Thermomechanics analysis of cryopreservation by vitrification of the popliteal artery.

This study aims at exploring packaging configurations and thermal protocols to reduce thermomechanical stress during cryopreservation by vitrification of the popliteal artery and thereby reducing the risk of structural damage. This study explores the potential advantages of preserving the blood vessel in spiral and helical configurations, in solid and hollow cylindrical containers. This study includes ideal rewarming scenarios of convective rewarming, nanowarming, and a combination of both. Results of this study indicate that the maximum stress in the blood vessel is comparable in all configurations examined and may be close to structurally hazardous levels. The maximum stress in the surrounding cryoprotective medium, however, might rise to much higher levels, exceeding the strength to fracture of the material. Once a fracture is initiated somewhere in the container it can rapidly propagate across it, and even through areas where the average stresses are lower. This study demonstrates that thermomechanical stress can be lowered below hazardous levels by careful selection of nanoparticle concentrations, in combination with a matching convective boundary condition. This study demonstrates how this combination can be tailored to various configurations. Finally, a special case is considered to explore the effects of transferring the specimen between cooling instrumentation during cryogenic storage. This study demonstrates that even a brief exposure to ambient temperature of 1 min or less can cause sudden stress spikes in the specimen, potentially exceeding the strength of the material. This special case demonstrates the need to carefully consider the feasibility and practicality of lab protocols when aiming to reduce the likelihood of structural damage.