EXPERIMENTAL INVESTIGATION OF A HYDRO-MAGNETICALLY SUPPORTED BLOOD PUMP WITH LARGE ROTOR-HOUSING GAPS:

The rotary blood pump “Hemobear”, which is developed by our group, has a hydromagnetically levitated rotor with only passive magnetic bearings. To allow the application of this concept also in disposable pump heads, comparably large rotor-housing gaps are a key goal of the design. To optimize the rotor and magnetic geometry, experimental studies were performed. A test facility was established, which provided a variation of the gaps within the pump housing and the position of the permanent magnetic drive position. The actual rotor position was measured with a Laser triangulation system. Various housing and rotor geometries were tested at different speeds and flow settings with viscosity adjusted test fluid. Stability was determined at blood gaps from 0.3 to 3 mm under working conditions up to 250 mmHg pressure load and a flow of 0–8 L/min. Best performance was achieved with rotors sliding on a fluid pillow at the outer surface of the cone at a gap distance between 150 and 250 um. The inner gap could he widened up to more than 1.5 mm at a stable performance also at sudden changes of resistance. First hemolysis tests even with the laboratory prototype system showed a considerable better hemolysis then the BioPump. In conclusion, Passive hydromagnetic bearing of rotary blood pumps is possible even at large gaps between rotor and housing at a wide variety of working points. Large gaps permit higher manufacturing tolerances and should therefore allow economical manufacturing.