Methodology for measuring the gap size using a fiber-optic displacement sensor exemplified by a centrifugal blood pump

In order to avoid blood clotting, in the second generation of rotary blood pumps the impeller is suspended without mechanical bearing, using the balance of magnetic and hydrodynamic forces. Reaching single tens of microns, the gap between the pump housing and the impeller is crucial for the level of blood traumatization by the pump. In this paper we would like to present the method of physical measurement of this gap on a running pump with the use of a commercial fiber-optic proximity sensor exemplified by the Polish rotary blood pump ReligaHeart ROT. We have also discussed the technical requirements of laboratory stand construction.