Physical modeling of flow boiling in microchannels and its induced vitrification of biomaterials

Vitrification preservation is a promising approach for long term storage of biomaterials (e.g. cell suspension) by avoiding intracellular ice formation, and ultra-fast cooling is the key factor to achieve vitrification. In this study, a novel cooling system is introduced and investigated. Physical processes, including flow boiling of liquid nitrogen in microchannels as well as cooling and solidification of the film-shaped sample solution in the system, are theoretically modeled. By simulating the local cooling rate and degree of crystallization in sample solution, the cooling performance of the system is evaluated. Case studies indicate ultra-high cooling rates and high vitrification tendency of sample solution are promisingly achieved with such system. Furthermore, the system dimensions can be adjusted in a flexible range to allow preserving of various volumes of samples. In conclusion, the novel cooling system will hopefully decrease the required concentration of cryoprotectant for vitrification and extend the application area of vitrification preservation, and the model presented in this study can be a useful tool to guide the design and application of such system.