Automated fabrication of polyurethane heart valves

We have developed an automated 'Arm Robot' Fabrication System (ARFS) to make the leaflets of a polyurethane (PU) valve for use in ventricular assist devices (VAD). Preliminary testing using the ARFS resulted in a 27% success rate of the valves fabricated, as compared to 50% for the hand made valves. To gain a better understanding of the deviations in thickness of the leaflet, we measured it at a 135 different points using a Miniature moire measuring system. Of the ARFS made valves, the max. deviation between the three leaflets was at 25μm. and 47μm. for the hand made valves, while the leaflet itself became thicker towards the base. This result indicated a much more even thickness distribution in the ARFS made valves. From valve fatigue testing and using the FEM (finite element method) it was evident a thickness of approximately 300μm. at the base of the leaflet is necessary to achieve long term durability. Although problems remain the ARFS, as the thickness of the valve is better controlled using this system, it is reasonable to assume parameters of valve performance including durability, leakage and pressure drop are also better controlled.