Piezoelectric Quartz Resonator Research Articles

Using Highly Sensitive Piezo Sensors in an Open System for the Diagnostic Analysis of Skin Volatile Substances

A single sensor with a piezoelectric quartz transducer is considered a platform for simulating an “electronic nose” that performs the function of a sensor array. The analytical task was to detect volatile organic compounds, component-by-component, in biosamples at diagnostically relevant concentrations without selecting mixtures or any sample preparation. We confirmed the fundamental possibility of utilizing a single sensor for the separate detection (recognition) of vapors of organic compounds and various functional states of a body during a short contact (60–80 s) with skin, the most representative and constantly performing bioassay. Modifying the electrodes of bulk acoustic wave piezoelectric quartz resonators with 2–4 μg of the nanohydroxyapatite phase is an essential step in solving the problem. The newly calculated adsorption kinetic parameters can be used to detect biomarkers of many diseases with high reliability, including С3–С5 alcohols, ketones, linear and cyclic amines, acids, aldehydes, etc. The hydroxyapatite sensor can detect molecules pointing to problems with many organs, and any abnormalities in the functioning of the nervous and cardiovascular systems. It can also measure the body’s responses and compensatory mechanisms in relation to stress, hunger, and fatigue. The sensor has a potential as a simple diagnostic and monitoring tool for point-of-care diagnostics of both adults and children.

Coupled-oscillator model to analyze the interaction between a quartz resonator and trapped ions

The novel application of a piezoelectric quartz resonator for the detection of trapped ions has developed in the observation of the quartz-ions interaction under non-equilibrium conditions, opening new perspectives for high-sensitive motional frequency measurements of radioactive particles. Energized quartz crystals have (long) constant-decay times in the order of milliseconds, permitting the coherent detection of charged particles within short times. In this publication we develop in detail a model governing the interaction between trapped $^{40}$Ca$^+$ ions and a quartz resonator connected to a low-noise amplifier. We apply this model to experimental data and extract relevant information like the coupling constant $g=2\pi \times 1.449(2)$~Hz and the ions' modified-cyclotron frequency in our 7-tesla Penning trap. The study on the latter is specially important for the use of this resonator in precision Penning-trap mass spectrometry. The improvement in sensitivity can be accomplished by increasing the coupling constant through the quality factor of the resonator. This can develop in the use of the hybrid quartz-ion system for other applications.

Piezoelectric Gas Sensors with Polycomposite Coatings in Biomedical Application

When developing methods for diagnosing pathologies and diseases in humans and animals using electronic noses, one of the important trends is the miniaturization of devices, while maintaining significant information for diagnostic purposes. A combination of several sorbents that have unique sorption features of volatile organic compounds (VOCs) on one transducer is a possible option for the miniaturization of sensors for gas analysis. This paper considers the principles of creating polycomposite coatings on the electrodes of piezoelectric quartz resonators, including the choice of sorbents for the formation of sensitive layers, determining the mass and geometry of the formation of sensitive layers in a polycomposite coating, as well as an algorithm for processing the output data of sensors to obtain maximum information about the qualitative and quantitative composition of the gas phase. A comparative analysis of the efficiency and kinetics of VOC vapor sorption by sensors with polycomposite coatings and a set of sensors with relevant single coatings has been carried out. Regression equations have been obtained to predict the molar-specific sensitivity of the microbalance of VOC vapors by a sensor with a polycomposite coating of three sorbents with an error of 5-15% based on the results of the microbalance of VOC vapors on single coatings. A method for creating "visual prints" of sensor signals with polycomposite coatings is shown, with results comparable to those from an array of sensors. The parameters Aij∑ are proposed for obtaining information on the qualitative composition of the gas phase when processing the output data of sensors with polycomposite coatings. A biochemical study of exhaled breath condensate (EBC) samples, a microbiological investigation of calf tracheal washes, and a clinical examination were conducted to assess the presence of bovine respiratory disease (BRD). An analysis of the gas phase over EBC samples with an array of sensors with polycomposite coatings was also carried out. The "visual prints" of the responses of sensors with polycomposite coatings and the results of the identification of VOCs in the gas phase over EBC samples were compared to the results of bacteriological studies of tracheal washes of the studied calves. A connection was found between the parameters Aij∑ of a group of sensors with polycomposite coatings and the biochemical parameters of biosamples. The adequacy of replacing an array of piezoelectric sensors with single coatings by the sensors with polycomposite coatings is shown.

An analytical and meshless modeling for vibration analysis of an infinite quartz resonator with non-circular electrodes

An analytical and meshless modeling for solving thickness shear vibration in an infinite piezoelectric quartz resonator with partial non-circular electrodes is proposed. Firstly, two-dimensional scalar differential equations derived by Tiersten and Smythe are adopted and transformed into the polar coordinate system. Secondly, displacement patterns for the electroded and unelectroded regions are assumed as a series of converging and outgoing cylindrical waves in the form of Bessel functions, where radiation conditions at infinity can be satisfied automatically. Finally, circumferential functions at interface are decomposed into Fourier series in order to deal with continuity conditions. It should be stressed that the general formulation proposed in this paper has a higher calculation accuracy and requires no division of the mesh compared to FEM/BEM, which can satisfy continuity conditions in an integrated manner over the whole interface or boundary. Resonance frequencies and mode shapes of different electrode shapes including circular, equilateral triangle, rectangular, elliptical, and pentagonal electrodes are numerically calculated and compared with FEM simulations, which efficiently validate high precision and wide applicability of this method. Utilizing this method, the influence of non-circular electrodes on the working performance of the quartz resonator is investigated systematically. The qualitative analysis and quantitative results obtained in this paper can provide the theoretical guidance for the design, measurement and manufacturing optimization of piezoelectric resonators.

Determination of the residual amounts of cefotaxime in liquid media using piezoelectric sensors

The goal of the study is to develop a piezoelectric sensor based on a molecularly imprinted polymer (MIP) for the determination of cefotaxime in liquid media. To obtain an antibiotic-selective sensor, the electrode surface of was modified with a molecularly imprinted polymer. A pre-polymerization mixture was prepared using a copolymer of 1,2,4,5-benzoltetracarboxylic acid and 4,4’-diaminodiphenyloxide, and an aqueous solution of cefotaxime in a ratio of 1:1. Then a two-stage thermoimidization was carried out in a drying cabinet at a temperatures of 80 and 120°C. After that, the sensor was cooled to room temperature and placed in distilled water for 24 h. An imprinting factor (IF = 40.9) and a selectivity coefficient were calculated to assess the ability of a sensor with MIP (cefotaxime) to recognize a template molecule. A low selectivity of a MIP sensor with the cefotaxime imprint to other cephalosporin antibiotics is revealed. The experiments were carried out on an original installation including a piezoelectric sensor, a portable generator, and an MP732 USB-frequency meter connected to a computer. Piezoelectric quartz resonators of AT-cut with silver electrodes with a diameter of 5 mm and a thickness of 0.3 mm with a nominal resonant frequency of 4.00 MHz were used as sensors. The determination of antibiotics in model solutions was carried out by the method of calibration schedule. The range of detectable concentrations (0.1 – 1.0 × 10–4 g/dm3) was experimentally determined. The detection limit of cefotaxime is 1.0 × 10–5 g/dm3. The correctness of the cefotaxime determination of in individual and binary model solutions was verified by the «spike-test». It has been shown that a sensor with MIP-cefotaxime is not sensitive to an extraneous antibiotic. The relative standard deviation does not exceed 10 %.

Rheological properties of suspensions of nanoparticles based on polyethylsiloxane

Suspensions of nanoparticles of silicon dioxide in polyethylsiloxane liquid used in engineering as greases and instrument oils have been synthesized. The effective viscosity of nanosuspensions depending on the shear stress was determined by the acoustic resonance method using a piezoelectric quartz resonator. An increase in the strength of the structure of nanosuspensions due to the formation of a supramolecular structure has been shown.

E-nose for the monitoring of plastics catalytic degradation through the released Volatile Organic Compounds (VOCs) detection

The work presents the results of an artificial olfaction E-nose system application for detection of Volatile Organic Compounds (VOCs) – destruction products of OXO-biodegradable polyethylene films when exposed to Ultraviolet (UV) irradiation and heating. The E-nose system was based on eight piezoelectric quartz resonator sensors coated with polymeric sensing materials with various selectivity to analytes. The effect of prooxidants, materials based on variable valence metals, such as D2w, ferric stearate and ferric carboxylate, addition on polyethylene films (PE) photo destruction was studied. The dependence of the composition of VOCs mixtures emitted by PE films on the processing time, the power of the UV irradiation and on the nature of the modifying additive was established. In addition, the main emitted volatile compounds were identified and the dynamics of their formation for different catalysts during the plastics destruction were studied. The proposed E-nose system has proved to be an effective tool for assessing catalyst-prooxidants properties.

A Perspective on Recent Advances in Piezoelectric Chemical Sensors for Environmental Monitoring and Foodstuffs Analysis

This paper provides a selection of the last two decades publications on the development and application of chemical sensors based on piezoelectric quartz resonators for a wide range of analytical tasks. Most of the attention is devoted to an analysis of gas and liquid media and to industrial processes controls utilizing single quartz crystal microbalance (QCM) sensors, bulk acoustic wave (BAW) sensors, and their arrays in e-nose systems. The unique opportunity to estimate several heavy metals in natural and wastewater samples from the output of a QCM sensor array highly sensitive to changes in metal ion activity in water vapor is shown. The high potential of QCM multisensor systems for fast and cost-effective water contamination assessments “in situ” without sample pretreatment is demonstrated.

Mycelial Extracts as Sensitive Element for Acoustoelectronic Gas Sensor

The main problem in development of the acoustoelectronic gas sensors is the search of the elements which are sensitive to the presence of different gases. In this paper we suggest to use for this purpose the piezoelectric quartz resonators with the mycelium films of mushroom Lentinula edodes strain F-249, which was cultivated in synthetic medium. The extract of mycelium was deposited on the surface of the resonator. The measurements of the frequency dependencies of the real and imaginary parts of electrical impedance of the resonator allowed finding the density, elastic constants and viscosity of the films under study. The influence of various gases (ammonia, formaldehyde, ethylacetate) and volatile liquids (acetone, acetic acid, chloroform) on physical properties of the extracts of mushroom Lentinula edodes mycelium has been investigated. It has been found that it is possible to use the mycelium films of mushroom Lentinula edodes prepared by different ways as sensitive film to ammonia, formaldehyde and ethyl acetate.

Acousto-electronic gas sensor based on mushroom mycelial extracts

The main problem in the development of acousto-electronic gas sensors is the search for materials which are sensitive to the presence of different gases. For this purpose in this paper we suggest the use of piezoelectric quartz resonators coated by the mycelium-origin films of the mushroom Lentinula edodes strain F-249, which were cultivated in a synthetic medium. The extract of mycelium was deposited on the surface of the resonator. Measurement of the frequency dependence of the complex electrical impedance of the resonator allowed us to evaluate the density, elastic constants, and mass of the films under test. The influence of different gases, such as ammonia, formaldehyde, ethylacetate, and volatile liquids: acetone, acetic acid, chloroform on the physical properties of the extracts of Lentinula edodes mushroom mycelium was investigated. The results have shown that this material prepared according to different technological procedures is suitable as a sensitive layer for development of gas sensors for detection of ammonia, formaldehyde, and ethylacetate.

Thickness-shear Modes and Energy Trapping in a Rectangular Piezoelectric Quartz Resonator with Partial Electrodes

We analyze thickness-shear vibrations of a rectangular plate of quartz piezoelectric crystal for acoustic wave resonator application. The plate is partially electroded in the central region. The scalar differential equation derived by Tiersten and Smythe is employed. Exact solution for the free vibration resonant frequencies and modes are obtained. Trapped modes with vibrations mainly under the electrodes are found. The results are useful to the understanding and design optimization of crystal resonators.

Sacrificial BSA to block non‐specific adsorption on organosilane adlayers in ultra‐high frequency acoustic wave sensing

This follow‐up study describes the implementation of recently developed cross‐linking trichlorosilane surface chemistry with acoustic wave sensing technology for the real‐time and label‐free detection of biotin/avidin interactions. Biosensing platforms consist of unelectroded piezoelectric quartz resonator discs onto which functionalizable mixed organosilane adlayers are prepared using a new trichlorosilane cross‐linker in combination with a shorter monofunctional diluent molecule. Thiolated or aminated biotin probes can next be anchored to the mixed assembly in a single, preactivation‐free step through site‐specific coupling at pentafluorophenyl ester head moieties. Biosensing properties are assessed at ultra‐high frequency (>0.74 GHz) with the highly sensitive electromagnetic piezoelectric acoustic sensor using micromolar buffered solutions of avidin. This biosensor prototype – which generally displays good reproducibility – uses sacrificial bovine serum albumin to block non‐specific adsorption. This preliminary work in buffer constitutes an important step towards the development of real‐world biosensors able to perform with more demanding biological samples. Copyright © 2013 John Wiley & Sons, Ltd.

The Possibilities of Applying QCM Method in Pulsed Mode for Investigating the Adsorption Dynamics of Volatile Compounds on Finely Dispersed Sorbents

In this study, the possibilities of applying quartz crystal microbalance (QCM) method in pulsed mode for investigating the adsorption dynamics of volatile compounds on finely dispersed sorbents is shown. The use of piezoelectric quartz resonator (PQR) sensors with chemical coverings on the base of metal stearates or thiolates, as well as other low-inertia sensors is proposed to evaluate the concentration of gas-phase sorbate current in the flow cell of electronic nose-type sensors. These sensors are placed in the cell in parallel to the PQR with a sorbent under investigation.

Replacement of Au and Ag with the Ni-P and Ni-B Alloys in Electronics

A new method of production of precise piezoelectric quartz resonators and filters, and monolithic piezoquartz filters with electrodes, made of electroless nickel-phosphorous alloy, for spacecraft, hydroacoustics and communication devices was developed. Electrical characteristics of quartz resonators with the deposited Ni-P coating are better than when gold and silver were used as electrode layers. A method of electroless deposition on polished quartz, glass and other nonmetallic polished materials was developed. Bulk and miniature resonators of piezoquartz and lithium niobate manufactured on the basis of the developed technology of electroless deposition of a nickel-phosphorus alloy, instead of gold and silver plating, were successfully used in industry. The technology was developed for the production of piezoceramic and ceramic devices by electroless deposition of electrode layers made of Ni-P or Cu.

Kinetic absorption of vapors of alkyl acetates C1-C4 and diethyl ether on thin films of modified piezoelectric quartz resonators

Sorption of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and diethyl ether on thin films of esters: poly(ethylene glycol) sebacate and phthalate, dinonyl phthalate, tween-40, pentaerythritol tetrabenzoate, triphenyl phosphate, Triton X-305, and stearic acid was studied. The mass of sorbent films was optimized, the sensitivity and selectivity of modifiers toward analytes was evaluated, and the time of maximum sorption was determined.

Influence of surface wettability on the accuracy of measurement of fluid shear modulus

The shear moduli of liquids and their dependence on the degree of purity of the piezocrystal surface are measured by acoustic resonance method using a piezoelectric quartz resonator. As a criterion of surface condition the coefficient of static friction is accepted, which is measured by tribometer of Derjaguin–Lazarev design. The various methods of surface treatment which give a wide range of friction coefficients are used. At the maximum value of the coefficient of friction vibrating piezoquartz surface is completely wetted by the liquid and the effective value of the shear modulus of the liquid is the highest.

Low-Frequency Shear Parameters Viscoelastic Relaxation Process

An experimental study of the shear parameters of viscoelastic liquids is carried out by the acoustic resonance method based on the changes in the natural frequency and Q factor of a piezoelectric quartz resonator. The liquid to be studied is placed between a stationary quartz strap and the piezoelectric quartz crystal vibrating at the resonance frequency. For a set of drilling mud, the values of the real and imaginary shear module are obtained at a frequency of 74 kHz. The measurements are performed with a liquid layer thickness much smaller than the shear wavelength. It is shown that the shear modulus decreases with increasing strain amplitude. A hole-cluster model based on the Isakovich- Chaban nonlocal diffusion theory is proposed for explaining the low-frequency viscoelastic relaxation process.DOI: http://dx.doi.org/10.5564/pmas.v0i4.46 Proceedings of the Mongolian Academy of Sciences 2009 No 4 pp.53-58

Determination of ammonia in the air using piezoelectric resonance sensors coated with humic acids

Natural macromolecular compounds, humic acids (HA), have been used to form gas-sensitive layers of piezoelectric resonance gravimetric sensors. HA have been extracted from humus using alkaline extraction and purified by electrodialysis through ion-exchange membranes. Species have been deposited onto the electrode surface of piezoelectric quartz resonators by air-spraying their aqueous solutions, the layer thickness being 100–200 nm. In determining ammonia with the sensor obtained on the basis of purified HA species, the detection limit is ∼10 mg/m3. Gas-sensitive layers on the basis of humic acids are more stable as compared to the conventionally used gas-sensitive layers based on pyridoxine hydrochloride or ascorbic acid.

Determination of volatile organic compounds using piezosensors modified with the Langmuir-Blodgett films of calix[4]resorcinarene

A sensor based on a piezoelectric quartz resonator modified with the Langmuir-Blodgett (LB) films of calix[4]resorcinarene is proposed for the detection of volatile organic compounds. Parameters for the formation of ordered LB films based on calix[4]resorcinarene were optimized, and the effects of the pH and metal ion content of the subphase on the behavior of the Langmuir monolayers of calix[4]resorcinarene were studied. The effects of the number of monolayers in a sensor coating, the pH of the subphase from which the monolayers were transferred, and the presence of copper ions in the subphase on the response of the resulting piezoelectric quartz sensors to the vapors of various volatile organic compounds (ethanol, benzene, toluene, ethylbenzene, ethyl acetate, acetone, hexane, and cumene) were studied. It was found that the proposed sensor was characterized by a short response time and reproducible measurements.

Quantitative Detection of Staphylococcal Enterotoxin B by Resonant Acoustic Profiling

A rapid and sensitive detection of staphylococcal enterotoxin B (SEB) was developed using a novel acoustic sensing technique: Resonant Acoustic Profiling (RAP), which utilizes high-frequency piezoelectric quartz resonators for monitoring biomolecular interactions. An automated four-channel instrument consisting of acoustic sensors covalently conjugated with anti-SEB antibodies was used. As the samples flowed across control and active sensors simultaneously, binding was measured as a change in the resonant frequency. The lower limit of detection (LLOD) for the label free direct format was 25 ng/mL. Detection sensitivity was increased by adding mass sequentially to the captured SEB on the sensor in the form of sandwich antibodies and biotin-avidin-based gold nanoparticles. The LLOD for the mass enhanced formats were 5 and 0.5 ng/mL of SEB, respectively. The lowest sensitivity corresponds to 1.3 fM in a 75 microL sample. The total assay time including the enhancement steps was less than 10 min. SEB was detected in both neat urine and PBS buffer-spiked samples, with linear correlations between resonant frequency signals and SEB concentrations (R(2) of 0.999 and 0.998, respectively). No significant cross-reactivity was observed with homologue toxins SEA, SED, and TSST, but some cross-reactivity was observed with the closely related toxin SEC(1) when we used a polyclonal antibody in the assay. SEC(1) cross-reactivity was not observed when a SEB-specific monoclonal antibody was employed in the assay. Thus the specificity of the assay presented here was dependent on the quality of the antibodies used. In addition to detection, we evaluated RAP's ability to measure the toxin in unknown samples rapidly by measuring the initial binding rate of the interaction, thereby further shortening the assay time to 6 min.