The very widespread illness coronary heart disease, and in particular heart attacks as a result of blocked coronary arteries, is the most common cause of death in industrial nations. Treating these blockages by implanting a stent has become a safe, inoffensive and relatively cost-efficient standard procedure; however, complications or late effects within the first 12 months still occur in approx. 5% of implantations. One reason for this can be found in the constructive manufacturing process of the applied stents, which, due to the currently available manufacturing procedures, can only be produced offering limited design flexibility.
The delicate meander structure of coronary stents with a strut thickness of less than 150µm is currently cut with lasers out of usually cylindrical tubes; this does not allow for any variation in radial strut thickness nor for deviating from the cylindrical form. This could be resolved by producing stents via the additive manufacturing technology metallic laser powder bed fusion (L-PBF), which has proved itself in prototype and small batch production. This technology adds the components layer after layer by melting metal powder with a laser. The procedure has already been used in medical engineering for many years for the production of implants such as hip replacements and other orthopaedic implants.
Philipp Lullas doctoral thesis, titled „Einfluss des Fertigungsverfahrens auf die mechanischen und biologischen Eigenschaften koronarer Stents" (Impact of the production method on mechanical and biological properties of coronary stents), thus aims to develop and establish the production of coronary stents with this procedure. As opposed to conventional manufacturing, there are not yet any established production parameters for additive manufacturing of coronary stents; these were therefore developed for surgical stainless steel 316L including the establishment of post-treatment. The thus developed stent design was manufactured both additively and conventionally. Subsequently, the final trial samples were compared with each other by means of tests based on the norms relevant for CE certification for stents.
Philipp Lulla is the first to have managed to prove with his doctoral thesis that it is possible to create new stent designs by means of additive manufacturing via L-PBF technology, which are able to compete mechanically as well as biologically with customary stents.
The doctoral work was carried out in the Labor für Medizinprodukte of the Faculty of Mechanical Engineering as part of the Regensburg Research Center of Biomedical Engineering and the Regensburg Research Center of Health Sciences and Technology and was supervised by Prof. Dr.-Ing. Thomas Schratzenstaller. Philipp Lullas research was furthermore supported by the Labor für Werkstoffrandschichtanalytik under Prof. Dr.-Ing. Ulf Noster (TC Parsberg-Lupburg) and the Labor Computional Mechanics and Materials under Prof. Dr.-Ing. Aida Nonn (TC Neustadt/Donau), both faculties of Mechanical Engineering at OTH Regensburg. Clinical partner was the Experimental Cardiac Surgery under Prof. rer.nat. Karla Lehle, which is part of the Department for Cardiac, Thoracic and Cardiovascular Surgery of the Universitätsklinikum Regensburg under Herrn Prof. Dr.med. Christof Schmid. Industrial partner was the Firma FIT Production from Parsberg/Lupburg. The project was also financially supported by the Federal Ministry of Education and Research (BMBF) by the project "Aortic Gen-i-Stent" (Förderkennzeichen: 13GW0391A) as well as by the Bavarian State Ministry of Science and the Arts as part of BayWISS.
Dr. Philipp Lulla completed his dissertation in human sciences (Dr. sc. hum.) at the University of Regensburg with excellent results, successfully defending his work on 16th March 2026.
German original: Prof. Dr.-Ing. Thomas Schratzenstaller - Ostbayerische Technische Hochschule Regensburg
Photograph: Matthias Widbiller