Fabrication of Colorimetric Fiber Optic Hydrazine Sensors

Hydrazine is a highly toxic compound that is widely used as a rocket fuel in U.S. space programs. Since very low concentrations of hydrazine are considered hazardous, there is need for sensors that are robust, cheap, sensitive and selective. Sigma Labs proposes a low cost manufacturing method for fiber optic sensors with reactive, colorimetric claddings. The coating process is characterized by a plasma cleaning and activation, followed by vapor deposition and curing of the reactive coating. A variety of reagents can be incorporated into the cladding layer. The reagents can be incorporated either as a guest or as a chemically bound reagent in a polymer matrix. A secondary, non-reactive layer can also be deposited during the process. In addition to providing increased durability and handling properties, this secondary layer may be used as a barrier layer for interfering compounds. Phase I of this project will focus on coating optical fibers with a reactive cladding that uses p-Dimethylaminobenzaldehyde as the reactive compound. An acrylate derivative of p-Dimethylaminobezalddehyde will also be synthesized so that comparisons can be made between the "guest-host" claddings and the chemically bound claddings. The fiber optic sensors will be tested in an absorbance mode and a phase-modulated mode.