Surface roughness and edge geometries in hemolysis with rotating disk flow

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Abstract
Judging biocompatibility of materials with blood includes assessment of hemolysis resulting from flow in contact with those materials. Such hemolysis is influenced in part by the surface roughness and specific hydrodynamic features of the device used. Using a rotating‐disk device, with polyethylene disks and human blood, it was shown that roughness under 4 μm has negligible effect and that hemolysis increases sharply for roughness above about 11 μm. Gross roughness (65 μm) causes qualitatively different hemolysis kinetics but not as severe hemolysis as extrapolated from low‐roughness data. In the disk geometry, the corner is a key region which generates high hemolysis and thus minor alterations cause hemolytic variations which may tend to obscure materials influences. A series of corner‐beveled polycarbonate disks were tested in comparison with the normal square corner and were found always to cause greater hemolysis. Tapering the bevel inward, so the taper angle was on the order of 2°−4°, reduced hemolysis relative to the 45° bevel but still was more hemolytic than the flat disk. Evidence suggests that glassy plastics can be machined with more reproducibility at the corners than plastics above their Tg such as polyethylene. General device design problems regarding hemolysis are discussed.

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