Scaffold morphological and mechanical properties are crucial for the efficacy of bone regenerative medicine, leading to numerous proposed scaffold designs in the past decade. These include graded structures that are well-suited for enhancing tissue ingrowth. These structures are primarily constructed using either randomly-structured foams or repeating unit cells. The methods are circumscribed by the spectrum of target porosities and their impact on mechanical characteristics. A smooth gradient of pore size from the core to the scaffold's perimeter is not easily produced using these techniques. This paper, in opposition to other methods, proposes a flexible design framework to generate a wide range of three-dimensional (3D) scaffold structures, including cylindrical graded scaffolds, originating from a user-defined cell (UC) by applying a non-periodic mapping. Conformal mappings are initially used to design graded circular cross-sections, followed by stacking these cross-sections, possibly incorporating a twist between layers, to achieve 3D structures. The mechanical performance of different scaffold designs is evaluated and contrasted using an energy-based numerical method, exhibiting the design process's capability of independently managing longitudinal and transverse anisotropic scaffold attributes. Amongst the presented configurations, a helical structure, demonstrating couplings between transverse and longitudinal properties, is highlighted as a proposal allowing the adaptability of the framework to be expanded. A portion of these designed structures was fabricated through the use of a standard stereolithography apparatus, and subsequently subjected to rigorous experimental mechanical testing to evaluate the performance of common additive manufacturing methods in replicating the design. The initial design's geometry, though distinct from the ultimately realised structures, was successfully predicted in terms of effective material properties by the computational method. Concerning self-fitting scaffolds with on-demand properties, the design offers promising perspectives, contingent on the specific clinical application.
The Spider Silk Standardization Initiative (S3I) employed tensile testing on 11 Australian spider species from the Entelegynae lineage, to characterize their true stress-true strain curves according to the alignment parameter, *. The S3I method's application yielded the alignment parameter's value in all instances, exhibiting a range spanning from * = 0.003 to * = 0.065. Previous results from other species investigated within the Initiative, when combined with these data, enabled a demonstration of this approach's potential by exploring two straightforward hypotheses related to the distribution of the alignment parameter across the lineage: (1) does a uniform distribution align with the data from studied species, and (2) is there a relationship between the distribution of the * parameter and the phylogeny? In this regard, the Araneidae group demonstrates the lowest values of the * parameter, and the * parameter's values increase as the evolutionary distance from this group becomes more pronounced. Although a general trend in the values of the * parameter is observable, numerous data points exhibit significant deviations from this trend.
The precise determination of soft tissue material properties is often necessary in various applications, especially in biomechanical finite element analysis (FEA). Unfortunately, the task of identifying representative constitutive laws and material parameters is complex and frequently creates a bottleneck, preventing the successful implementation of finite element analysis procedures. Hyperelastic constitutive laws are frequently used to model the nonlinear response of soft tissues. Identifying material characteristics in living systems, where standard mechanical tests like uniaxial tension and compression are not applicable, is commonly accomplished using finite macro-indentation testing. Because analytical solutions are unavailable, inverse finite element analysis (iFEA) is frequently employed to determine parameters. This method involves repetitive comparisons between simulated and experimental data. Nevertheless, pinpointing the necessary data to establish a unique parameter set precisely still poses a challenge. This work investigates the responsiveness of two forms of measurement: indentation force-depth data (such as those from an instrumented indenter) and complete surface displacements (measured using digital image correlation, for example). Using an axisymmetric indentation finite element model, synthetic data sets were generated to correct for potential errors in model fidelity and measurement, applied to four two-parameter hyperelastic constitutive laws, including compressible Neo-Hookean, and nearly incompressible Mooney-Rivlin, Ogden, and Ogden-Moerman. We calculated objective functions for each constitutive law, demonstrating discrepancies in reaction force, surface displacement, and their interplay. Visualizations encompassed hundreds of parameter sets, drawn from literature values relevant to the soft tissue complex of human lower limbs. read more We implemented a quantification of three identifiability metrics, giving us understanding of the unique characteristics, or lack thereof, and the inherent sensitivities. For a clear and structured evaluation of parameter identifiability, this approach is independent of the optimization algorithm's selection and the initial estimations required in iFEA. Parameter identification using the indenter's force-depth data, while common, demonstrated limitations in reliably and precisely determining parameters for all the investigated material models. In contrast, surface displacement data enhanced parameter identifiability in every case studied, though the accuracy of identifying Mooney-Rivlin parameters still lagged. From the results, we then take a look at several distinct identification strategies for every constitutive model. To facilitate further investigation, the codes employed in this study are provided openly. Researchers can tailor their analysis of indentation problems by modifying the model's geometries, dimensions, mesh, material models, boundary conditions, contact parameters, or objective functions.
The effectiveness of surgical procedures can be analyzed using synthetic models (phantoms) of the brain-skull system, a method that overcomes the challenges of direct human observation. Until this point, very few studies have mirrored, in its entirety, the anatomical connection between the brain and the skull. In neurosurgical studies encompassing larger mechanical events, like positional brain shift, these models are imperative. A new fabrication workflow for a biofidelic brain-skull phantom is showcased in this work. Key components include a complete hydrogel brain with fluid-filled ventricle/fissure spaces, elastomer dural septa, and a fluid-filled skull. This workflow hinges on the utilization of the frozen intermediate curing phase of a validated brain tissue surrogate, facilitating a unique molding and skull installation method for a more complete anatomical recreation. The phantom's mechanical accuracy, determined through brain indentation testing and simulated supine-to-prone brain shifts, was contrasted with the geometric accuracy assessment via magnetic resonance imaging. The developed phantom's novel measurement of the supine-to-prone brain shift event precisely reproduced the magnitude observed in the literature.
Utilizing a flame synthesis approach, pure zinc oxide nanoparticles and a lead oxide-zinc oxide nanocomposite were prepared and then subjected to structural, morphological, optical, elemental, and biocompatibility analyses in this research. The structural analysis of the ZnO nanocomposite revealed a hexagonal structure for ZnO, coupled with an orthorhombic structure for PbO. PbO ZnO nanocomposite SEM images showcased a nano-sponge-like surface. Subsequent energy-dispersive X-ray spectroscopy (EDS) confirmed the absence of unwanted impurities. Employing transmission electron microscopy (TEM), the particle size was determined to be 50 nanometers for zinc oxide (ZnO) and 20 nanometers for lead oxide zinc oxide (PbO ZnO). Optical band gap measurements on ZnO and PbO, using the Tauc plot method, resulted in values of 32 eV and 29 eV, respectively. Surgical antibiotic prophylaxis The cytotoxic activity of both compounds, crucial in combating cancer, is confirmed by anticancer research. The PbO ZnO nanocomposite stands out for its high cytotoxic activity against the HEK 293 tumor cell line, with an IC50 value of only 1304 M.
An expanding range of biomedical applications is leveraging the properties of nanofiber materials. Nanofiber fabric material characterization often employs tensile testing and scanning electron microscopy (SEM). Cellular mechano-biology The results from tensile tests describe the complete sample, but do not provide insights into the behavior of individual fibers. SEM imaging, however, concentrates on the specific characteristics of individual fibers, though this analysis is confined to a limited area close to the surface of the specimen. To acquire data on fiber-level failures subjected to tensile stress, monitoring acoustic emission (AE) presents a promising, yet demanding, approach due to the low intensity of the signals. The acoustic emission recording method reveals beneficial data on hidden material failures, without jeopardizing the accuracy of tensile tests. The current work details a technology using a highly sensitive sensor to capture the weak ultrasonic acoustic emissions generated during the tearing of nanofiber nonwoven materials. The method's functional efficacy is shown using biodegradable PLLA nonwoven fabrics. In the stress-strain curve of a nonwoven fabric, a barely noticeable bend clearly indicates the potential for benefit in terms of substantial adverse event intensity. AE recording procedures have not been applied to the standard tensile tests of unembedded nanofiber materials destined for safety-critical medical uses.