Untitled

Funder

Organizational Unit

Publications

Recent Advances of PDMS In Vitro Biomodels for Flow Visualizations and Measurements: From Macro to Nanoscale Applications

Publication . Souza, Andrews; Nobrega, Glauco Tapijara Vallicelli; Neves, Lucas Boniatti; 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.

2024Journal article

Open access

Experimental and numerical analyses of the hemodynamics impact on real intracranial aneurysms: A particle tracking approach

Publication . Souza, Andrews; Lopes, Diogo; Souza, Sérgio; Ribeiro, J.E.; Ferrera, Conrado; Lima, Rui A.

This study investigates the impact of hemodynamics on real intracranial aneurysms (IAs) using experiments and computational fluid dynamics (CFD) simulations. A particle tracking velocimetry (PTV) approach was used to study the vortical structures inside a real aneurysm and validate numerical simulations performed at a steady regime for different flow rates. Moreover, this and two additional patient-specific cases have been numerically analyzed, focusing on flow patterns, wall shear stress (WSS), relative residence time (RRT), and oscillatory shear index (OSI) for transient studies. For the transient simulations, vorticity profiles indicated significant rotation of fluid particles in the neck and outlet arteries. TAWSS analysis revealed high WSS values in the bifurcation zone, neck, and middle cerebral artery (MCA), with variations among the patients. OSI and RRT plots provided insights into disturbed flow patterns, low or oscillatory WSS areas, and regions with prolonged residence time. This study shows great potential for combining PTV and CFD to obtain detailed insights into flow structures in aneurysms, which are crucial to developing effective treatments and interventions for IA management.

2024Journal article

Open access

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.

2024Journal article

Open access