AMADEus Seminar - Dr. Vesselin Shanov - Monday 3 december 2018 - 2:00 pm -ICMCB (Amphi)

Dr. Vesselin Shanov is Professor of Chemical and Materials Engineering at the University of Cincinnati, USA. He completed his Ph.D. in Solid State Chemistry at the University of Chemical Technology and Metallurgy, Sofia, Bulgaria and at the University of Regensburg, Germany. Dr. Shanov has received several prestigious awards, including the Fulbright Award for Research and Teaching in USA and German Academic Foundation (DAAD) Grants. His recent research focuses on synthesis, characterization and processing of carbon nanotubes and graphene, with applications in the areas of energy storage, electronics and aerospace, as well as on biodegradable Mg for medical implants. He is co-founder and co-director of the teaching and research facility NANOWORLD Lab at the University of Cincinnati. Dr. Shanov has more than 300 scientific publications, including 16 patents, 12 provisional patents and 5 books, cited in about 3,200 different references.

               Magnesium is known with its biocompatibility and the ability to resorb in body, thus making it a promising material for medical implants. Magnesium single crystal reveals absence of grain boundaries which is expected to result in high strength, non-catastrophic failures, high purity and increased corrosion resistance. Crystals with orientation (0001), diameter of 30mm and length 140mm have been grown at UC using modified Bridgman-Stockbarger method. Their crystal structure was investigated by different XRD techniques. Mechanical properties showed modulus and strength of the crystal close to that of the natural bone and high ductility that can reduce the risk of catastrophic failures in implants. In vitro and in vivo corrosion studies of implanted Mg single crystal devices will be reported. Anterior Cruciate Ligament (ACL) rings implanted in goats successfully repaired damaged ligaments. Single crystal Mg plates and screws showed promising resorption and bone overgrowth around the device when implanted in a rabbit ulna fracture model. Current efforts will be presented on fabricating stents from Mg single crystal taking advantage of its great ductility.

            The second part of the talk will discuss design and in vitro plus in vivo testing of Mg stents fabricated by photo-chemical etching. Manufacturing stents by laser cutting is an expensive approach that reveals some technical issues. Our patented photo-chemical etching method transfers a pattern of the stent onto a Mg sheet, followed by chemical etching. Finally, etched sheets with desired dimensions are rolled to cylinders and laser welded along the side seam. This inexpensive process does not generate residual stress in the material during processing. For fabricating helical stent, two-dimensional patterned Mg ribbon was coiled to a spiral shape. This stent revealed different mode of expansion allowing 2 times enlargement beyond its initial diameter. The corrosion properties of uncoated and polymer coated Mg stents have been studied in vitro using static and dynamic (DMEM fluid) flow. In vivo tests of the photo-chemically etched Mg stents have been conducted using a pig model in an arteriovenous fistula (AVF) and in peripheral artery environments. In vitro and in vivo studies of Mg photo-chemically etched stents provided promising data for vascular applications of these devices.