Investigation of time-dependent changes in geometrical, mechanical and optical properties of PVA hydrogel for...

Polyvinyl alcohol hydrogel (PVA-H) is increasingly used as vascular modeling material due to its low friction and high transparency. Since mechanical, fluid dynamic and implant performance tests are commonly performed in aqueous environments, a thorough understanding of time-dependent changes in geometrical, mechanical and optical properties of PVA-H in water is imperative. In this study, a comprehensive analysis of the short- and long-term behavior of PVA-H in water for vascular modelling applications has been performed. PVA-H properties were investigated for six weeks, with the swelling behavior characterized by mass and area change. Young's modulus was assessed, as well as compliance for medium-sized (Ø 6.8 mm) and large artery models (Ø 30 mm). Friction coefficients were determined via planar sliding test and UV-Vis spectroscopy served to assess optical transparency of PVA-H. Geometric analysis revealed initial slight swelling of the PVA-H, followed by shrinkage up to -33.3 ± 0.5 % after six weeks. Compliance increased considerably within the first hours of water exposure, followed by an increase in Young's modulus and a decrease in compliance over days to weeks. Furthermore, friction coefficients increased considerably from 0.110 ± 0.001 after half an hour up to 1.142 ± 0.038 after five weeks. Optical transparency initially fluctuated and subsequently stabilized above 90 % up to six weeks. In conclusion, this study provides a comprehensive understanding of short- and long-term changes in geometrical, mechanical, and optical properties of PVA-H in water, demonstrating that precise timing is required when used as models for vascular research and implant testing.