Automated device for rapid sample cooling via controlled submersion

Abstract

An automated device is described which enables programmable submersion in liquid nitrogen to enable rapid specimen cooling for vitrification applications. The device presented here is low-cost, portable, and compatible with a range of cryogenic containers. The device is capable of submerging samples at a range of speeds, enabling the user to optimize the cooling rates based on the thermal mass of the sample as well as the thermal properties of the container and biospecimen. The device consists of a stepper motor that drives a linear actuator, which enables the movement of a 3D-printed robotic arm in the vertical plane which is used to submerge the specimen rapidly into the cryogen. After development, the device was validated for its design parameters. The relative error in starting height and submersion distance was less than 1.5%, indicating a high degree of precision and consistency in positioning during operation. The resulting cooling rates showed no significant difference between manual and automated submersion, confirming the device's performance and reliability. The device performance was further assessed using a 0.25 mL insemination straw to evaluate its practical application. The cooling rate achieved was well within the range cited in previous reports as well as that predicted computationally, confirming the device's functionality. Importantly, this device can be constructed using commercially available materials at relatively low costs.

Keywords: Rapid submersion; Ultra-fast cooling; Vitrification.