Chemical sensors Study on Absorption of VOCs into PDMS Film using Heterodyne Interferometry for Application of VOCs Sensing

International audienceA heterodyne interferometer using a Mach-Zehnder optical configuration is designed for detection of airborne VOCs. The design is based on film-mediated sensing technique in which the response of intermediate sensing film is monitored using interferometry. PDMS is used as a sensing film, which changes its volume and refractive index when absorbed VOCs molecules. Thin film of PDMS acts as a phase object and any variation in its state causes a proportional phase shifts in the transmitted light beam. The Mach-Zehnder interferometer is integrated with a microscope and acoustic-optic modulators. The information of the absorbed gas concentration into the film are encoded in the fringe patterns and are extracted by a temporal phase extraction heterodyne method. The film is exposed to different concentrations of airborne toluene and its response is measured using interferometry