基于气态氮梯度降温的低共熔保护剂降温速率优化研究
Research on the Optimization of Cooling Rates of Deep Eutectic Protectants Based on the Gradient Cooling with Gaseous Nitrogen

低温生物医学领域中，低共熔保护剂体系凭借其氢键网络介导的冰晶抑制能力与低渗透损伤特性，被视为替代传统低温保护剂(如DMSO、甘油)的革新方向。然而，其优势的实现高度依赖精准的降温速率控制：过慢冷却易引发过冷态冰晶生长，过快冷却则导致热应力损伤。当前主流的程序降温仪虽可调控速率，但其高昂成本与操作复杂性限制了推广应用；被动降温装置虽成本低廉，但其固定速率(约？1℃/min)无法适配低共熔体系的中等速率需求。针对这一矛盾，本研究提出一种基于液氮蒸汽层的梯度降温策略，通过气态氮温度场的分布实现降温速率的灵活适配。结合COMSOL Multiphysics多物理场耦合模型，分析了冻存管在气态氮梯度温度(？196℃至？56℃)下的传热特性。数值模拟表明：气态氮温度梯度可精准控制冻存管内部降温速率。例如，在？196℃~？56℃的液氮蒸汽下，实现了？22.37~？7.98℃/min的降温速率，可以满足低共熔保护剂体系的降温需求。研究结果为低共熔保护剂的应用提供了兼具经济性与灵活性的解决方案，推动低温保存技术从“设备驱动”向“环境调控”的范式转型，为活性生物样本的长期储存奠定了理论与技术基础。
In the field of cryobiomedicine, deep eutectic cryoprotectant systems are regarded as a revolutionary alternative to traditional cryoprotective agents (e.g., DMSO, glycerol) due to their hydrogen bond network-mediated ice crystal inhibition capability and reduced osmotic damage. However, the efficacy of these systems critically depends on precise cooling rate control: excessively slow cooling may trigger ice crystal growth in the supercooled state, while overly rapid cooling can induce thermal stress damage. Although mainstream programmable cooling devices allow adjustable rates, their high costs and operational complexity hinder widespread adoption. Passive cooling devices, though cost-effective, offer a fixed cooling rate (approximately ？1？C/min), which fails to meet the intermediate rate requirements (？20 to ？50？C/min) of deep eutectic systems. To address this challenge, this study proposes a gradient cooling strategy based on liquid nitrogen vapor layer dynamics, achieving flexible cooling rate adaptation through the spatial modulation of gaseous nitrogen temperature fields. By employing a COMSOL Multiphysics-based multiphysics coupling model, we analyzed the heat transfer characteristics of cryovials under gaseous nitrogen gradient temperatures (？196？C to ？56？C). Numerical simulations demonstrate that gaseous nitrogen temperature gradients enable precise control of internal cooling rates. For instance, within a liquid nitrogen vapor temperature range of ？196？C to ？56？C, cooling rates of ？22.37 to ？7.98？C/min were achieved, effectively satisfying the cooling demands of deep eutectic cryoprotectant systems. These results provide an economically viable and adaptable solution for the application of deep eutectic protectants, driving a paradigm shift in