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22 February 2018 Mach-Zehnder interferometer applied to the study of polymer's relative humidity response
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Proceedings Volume 10545, MOEMS and Miniaturized Systems XVII; 1054517 (2018)
Event: SPIE OPTO, 2018, San Francisco, California, United States
The use of electronic Relative Humidity (RH) sensors is widespread. However, when spark-free methods in explosive areas are needed optical RH methods could be employed. Here we present the application of the Mach-Zehnder (MZ) interferometer to study the response of thin films to changes in RH. These films could be used as the sensor element in RH instruments. As an example three types of films have been studied: poly(vinyl alcohol), an Interpenetrated Polymer Hydrogel (IPH) and gelatin. The configuration to study the polymer’s response consists of a climatic chamber where the MZ interferometer is immersed. The thin film is inserted in one arm. When humidity or water vapor increases the film thickness increases and its refractive index decreases. These phenomena will cause the shifting or lateral movement of the interference pattern. By sampling the interference pattern with a fixed point sensor it is possible to find a plot relating light intensity as a function of RH. These plots characterize the material. Several thin films parameters have been studied like Molecular Weight (MW) of poly(vinyl alcohol); thicknesses, hardness, and polymer ratio of an IPH and finally gelatin hardness.
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Sergio Calixto, Maria Elena Calixto Olalde, Jose Hernandez Barajas, and Omar Vazquez Espitia "Mach-Zehnder interferometer applied to the study of polymer's relative humidity response", Proc. SPIE 10545, MOEMS and Miniaturized Systems XVII, 1054517 (22 February 2018);

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