Signal amplification with multilayer arrangements on chemicalquartz-crystal-resonator sensors

摘要

Viscoelastic properties of chemically sensitive coatings cannenhance the mass sensitivity of quartz-crystal-microbalance (QCM)nsensors. If analyte sorption is accompanied by a change of thenviscoelastic properties of the coating material, the accumulated massncannot be calculated from the frequency shift without furtherninformation. We developed a sensor concept, which is based on andouble-layer arrangement, permitting acoustic amplification and chemicalnsensitivity to be separated. With a proper selection of materials, thenfirst layer realizes a constant acoustic amplification of the massneffect; the chemically sensitive layer acts purely gravimetrically.nMajor sensor design parameters are the shear modulus and the thicknessnof the first layer. From the acoustic point of view, the thickness ofnthe chemically active layer and its material properties are lessncritical; a glasslike, rigid coating is preferred for a stable sensorntransfer function. Simultaneous measurement of the resonant frequency ofnthe quartz crystal and its motional resistance can be exploited to checknthe acoustic amplification