Search for: All records

ABSTRACT Polyetheretherketone (PEEK) is a member of the polyaryletherketone (PAEK) family of semi‐crystalline thermoplastics that is increasingly considered as an alternative to metals for use in permanent implants. Another member of the PAEK family, polyetherketoneketone (PEKK), has many similar properties to PEEK, but can vary in its crystallization kinetics due to its varying terephthalic and isophthalic acid (T/I) ratios during manufacturing. We hypothesized that PEKK's differences in chemical structure may produce a better surface for cell adhesion, increasing in vitro osteoblastic performance when compared to PEEK. Solid and porous samples were printed under comparable conditions and cultured with MC3T3‐E1 mouse pre‐osteoblasts for up to 28 days. A laser confocal microscope was used to evaluate surface roughness of samples as one possible explanation for differences in in vitro performance. Micro‐CT was used to visualize the accuracy in printing of porous samples when compared to a digital model. PEKK samples were found to have significantly increased cell attachment, normalized alkaline phosphatase activity, and osteoblastic mineralization at multiple time points (p < 0.05). PEKK samples were also found to be significantly smoother than PEEK samples on the micron scale. Based on micro‐CT images, PEKK samples were found to more closely resemble the desired triply periodic minimal surface geometry than PEEK samples. This study suggests that PEKK should be considered in future studies investigating the biological performance of PEEK due to PEKK's encouraging in vitro biocompatibility. 

Abstract MXenes are a class of 2D materials that have gained significant attention for their potential applications in energy storage, electromagnetic interference shielding, biomedicine, and (opto)electronics. Despite their broad range of applications, a detailed understanding of the internal architecture of MXene‐based materials remains limited due to the lack of effective 3D imaging techniques. This work demonstrates the application of X‐ray micro‐computed tomography (micro‐CT) to investigate various MXene systems, including nanocomposites, coated textiles, and aerogels. Micro‐CT enables high‐resolution, 3D visualization of the internal microstructure, MXene distribution, infiltration patterns, and defect formations, which significantly influence the material's performance. Moreover, the typical technical challenges and limitations encountered during sample preparation, scanning, and post‐processing of micro‐CT data are discussed. The information obtained from optical and electron microscopy is also compared with micro‐CT, highlighting the unique advantages of micro‐CT in providing comprehensive 3D imaging and quantitative data. This study highlights micro‐CT as a powerful and nondestructive imaging tool for characterizing MXene‐based materials, providing insights into material optimization and guidelines for developing future advanced applications. 

Abstract   Metal injection molding (MIM) processes are generally more cost-effective for the generation of metallic AM components. However, the thermal processing required to remove the polymer and sinter the metal powder is not well understood in terms of resulting mechanical response and damage evolution, especially in ambient atmospheres where contamination is present. This study aims to provide a range of achievable mechanical properties of copper produced using a MIM-based method called fused filament fabrication (FFF) that is post-processed in a nonideal environment. These results showed direct correlations between sintering temperature to multiple aspects of material behavior. In addition, Nondestructive Evaluation (NDE) methods are leveraged to understand the variation in damage evolution that results from the processing, and it is shown that the higher sintering temperatures provided more desirable tensile properties for strength-based applications. Moreover, these results demonstrate a potential to tailor mechanical properties of FFF manufactured copper for a specific application. 

Abstract Polyvinylidene fluoride (PVDF) is a semicrystalline polymer used in thin‐film dielectric capacitors because of its inherently high dielectric constant and low loss tangent. Its dielectric constant can be increased by the formation and alignment of its β‐phase crystalline structure, which can be facilitated by 2D nanofillers. 2D carbides and nitrides, MXenes, are promising candidates due to their notable dielectric permittivity and ability to increase interfacial polarization. Still, their mixing is challenging due to weak interfacial interactions and poor dispersibility of MXenes in PVDF. This work explores a novel method for delaminating Ti₃C₂T_xMXene directly into organic solvents while maintaining flake size and quality, as well as the use of a non‐solvent‐induced phase separation method for producing both dense and porous PVDF‐MXene composite films. A deeper understanding of dielectric behavior in these composites is reached by examining MXenes with both mixed and pure chlorine terminations in PVDF matrices. Thin‐film capacitors fabricated from these composites display ultrahigh discharge energy density, exceeding 45 J cm⁻³with 95% efficiency. The PVDF‐MXene composites are also processed using a green and sustainable solvent, propylene carbonate. 

Abstract An innovative process to multifunctional vitrimer nanocomposites with a percolative MXene minor phase is reported, marking a significant advancement in creating stimuli‐repairable, reinforced, sustainable, and conductive nanocomposites at diminished loadings. This achievement arises from a Voronoi‐inspired biphasic morphological design via a straight‐forward three‐step process involving ambient‐condition precipitation polymerization of micron‐sized prepolymer powders, aqueous powder‐coating with 2D MXene (Ti₃C₂T_z), and melt‐pressing of MXene‐coated powders into crosslinked films. Due to the formation of MXene‐rich boundaries between thiourethane vitrimer domains in a pervasive low‐volume fraction conductive network, a low percolation threshold (≈0.19 vol.%) and conductive polymeric nanocomposites (≈350 S m⁻¹) are achieved. The embedded MXene skeleton mechanically bolsters the vitrimer at intermediate loadings, enhancing the modulus and toughness by 300% and 50%, respectively, without mechanical detriment compared to the neat vitrimer. The vitrimer's dynamic‐covalent bonds and MXene's photo‐thermal conversion properties enable repair in minutes through short‐term thermal treatments for full macroscopic mechanical restoration or in seconds under 785 nm light for rapid localized surface repair. This versatile fabrication method to nanocoated pre‐vitrimer powders and morphologically complex nanocomposites is compatible with classic composite manufacturing, and when coupled with the material's exceptional properties, holds immense potential for revolutionizing advanced composites and inspiring next‐generation smart materials. 

Nanoparticles with aerodynamic diameters of less than 100 nm pose serious problems to human health due to their small size and large surface area. Despite continuous progress in materials science to develop air remediation technologies, efficient nanoparticle filtration has appeared to be challenging. This study showcases the great promise of MXene-coated polyester textiles to efficiently filter nanoparticles, achieving a high efficiency of ~90% within the 15–30 nm range. Using alkaline earth metal ions to assist textile coating drastically improves the filter performance by ca. 25%, with the structure–property relationship thoroughly assessed by electron microscopy and X-ray computed tomography. Such techniques confirm metal ions’ crucial role in obtaining fully coated and impregnated textiles, which increases tortuosity and structural features that boost the ultimate filtration efficiency. Our work provides a novel perspective on using MXene textiles for nanoparticle filtration, presenting a viable alternative to produce high-performance air filters for real-world applications. 

Ultra-high-molecular-weight polyethylene (UHMWPE) components for orthopedic implants have historically been integrated into metal backings by direct-compression molding (DCM). However, metal backings are costly, stiffer than cortical bone, and may be associated with medical imaging distortion and metal release. Hybrid-manufactured DCM UHMWPE overmolded additively manufactured polyetheretherketone (PEEK) structural components could offer an alternative solution, but are yet to be explored. In this study, five different porous topologies (grid, triangular, honeycomb, octahedral, and gyroid) and three surface feature sizes (low, medium, and high) were implemented into the top surface of digital cylindrical specimens prior to being 3D printed in PEEK and then overmolded with UHMWPE. Separation forces were recorded as 1.97–3.86 kN, therefore matching and bettering the historical industry values (2–3 kN) recorded for DCM UHMWPE metal components. Infill topology affected failure mechanism (Type 1 or 2) and obtained separation forces, with shapes having greater sidewall numbers (honeycomb-60%) and interconnectivity (gyroid-30%) through their builds, tolerating higher transmitted forces. Surface feature size also had an impact on applied load, whereby those with low infill-%s generally recorded lower levels of performance vs. medium and high infill strategies. These preliminary findings suggest that hybrid-manufactured structural composites could replace metal backings and produce orthopedic implants with high-performing polymer–polymer interfaces.