Fabrication and testing of a microdynamic rotor for blood flow measurements

Abstract

Flow studies have been conducted, in vitro, on prototype microfabricated blood flow sensors. The envisioned measurement principle is the detection of the rotation of a micromachined polysilicon rotor of diameter 300 mu m. Repeatable rotation rates as a function of media velocity were obtained for both nitrogen and water. Fluid flow asymmetries, necessary to produce a torque on the rotor, were created by integrating a 2 mu m thick polysilicon cap over half the rotor. Blade deflection, due to intrinsic stress in the polysilicon films, was eliminated by thermal annealing. This allows the rotor, 2 mu m thick, to rotate in the 7 mu m gap between the substrate and the polysilicon cap. Operation of the device in heparinized dog blood resulted in considerable numbers of erythrocytes sticking to the polysilicon elements.