There are two types of containers used for cell storage, one is an experimental refrigerator, which is cooled by electricity, and the other is a liquid nitrogen Dewar, which is cooled by liquid nitrogen.
Electric cooling only requires electricity, but liquid nitrogen cooling requires considering the liquid level of the liquid nitrogen. Is the liquid level high or low? Is it appropriate to wait?
The manufacturer tells you: it is based on the cell height!
Using the cells as a reference, the liquid nitrogen level should cover the high level of the cells to ensure that all cells are submerged!
The reason is that although liquid nitrogen is excellent at cryogenic -196°C, it has a low boiling point and is a cryogenic liquid that easily volatilizes. When placed in a liquid nitrogen Dewar container with a vacuum structure, it isolates most of the heat, but it cannot prevent cells from being taken. When heat enters from the mouth of the jar, it volatilizes when it comes into contact with heat, and when it volatilizes, there is gas.
Considering that the accumulated gas after volatilization will bring pressure, the liquid nitrogen Dewar of the storage cell designed the neck plug to be relatively loose and left an exhaust port at the mouth of the tank to prevent this part of naturally volatile gas from accumulating into pressure and causing safety issues. .
In this way, the natural volatilization of liquid nitrogen becomes even more unstoppable. After evaporation, the liquid level drops. Samples that cannot be covered by liquid nitrogen will lose the liquid to isolate oxygen. The temperature will inevitably fluctuate, which will have a negative impact on cell preservation. If the liquid level of the liquid nitrogen Dewar cell storage is not reached at the beginning, and the upper cells are not soaked in liquid nitrogen, as the liquid level drops, it is difficult to ensure the activity of the top cells.
Therefore, if it is a liquid nitrogen Dewar that stores cells, be sure to ensure that the liquid level covers the top of the cells, and replenish it immediately when it is about to cover the top!