Medical sterilization system for NASA Space Exploration Missions

With the goal of sending humans to explore asteroids and Mars soon, NASA aims to improve its current medical capabilities for long duration missions. NASA needs to increase sterilization capabilities while reducing medical payload mass, volume, power, and costs. The medical payload contains small medical devices, such as scalpels and forceps; as well as disposable items, such as sanitary wipes. On the International Space Station, all carried medical equipment are disposable to ensure they are sanitary. This approach must be analyzed against a sanitize and reuse strategy for long duration missions. In order to address the problem, a cold plasma sterilization system capable of sterilizing small medical devices aboard a spacecraft is developed. System requirements were defined based on information gathered during literature review and input from NASA clients. Evaluation of the different cold plasma technologies, through the use of an analytical hierarchy process, resulted in selecting the Floating Electrode Dielectric Barrier Discharge configuration for the system. In this configuration, there are mechanical and electrical subsystems. The electrical subsystem contains a DC to DC converter unit, a high voltage switching unit, and a signal generator. The mechanical subsystem contains the application device, which is comprised of an outer polytetrafluorethylene housing, a copper electrode, a quartz dielectric, and electrical sealant. The system configuration of the device will generate pulsed plasma species in the discharge gap between itself and the substrate, in this case, K-12 strain Escherichia coli. Experiments were conducted to evaluate dependent measures while varying the number of doses, the voltage, and the air gap distance from the quartz dielectric to the grounded source, in this case the surface of the petri dish.