A Smart Box with Adjustable Cooling Rate for Cryopreservation.

BACKGROUND: The box-in-box (BIB) has recently been developed as a reliable low-cost device with a passively controlled cooling rate. However, the typical box-in-box design is only applicable to -80°C freezer. The transfer process to liquid nitrogen may affect the quality of the sample. OBJECTIVE: To develop a smart cooling BIB that can be immersed directly into liquid nitrogen. MATERIALS AND METHODS: Different thickness and materials of the box were used to alter the cooling rate. Experiments were carried out to measure the cooling rate and modeling was performed to verify experimental results. RESULTS: The average cooling rate of the solid cassette with a wall thickness of 10 mm was 7°C/min. The average cooling rate of the hollow boxes was about 2.5°C/min and 1.5°C/min for polystyrene box and aerogel box, respectively. CONCLUSION: The cooling rate of the internal sample can be controlled by controlling the thickness of the box as well as by changing the filling material of the hollow box for cooling by immersion into liquid nitrogen.