**2.3.2 Haemolysis rate test of TiNi SMA after surface modification**

When blood connects with a foreign material surface some red cells will be destroyed to release hemoglobin, that is, haemolysis occurring. A material with good blood compatibility should have a lower haemolysis rate. Figure 2-4 shows a haemolysis rate tested result of TiNi SMA samples, which were untreated, anodically-oxidized and cathodically-electrodeposited respectively. It can be seen that the TiNi SMA and its surface-modified materials have met the medical requirement (<5%) for a biomaterial. Haemolysis rate of the modified material has decreased somewhat. And haemolysis rate of anodically-oxidized sample was lower than that of cathodically-electrodeposited one. This is because of that, TiO2 crystals have a good blood compatibility. Besides, the material surface smoothness and film quality have effects on haemolysis rate. Haemolysis rate of cathodically-electrodeposited sample is higher than that of anodically-oxidized one. This is relevant to the smoothness differences on sample surface.

Fig. 2-4. Haemolysis rate of modified TiNi SMA
