A carregar...
Projeto de investigação
i9Models: Development of innovative in vitro models to study the wall deformability and blood flow in aneurysms.
Financiador
Autores
Publicações
Stress Concentration on PDMS: An evaluation of three numerical constitutive models using digital image correlation
Publication . Sales, Flaminio; Souza, Andrews; Oliveira, Fallconny Rodrigues Sensato; Lima, Rui A.; Ribeiro, J.E.
The examination of hyperelastic materials’ behavior, such as polydimethylsiloxane (PDMS), is crucial for applications
in areas as biomedicine and electronics. However, the limitations of hyperelastic models for specific
stress scenarios, with stress concentration, are not well explored on the literature. To address this, firstly, three
constitutive models were evaluated (Neo-Hookean, Mooney-Rivlin, and Ogden) using numerical simulations and
Digital Image Correlation (DIC) analysis during a uniaxial tensile test. The samples were made of PDMS with
stress concentration geometries (center holes, shoulder fillets, and edge notches). Results of ANOVA analysis
showed that any of the three models can be chosen for numerical analysis of PDMS since no significant differences
in suitability were found. Finally, the Ogen model was chosen to obtain the stress concentration factors for
these geometries, a property which characterize how discontinuities change the maximum stress supported by an
element. Our study provides new values for variables needed to analyze and design hyperelastic elements and
produce a foundation for understanding PDMS stress-strain behavior.
Contributions to accelerating a numerical simulation of free flow parallel to a porous plane
Publication . Schepke, Claudio; Spigolon, Roberta A.; Rufino, José; Cristaldo, Cesar F. Da C.; Pizzolato, Glener L.
Flow models over flat p orous surfaces have applications in natural processes, such as material, food, chemical processing, or mountain mudflow simulations. The development
of simplified a nalytical or numerical models can predict characteristics such as velocity, pressure, deviation length, and even temperature of such flows for geophysical and engineering purposes. In this context, there is considerable interest in theoretical and experimental models. Mathematical models to represent such phenomena for fluid mechanics have continuously been developed and implemented. Given this, we propose a mathematical and simulation model to describe a free-flowing flow pa rallel toa
porous material and its transition zone. The objective of the application is to analyze the influence o f t he p orous matrix on the flow u nder d ifferent m atrix p roperties. W e i mplement a Computational Fluid Dynamics scheme using the Finite Volume Method to simulate and calculate the numerical solutions for case studies. However, computational applications of this type demand high performance, requiring parallel execution techniques. Due to this, it is necessary to modify the sequential version of the code. So, we propose a methodology describing the steps required to adapt and improve the code. This approach decreases 5.3% the execution time of the sequential version of the code. Next,
we adopt OpenMP for parallel versions and instantiate parallel code flows and executions on multi-core. We get a speedup of 10.4 by using 12 threads. The paper provides simulations that offer the correct understanding, modeling, and construction of abrupt transitions between free flow a nd porous media. The process presented here could expand to the simulations of other porous media problems. Furthermore, customized simulations require little processing time, thanks to parallel processing.
Flow visualizations in polydimethylsiloxane cerebral aneurysm biomodels
Publication . Souza, Andrews; Nobrega, Glauco; Ferrera, Conrado; Puga, Helder; Lima, Rui A.; Ribeiro, J.E.
This chapter focuses on the study of intracranial aneurysms (IAs), which are localized dilations of arteries within the skull caused by weakened blood vessel walls. IAs pose a significant risk of rupture, leading to strokes with high mortality and dependency rates. The chapter emphasizes the importance of understanding the hemodynamics and geometry of blood vessels to prevent aneurysm rupture.
The authors present an innovative technique for manufacturing intracranial aneurysm biomodels using Polysmooth as a sacrificial material and polydimethylsiloxane (PDMS) for the final model. PDMS is chosen for its transparency, flexibility, and ease of manufacturing, which facilitates flow visualization tests. The biomodels are designed with different geometric configurations (60° and 180° angles between inlet and outlet channels) to analyze the effects of channel geometry on blood flow patterns.
The experimental setup includes high-speed video equipment, an inverted microscope, and a syringe pump to simulate blood flow using a glycerol-water solution with suspended particles. The flow visualization tests reveal differences in recirculation areas within the aneurysm based on the channel geometry, highlighting the impact of arterial structure on hemodynamics.
The study concludes that the presented manufacturing technique is effective for creating realistic biomodels, enabling detailed analysis of blood flow behavior in aneurysms. This research provides valuable insights for developing numerical models and strategies to prevent aneurysm rupture
Recent Advances of PDMS In Vitro Biomodels for Flow Visualizations and Measurements: From Macro to Nanoscale Applications
Publication . Souza, Andrews; Nobrega, Glauco; Neves, Lucas B.; Barbosa, Filipe; Ribeiro, J.E.; Ferrera, Conrado; Lima, Rui A.
Polydimethylsiloxane (PDMS) has become a popular material in microfluidic and macroscale in vitro models due to its elastomeric properties and versatility. PDMS-based biomodels are widely used in blood flow studies, offering a platform for improving flow models and validating numerical simulations. This review highlights recent advances in bioflow studies conducted using both PDMS microfluidic devices and macroscale biomodels, particularly in replicating physiological environments.
PDMS microchannels are used in studies of blood cell deformation under confined conditions, demonstrating the potential to distinguish between healthy and diseased cells. PDMS also plays a critical role in fabricating arterial models from real medical images, including pathological conditions such as aneurysms. Cutting-edge applications, such as nanofluid hemodynamic studies and nanoparticle drug delivery in organ-on-a-chip platforms, represent the latest developments in PDMS research. In addition to these applications, this review critically discusses PDMS properties, fabrication methods, and its expanding role in micro- and nanoscale flow studies.
Mechanical and optical properties assessment of an innovative PDMS/beeswax composite for a wide range of applications
Publication . Ariati, Ronaldo; Souza, Andrews; Souza, Maria S.; Zille, Andrea; Soares, Delfim; Lima, Rui A.; Ribeiro, J.E.
Polydimethylsiloxane (PDMS) is an elastomer that has received primary attention from researchers due to its excellent physical, chemical, and thermal properties, together with biocompatibility and high flexibility properties. Another material that has been receiving attention is beeswax because it is a natural raw material, extremely ductile, and biodegradable, with peculiar hydrophobic properties. These materials are applied in hydrophobic coatings, clear films for foods, and films with controllable transparency. However, there is no study with a wide range of mechanical, optical, and wettability tests, and with various proportions of beeswax reported to date. Thus, we report an experimental study of these properties of pure PDMS with the addition of beeswax and manufactured in a multifunctional vacuum chamber. In this study, we report in a tensile test a 37% increase in deformation of a sample containing 1% beeswax (BW1%) when compared to pure PDMS (BW0%). The Shore A hardness test revealed a 27% increase in the BW8% sample compared to BW0%. In the optical test, the samples were subjected to a temperature of 80 ◦C and the BW1% sample increased 30% in transmittance when compared to room temperature making it as transparent as BW0% in the visible region. The thermogravimetric analysis showed thermal stability of the BW8% composite up to a temperature of 200 ◦C. The dynamic mechanical analysis test revealed a 100% increase in the storage modulus of the BW8% composite. Finally, in the wettability test, the composite BW8% presented a contact angle with water of 145◦. As a result of this wide range of tests, it is possible to increase the hydrophobic properties of PDMS with beeswax and the composite has great potential for application in smart devices, food and medicines packaging films, and films with controllable transparency, water-repellent surfaces, and anti-corrosive coatings.
Unidades organizacionais
Descrição
Palavras-chave
Contribuidores
Financiadores
Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
POR_NORTE
Número da atribuição
2021.07961.BD