Thermomechanical responses facilitating survival mechanisms in pronounced supercooled insects.

ABSTRACT

Cryopreservation can keep the bioactivity of biological specimens in long-term storage, but it is hard to retain the structural integrity due to serious thermomechanical stress during cooling and warming procedures, especially for complex living organisms. Few studies have reported on the thermomechanical stress of biological specimens in a pre-freezing supercooled state, which is a widespread phenomenon in slow-rate freezing cryopreservation. Here, we develop a thermomechanical coupling model to study transient thermal and mechanical fields of supercooled biological specimens experiencing freezing procedures. The results show that cryoprotectant accumulation in insects causes pronounced supercooled phenomena with severe deformation and thermomechanical stress in the initial state of phase transition. However, the loss of freezable water induced that final deformation and stress decrease, which is beneficial to organism survival after freezing. This numerical method is proved to be a guideline for optimizing slow-rate freezing cryopreservation protocols efficiently and economically. These results reveal survival mechanisms of insects with supercooled phenomena after freezing and assist researchers in exploring more valuable cryopreservation methods for biological specimens.