Smart Materials in Manufacturing最新文献

As a metallic biomaterial used to replace failed hard tissues, β-type titanium alloys subjected to a long-term loading, may lead to the creep deformation at room temperature. Here we report the room temperature creep behavior and its influence on the superelasticity in the Ti-7.5Nb–4Mo–2Sn based shape memory alloy, which exhibits a good superelasticity at room temperature. It is found that the stress level has a remarkable effect on the creep behavior of the alloy. The alloy exhibits an obvious creep deformation under a stress more than critical stress for inducing martensitic transformation, σ_SIM. As the applied stress is slightly higher than σ_SIM, it exhibits a significant creep deformation at room temperature due to the stress-induced martensitic transformation, but with the applied stress further increasing, the creep deformation decreases due to occurrence of the assisted detwinning. The room temperature creep deformation of the alloy is mainly controlled by the domino detwinning of the twinned martensites, companying with the slide of dislocations.

Flexible piezoresistive sensors are often fabricated by depositing a conductive layer such as platinum, gold, graphene thin films, or conductive nanoparticles onto an elastic substrate. However, due to the intrinsic brittleness of the conductive materials, this method usually results in sensors with limited stretchability. Herein, we demonstrate a new technique to greatly increase the stretchability of piezoresistive strain sensors based on gold (Au) thin films by being hybridized with carbon nanofibers (CNFs). Sensors based on Au thin film fail electrically at a very small strain (∼ 4.5%). In contrast, the sensors based on hybridized Au-CNFs thin film show a significantly increased failure strain up to ∼ 225%. Introducing one-dimensional CNFs enables a greatly enlarged workable strain range by bridging and deflecting the microcracks formed in the Au thin film during stretching. This can effectively prevent the formation of lengthy, channel-like straight cracks that cause electrical failure under low strains. The high-performance sensors have shown great potential for use as wearable sensors for motion detection, such as detecting joint bending. Moreover, the potential of the sensors in detecting airflow similar to human respiratory airflow level has been demonstrated.

A phase field model for cubic to orthorhombic martensitic transformation (MT) at the nanoscale in a β titanium (Ti) alloy Ti–24Nb–4Zr–8Sn (in wt.%) is investigated by finite element simulation. The approach is based on phase field theory, time-dependent Ginzburg-Landau theory, and mechanical equilibrium equations. Partial differential equations (PDEs) were solved using the commercial software COMSOL Multiphysics. The morphology of the product phase exhibits plate-like or needle-like shapes that reduce the elastic strain energy of the system. The simulation result for random initial order parameters is in agreement with previous experimental observations. The final volume fractions of two different orthorhombic martensitic variants are not dependent on the initial conditions.

Polylactic acid (PLA) is a well-known biomaterial on account of its biocompatibility and biodegradability. Zinc oxide (ZnO) nanofillers may endow PLA with advantageous antibacterial and tissue regenerative properties, but may also compromise the biocompatibility of PLA. Several strategies have been developed to improve the biomedical practicality of such composites. The importance of surface properties on amplifying the therapeutic properties and safety of a material enables two potential strategies: (i) surface modification of ZnO nanoparticles, and (ii) surface engineering of the PLA/ZnO composites. Moreover, the controllable biodegradation of PLA allows a third possible strategy: (iii) biodegradation-controlled release of ZnO. The first part of this review introduces the controllable degradation of PLA and the mechanisms of therapeutic properties and cytotoxicity of ZnO. Following this, the paper highlights current research trends regarding the biomedical application of PLA-based ZnO nanocomposites. The final section of this review discusses the potential use of ZnO in tuning the degradation rate of PLA, and the possibility of manipulating the surface properties of ZnO nanoparticles and PLA/ZnO composites in order to optimize the therapeutic properties and safe usage of PLA/ZnO composites in the biomedical field.

The physiological environment of the human body is an extremely complex system, containing not only inorganic ions but also organic molecules; thus it is necessary to understand the influences of the different functional groups of three six-carbon small organic molecules (glucose (Glu), vitamin C (Vc), and citric acid (CA)) on the degradation mechanisms of pure magnesium (Mg). Electrochemical polarization and impedance spectroscopy, hydrogen evolution rates, and pH monitoring tests were used to characterize the degradation behaviors of pure Mg in 0.9 ​wt% NaCl and phosphate-buffered saline (PBS) solutions. Using scanning electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, the compositions, phase structures, and morphologies of the degradation products were investigated. Results indicated that Glu enhanced the biodegradation rate of pure Mg in 0.9 ​wt% NaCl solution, whereas Vc and CA slowed down their biodegradation rate. In the PBS solution, both Glu and Vc reduced the biodegradation rate of pure Mg, while CA accelerated its initial biodegradation and retarded its long-term biodegradation. In addition, Raman spectroscopy demonstrated the formation of Mg-(gluconate, l-threonic acid, oxalate, and citrate) on the pure Mg. Plausible biodegradation mechanisms of pure Mg are proposed regarding the influences of Glu, Vc, and CA.

New methods are emerging to combine the self-assembly of matter and additive manufacturing, so that new devices and constructs can simultaneously harness the unique molecular and nanostructural features afforded by self-assembly and the macroscale design freedom of additive manufacturing. The aim of this review is to analyse the body of literature and explore the crossover area where boundaries dissolve and self-assembly meets additive manufacturing (SAMAM). As a preliminary framework for this new area of research, the different experimental approaches to SAMAM can be grouped in three main categories, whereby SAMAM can be based on local interactions between molecules or nanoparticles, on 3D-printing induced forces, or on externally applied force fields. SAMAM offers numerous opportunities, such as the design of new printable materials, the ability to surpass conventional trade-offs in materials properties, the control of structural features across different length scales, process intensification and improved eco-sustainability. However, most research so far has been focused on polymer-based materials, and additional effort is needed to understand how SAMAM can be leveraged in metal- and ceramic-based additive manufacturing. On account of the weak inter-layer bonding often reported along the growth direction, it would also be interesting to explore whether SAMAM could effectively remediate undesidered anisotropic effects in additively manufactured parts.

The precision in the design and manufacturing of scaffolds with ideal properties such as biocompatibility, biodegradability, mechanical and surface characteristics is very crucial for applications in tissue engineering. Furthermore, these techniques should be able to translate manufactured scaffolds from bench to potential applications. Numerous fabrication technologies have been employed to design ideal three-dimensional scaffolds with controlled nano-to-micro-structures to achieve the final biological response. This review highlights the ideal parameters (biological, mechanical and biodegradability) of scaffolds for different biomedical and tissue engineering applications. It discusses in detail about the various designing methods developed and used for the fabrication of scaffolds, namely solvent casting/particle leaching, freeze drying, thermal induced phase separation (TIPS), gas foaming (GF), powder foaming, sol-gel, electrospinning, stereolithography (SLA), fused deposition modelling (FDM), selective laser sintering (SLS), binder jetting technique, inkjet printing, laser-assisted bioprinting, direct cell writing and metal based additive manufacturing with a focus on their benefits, limitations and applicability in tissue engineering.

Metallic biomaterials are widely used as short and long-term implantable devices by virtue of their outstanding mechanical properties, such as high load-bearing capacity and fatigue resistance. Due to their inherent bioinertness, potential corrosion, and some inferior surface properties, metallic biomaterials generally require coating and surface modification to improve their function and extend their lifespan in the body. High entropy alloys (HEAs) are a novel class of materials that are composed of at least five principal metallic elements with equiatomic or close-to-equiatomic compositions. Some of the unique properties of HEAs for surface modification and coating include excellent corrosion resistance, remarkable wear resistance, high strength/hardness, and strong diffusion resistance. The coating of HEAs on metallic substrates can be achieved through different techniques, including thermal spraying, laser deposition, and vapor deposition. HEAs have become a promising candidate for biomedical applications by combining tailor-made surface topography, excellent biocompatibility, appropriate surface chemistry, and element composition design. The present article is a thorough review of the research on the surface modification and coating of metallic biomaterials using HEAs.

Suture anchors are widely used for attaching soft tissue to bone due to their ease of insertion, fixation strength, and small size. The past few decades have seen great advances in the materials and designs of suture anchors. They were originally constructed of non-biodegradable metals and polymers, but in recent years there has been a considerable move toward biodegradable polymers. The biodegradable polymer anchors offer advantages such as gradual degradation over time, minimized risk of migration, less complex revision surgery, no need for a removal operation, and improved postsurgical imaging. However, these anchors have lower fixation strength than metal anchors and suffer from adverse local tissue reactions, inflammatory responses, and rapid degradation. Biodegradable metals appear to be ideal candidates for the future of suture anchors. They have high fixation strength and low elastic modulus close to that of bone, which promote osseointegration and allow the design of thinner and lower volume implants. The current article gives an overview of the application and manufacturing of biodegradable metallic suture anchors and summarizes their current concepts and properties in this area of continual development.

Elastomers known as rubber are ubiquitous in industrial applications, but they often contain chronic additives, such as zinc oxide, tetramethylthiuram monosulfide (denoted TMTM), and copper dimethyldithiocarbamate (CDD) that has a higher melting point than the common vulcanization temperature. These additives are released into the environment either through the wear and tear of tires and the landfilling of waste rubber. It is imperative to identify and adopt safe, cost-effective alternatives to replace zinc oxide and TMTM, both of which have moderate chronicity rating. Styrene-butadiene rubber (SBR) in this study is cured by using sulphur, zinc stearate, and dipentamethylenethiuram hexasulfide (TRA). The curing characteristics and the morphology and mechanical properties of the cured SBR are investigated. Zinc stearate and TRA exhibit a commendable rating of zero in terms of both chronicity and toxicity, making them promising candidates for substituting chronic additives. Adding 0.25 phr of zinc stearate into SBR can significantly enhance the crosslinking density while exhibiting anti-reversion performance, in comparison with a recipe that includes 5 phr of zinc oxide and 8 phr of TMTM. Transmission electron microscopy reveals that the zinc oxide (nano) particles are not soluble in SBR, and thus only the particle surface contributes to vulcanization. TRA is “dissolvable” in SBR, making it an ideal replacement for CDD which is insoluble due to its high melting point. Therefore, we strongly advise against the utilization of curing additives with melting points that exceed the vulcanization temperature. This work contributes to the green manufacture of elastomers.