Background: This article describes an automated facility for storing biological samples at -80 degrees C, designed to meet the needs of The UK Biobank. No store of this size has previously used liquid nitrogen as refrigerant, and so it was important to confirm the storage compartments could achieve and maintain uniform conditions with efficient use of the coolant. In addition, the store incorporates a novel system of drawers designed to allow robotic access whilst maintaining storage conditions. Experiments were undertaken to prove the performance of both these factors in maintaining the temperature of stored samples, both in steady-state conditions and during sample access.
Methods: Sample tubes containing water were placed in key locations within a prototype storage compartment. Thermocouples inside these sample tubes were used to together with automated data loggers to accumulate continuous records of the temperature of the samples during the experiments.
Results: Results show that the design of refrigeration system and storage compartment, using LN(2) as refrigerant, enables efficient use of coolant and maintains uniform temperature over the entire compartment. The results also show that samples within the compartment remain at the intended storage temperature during automated retrieval operations, including the situation when an access drawer remains open indefinitely.
Conclusions: These results confirm that the store design meets the requirements for the UK Biobank, and have given both the manufacturer (The Automation Partnership) and the UK Biobank the confidence to proceed with the implementation of a full sized automated store to hold 10 million samples.