Scaffold designs have diversified significantly in the past decade, with many incorporating graded structures to maximize tissue ingrowth, as the success of bone regenerative medicine hinges upon the scaffold's morphology and mechanical properties. Either foams characterized by a haphazard pore distribution or the regular recurrence of a unit cell are the foundations for most of these structures. 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. Differing from prior work, this contribution seeks to provide a adaptable design framework for producing diverse three-dimensional (3D) scaffold structures, specifically including cylindrical graded scaffolds, by implementing a non-periodic mapping scheme from a UC definition. 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. Different scaffold configurations' mechanical properties are compared through an efficient numerical method based on energy considerations, emphasizing the design approach's capacity for separate control of longitudinal and transverse anisotropic scaffold characteristics. A helical structure, exhibiting couplings between transverse and longitudinal properties, is proposed within these configurations, thereby enhancing the framework's adaptability. In order to determine the capability of standard additive manufacturing methods to create the suggested structures, a subset of these designs was produced using a standard SLA setup and put to the test through experimental mechanical analysis. Despite variations in the geometric characteristics between the original blueprint and the physical structures, the proposed computational method provided satisfactory estimations of effective properties. Concerning on-demand self-fitting scaffolds, promising perspectives on their design are presented in relation to clinical applications.
Tensile testing, undertaken within the Spider Silk Standardization Initiative (S3I), classified true stress-true strain curves of 11 Australian spider species from the Entelegynae lineage, using the alignment parameter, *. In each scenario, the application of the S3I methodology allowed for the precise determination of the alignment parameter, which was found to be situated within the range * = 0.003 to * = 0.065. Utilizing these data alongside earlier results from other species within the Initiative, the potential of this method was highlighted by testing two basic hypotheses concerning the distribution of the alignment parameter throughout the lineage: (1) whether a uniform distribution conforms with the obtained values from the studied species, and (2) whether a pattern can be established between the * parameter's distribution and phylogeny. With respect to this, some members of the Araneidae family exhibit the lowest values for the * parameter, and higher values seem to correlate with increasing evolutionary distance from that group. Even though a general trend in the values of the * parameter is apparent, a noteworthy number of data points demonstrate significant variation from this pattern.
Finite element analysis (FEA) biomechanical simulations frequently require accurate characterization of soft tissue material parameters, across a variety of applications. 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. Frequently, hyperelastic constitutive laws are utilized to model the nonlinear characteristics 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. Yet, the determination of the requisite data for a precise and accurate definition of a unique parameter set is not fully clear. 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). To eliminate variability in model fidelity and measurement errors, we implemented an axisymmetric indentation finite element model to create simulated data sets for four two-parameter hyperelastic constitutive laws: compressible Neo-Hookean, nearly incompressible Mooney-Rivlin, Ogden, and Ogden-Moerman. Discrepancies in reaction force, surface displacement, and their combined effects were evaluated for each constitutive law, utilizing objective functions. We graphically illustrated these functions across hundreds of parameter sets, employing ranges typical of soft tissue in the human lower limbs, as reported in the literature. Atezolizumab in vivo Moreover, we assessed three metrics for identifiability, providing clues about the uniqueness and the degree of sensitivity. A clear and systematic evaluation of parameter identifiability, independent of the optimization algorithm and initial guesses within iFEA, is a characteristic of this approach. Our investigation of the indenter's force-depth data, although a common method for parameter identification, demonstrated limitations in reliably and accurately determining parameters for all the materials studied. In contrast, incorporating surface displacement data improved the parameter identifiability in all cases; however, the Mooney-Rivlin parameters were still difficult to reliably pinpoint. Informed by the outcomes, we then discuss a variety of identification strategies, one for each constitutive model. Finally, the code employed in this study is publicly available for further investigation into indentation issues, allowing for adaptations to the models' geometries, dimensions, mesh, materials, boundary conditions, contact parameters, and objective functions.
The study of surgical procedures in human subjects is facilitated by the use of synthetic models (phantoms) of the brain-skull system. The complete anatomical brain-skull system replication in existing studies is, to date, a relatively uncommon occurrence. Neurosurgical studies of global mechanical events, such as positional brain shift, necessitate the use of such models. A novel fabrication workflow for a biofidelic brain-skull phantom is presented in this work. This phantom is comprised of a full hydrogel brain, fluid-filled ventricle/fissure spaces, elastomer dural septa, and a fluid-filled skull. Crucial to this workflow is the use of the frozen intermediate curing phase of an established brain tissue surrogate, enabling a novel technique for skull installation and molding, resulting in a far more complete anatomical recreation. By means of indentation tests on the phantom's brain and simulations of supine-to-prone shifts, the mechanical reality of the phantom was verified. Meanwhile, magnetic resonance imaging substantiated its geometric realism. A novel measurement of the supine-to-prone brain shift, captured by the developed phantom, demonstrates a magnitude precisely mirroring the findings in the existing literature.
This work involved the preparation of pure zinc oxide nanoparticles and a lead oxide-zinc oxide nanocomposite via flame synthesis, followed by investigations into their structural, morphological, optical, elemental, and biocompatibility characteristics. The structural analysis of the ZnO nanocomposite revealed a hexagonal structure for ZnO, coupled with an orthorhombic structure for PbO. A nano-sponge-like surface morphology was observed in the PbO ZnO nanocomposite through scanning electron microscopy (SEM). Energy-dispersive X-ray spectroscopy (EDS) analysis confirmed the absence of any undesirable impurities. The particle sizes, as observed in a transmission electron microscopy (TEM) image, were 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. Microbiota functional profile prediction The efficacy of the compounds in fighting cancer is evident in their remarkable cytotoxic activity, as confirmed by studies. The PbO ZnO nanocomposite demonstrated exceptional cytotoxicity against the HEK 293 tumor cell line, achieving a remarkably low IC50 value of 1304 M.
The biomedical field is increasingly relying on nanofiber materials. Nanofiber fabric material characterization often employs tensile testing and scanning electron microscopy (SEM). Gel Imaging While comprehensive in their assessment of the entire specimen, tensile tests do not account for the properties of individual fibers. Conversely, SEM images analyze individual fibers in detail, but are limited in scope to a small region near the surface of the analyzed sample. To evaluate fiber-level failures under tensile force, recording acoustic emission (AE) signals is a potentially valuable technique, yet weak signal intensity poses a challenge. Acoustic emission recording techniques permit the detection of hidden material weaknesses and provide valuable findings without impacting the reliability of tensile test results. This research introduces a methodology for recording weak ultrasonic acoustic emissions from tearing nanofiber nonwovens, utilizing a highly sensitive sensor. Biodegradable PLLA nonwoven fabrics are used to functionally verify the method. The nonwoven fabric's stress-strain curve displays a near-invisible bend, directly correlating with a considerable adverse event intensity and demonstrating potential benefit. AE recording is not currently part of the standard tensile tests for unembedded nanofiber materials intended for medical applications with safety concerns.