Formulation of Generalized Mass Transfer Correlations for Blood Oxygenator Design

This paper numerically investigates non-Newtonian blood flow with oxygen and carbon dioxide transport across and along an array of uniformly square and staggered arranged fibers at various porosity (ε) levels, focussing on a low Reynolds number regime (Re < 10). The objective is to establish suitable mass transfer correlations, expressed in the form of Sherwood number (Sh = f(ε, Re, Sc)), that identifies the link from local mass transfer investigations to full-device analyses. The development of a concentration field is initially investigated and expressions are established covering the range from a typical deoxygenated condition up to a full oxygenated condition. An important step is identified where a cut-off point in those expressions is required to avoid any under- or over-estimation on the Sherwood number. Geometrical features of a typical commercial blood oxygenator is adopted and results in general show that a balance in pressure drop, shear stress, and mass transfer is required to avoid potential blood trauma or clotting formation. Different definitions of mass transfer correlations are found for oxygen/carbon dioxide, parallel/transverse flow, and square/staggered configurations, respectively. From this set of correlations, it is found that transverse flow has better gas transfer than parallel flow which is consistent with reported literature. The mass transfer dependency on fiber configuration is observed to be pronounced at low porosity. This approach provides an initial platform when one is looking to improve the mass transfer performance in a blood oxygenator without the need to conduct any numerical simulations or experiments.

Pore-Scale Modeling of Non-Newtonian Shear-Thinning Fluids in Blood Oxygenator Design

This paper reviews and further develops pore-scale computational flow modeling techniques used for creeping flow through orthotropic fiber bundles used in blood oxygenators. Porous model significantly reduces geometrical complexity by taking a homogenization approach to model the fiber bundles. This significantly simplifies meshing and can avoid large time-consuming simulations. Analytical relationships between permeability and porosity exist for Newtonian flow through regular arrangements of fibers and are commonly used in macroscale porous models by introducing a Darcy viscous term in the flow momentum equations. To this extent, verification of analytical Newtonian permeability–porosity relationships has been conducted for parallel and transverse flow through square and staggered arrangements of fibers. Similar procedures are then used to determine the permeability–porosity relationship for non-Newtonian blood. The results demonstrate that modeling non-Newtonian shear-thinning fluids in porous media can be performed via a generalized Darcy equation with a porous medium viscosity decomposed into a constant term and a directional expression through least squares fitting. This concept is then investigated for various non-Newtonian blood viscosity models. The proposed methodology is conducted with two different porous model approaches, homogeneous and heterogeneous, and validated against a high-fidelity model. The results of the heterogeneous porous model approach yield improved pressure and velocity distribution which highlights the importance of wall effects.

Surface modification of poly(dimethylsiloxane) with a covalent antithrombin–heparin complex for the prevention of thrombosis: use of polydopamine as bonding agent

PDMS surface for blood oxygenator modified with antithrombin–heparin complexviapolydopamine.

Surface Modification of Polypropylene Blood Oxygenator Membrane by Poly Ethylene Glycol Grafting

Blood oxygenators play key role in Extra Corporeal Membrane Oxygenator (ECMO) system using for patients with acute respiratory problems, immature fetal and also in open heart surgery. Interaction between blood and blood oxygenator polymeric membrane surface lead to fouling phenomena which have negative effect on performance of this important medical device. A modification comprising surface activation, PEG immersing and PEG graft polymerization carried out to provide acceptable blood oxygenator performance, blood compatibility and reduction in heparin consumption at the same time. Modified membranes characterized by FTIR, contact angle measurements and Atomic Force Microscopy (AFM) analyses. Blood compatibility of modified surface was also detected by SEM images. Results clearly indicate that modifying membranes by PEG is an effective way for anti-fouling properties. Water contact angel reduction from 110ْ to 72ْ shows hydrophilicity enhancement, roughness increasing from 15 to 20 and blood compatibility improvement was investigated by SEM and AFM analysis results respectively.