Validating a test method to evaluate the adhesion force of electrospun nanofiber covered nitinol stents and evaluating the adhesion force of differently treated stents

The main objective of this study is to measure the adhesion force between braided structured nitinol stent's surface and thermoplastic polyurethane (TPU) electrospun nanofibers. Further, the influence of different treatments on the adhesion force should be investigated, and a method to enhance adhesion should be found. To measure the adhesion force of TPU nanofiber covered stents, first, a method was validated using different surface materials and adhesives. After that test method validation, the adhesion force is measured. Later, different approaches are followed to evaluate the adhesion force, such as different electrospinning processes, braided structures, and treatments. From the validation part, it has been observed that the adhesion forces of 2D and 3D surfaces are quite coherent and reproducible. Similar results have been found for 2D, and 3D structured nanofiber covered stents. In terms of different approaches, higher adhesion forces have been observed for horizontal electrospinning setups and braided structures with higher forwarding speeds. After plasma treatment, adhesion forces were increased by 2 times, while for heat treatment, it was increased by 1.5 times. The average adhesion force of the stent after plasma and heat treatment was 41.8 cN and 26.41 cN, respectively, while the reference stent without treatment measured 16.75 cN. Keywords: nitinol stents, electrospun nanofiber, adhesion force, test method validation