Author :
Rabe, Jens ; Büttgenbach, Stephanus ; Schröder, Jens ; Hauptm, Peter
Abstract :
We report on the design, fabrication, and application of novel monolithic miniaturized quartz microbalance (QMB) arrays. Up until now, almost all reported resonator arrays (often designated as "electronic noses" or "electronic tongues", respectively, dependent on their application) are assembled from single QMBs. We fabricate arrays with up to 36 QMBs on a single AT-cut quartz blank. Mass sensitive devices based on AT-cut quartz resonators are suitable as (bio)chemical sensors. A frequency shift caused by mass accumulation on the sensor surface increases theoretically with f2, hence the detection limits for the application as chemical sensors should be decreased with increasing frequency. Since the quality factor Q of a quartz crystal decreases with f, the frequency stability is reduced, thus limiting mass sensitivity. The mass sensitivity of resonators with different resonant frequencies was examined by means of electrochemical copper deposition on their surface. Subsequently, the manufactured resonators were coated with different layers (polystyrene, amyl-calix[8]arene, β-cyclodextrine). In order to examine the applicability of such coatings as sensitive layers, their sensitivities to toluene in water were investigated. Moreover, arrays with up to four different resonant frequencies on one chip were fabricated for comparing the resonator behavior of the same coating at different frequencies. In another test setup, different layers were sprayed onto an array of microbalances having all the same resonant frequency. This allowed for comparing the different coating behavior under equivalent test conditions. Arrays were tested for viscosity measurement to find an optimum resonant frequency.
Keywords :
biosensors; chemical sensors; copper; crystal resonators; frequency stability; microbalances; organic compounds; polymer films; viscosity measurement; β-cyclodextrine; AT-cut quartz; Cu; QMB arrays; SiO2; amyl-calix[8]arene; biochemical sensors; detection limits; electrochemical copper deposition; electronic noses; electronic tongues; frequency stability; liquid chemical sensor; mass sensitive devices; mass sensitivity; miniaturized quartz microbalance; monolithic microbalance array; piezoelectric devices; polystyrene; quartz crystal Q factor; quartz resonator; resonant frequency; resonator arrays; resonator coating; resonator frequency shift; sensor surface mass accumulation; toluene; viscosity measurement; Assembly; Biosensors; Chemical sensors; Coatings; Electronic noses; Fabrication; Liquids; Resonant frequency; Sensor arrays; Testing;