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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.

Flexibility of guidewires

Pelyhe L., Kertész A.

Selected Engineering Problems

2013

nr 4

133--138

The guidewire is a flexible medical device, which subserves the navigation and positioning of devices for angiography and angioplasty. In our study we present a method for the determination of guidewires' bending stiffness and flexibility (reciprocal of the bending stiffness) improved by our research group. With this method the flexibility can be detachedly defined, it is quantitative and by this new technique different guidewires can be compared. We characterized the bending stiffness, which value does not change at the first 15 mm of the guidewires’ distal end (this part is inserted into the patient). The deflection of guidewires was performed by a tensile test machine. We examined three guidewires. As for the reliability of our method, we drew conclusions from the coefficients of variation. Our three coefficients were between 0.8-0.13 so our methodology is reliable; it is suitable for the objective determination and comparative analysis of the flexibility of guidewires.