Liquid sensor based on a piezoelectric lateral electric field-excited resonator

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Novel bio-materials, like chitosan and its derivatives, appeal to finding a new niche in room temperature gas sensors, demonstrating not only a chemoresistive response, but also changes in mechanical impedance due to vapor adsorption. We determined the coefficients of elasticity and viscosity of chitosan acetate films in air, ammonia, and water vapors by acoustic spectroscopy. The measurements were carried out while using a resonator with a longitudinal electric field at the different concentrations of ammonia (100–1600 ppm) and air humidity (20–60%). It was established that, in the presence of ammonia, the longitudinal and shear elastic modules significantly decreased, whereas, in water vapor, they changed slightly. At that, the viscosity of the films increased greatly upon exposure to both vapors. We found that the film’s conductivity increased by two and one orders of magnitude, respectively, in ammonia and water vapors. The effect of analyzed vapors on the resonance properties of a piezoelectric resonator with a lateral electric field that was loaded by a chitosan film on its free side was also experimentally studied. In these vapors, the parallel resonance frequency and maximum value of the real part of the electrical impedance decreased, especially in ammonia. The results of a theoretical analysis of the resonance properties of such a sensor in the presence of vapors turned out to be in a good agreement with the experimental data. It has been also found that with a growth in the concentration of the studied vapors, a decrease in the elastic constants, and an increase in the viscosity factor and conductivity lead to reducing the parallel resonance frequency and the maximum value of the real part of the electric impedance of the piezoelectric resonator with a lateral electric field that was loaded with a chitosan film. This leads to an increase in the sensitivity of such a sensor during exposure to these gas vapors.

Section: Introductionmentioning

confidence: 99%

Evaluation of Elastic Properties and Conductivity of Chitosan Acetate Films in Ammonia and Water Vapors Using Acoustic Resonators

Зайцев

Teplykh

Fedorov

et al. 2020

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“…In this case, the selected shape of the electrodes retains the axial symmetry of the disk, which greatly simplifies its mathematical modeling by a two-dimensional finite element method. This is the advantage of the presented type of resonators relative to resonators with a transverse exciting field with flat electrodes [5][6][7][8], which cannot be correctly modeled by a two-dimensional finite element method in a wide frequency range. The combination of these properties makes it possible to apply the methods of broadband ultrasonic spectroscopy both to the resonator itself to refine its characteristics and to the resonator in acoustic contact with the medium under study, which makes it possible to determine the acoustic and electrical characteristics of the medium using just one broadband measurement.…”

Section: Discussionmentioning

confidence: 99%

“…Cylindrical piezoelectric transducers operating on a longitudinal acoustic mode are used for the emission and receiving of ultrasound in a liquid [1,2] and piezoelectric energy harvesting solutions [3,4]. Resonators with a transverse electric field are used for various sensor applications [5][6][7][8][9]. Resonators of this type are sensitive to mechanical and electrical properties of the medium, which borders on the free surface of the resonator [7,8].…”

Section: Introductionmentioning

confidence: 99%

The Radial Electric Field Excited Circular Disk Piezoceramic Acoustic Resonator and Its Properties

Teplykh

Зайцев

Semyonov

et al. 2021

A new type of piezoceramic acoustic resonator in the form of a circular disk with a radial exciting electric field is presented. The advantage of this type of resonator is the localization of the electrodes at one end of the disk, which leaves the second end free for the contact of the piezoelectric material with the surrounding medium. This makes it possible to use such a resonator as a sensor base for analyzing the properties of this medium. The problem of exciting such a resonator by an electric field of a given frequency is solved using a two-dimensional finite element method. The method for solving the inverse problem for determining the characteristics of a piezomaterial from the broadband frequency dependence of the electrical impedance of a single resonator is proposed. The acoustic and electric field inside the resonator is calculated, and it is shown that this location of electrodes makes it possible to excite radial, flexural, and thickness extensional modes of disk oscillations. The dependences of the frequencies of parallel and series resonances, the quality factor, and the electromechanical coupling coefficient on the size of the electrodes and the gap between them are calculated.

“…The BAW filters are more frequently used in high-frequency communication and sensing because of their higher power tolerance. The BAW filters are divided into film bulk acoustic resonator (FBARs) [ 2 , 3 , 4 ], solidly mounted resonators (SMRs) [ 5 , 6 ], and laterally-excited bulk-wave resonators (XBARs) [ 7 , 8 , 9 ], based on the structure difference. At present, the piezoelectric film materials used in the BAW resonators mainly include aluminum nitride, zinc oxide, and PZT.…”

Section: Introductionmentioning

confidence: 99%

High-Order Harmonic Film Bulk Acoustic Resonator Based on a Polymer Reflector

Dong

Liu

et al. 2022

A film bulk acoustic resonator (FBAR), based on a polymer air cavity, is presented. The polymer reflective layer on the polymer air cavity can serve both as the reflective layer and the function layer for inducing the high-order mode resonance. With the aluminum nitride as the piezoelectric layer, the resonance frequency of the FBAR can reach 6.360 GHz, based on the finite element method. The product of the corresponding frequency and the quality factor, f × Q is more than 2 × 1013. This design model provides a good solution for the high-frequency filters and high-sensitivity sensor designs.