Development of high resolution particle image velocimetry for use in artificial heart research

Both high and low wall shear stresses have been implicated as causes for device failure after implantation. Previous studies have shown that the local flow field characteristics of artificial hearts do not scale simply as the device is reduced in size. To address this problem, a high resolution particle image velocimetry (PIV) system was developed to investigate the near wall flow field characteristic of the 50cc Penn State Artificial Heart. The PIV system has a resolution of roughly 6 microns per pixel and uses fluorescent particles to reduce noise due to reflections in the near wall region. The system was validated by measuring the laminar flow field in a 3×3 mm square tube. Valid velocity data were obtained in the central region of the tube and as close as 200 microns from the wall. Measured velocity profiles agreed with the analytical profile. The PIV system was then used to measure the flow field characteristics along the wall of the inlet section of the 50cc pump at peak diastole. Velocity profiles were obtained within a 5 mm region from the wall and exhibited wall strain rates varying from 1000-5000 s^-1. The current focus is to increase the resolution and accuracy of the PIV measurements and to determine the optimal method of determining wall strain rate.