Cell-free layer analysis in a polydimethysiloxane microchannel: A global approach

The cell-free layer (CFL) is a hemodynamic phenomenon that has an important contribution to the rheological properti es of blood flowing in microvessels. The present work aims to find the closest function describing RBCs flowing around the cell depleted layer in a polydimethysiloxane (PDMS) microchannel with a diverging and a converging bifurcation. The flow behaviour of the CFL was investigated by using a high-speed video microscopy system where special attention was devoted to its behaviour before the bifurcation and after the confluence of the microchannel. The numerical data was first obtained by using a manual tracking plugin and then analysed using the genetic algorithm approach. The results show that for the majority of the cases the function that more closely resembles the CFL boundary is the sum of trigonometric functions.The authors acknowledge the financial support provided by PTDC/SAU-ENB/116929/ 2010 and EXPL/EMS-SIS/2215/2013 from FCT (Science and Technology Foundation), COMPETE, QREN and European Union (FEDER). R.O. Rodrigues, D. Pinho and V. Faustino acknowledge respectively, the PhD scholarships SFRH/BD/97658/2013, SFRH/BD/89077/2012 and SFRH/BD/99696/2014 granted by FCT.info:eu-repo/semantics/publishedVersio

Injection of Deformable Capsules in a Reservoir:a Systematic Analysis

Motivated by red blood cell dynamics and injectable capsules for drug delivery, in this paper, a computational study of capsule ejection from a narrow channel into a reservoir is undertaken for a combination of varying deformable capsule sizes and channel dimensions. A mass-spring membrane model is coupled to an Immersed Boundary–Lattice Boltzmann model solver. The aim of the present work is the description of the capsules’ motion, deformation and the response of the fluid due to the complex particles’ dynamics. The interactions between the capsules affect the local velocity field and are responsible for the dynamics observed. Capsule membrane deformability is also seen to affect inter-capsule interaction. We observe that the train of three particles locally homogenises the velocity field and the leading capsule travels faster than the other two trailing capsules. Variations in the size of reservoir do not seem to be relevant, while the ratio of capsule diameter to channel diameter as well as the ratio of capsule diameter to inter-capsule spacing play a major role. This flow set-up has not been covered in the literature, and consequently we focus on describing capsule motion, membrane deformation and fluid dynamics, as a preliminary investigation in this field

Computational haemodynamics of small vessels using the Moving Particle Semi-implicit (MPS) method

The simulation of whole blood stands as a complex multi-body problem. The Moving Particle Semi-implicit method, a Lagrangian particle method to solve the incompressible Navier-Stokes (NS) equations, is developed to perform simulations in complex periodic domains. Red blood cells are modelled using the spring network approach, that act as body force terms in the NS equations. Detailed presentation and derivation of both the MPS method and different spring network models is given. An adaptive time step and an implicit scheme are adopted, improving the stability and overall computational effciency.The findings from the simulations show evidence that in proximity to the vessel wall, the red blood cells expose a larger surface area by orientation and deformation, due to the presence of a high velocity gradient. The greatest membrane internal stresses occur in the core region of the flow. The intra-cell interaction is driven by a complex flow field that can be visualised in a Lagrangian framework, and highlights vortex structures in the wakes and in between the cells. The stresses the blood exerts on the vessel wall is influenced by this complex flow field and by the presence of red blood cells

Meshfree and Particle Methods in Biomechanics: Prospects and Challenges

The use of meshfree and particle methods in the field of bioengineering and biomechanics has significantly increased. This may be attributed to their unique abilities to overcome most of the inherent limitations of mesh-based methods in dealing with problems involving large deformation and complex geometry that are common in bioengineering and computational biomechanics in particular. This review article is intended to identify, highlight and summarize research works on topics that are of substantial interest in the field of computational biomechanics in which meshfree or particle methods have been employed for analysis, simulation or/and modeling of biological systems such as soft matters, cells, biological soft and hard tissues and organs. We also anticipate that this review will serve as a useful resource and guide to researchers who intend to extend their work into these research areas. This review article includes 333 references