Fabrication and testing of a microdynamic rotor for blood flow measurements

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 μm. 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 μm 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 μm thick, to rotate in the 7 μm 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.