Miniature Flexible Humidity Sensitive Patches for Space Suits

Advanced space suit technologies demand improved, simplified, long-life regenerative sensing technologies, including humidity sensors, that exceed the performance of current commercial devices. Intelligent Optical Systems proposes to develop luminescence-based optical sensors to monitor relative humidity (RH). The proposed sensors will offer flexible packaging designs and outstanding performance at high RH levels and under water saturation. Miniature flexible humidity-sensitive patches, connected to an optoelectronics reader by an optical fiber, will allow great flexibility in fitting the sensor element into the space suit. The sensor materials will consist of a luminescent indicator, whose emission lifetime depends on humidity, supported in chemically and mechanically passive polymer film. Since measurements that rely on emission lifetime are insensitive to indicator bleaching, and fluctuations in the light source and/or the photodetector, the measurements will be reliable and stable. The advantages of using optical sensors include easy miniaturization, immunity to electric and electromagnetic fields, and amenability to multiplexing. In Phase I, we will develop and analytically characterize humidity-sensitive materials, and prepare flexible sensor patches. In Phase II, we will manufacture prototypes for aeronautic qualification and conduct extensive testing under simulated environmental conditions. Sensitive patches to O2 and CO2 interrogated by the same electronic unit could be incorporated.

Humidity sensors with high performances requirements are used in a number of aeronautic applications. IOS will explore the advantages of developing miniature humidity-sensitive patches that can be interrogated through an optical cable for monitoring humidity in aircraft applications. A number of industries can benefit from using high performance relative humidity sensors to control their processes. Examples include construction materials manufacturing, paper manufacturing, and the food industry, where accurate and reliable humidity monitoring could provide manufacturers with a competitive advantage. A number of well-established companies offer humidity monitors to these industries. To our knowledge, however, none of these companies offer fiber-optic humidity sensors. The basic technology of these companies is comprised of hydroscopic polymers and capacitance measures. The specific features of the optical sensors developed by IOS will be exploited by collaborating with and establishing licensing agreements with, companies already established in this market.

Accurate humidity sensing is needed not only in space suits, but also in the monitoring and control of the spacecraft environment and in several other NASA applications, such as in the monitoring of life support systems or cryogenic gases. Each application entails different problems associated with the measurement of humidity. IOS is pursuing the development of a common base technology that can address monitoring needs in each application area by properly selecting and designing the humidity sensing material, and adapting the read-out unit as necessary. The sensitivity and dynamic range of the sensors proposed by IOS can be tuned by selecting different supports for the moisture indicator. In the proposed project, we will develop miniature humidity-sensitive patches for space suits that can monitor relative humidity up to 100% saturation, and that will be capable of withstanding condensation conditions. Sensors capable of monitoring traces of water in CO2, O2 and H2, among other gases, and that would improve life support systems control, could be designed using the same sensing technology and optoelectronic unit. Such an approach will extend the potential application of IOS's humidity sensors to address different NASA needs. The advantages of using optical sensors include easy miniaturization, immunity to electric and electromagnetic fields, and amenability to multiplexing.

This is early/mid-stage (TRL 5) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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