Microscale analysis of strain-stress state for TiN nanocoating of POLVAD and POLVAD_EXT.

The main purpose of the research was to develop the micromodel of biocompatible titanium nitride nanocoating deposited on polymer by pulsed laser deposition method in blood chambers of Polish ventricular assist devices: POLVAD and POLVAD_EXT. The analysis of the parameters of micromodel crucial for the phenomenon of loss of cohesion occurring between coating and substrate was carried out as well. The micromodel takes into account residual stress, material model of nanocoating, stress resulting from blood pressure in chamber, the thickness of coating and wave parameters of nanocoating (wavelength and antinode). The investigation shows that thickness and residual stress are the most influential parameters. The phenomenon of the loss of cohesion will be observed more frequently for thicker coatings with higher residual stresses.