中文摘要：

对微液滴冻结行为的认识在低温生物学、分析化学等方面具有重要意义。引入飞秒激光实验手段研究液滴及微量生物材料（蛋白）的冻结相变特性。实验考察了样品在多次冻结过程中荧光光谱的变化规律，结果表明：生物材料与非生物材料在冻结及复温过程中的荧光光谱变化趋势存在差异，非生物试剂在冻结过程中光谱下降，经历复温后，其光谱可回复到初始状态；而蛋白在冻结过程中光谱上升，经历复温后，由于降温／升温过程对其造成的不可逆损伤，光谱无法回复到初始状态。基于此提出了用以评估生物样品活性的非接触式飞秒激光测量方法。

英文摘要：

Understanding the freezing behavior of a micro liquid droplet is significant in a variety of areas such as cryobiology and analytical chemistry etc. This paper aimed to investigate the phase change behaviors of ordinary liquid droplet and biological material （egg white） subject to freezing using experimental femtosecond laser device. It was observed that an evident variation has been caused on the fluorescence spectrum of the egg white before and after it was frozen. However, such variation trend is different from that of non-biological material, in which the fluorescence spectrum would drop during freezing and recover to its initial state after.thawing. But for the biological material, the spectrum would increase during freezing, and however never be able to resume its original state because of the irreversible damage caused due to freezing and thawing process. Following such property, a non-contact femtosecond laser detection method to evaluate the viability of biological sample was proposed.