Smart Materials in Manufacturing最新文献

The rapid degradation and delayed endothelialization of magnesium (Mg) alloys are the bottlenecks that limit their application in the direction of cardiovascular stents. In the previous work, we have reported a novel compound coating composed of three newly synthesized Schiff bases which significantly improved the corrosion resistance of the Mg alloy. However, the effect of electrostatic spraying time on the physicochemical properties, corrosion resistance and biocompatibility of the compound coating has not been systematically explored. In the present study, the compound Schiff base coating was electrostatic-sprayed on to the Mg alloy surface with 1.0 ​min (CP-1.0), 1.5 ​min (CP-1.5), 2.0 ​min (CP-2.0) and 2.5 ​min (CP-2.5), respectively. Our data suggested that CP-1.5 possessed more homogeneous surface, better corrosion resistance, stronger hemocompatibility and pro-endothelialization ability. Our study may give inspiration for designing the special coatings only for the biodegradable Mg alloy stents for vascular application.

Material extrusion (MEx) related technologies are widely common and popular in the industry due to their ability to handle wide variety of polymeric materials, user friendly printing process, and lower initial and running cost. Fused deposition modelling (FDM) is a commonly used material extrusion based three-dimensional printing process. Marble - Polylactic acid (Marble - PLA) is a derivative of regular Polylactic acid (PLA), where fine marble powder is mixed with the matrix of PLA. Marble PLA combines the desirable properties of PLA with the aesthetic appeal of marble. The said material is getting popular in the applications related to the decorative ornaments, architectural model, art-based sculptures, and customized home décor etc. However, when it comes to the performance and mechanical characteristics there is not much information available in the literature. This paper applied Taguchi's design of experiment methodology and grey relational analysis to optimize the printing of Marble-PLA. The study varied three parameters of layer height (0.2 mm, 0.3 mm and 0.4 mm), print speed (30 mm/s, 40 mm/s and 50 mm/s) and cell geometry (triangular, diamond and hexagon). Tensile testing was performed on each sample after preparing them using ASTM D638 standard. The out responses were comprised of modulus of toughness, resilience, Young's modulus, yield strength, ultimate tensile strength and strain at fracture. The study revealed optimal conditions of layer height was kept 0.3 mm, print speed was 50 mm/s and triangular cell geometry. The grey relational analysis provided the improvement of 0.16747 in the grey relational grade.

Bacterial infection is one of the most common complications following the implantation of biomaterials and can lead to aseptic loosening, prosthesis failure, and even morbidity or mortality. Some physicochemical surface properties of metallic implants such as surface topography, roughness, pore size, and degree of porosity, play key roles in bone formation. However, highly porous and roughened surfaces result in weaker mechanical properties and more bacterial adhesion. Due to existing complications in removing bacterial biofilms, more attention is needed to produce porous and/or rough additively manufactured materials that exhibit high biocompatibility and antimicrobial efficacy. The rough surfaces generated by additive manufacturing technologies require researchers to discover methods for biofilm removal via the incorporation of additional biofunctionalities to reduce the rate of bacterial colonization of implants. Furthermore, complex 3D-printed structures fabricated by additive manufacturing methods possess larger surface areas and thus are more susceptible to bacterial infection. This necessitates the development of non-pharmacological techniques to reduce the danger of bacterial colonization. The current review provides insight into the formation of pathogens on the surfaces of additively manufactured metallic biomaterials and discusses active antipathogenic surface modifications to inhibit or control infection.

Zinc (Zn) and its alloys have promising potential application in biodegradable bone implants, attributable to their moderate degradation rate and biological safety in the human body. Nevertheless, the insufficient mechanical properties of pure Zn are challenging in meeting the mechanical property requirements for bone-implant materials. Here, we report the effects of alloying and hot rolling on the microstructure, mechanical properties, corrosion and degradation behavior, friction and wear performance, cytocompatibility, and antibacterial ability of Zn–2Cu–xLi (x ​= ​0, 0.4, and 0.8 ​wt%) alloys. Our results indicate that the hot-rolled (HR) Zn–2Cu–0.4Li alloy exhibited the best comprehensive set of mechanical properties with yield strength of 280.8 ​MPa, ultimate tensile strength of 394.6 ​MPa, and elongation of 62.2%. The corrosion rate of HR Zn–2Cu–xLi samples in Hanks’ solution increased with the increasing addition of Li and the HR Zn–2Cu–0.4Li alloy showed an appropriate corrosion performance with I_corr of 33.8 ​μA/cm², V_corr of 488 μm/a, and a degradation rate of 33 μm/a, making it suitable for bone-implant applications. The Zn–2Cu–xLi samples exhibited increased wear resistance with increasing Li addition. The diluted extracts of HR Zn–2Cu–xLi at 12.5% concentration exhibited non-cytotoxicity and the HR Zn–2Cu–0.4Li alloy showed the highest cell viability toward MG-63 ​cells. Further, the HR Zn–2Cu–0.4Li showed effective antibacterial ability toward S. aureus. Overall, the HR Zn–2Cu–0.4Li alloy can be considered a promising biodegradable metallic biomaterial for bone-implant applications.

Pristine polyurea elastomers are usually limited by insufficient strength and lack of functionality. Smart, multifunctional and mechanically resilient nanocomposites were manufactured in this study by compounding functionalized graphene nanoplatelets (F-GNPs) with polyurea via in situ polymerization. This was followed by investigation of the mechanical properties, resistance to chemical media, electrical conductivity and sensing performance of the nanocomposites. A nanocomposite at 0.2 ​wt% of F-GNPs exhibited improvements in tensile strength (60.7%) and elongation (92.1%) as well as obviously enhanced impact performance. The nanocomposite was then investigated as a multifunctional sensor, which exhibited high stretchability with a large workable strain range (5%) and good cyclic stability (9100 cycles). As a temperature sensor, the nanocomposite demonstrated high repeatability and stability in response to cyclic changes from −20 ​°C to 110 ​°C. Its self-sensing capability made possible detecting and tracking its own damage at varying impact levels.

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.