The last decade has witnessed the proliferation of scaffold designs, many featuring graded structures, in response to the crucial role of scaffold morphology and mechanics in the success of bone regenerative medicine, thereby optimizing tissue integration. The majority of these structures are built upon either foams with a non-uniform pore structure or the periodic replication of a unit cell's geometry. Due to the limited porosity range and resultant mechanical strengths, the use of these approaches is restricted. The creation of a graded pore size distribution across the scaffold, from the core to the edge, is not easily facilitated by these methods. 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. The initial step involves using conformal mappings to generate graded circular cross-sections. These cross-sections are then stacked, with or without twisting between layers, to create the final 3D structures. Numerical simulations, using an energy-based approach, reveal and compare the effective mechanical properties of diverse scaffold designs, emphasizing the methodology's capacity to independently manage longitudinal and transverse anisotropic scaffold characteristics. In this set of configurations, a helical structure featuring couplings between transverse and longitudinal properties is suggested, which expands the applicability of the proposed framework. To examine the capabilities of common additive manufacturing methods in creating the proposed structures, a selection of these designs was produced using a standard stereolithography system, and then put through experimental mechanical tests. The computational method effectively predicted the effective properties, even though noticeable geometric discrepancies existed between the starting design and the built structures. The self-fitting scaffold design promises promising perspectives concerning on-demand properties, specific to the targeted clinical application.
To contribute to the Spider Silk Standardization Initiative (S3I), the true stress-true strain curves of 11 Australian spider species from the Entelegynae lineage were established through tensile testing and sorted by the values of the alignment parameter, *. The alignment parameter's determination, using the S3I methodology, occurred in all cases, showing a range of values between * = 0.003 and * = 0.065. Building upon earlier findings from other species within the Initiative, these data allowed for the exploration of this strategy's potential through the examination of two simple hypotheses on the alignment parameter's distribution throughout the lineage: (1) whether a consistent distribution can be reconciled with the values observed in the studied species, and (2) whether a trend emerges between the distribution of the * parameter and phylogenetic relationships. In this analysis, the Araneidae group showcases the lowest * parameter values, and increasing evolutionary distance from this group is linked to an increase in the * parameter's value. Yet, a substantial number of data points are presented that stand apart from the general pattern observed in the values of the * parameter.
Applications, notably those relying on finite element analysis (FEA) for biomechanical modeling, regularly demand the reliable determination of soft tissue parameters. Nevertheless, the process of establishing representative constitutive laws and material parameters presents a significant hurdle, frequently acting as a bottleneck that obstructs the successful application of finite element analysis. Frequently, hyperelastic constitutive laws are utilized to model the nonlinear characteristics of soft tissues. Material parameter identification within living organisms, a process typically hampered by the limitations of standard mechanical tests like uniaxial tension or compression, is often accomplished via finite macro-indentation testing. Given the absence of analytic solutions, parameter identification often relies on inverse finite element analysis (iFEA). This process entails iterative comparisons of simulated outcomes against experimental observations. Undoubtedly, the specific data needed for an exact identification of a unique parameter set is not clear. This research delves into the sensitivities of two measurement categories: indentation force-depth data (obtained from an instrumented indenter) and full-field surface displacements (using digital image correlation, as an example). To account for model fidelity and measurement errors, an axisymmetric indentation FE model was employed to produce synthetic datasets for four 2-parameter hyperelastic constitutive laws, including compressible Neo-Hookean, and nearly incompressible Mooney-Rivlin, Ogden, and Ogden-Moerman. We employed objective functions to measure discrepancies in reaction force, surface displacement, and their combination across numerous parameter sets, representing each constitutive law. These parameter sets spanned a range typical of bulk soft tissue in human lower limbs, consistent with published literature data. selleck inhibitor Subsequently, we determined three measures of identifiability, providing insight into the uniqueness (or lack of it) and the associated 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. Following the results, we subsequently examine various identification strategies 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.
Phantom models of the brain-skull anatomy prove useful for studying surgical techniques not easily observed in human subjects. The anatomical replication of the full brain-skull system, in the available research, remains an underrepresented phenomenon. Neurosurgical studies of global mechanical events, such as positional brain shift, necessitate the use of such models. We present a novel fabrication workflow for a realistic brain-skull phantom, which includes a complete hydrogel brain, fluid-filled ventricle/fissure spaces, elastomer dural septa, and a fluid-filled skull, in this work. The frozen intermediate curing state of an established brain tissue surrogate is fundamental to this workflow, allowing for a novel approach to skull installation and molding that facilitates a more thorough reproduction of the anatomy. The mechanical verisimilitude of the phantom was substantiated by indentation testing of the phantom's brain and simulation of the supine-to-prone transition, while the phantom's geometric realism was demonstrated via magnetic resonance imaging. A novel measurement of the brain's shift from supine to prone, precisely mirroring the magnitudes found in the literature, was captured by the developed phantom.
Through flame synthesis, pure zinc oxide nanoparticles and a lead oxide-zinc oxide nanocomposite were produced, and their structural, morphological, optical, elemental, and biocompatibility properties were investigated in this research. Zinc oxide (ZnO) exhibited a hexagonal structure and lead oxide (PbO) an orthorhombic structure, as determined by the structural analysis of the ZnO nanocomposite. Scanning electron microscopy (SEM) imaging revealed a nano-sponge-like surface texture of the PbO ZnO nanocomposite. Energy-dispersive X-ray spectroscopy (EDS) data validated the absence of contaminating elements. 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). Through the Tauc plot, the optical band gap of ZnO was found to be 32 eV, while PbO exhibited a band gap of 29 eV. hepatic oval cell The efficacy of the compounds in fighting cancer is evident in their remarkable cytotoxic activity, as confirmed by studies. 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.
Biomedical applications of nanofiber materials are expanding considerably. Nanofiber fabric material characterization often employs tensile testing and scanning electron microscopy (SEM). implantable medical devices Although tensile tests offer insights into the overall sample, they fail to pinpoint details specific to individual fibers. Though SEM images exhibit the structures of individual fibers, their resolution is limited to a very small area on the surface of the specimen. The recording of acoustic emission (AE) provides a promising means of comprehending fiber-level failures induced by tensile stress, albeit the weak signal makes it challenging. Acoustic emission data acquisition facilitates the discovery of valuable information about invisible material failures without influencing the outcomes of tensile tests. A highly sensitive sensor is integral to the technology introduced in this work, which records weak ultrasonic acoustic emissions from the tearing of nanofiber nonwovens. The method's functional efficacy is shown using biodegradable PLLA nonwoven fabrics. The stress-strain curve's almost imperceptible bend in the nonwoven fabric underscores the potential benefit, manifesting as a noteworthy level of adverse event intensity. For unembedded nanofiber materials intended for safety-related medical applications, standard tensile tests have not been completed with AE recording.