Researchers at NASA's Marshall Space Flight Center have developed a solid-state humidity sensing element that offers ultra-high sensitivity across a wide range of humidity levels. The sensing element is based on a novel ceramic dielectric material that exhibits large changes in capacitance as a function of small changes in humidity.
The dielectric sensing element layer can be formed via a range of printing methods. With further conditioning and packaging, the sensor device can be used to measure very small changes in humidity across a range of humidity levels.
NASA is currently seeking opportunities with companies who are interested in bringing the humidity sensing element technology to the marketplace for applications where the reliable and simple measurement of humidity is needed, particularly for applications requiring high sensitivity and/or robust or higher-temperature performance capabilities.
The novel ceramic dielectric material enables extremely high-sensitivity humidity sensing. The ceramic sensing element is robust, can be manufactured using printing processes, and exhibits fast response and recovery speeds with large capacitance response/change per relative humidity unit change across a wide range of humidity levels in a log-linear response. Preliminary test data conducted in a humidity test chamber show a log-linear measured response in capacitance from 5 nanofarads (at 30% relative humidity, room temperature) to 0.2 millifarads (at 90% relative humidity, room temperature).
The inventors discovered the humidity sensing element technology during their efforts to develop next-generation energy storage materials and devices for NASA. The inventors were initially puzzled by large swings in capacitance observed over the course of any given day in one particular dielectric composition, and, ultimately, they were able to trace these unexpected changes in capacitance back to corresponding changes in relative humidity.
The sensor element can be formed using a dielectric ink or paste formulation, also developed by NASA, via traditional screen printing or advanced inkjet, aerosol, or 3D printing methods. The printed sensor element can be very thin, on the order of microns in thickness, with a small footprint of one square centimeter or less.