Design, simulation, and fabrication of an ingestible capsule with gastric balloon for obesity treatment.

The treatment of obesity based only on lifestyle changes has been shown ineffectiveness in a long-term period. The development of more definitive and non-invasive therapies has been the subject of study. In this paper, a magnetically driven ingestible capsule with the capacity to inflate a gastric balloon is devised, simulated, and fabricated. The balloon is inflated to a volume of 150 ml using an acid-base reaction between citric acid and potassium bicarbonate. Finite element method simulations were performed to study the interaction between the permanent external magnet and the ingestible capsule and confirm the magnetic activation mechanism. A fabrication process was proposed to manufacture a polydimethylsiloxane (PDMS) balloon in a simple, functional, and reproducible way. The two layers and 1:8 ratio balloons are the most cost-effective without compromising their mechanical properties. The capsule body parts manufactured by a three-dimensional (3D) printing process - Digital Light Processing (DLP) showed high accuracy and excellent resolution. This study demonstrated that the proposed ingestible capsule would successfully inflate the gastric balloon to treat obesity.

Macro-, meso- and microstructural characterization of metallic lattice structures manufactured by additive manufacturing assisted investment casting.

Cellular materials are recognized for their high specific mechanical properties, making them desirable in ultra-lightweight applications. Periodic lattices have tunable properties and may be manufactured by metallic additive manufacturing (AM) techniques. However, AM can lead to issues with un-melted powder, macro/micro porosity, dimensional control and heterogeneous microstructures. This study overcomes these problems through a novel technique, combining additive manufacturing and investment casting to produce detailed investment cast lattice structures. Fused filament fabrication is used to fabricate a pattern used as the mold for the investment casting of aluminium A356 alloy into high-conformity thin-ribbed (~ 0.6 mm thickness) scaffolds. X-ray micro-computed tomography (CT) is used to characterize macro- and meso-scale defects. Optical and scanning electron (SEM) microscopies are used to characterize the microstructure of the cast structures. Slight dimensional (macroscale) variations originate from the 3D printing of the pattern. At the mesoscale, the casting process introduces very fine (~ 3 µm) porosity, along with small numbers of (~ 25 µm) gas entrapment defects in the horizontal struts. At a microstructural level, both the (~ 70 µm) globular/dendritic grains and secondary phases show no significant variations across the lattices. This method is a promising alternative means for producing highly detailed non-stochastic metallic cellular lattices and offers scope for further improvement through refinement of filament fabrication.

Blood flow simulations in patient-specific geometries of the carotid artery: A systematic review.

Computational Fluid Dynamics (CFD) and Fluid-Structure Interaction (FSI) are currently widely applied in the study of blood flow parameters and their alterations under pathological conditions, which are important indicators for diagnosis of atherosclerosis. In this manuscript, a systematic review of the published literature was conducted, according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, on the simulation studies of blood flow in patient-specific geometries of the carotid artery bifurcation. Scopus, PubMed and ScienceDirect databases were used in the literature search, which was completed on the 3rd of August 2020. Forty-nine articles were included after the selection process and were organized in two distinct categories: the CFD studies (36/49 articles), which comprise only the fluid analysis and the FSI studies (13/49 articles), which includes both fluid and Fluid-Structure domain in the analysis. The data of the research works was structured in different categories (Geometry, Viscosity models, Type of Flow, Boundary Conditions, Flow Parameters, Type of Solver and Validation). The aim of this systematic review is to demonstrate the methodology in the modelling, simulation and analysis of carotid blood flow and also identify potential gaps and challenges in this research field.

Influence of the Adopted Balloon Modeling Strategies in the Stent Deployment Procedure: An In-Silico Analysis.

PURPOSE: As the promoter of the stent expansion, the balloon plays a very important role, offering a strong influence on the deployment process. Balloon-artery interaction is pointed as a probable cause of restenosis, stressing the relevance of balloon modeling when simulating the stenting procedure. In this work, an in-silico study of the balloon modeling strategies is performed. METHODS: Ultrasonic-microcasting is a novel technology that allows obtaining stents manufactured in magnesium alloys, being suggested as a promising solution. However, this technique demands superior stent strut thickness, which may have an impact on the stent deployment procedure. The influence of the balloon modeling is studied through the simulation of different balloon geometries (open- or taper-ended) and material constitutive model (linear elastic or hyperelastic) on the expanded configuration of a stent manufactured through ultrasonic-microcasting. RESULTS: The results obtained suggest that the choice of balloon type has small impact in terms of demanded pressure to inflate the balloon and in the stent final radius achieved at fully-expanded configuration. Additionally, it was proved that the balloon-type influences the stent expanded profile along its length and diameter as a result of the different deformation behavior exhibited by the balloon. CONCLUSION: The hyperelastic taper-ended balloon suggests being the model that better correlates with both experimental and clinical results regarding the expanded balloon profile during the procedure.