Dielectric characterization of PEBA and PDMS for capacitive interdigital vapour sensors

During the wine fermentation process the aroma profile produced is very complex and changes notably due to the yeast metabolism, while ethanol is produced simultaneously in much higher concentrations (up to 10 wt.%) relatively to aroma compounds (in the ppm range), making very difficult to follow the aroma profile with the conventional sensors. An automated aroma sensing system for the wine-must fermentation may render possible to detect and correct undesired off-flavors, representing major losses for the wine-industry. We are developing an Interdigital Capacitor (IDC) sensor array to be part of an electronic nose for on-line and real-time monitoring of wine fermentation process. The basic transducer has an interdigital electrode configuration (typical gap and finger of 100 /spl mu/m) made on a glass substrate coated with a polymer sensitive layer. We had developed an analytical model for the interdigital geometries to predict the capacitance in accordance with the geometry of the electrodes and the change of capacitance with the change of permittivity and thickness of the sensitive layer. Numerical simulation of the sensors geometry has been made for the validation of the analytical model. The capacitance measured for the sensors are in good agreement with our analytical model. Polydimethylsiloxane (PDMS) and polyetherblockamide (PEBA) have been chosen for the sensitive layer and are characterized.