Figure 1: Difference between the cooling rates during liquid nitrogen fumigation of three types of straws. (a) Images of the structure of 0.25 ml straw, 0.5 ml straw, and LSL straw. Micro-straws (LSL straws) are made of an outer metal shell and an inner tube. (b) The cooling rate of three different types of straws. The cooling rate of LSL straw was significantly faster than that of 0.25 mL and 0.5 mL straws, and the cooling rates of 0.25 mL straws showed obviously faster than that of 0.5 mL straws, but with the similar trends of changes.