Abstract
Arrays with polymer-coated acoustic sensors, such as surface acoustic wave (SAW) and surface transverse wave (STW) sensors, have successfully been applied for a variety of gas sensing applications. However, the stability of the sensors’ polymer coatings over a longer period of use has hardly been investigated. We used an array of eight STW resonator sensors coated with different polymers. This sensor array was used at semi-annual intervals for a three-year period to detect organic solvent vapors of three different chemical classes: a halogenated hydrocarbon (chloroform), an aliphatic hydrocarbon (octane), and an aromatic hydrocarbon (xylene). The sensor signals were evaluated with regard to absolute signal shifts and normalized signal shifts leading to signal patterns characteristic of the respective solvent vapors. No significant time-related changes of sensor signals or signal patterns were observed, i.e., the polymer coatings kept their performance during the course of the study. Therefore, the polymer-coated STW sensors proved to be robust devices which can be used for detecting organic solvent vapors both qualitatively and quantitatively for several years.
Highlights
Today, a large variety of acoustic wave devices is available, exploiting a number of different piezoelectric substrate materials and designs
MHz supplied by surface acoustic wave (SAW) Components, surface transverse wave (STW) resonators an operating frequency of
Thedifference resulting frequency shifts were plotted as radar obtainas characteristic forcharacteristic the organic solvents normalized difference frequency shiftscharts wereto plotted radar chartspatterns to obtain patterns which were applied as for the organic solvents which were applied as volatile organic compounds (VOCs) samples
Summary
A large variety of acoustic wave devices is available, exploiting a number of different piezoelectric substrate materials and designs. These solvents were chosen to represent a halogenated aliphatic compound, an alkane, and an aromatic compound, respectively Both frequency shifts and signal patterns of the array were evaluated to Sensors 2017, 17, 2529 determine the long-term suitability of the chosen set of polymer-coated STW sensors regarding compound, respectively. Both frequency shifts and signal patterns of the array were evaluated to quantitative and qualitative results in VOC sensing applications. Determine the long-term suitability of the chosen set of polymer-coated STW sensors regarding quantitative and qualitative results in VOC sensing applications
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