In biomechanical research, defining material models of human tissues precisely is increasingly important. Investigated tissues include homografts and replacement tissues. Verified material models aid in medical applications through numerical modelling. Budapest University of Technology and Economics (BUTE) and ZHAW cooperate with the Heart and Vascular Centre, Semmelweis University Budapest (SE), on human aorta and aneurysm research, and with the Gottsegen National Cardiovascular Center Budapest (GOKVI) on child pulmonary arteries.

These cooperations enable sample acquisition and histopathological investigations. In this project tissues are obtained from these institutions and shipped to ZHAW for examination. Examining pericardial tissue is crucial. Surgeries at GOKVI relieve stenosis in pediatric pulmonary arteries by suturing pericardial tissue, creating a realistic lumen size. However, the sutured tissue's properties differ from the vessel, causing collapse due to changed flow conditions. Eventually, finite element studies will investigate this stability phenomenon. To do so, precise knowledge of material behavior is essential, including the effects of storage, freezing, and thawing.

A distinct project highlight is the deployment of the new biaxial testing machine at ZHAW. Tensile tests to be performed at ZHAW describe global material behavior of tissue samples. The research will determine characteristics of collagen fiber-reinforced human soft tissues. Model parameters are determined by fitting models to data, including anisotropic hyperelastic models for collagenous tissues. Testing ranges depend on stretching rates, enabling broader exploration of material behavior. Anisotropy can be revealed by biaxial tests on the new ZHAW testing machine. A manifold of measurements also enables statistical analysis; therefore, it is important to conduct the measurements and potentially extend the series as long as possible.

The determined material properties serve as indispensable input data in numerical simulations in subsequent research projects. Statistical evaluation of measurement data enables more accurate patient-specific modelling with respect to several categories (age, gender, etc.). In addition to the material calibration for the understanding of soft tissue behavior, patient specific material parameters also facilitate further cooperation opportunities of the participating research groups.

We intend to continue the cooperation within the framework of an internationally funded research project (Horizon Europe, Eureka), which will focus, among other things, on the preparation of full-fledged finite element modelling and simulation of real surgical interventions as well as the biomechanically sound deployment of homografts and replacement tissues in the human body. We plan to publish the results of this research in a peer-reviewed journal article and to present major findings at scientific conferences.