Fig. 2.

The structure and operation procedure of the vitrification storage box. The vitrification storage box (a) and its internal structure (b). b: The main body of the vitrification storage box (75 × 75 × 12 mm) and its lid (75 × 75 × 5 mm) are both made of stainless steel perforated plates (1 mm in thickness), and they are connected by a hinge. Both the main body and the lid have a built-in liquid nitrogen (LN) absorbent. c: Three vitrification storage boxes can be accommodated in a stainless storage rack (76 × 78 × 57 mm). The storage rack can be accommodated in an LN container canister (d-3). d: The operation procedure of the vitrification storage box. (1) Place the cell sheet wrapped in the vitrification package on the perforated plate of the main body of the box that was immersed and cooled in LN. (2) Vitrify the cell sheet in the vitrification storage box by exposing it to LN vapor (−150 °C) discharged from the LN absorbents. (3, 4) Place up to three vitrification storage boxes in a canister using the storage rack (3) and store them in LN vapor in the LN container (4). The vitrification storage box was prepared on a special order by Umihira Co. Ltd., Kyoto, Japan.