Vitrification by Transient Vacuum Flashing Spray Cooling of Liquid Nitrogen

Abstract

BACKGROUND: The transient vacuum flashing spray cooling of liquid nitrogen (LN2 ) on a microstructured surface can provide ultra-fast cooling rate and may improve cell survival rates. OBJECTIVE: To utilize flashing spray cooling of LN2 instead of film boiling to improve further cell vitrification. METHOD: This study analyzed the effects of the three key parameters (flow rate of liquid nitrogen, ambient pressure, and spray distance) on the cooling process by experimentation. RESULTS: The experimental results showed that the vacuum flashing spray cooling of LN2 can gain higher cooling rates than that achieved by film boiling in conventional vitrification methods. The three parameters all affected the vacuum flash evaporation spray cooling of LN2, and their effect trends were not monotonous but followed a parabolic trend that increased and then decreased. That is, the three parameters all have optimum values to the cooling process. CONCLUSION: Vacuum flash evaporation spray cooling can develop the ultra-fast cooling rates needed to enhance cell vitrification.