterials still remains a critical issue to address. At present, some polymeric biomaterials are still encountering with the difficulty of foreign body responses (FBRs) including blood–material interactions, inflammation, and immune system responses. It has been widely reported that controlling the physiochemical properties of biomaterials could potentially lead to having a precise control over the kind, quantity, conformation, and duration of adsorbed proteins onto the polymer’s surface. It has been well accepted that the interactions between biomaterials and immune cells could be to a great extent controlled through regulating the protein adsorption mechanism. In this review, the role of adsorbed proteins, as important players in the initiation of interactions between cells and polymers, will be discussed in detail. Furthermore, the critical physicochemical properties of the polymer’s surface which significantly impact on the functions of proteins and cells will be given. The discussion will then address the recent contradicting reports, for which a range of engineering solutions have been suggested. There are promising ways for controlling the proteins adsorption and subsequent cellular responses to polymeric biomaterials.
70 citations
TL;DR: In this paper, the influence of microstructure on the hydrogen embrittlement of advanced high-strength steels is addressed, showing that fracture initiation is typically intergranular, transgranular or quasi-cleavage.
Abstract: This work addresses the influence of microstructure on the hydrogen embrittlement of advanced high-strength steels. With sufficient hydrogen, fracture initiates at the ultimate tensile stress, but initiation is at the specimen surface. Fracture initiation is typically intergranular, transgranular or quasi-cleavage. These micro-fracture modes suggest that planar defects are important, such as prior austenite grain boundaries and lath and block boundaries. Fracture propagation is by shear fracture indicating a major influence of hydrogen-dislocation interactions. These hydrogen assisted fractures occur at a fast rate, probably approaching the speed of sound, that is at fracture velocities greater than 1000 m/s.
61 citations
TL;DR: In this article, the green synthesis and biological evaluation of Pongamia pinnata leaf extract coated zinc oxide nanoparticles (Pp-ZnO NPs) on the pulse beetle, C. maculatus was reported.
Abstract: Callosobruchus sp. is the major cause of damage to stored pulses. Recent advances in nanotechnology have provided us a promising tool for the management of insect pest of essential commodities. In the present study, we report the green synthesis and biological evaluation of Pongamia pinnata leaf extract coated zinc oxide nanoparticles (Pp-ZnO NPs) on the pulse beetle, C. maculatus. The green synthesized Pp-ZnO NPs were bio-physically characterized by UV–vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), Selective area electron diffraction (SAED), Energy dispersive X-ray (EDX) analysis and zeta potential. The bio-physical characterization revealed that the Pp-ZnO NPs has a hexagonal wurtzite structures with a mean particle size of 21.3 nm. In addition, zeta potential measurement demonstrated that the Pp-ZnO NPs are negatively charged (−12.45 mV) and are moderately stable. The pesticidal effect of Pp-ZnO NPs was tested against the pulse beetle, C. maculatus. Pp-ZnO NPs reduced the fecundity (eggs laid) and hatchability of C. maculatus in a dose-dependent manner. A significant delay in the larval, pupal and total development period of C. maculatus was observed after treatment with Pp-ZnO NPs at 25 μg mL−1. Furthermore, Pp-ZnO NPs are more effective in the control of C. maculatus and caused 100% mortality at 25 μg mL−1. The LC50 value was estimated to be 10.85 μg mL−1. In addition, treatment with Pp-ZnO NPs decreased the mid-gut α-amylase, cysteine protease, α-glucosidase, β-glucosidase, glutathione S-transferase (GST) and lipase activity in C. maculatus. This study concludes that Pp-ZnO NPs are effective against C. maculatus and could be used as an alternative pest control agent in the management of stored grain insect pests in the future.
TL;DR: In this article, the authors investigated the ionic conductivity and transports properties of biopolymer electrolytes (BEs) based on kappa-carrageenan (KC) by incorporating NH4Br as polymer-salt system.
Abstract: The present work deals with the investigation on ionic conductivity and transports properties of biopolymer electrolytes (BEs) based on kappa-carrageenan (KC) by incorporating NH4Br as polymer-salt system. The BEs was successfully prepared via solution-casting method and characterized by means of Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). It was established that the ionic conductivity for BEs system increased and achieved an optimum value of 3.89 × 10−4 S/cm for a sample containing 20 wt.% NH4Br at ambient temperature (303 K). XRD analysis indicates that the highest ion conductivity complex exhibits optimum amorphous nature via the evaluation of the degree of crystallinity (Xc %). The conducting element in the BEs does favor the association of ion count from NH4Br where the ionic mobility and diffusion coefficient of the transport properties were found increase parallel with the conductivity until it reaches optimum composition of BEs.
TL;DR: In this paper, the authors used cellulose nanocrystals (CNC) to produce fully biodegradable nanocomposite filaments with improved thermo-mechanical properties, to be used in the FDM 3D printing process.
Abstract: The aim of this work is to produce fully biodegradable nanocomposite filaments with improved thermo-mechanical properties, to be used in fused deposition modeling (FDM) 3D printing process. At this aim, nanocomposites consisting of poly(vinyl alcohol) (PVOH) containing various amounts (from 2 to 20 wt%) of cellulose nanocrystals (CNC) were produced by solution mixing, grinded and extruded into filaments by a single screw extruder. The obtained nanocomposite filaments were then used to feed a desktop 3D printer. In both filaments and 3D printed specimens, CNC promoted a progressive enhancement of thermal stability manifested in an increase of the glass transition temperature measured by differential scanning calorimetry. Moreover, both dynamic storage and loss moduli were also increased proportionally to the filler content, and a positive reduction of the creep compliance was observed. For a CNC content of 10 wt% the creep compliance at a given loading time (one hour) decreased in both filament (by 47%) and in 3D printed samples (by 35%) in comparison to neat PVOH. Ultimate mechanical properties of filaments also increased with the introduction of CNC till 10 wt%, with a maximum reinforcement effect observed at 2 wt% of CNC for which an increase of 81% in the values of tensile energy to break and 45% in the stress at break were observed. An enhancement in tensile properties was observed also for 3D printed samples at 5 wt% of CNC for which the stress at break manifested an improvement of 73%. Adhesion between layers in 3D printed parts resulted to play a major role in the fracture behavior.
TL;DR: In this paper, the authors proposed an approach for water purification widely used in households with limited access to fresh water, which relies on microorganism inactivation triggered by sunlight energy in the UV spectrum and requires processing times of up to 48 hr.
Abstract: Solar disinfection of drinking water (SODIS) is an approach for water purification widely used in households with limited access to fresh water. SODIS relies on microorganism inactivation triggered by sunlight energy in the UV spectrum and requires processing times of up to 48 hr. Water treatment rate is drastically increased by using photocatalytic materials, such as TiO_2, which can harvest sunlight to promote generation of reactive oxygen species (ROS) that inactivate bacteria within few hours. One main challenge that impedes the insertion of photocatalysts in most water treatment approaches is the need to populate the catalyst particles on a three-dimensional (3D) structure with a high-surface area that is stable under water flow.
TL;DR: In this article, the feasibility of using a hierarchical lattice liners for helmets was studied and the results show that using such liners has the potential of significantly reducing the risk of head injury compared to a helmet with traditional EPS liners and could potentially be considered as the new generation of energy absorbing liners.
Abstract: Helmets are the most important piece of protective equipment for motorcyclists. The liner of the helmet is the main part of the helmet which dissipates the impact energy and mitigates the load transmitted to the head. Therefore, optimizing the material that absorbs most of the impact energy would improve the helmet’s protection capacity. It is known that the energy absorption of the helmet liner can be optimized by means of using liners with varying properties through the thickness, however currently the majority of used liners exhibit constant properties through the thickness. Advances in the field of topology optimization and additive manufacturing provide the ability of building complex geometries and tailoring mechanical properties. Along those lines, in the present work the feasibility of using a hierarchical lattice liner for helmets was studied. Finite element method was employed to study whether a hierarchical lattice liner could reduce the risk of head injuries in comparison to currently used liner materials. The results show that using a hierarchical lattice liner has the potential of significantly reducing the risk of head injury compared to a helmet with traditional EPS liner and could potentially be considered as the new generation of energy absorbing liners for helmets.
TL;DR: In this article, the longitudinal compressive and tensile behaviour of unidirectional natural fibres is studied through a parametric analysis taking into account the nature of the fibre (flax or jute), the matrix (thermoplastic and thermoset: PP, PP/MAPP, PA11, epoxy or acrylic), the fibre volume fraction and the fibre/matrix bond strength.
Abstract: Despite the wide development of biocomposites, their compressive behaviour is still not well understood. In this paper, the longitudinal compressive and tensile behaviour of unidirectional natural fibres is studied through a parametric analysis taking into account the nature of the fibre (flax or jute), the matrix (thermoplastic and thermoset: PP, PP/MAPP, PA11, epoxy or acrylic), the fibre volume fraction and the fibre/matrix bond strength. In parallel with this approach, the quasi-static tensile behaviour is also investigated to allow comparisons. At low strains, the compressive and tensile moduli are closely similar. On the other hand, the compressive strength is systematically lower than the tensile strength whatever the fibre and matrix used. With a PP matrix, use of a coupling agent (MA) to improve the Interfacial Shear Strength (IFSS) leads to an increase of strength, which highlights the importance of this parameter. The compressive strength increases with the fibre volume fraction, but the maximum value remains lower than 140 MPa. Back calculation allows us to estimate the compressive strength of the flax fibres as 240 MPa, which appears as a current limit for the dimensioning of biocomposite structures.
TL;DR: In this article, a 3D printable thermoplastic polyurethane (TPU) blends with thermal energy storage (TES) capabilities were developed for winter sport equipment.
Abstract: The aim of this work was to develope novel 3D printable thermoplastic polyurethane (TPU) blends with thermal energy storage (TES) capabilities. The target are potential applications for winter sport equipment. Different amounts of an encapsulated paraffin were added to a TPU matrix, and the resulting blends were then used to produce 3D printed samples. FESEM observation evidenced a homogeneous distribution of the capsules in the polymer matrix and a good adhesion between the layers in the 3D printed parts. DSC tests indicated that an effective energy storage/release capability was obtained in the 3D printed parts, with melting enthalpy values up to 70 J/g. The hard shells of the microcapsules, made of melamine formaldehyde resin, induced an increase of the stiffness, of the creep stability and of the Shore A hardness of the material, accompanied by a decrease of the elongation at break.
TL;DR: In this paper, a glassy carbon electrode (GCE) with the help of conducting binders called nafion was used for the detection of various toxic and hazardous chemical pollutants to promote friendly and green environment.
Abstract: 4-Nitrophenol (4-NP) is toxic organic compound and was determined by silver doped neodymium oxide aggregated nanoparticles (Ag@Nd2O3 NPs) The aggregated nanoparticles (NPs) were prepared by wet chemical process and was characterized by UV–vis, FT-IR, XRD, FE-SEM, XPS, and XEDS techniques The NPs were applied to the glassy carbon electrode (GCE) with the help of conducting binders called nafion The fabricated Ag@Nd2O3/Nafion/GCE has good selectivity and sensitivity and is linear over concentration ranging from 10 pM –01 mM The sensitivity value of the fabricated GCE was 02215 μA μM−1 cm-2 The above mentioned electrode has lower value of limit of detection which was 043 pM The electrode prepared was simple and was easy to handle with electrometer In shortly, the prepared chemical sensor was environment and eco-friendly for the detection of various toxic and hazardous chemical pollutants to promote friendly and green environment
TL;DR: In this paper, the optimum hot working window with full dynamic recrystallization microstructure for Inconel 740 superalloy was established by integrating the activation energy map with the hot processing map.
Abstract: The optimum hot working window with full dynamic recrystallization microstructure for Inconel 740 superalloy was established by integrating the activation energy map with the hot processing map. The activation energy map and the hot processing map were obtained respectively to characterizing the hot workability based on the isothermal compression tests at various temperatures and strain rates. Hot deformation characteristics of Inconel 740 superalloy was investigated by analyzing the microstructure evolution. The results show that the flow instability is significantly dependent on the high activation energy. Whereas, the good hot workability is attributed to the low activation energy, in which case the original microstructure is replaced by the fine and equiaxed recrystallization grains.
TL;DR: In this paper, the authors proposed a novel classification for the compressive failure modes of fiber reinforced polymer composites based on an extensive literature review as well as in microscopic investigations performed on different composite laminates via scanning electron microscopy.
Abstract: The fractographic aspects of compression failures remain inadequately explored, mainly due to the damages that the compressive load promotes on the fracture surfaces, which difficult the identification of fracture aspects. In addition, despite the large quantity of studies on the literature, there is no consensus concerning the existing compressive failure modes. Aiming to contribute in this research field, this paper has the objective of proposing a novel classification for the compressive failure modes of fiber reinforced polymer composites. The classification proposed here was based on an extensive literature review as well as in microscopic investigations performed on different composite laminates via scanning electron microscopy. It can be said that this classification has a phenomenological nature, since the failure modes were grouped according to the dominant characteristic. Furthermore, the sequence of events that lead to failure was described for each failure mode. This approach eases its application and allows its use for different types fiber composites, besides allowing the investigation of failed composite structures by means of post-mortem analyses. Finally, the wedge splitting failure mode was identified for the first time on fiber reinforced polymer composites.
TL;DR: In this paper, ZnAl2O4 nano-powders have been successfully prepared via citrate sol-gel technique and all powder samples were annealed at 600°C for 1, 2, and 3
Abstract: ZnAl2O4 nano-powders have been successfully prepared via citrate sol-gel technique. All powder samples were annealed at 600 °C for 1, 2, and 3 h. Thermogravimetric analysis (TGA) confirmed that the minimum annealing temperature of crystallization is ∼400 °C. Fourier Transform Infrared (FTIR) results showed a series of absorption peaks in the range of 810–4000 cm−1. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) results showed that the prepared nano-crystals consists of the mixture of both cubic (ZnAl2O4) and hexagonal (ZnO) structures. Ultra violet visible (UV–vis) spectroscopy revealed that the annealing time (AT) influences the band gap of the prepared phosphor materials. When the samples were excited at 275 nm, two emission peaks at 428 nm (violet) and 561 nm (green-yellow) were observed and they are attributed to the defects levels within the ZnO and ZnAl2O4 band gaps. The Commission Internationale de l’Elcairage (CIE) colour coordinates confirmed that all the prepared samples exhibit the violet emission and varying the AT does not influence the emission colour.
TL;DR: In this article, a 3D sand-printing floor is proposed based on principles of shallow arching action and discrete structural systems to initiate internal compressive stresses rather than exclusively flexural stresses.
Abstract: This paper describes the concept, design, fabrication and experimental testing of prototype 3D sand-printed floors, derived from principles of shallow arching action and discrete structural systems to initiate internal compressive stresses rather than exclusively flexural stresses. Using industrial 3D printing with silica sand, the presented system enables significant weight reduction of up to 70% when compared to conventional concrete floor slabs, by placing the 3D printed material in key structural areas and by externalising tension forces. The form-finding process for the global shape of the floors and the generation of structurally optimised print mesh geometries are presented. Three floor prototypes with varying rib geometries and discretisation layouts were studied. The results from the serviceability and ultimate load testing of the floors are documented in detail. The data showed that this relatively weak material can be used, without internal reinforcement, to print a floor that is able to support loads in excess of typical design code levels.
TL;DR: In this paper, the authors present an approach that supports the search for local materials that are suitable as material input for additive manufacturing and are recyclable to serve multiple product lifecycles.
Abstract: The potential of additive manufacturing (AM) for distributed production is often mentioned as an enabler for sustainable manufacturing within a circular economy. Currently, even if manufacturing with AM is distributed, the used materials can rarely be acquired locally and are usually obtained from a centralized location. Addressing this issue, we are developing an approach that supports the search for local materials that are suitable as material input for AM and are recyclable to serve multiple product lifecycles. The approach is an iterative process consisting of four phases; “material in AM context”, “recycling opportunities”, “material property testing”, and “application possibilities”. As an initial example, we present a process to adapt mussel shell waste into AM material. Mussel shells are a voluminous waste stream in the Netherlands. The shells, which mainly exist of calcium carbonate, are ground into a powder and combined with sugar water. Using a modified material extrusion process, 3D objects are created. In this paper, we discuss the iterations through our approach and illustrate the initial 3D printed results. With this project, we intend to demonstrate the potential of using local waste streams for AM processes for a circular economy. This is a first step towards the development of a methodology for linking local material streams to novel AM processes and meaningful applications.
TL;DR: In this article, an equal-molar CoCrFeMnNi, face-centered-cubic high-entropy alloy system was investigated using in-situ angular-dispersive X-ray diffraction under hydrostatic compression up to 20 GPa via diamond anvil cell.
Abstract: An equal-molar CoCrFeMnNi, face-centered-cubic high-entropy alloy system is investigated using in-situ angular-dispersive X-ray diffraction under hydrostatic compression up to 20 GPa via diamond anvil cell. The evolutions of multiple diffraction peaks are collected simultaneously to elucidate the phase stability field. The results indicated that an irreversible phase transformation had occurred in the high entropy alloy upon decompression to ambient pressure. A reference material (n-type silicon-doped gallium arsenide) was investigated following the same protocol to demonstrate the different deformation mechanisms. It is suggested that the atomic bonding characteristics on the phase stability may play an important role in the high entropy alloys.
TL;DR: In this paper, a reactive mixture deposition approach was developed to enable 3D printing of polymer materials at over 100 times the volumetric deposition rate, enabled by a greater than 10X reduction in print head mass compared to existing large-scale thermoplastic deposition methods, with material chemistries tuned for specific properties.
Abstract: Additive Manufacturing (AM) has the potential to offer many benefits over traditional manufacturing methods in the fabrication of complex parts with advantages such as low weight, complex geometry, and embedded functionality. In practice, today’s AM technologies are limited by their slow speed and highly directional properties. To address both issues, we have developed a reactive mixture deposition approach that can enable 3D printing of polymer materials at over 100X the volumetric deposition rate, enabled by a greater than 10X reduction in print head mass compared to existing large-scale thermoplastic deposition methods, with material chemistries that can be tuned for specific properties. Additionally, the reaction kinetics and transient rheological properties are specifically designed for the target deposition rates, enabling the synchronized development of increasing shear modulus and extensive cross linking across the printed layers. This ambient cure eliminates the internal stresses and bulk distortions that typically hamper AM of large parts, and yields a printed part with inter-layer covalent bonds that significantly improve the strength of the part along the build direction. The fast cure kinetics combined with the fine-tuned viscoelastic properties of the mixture enable rapid vertical builds that are not possible using other approaches. Through rheological characterization of mixtures that were capable of printing in this process as well as materials that have sufficient structural integrity for layer-on-layer printing, a “printability” rheological phase diagram has been developed, and is presented here. We envision this approach implemented as a deployable manufacturing system, where manufacturing is done on-site using the efficiently-shipped polymer, locally-sourced fillers, and a small, deployable print system. Unlike existing additive manufacturing approaches which require larger and slower print systems and complex thermal management strategies as scale increases, liquid reactive polymers decouple performance and print speed from the scale of the part, enabling a new class of cost-effective, fuel-efficient additive manufacturing.
TL;DR: In this paper, a facile fabrication approach for sensitive theranostic nanoprobe - gold nanostars@MnO2 nanosheets, by which gold nanopostars were grown on the surface of MnO2 nano-heets.
Abstract: We report a facile fabrication approach for sensitive theranostic nanoprobe - gold nanostars@MnO2 nanosheets, by which gold nanostars were grown on the surface of MnO2 nanosheets. Owing to the ability of gold nanostars to absorb light at near infrared (NIR) wavelength, the nanoprobe showed excellent photothermal conversion effect, while exhibited tumor microenvironment-responsive magnetic resonance imaging property due to the redox property of MnO2 nanosheets. Amazingly, photothermal irradiation experiment showed that the nanoprobe sensitively triggered lung cancer cell death, while produced negligible effect on normal lung epithelial cells. Therefore, these demonstrate that the nanoprobe may have potential application in magnetic resonance imaging-guided photothermal therapy of lung cancer.
TL;DR: In this paper, an effort has been made to develop in house feed stock filament wire made up of recycled polymer waste as base matrix with SiC/Al2O3 reinforcement for sustainable development.
Abstract: In this research work an effort has been made to develop in house feed stock filament wire made up of recycled polymer waste as base matrix with SiC/Al2O3 reinforcement for sustainable development. The process starts with collection of waste polymer (high density polyethylene (HDPE) as a case study) from local industry. After manual segregation of contamination from waste polymer, initially rheological and thermal properties like: melt flow index (MFI), melting temperature, decomposition and enthalpy of the base polymer as well as reinforced with ceramic particle in different proportions, were tested. Further based upon thermal properties different proportions of HDPE, SiC and Al2O3 were prepared by using mini compounder (twin screw extruder) to ensure uniform dispersion. After this single screw extruder was used to prepare filament wire of uniform diameter for fused deposition modelling (FDM) setup. The filament wire so prepared was tested for its tensile properties by using universal testing machine (UTM) and various mechanical properties like: peak strength, break strength, percentage elongation and peak load etc. were established. Finally scanning electron micrographs (SEM) were obtained to understand the distribution of ceramic particles in filament wire. This study highlights the detailed procedure for managing the polymer waste with novel method by using recycled polymer as rapid tooling. This will enhance the sustainability and also helps to develop low cost, in-house open source FDM setup, rapid tooling (as ceramic particles in filament wire will enhance surface properties).
TL;DR: Novel nanoparticulate formulations utilized for the treatment of RA may enhances the solubility of poorly water soluble drugs, improves the bioavailability, affords targetability and may improve the therapeutic activity.
Abstract: Rheumatoid arthritis (RA) is the most common complex multifactorial joint related autoimmune inflammatory disease with unknown etiology accomplished with increased cardiovascular risks. RA is characterized by the clinical findings of synovial inflammation, autoantibody production, and cartilage/bone destruction, cardiovascular, pulmonary and skeletal disorders. Pro-inflammatory cytokines such as IL-1, IL-6, IL-8, and IL-10 were responsible for the induction of inflammation in RA patients. Drawbacks such as poor efficacy, higher doses, frequent administration, low responsiveness, and higher cost and serious side effects were associated with the conventional dosage forms for RA treatment. Nanomedicines were recently gaining more interest towards the treatment of RA, and researchers were also focusing towards the development of various anti-inflammatory drug loaded nanoformulations with an aid to both actively/passively targeting the inflamed site to afford an effective treatment regimen for RA. Alterations in the surface area and nanoscale size of the nanoformulations elicit beneficial physical and chemical properties for better pharmacological activities. These drug loaded nanoformulations may enhances the solubility of poorly water soluble drugs, improves the bioavailability, affords targetability and may improve the therapeutic activity. In this regimen, the present review focus towards the novel nanoparticulate formulations (nanoparticles, nanoemulsions, solid lipid nanoparticles, nanomicelles, and nanocapsules) utilized for the treatment of RA. The recent advancements such as siRNA, peptide and targeted based nanoparticulate systems for RA treatment were also discussed. Special emphasis was provided regarding the pathophysiology, prevalence and symptoms towards the development of RA.
TL;DR: In this article, a solar-assisted photodegradation of Methyl Orange (MO) dye was investigated using Cu-doped ZnO nanorods synthesized through a chemical method using a solution of zinc chloride (ZnCl2) as precursor, and with the addition of different concentrations of Cu(NO3)2 and NaOH at 65°C.
Abstract: This paper focuses on the solar-assisted photodegradation of Methyl Orange (MO) dye as model molecule using Cu-doped ZnO nanorods synthesized through a chemical method using a solution of zinc chloride (ZnCl2) as precursor, and with the addition of different concentrations of Cu(NO3)2 and NaOH at 65 °C. The samples were characterized by TEM, XRD, XPS, BET and UV–vis spectroscopy. The amount of Cu and catalyst dosage on the rate of photodegradation were investigated. The measurements of the band gap made by visible UV–vis spectroscopy showed that it decreased as the dopant material increased. The Cu-doped ZnO nanorods showed excellent photodegradation efficiency and good recycling performance. The decomposition reaction was found to be pseudo–first order. Optimal experimental conditions were determined for Cu-doped ZnO nanorods with a catalyst dose of 0.3 g/L and 99% of MO degradation was obtained after 120 min of solar exposure.
TL;DR: In this article, waste SLS powder is employed to prepare feedstock for inexpensive high-value FDM products, which demonstrates that SLS refuse could be utilized for mass production of FDM feedstock.
Abstract: As additive manufacturing (AM) is heading towards mass production and mass customization, the process needs to be environment-friendly and energy-efficient in order to be self-sustainable. Selective laser sintering (SLS) and fused deposition modeling (FDM) are two processes contributing massively towards plastic additive manufacturing. In SLS, the powders that do not contribute to the mass of products become unusable (after some number of reuse) and finally turn into waste. As high energy is required for production of powders, generation of these wastes impacts environment sustainability. A contrivance needs to be developed to convert these waste powders into high-value products to make the process sustainable. FDM has the largest market share in terms of number of AM systems sold and is the most popular for fabricating low-value products. Its usefulness will be further expanded if inexpensive high-value products could be made through this process. In the present work, waste SLS powder is employed to prepare feedstock for inexpensive high-value FDM products, which demonstrates that SLS refuse could be utilized for mass production of FDM feedstock. If two processes (SLS & FDM) will be connected as proposed here, it will make plastic additive manufacturing energy-efficient, self-sustainable, and will contribute to environment sustainability, in general.