From the executive summary, the team is developing the Variable-Temperature Cryocooler (VTC), a freezer intended for biological research operations. RNA samples, crucial to research into many emerging diseases, need to be preserved at low temperatures of -80\degree C. Many emerging diseases are primarily found in developing countries in areas without reliable grid power, which makes reliable sample preservation and obtaining usable data difficult. Therefore, the VTC is also designed for off-grid operation.
In addition to the specific use case of RNA sample storage, the team also noted that the market for cryogenic cooling lacked compact devices that offered storage at temperatures below -80\degree C. We saw this as an opportunity to provide novel innovation, as other biological samples such as stem cells are stored at -150\degree C. The VTC is designed to operate at temperatures between -150\degree C and -20\degree C.
The variable-temperature cryocooler uses a free-piston stirling cycle (FPSC). FPSC technology is smaller in size than traditional cooling cycles and minimizes moving parts for higher robustness. An electronic control system, connect to the FPSC system to adjust the set point temperature of the storage volume. To ensure temperature reliability, the storage volume also contains temperature sensors to monitor and display the interior temperature to the user.
The cold storage volume and surrounding structures are designed to minimize cold loss, offering more stable internal temperatures and reducing power use. The storage volume is surrounded by vacuum-insulated paneling, which greatly reduces thermal losses to the ambient air. The storage volume can accommodate 486 biological sample cryovials. The cryovials slot into a solid aluminum drawer, to maximize conductive heat transfer and minimize the amount of hot air that enters the system when the cooler contents are accessed. The system is also designed with a phase-change material chamber. Phase-change material panels are used for shipment of biological samples, and they can also act as a thermal battery.
In order to provide consistent power to the system in areas where the electrical grid experiences frequent outages, our system has a robust power management system comprised of a generator and backup battery. When there is a power outage, an automatic transfer switch will trigger the generator. The battery serves as a power source to bridge the generator startup time.
Link to Google Slides
Screen-capture from Michael's video of our presentation