Chemically selective polymer coatings for acoustic vapor sensors and arrays

Defined generally, a microsensor consists of a physical transducer and a chemically selective layer. In gas phase detection applications, the transducer does not directly detect the analyte molecules in the gas phase; instead, it senses changes in the physical properties of the layer on its surface when the analyte is sorbed. When rubber polymers are used as the chemically selective layer, vapor molecules are absorbed into the bulk of the polymer material. On surface acoustic wave (SAW) sensors, a frequency decrease is then observed that reflects the mass of the vapor and the decrease in modulus of the polymer. The process of sorption, and the factors influencing selectivity, can be understood by considering the vapor´s solubility properties, the polymer´s solubility properties, and how they interact. Specific functional groups are recommended for inclusion in sensor coating materials in order to maximize particular interactions