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Analysis and development of the adhesion of stent coatings

Bognar E., Ozsvath P., Kertesz A., Pelyhe L., Devenyi L.

Selected Engineering Problems

2014

nr 5

15--20

The influence of the surface roughness on adhesion strength of polyurethane coating on stainless steel alloy (316LVM) is introduced. These coatings are one of the development directions in coronary stent production. One of the widely spread stent base material is the 316LVM, so in the presented study these materials were involved. The samples were prepared by etching and electro-polishing. The current density and polishing time were changed to create samples with different surface roughness. After electro-polishing polyurethane (Chronoflex®) coating was applied. The adhesion of the coating on different surfaces was tested by scratch test (nano indenter technique). The increasing surface roughness gives stronger adhesion. According to our experiments it was concluded that the coronary stents, treated by etching without polishing could cut out the balloons during expansion, therefore the surface roughness should be under this value. It is recommended to use an electro-chemical treatment that is resulting Ra=1.5-2.0 μm roughness.

Chemical etching of Nitinol stents

Katona B., Bognar E., Berta B., Nagy P., Hirschberg K.

Acta of Bioengineering and Biomechanics

2013

Vol. 15, no. 4

3--8

At present the main cause of death originates from cardiovascular diseases. Primarily the most frequent cause is vessel closing thus resulting in tissue damage. The stent can help to avoid this. It expands the narrowed vessel section and allows free blood flow. The good surface quality of stents is important. It also must have adequate mechanical characteristics or else it can be damaged which can easily lead to the fracture of the implant. Thus, we have to consider the importance of the surface treatment of these implants. In our experiments the appropriate design was cut from a 1.041 mm inner diameter and 0.100 mm wall thickness nitinol tube by using Nd:YAG laser device. Then, the stent was subjected to chemical etching. By doing so, the burr created during the laser cutting process can be removed and the surface quality refined. In our research, we changed the time of chemical etching and monitored the effects of this parameter. The differently etched stents were subjected to microscopic analysis, mass measurement and in vivo environment tests. The etching times that gave suitable surface and mechanical features were identified.