Ammonia Sensor Works by Diffusion

That chip on the bee's back is a 1 3 1 3 0.38 mm hydrogen sensor. It detects hydrogen from 0% to 100% lower explosive limit, is not cross-sensitive to methane and other flammable gases, and has a power consumption of <25 mW. Here's how it works: Hydrogen has an affinity to palladium and its alloys, and it is well known that palladium readily absorbs hydrogen gas up to 900 3 its own volume. This MEMS-based sensor incorporates a palladium-nickel alloy thin-film sensing element whose surface catalytically breaks the H-H bond in diatomic hydrogen (the hydrogen gas molecule). Once the bond is broken, the monatomic hydrogen diffuses into the alloy lattice structure. The amount of hydrogen dissolved is proportional to the amount of hydrogen gas present, and the lattice's electrical resistance increases proportionally to the level of dissolved hydrogen. This resistance change is reversible; there is an equilibrium between the dissolved or absorbed hydrogen and the hydrogen level present. When the ambient hydrogen diminishes, desorption of hydrogen from the lattice causes a decrease of its electrical resistance. By monitoring and measuring the electrical resistance of the alloy, the level of hydrogen can be inferred. A proprietary method of nanostructuring the alloy was used to increase the detector's sensitivity by increasing the surface of the alloy without expanding the device's physical dimensions.

 The hydrogen sensor s minuscule size will make it easy to build it into personal monitors.
The hydrogen sensor s minuscule size will make it easy to build it into personal monitors.

The research project has received a Phase I SBIR grant from NASA Kennedy Space Center, contract #NNK05OA21C, for "Hydrogen Sulfide Micro-Sensor for Biomass Fouling Detection."

The sensor s functional components are revealed in this cross section.
The sensor s functional components are revealed in this cross section.

Contact Mo Kebaili, Ph.D., CTO, Kebaili Corp., Laguna Beach, CA; 949-494-5892, [email protected], www.kebaili.com.

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