Quartz Crystal Microbalance Resonance Research Articles

Quantification of Particle Filtration Using a Quartz Crystal Microbalance Embedded in a Microfluidic Channel.

To quantify colloidal filtration, a quartz crystal microbalance (QCM) with a silicon dioxide surface is embedded on the inner surface of a microfluidic channel to monitor the real-time particle deposition. Potassium chloride solution with micrometer-size polystyrene particles simulating bacterial strains flows down the channel. In the presence of intrinsic Derjaguin-Landau-Verwey-Overbeek (DLVO) intersurface forces, particles are trapped by the quartz surfaces, and the increased mass shifts the QCM resonance frequency. The method provides an alternative way to measure filtration efficiency in an optically opaque channel and its dependence on the ionic concentration.

Effect of Electrode Thickness on Quality Factor of Ring Electrode QCM Sensor.

As a key type of sensor, the quartz crystal microbalance (QCM) has been widely used in many research areas. Recently, the ring electrode QCM sensor (R-QCM) with more uniform mass sensitivity has been reported. However, the quality factor (Q-factor) of the R-QCM has still not been studied, especially regarding the effect of electrode thickness on the Q-factor. Considering that the Q-factor is one of crucial parameter to the QCM and it is closely related to the output frequency stability of the QCM, we study the effect of different electrode thicknesses on the Q-factor of the R-QCM in this paper. On the other hand, we clarify the relationship between the electrode thickness and the Q-factor of the R-QCM. The measurement results show that the average Q-factor increases with increases in the thickness of ring electrodes generally; however, the resonance frequency of the QCM resonator decreases with increases in the thickness. The low half-bandwidth (2Γ < 1630 Hz) of the R-QCM shows that the frequency performance is good. Additionally, the R-QCM has a higher Q-factor (Q > 6000), which indicates that it has a higher frequency stability and can be applied in many research areas.

Exploration of the Mass Sensitivity of Quartz Crystal Microbalance under Overtone Modes Using Electrodeposition Method.

With the in-depth application of quartz crystal microbalance (QCM) sensors in the fields of science and engineering, there is an urgent need for QCM sensors with high mass sensitivity. The mass sensitivity of a QCM is closely related to its resonance frequency, and the high resonance frequency leads to improve its mass sensitivity. However, the resonance frequency of a QCM resonator cannot be increased all the time due to the fragility of quartz wafer and the limits of energy trapping effect. Few studies are associated with mass sensitivity of a QCM resonator under overtone modes. Herein, we propose to make a QCM resonator work in its n-th overtone (n = 3, 5, 7, 9 in this study) mode to increase its resonance frequency during operating. Thereby, the purpose of improving QCM mass sensitivity is achieved, and the mass sensitivity of a QCM working in the n-th overtone mode can be called as n-th overtone mass sensitivity. Then, the n-th overtone mass sensitivity of a QCM sensor is measured by an electrodeposition method. The experimental results show that the n-th overtone mass sensitivity of a QCM is a bit more than n times that of the fundamental mass sensitivity, and it is consistent with the theoretical calculation results. The application of overtone mass sensitivity will greatly improve the sensitivity of QCM sensors, which is very attractive for the research fields that require QCM sensors with high sensitivity.

Materials Design, Sensing Performance and Mechanism of Anhydrous Hydrogen Fluoride Gas Sensor Based on Amino-Functionalized MIL-101(Cr) for New Energy Vehicles

To guarantee the security of new energy vehicles (NEV), which include energy storage devices such as batteries, a quartz crystal microbalance (QCM) sensor was designed to detect online the HF gas produced from the leakage of electrolyte in the power system. Based on the chemical properties of HF gas, an amino-functionalized metal–organic framework NH2-MIL-101 (Cr) was synthesized as a sensing material of a QCM transducer to detect HF gas for NEV safeguard. The sensing materials are designed based on the hydrogen bond interaction between the amino group and HF molecular and were characterized by powder X-ray diffraction, Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), etc. The performance of this sensor showed high sensitivity, with a limit of detection at 500 ppb, short response/recovery time and good reproducibility for anhydrous hydrogen fluoride (AHF) detection. Additionally, the sensing mechanism of NH2-MIL-101(Cr) QCM resonator to AHF is revealed to be reversible chemical adsorption by Gaussian 09. It is well-matched with a result of experimental determination through temperature-varying microgravimetric experiments. Therefore, the amino-functionalized MIL-101(Cr) QCM resonator may be a good candidate for an NEV safety monitor due to its rapid response to HF leaked from the decomposition of the electrolyte.

Phenolic Resin Dual-Use Stamps for Capillary Stamping and Decal Transfer Printing.

We report an optimized two-step thermopolymerization process carried out in contact with micropatterned molds that yields porous phenolic resin dual-use stamps with topographically micropatterned contact surfaces. With these stamps, two different parallel additive substrate manufacturing methods can be executed: capillary stamping and decal transfer microlithography. Under moderate contact pressures, the porous phenolic resin stamps are used for nondestructive ink transfer to substrates by capillary stamping. Continuous ink supply through the pore systems to the contact surfaces of the porous phenolic resin stamps enables multiple successive stamp-substrate contacts for lithographic ink deposition under ambient conditions. No deterioration of the quality of the deposited pattern occurs, and no interruptions for ink replenishment are required. Under a high contact pressure, porous phenolic resin stamps are used for decal transfer printing. In this way, the tips of the stamps' contact elements are lithographically transferred to counterpart substrates. The granular nature of the phenolic resin facilitates the rupture of the contact elements upon stamp retraction. The deposited phenolic resin micropatterns characterized by abundance of exposed hydroxyl groups are used as generic anchoring sites for further application-specific functionalizations. As an example, we deposited phenolic resin micropatterns on quartz crystal microbalance resonators and further functionalized them with polyethylenimine for preconcentration sensing of humidity and gaseous formic acid. We envision that also preconcentration coatings for other sensing methods, such as attenuated total reflection infrared spectroscopy and surface plasmon resonance spectroscopy, are accessible by this functionalization algorithm.

Molecularly Imprinted Chitosan-Based Thin Films with Selectivity for Nicotine Derivatives for Application as a Bio-Sensor and Filter.

This study reports the feasible use of chitosan as a thin film biosensor on the very sensitive quartz crystal micro balance system for detection of blends of multiple templates within a single matrix. The development of chitosan-based thin film materials with selectivity for nicotine derivatives is described. The molecular imprinting of a combination of nicotine derivatives in N-diacryloyl pipiradine-chitosan-methacrylic acid copolymer films on quartz crystal resonators was used to generate thin films with selectivity for nicotine and a range of nicotine analogues, particularly 3-phenylpyridine. The polymers were characterized by spectroscopic and microscopic evaluations; surface area, pore size, pore volume using Breuner-Emmet-Teller method. Temperature characteristics were also studied. The swelling and structure consistency of the Chitosan was achieved by grafting with methylmethacrylic acid and cross-linking with N-diacrylol pipiradine. A blend of 0.002 g (0.04 mmol) of Chitosan, 8.5 μL Methylmethacrylic Acid and 1.0 mg N-diacrylol pipradine (BAP) presented the best blend formulation. Detections were made within a time interval of 99 s, and blend templates were detected at a concentration of 0.5 mM from the Quartz crystal microbalance resonator analysis. The successful crosslinking of the biopolymers ensured successful control of the swelling and agglomeration of the chitosan, giving it the utility potential for use as thin film sensor. This successful crosslinking also created successful dual multiple templating on the chitosan matrix, even for aerosolized templates. The products can be used in environments with temperature ranges between 60 °C and 250 °C.

Method for QCM Resonator Device Equivalent Circuit Parameter Extraction and Electrode Quality Assessment.

Quartz crystal microbalance (QCM) resonators are used in a wide range of sensors. Current QCM resonators achieve a simultaneous measurement of multiple physical quantities by analyzing lumped-element equivalent parameters, which are obtained via the introduction of external devices. This introduction of external devices will probably increase measurement error. To realize the measurement of multiple physical quantities while eliminating the measurement error caused by external devices, this paper proposes a measurement method for the lumped-element equivalent parameters of QCM resonators without the need for extra external devices. Accordingly, a numerical method for solving nonlinear equations with fewer data points required and a higher accuracy was adopted. A standard crystal resonator parameter extraction experiment is described. The extracted parameters were consistent with the nominal parameters, which confirms the accuracy of this method. Furthermore, six QCM resonator device samples with different electrode diameters and materials were produced and used in the parameter measurement experiment. The linear relationship between the electrode material conductivity and motional resistance R1 is discussed. The ability of this method to characterize the electrode material and to detect the rust status of the electrode is also demonstrated. These abilities support the potential utility of the proposed method for an electrode quality assessment of piezoelectric devices.

Effect of titanium precursors used in the preparation of graphene oxide/TiO2 composite for gas sensing utilizing quartz crystal microbalance

Graphene oxide/TiO2 (GO/TiO2) composites were prepared from four Ti precursors, namely, ammonium hexaflourotitanate (AHFT), titanium(IV) chloride, titanium(IV) isopropoxide, and titanium(IV) butoxide. These composites were used to determine the precursor dependence of the gas sensing ability of GO/TiO2 composites using quartz crystal microbalance (QCM). The X-ray diffraction (XRD) analysis indicated that the non-annealed TiO2 obtained from AHFT has the highest crystallinity of the anatase phase. Further, the X-ray photoelectron spectroscopic (XPS) and Fourier transform infrared (FT-IR) spectroscopic analyses confirmed that F and N present in the precursor has been attached to the specific sites of the TiO2 surface via ligand exchange reactions but not substituted into the TiO2 lattice. Although TiO2 alone does not show significant gas adsorption ability, when GO is modified with TiO2, the replacement of surface hydroxyl groups by fluoride groups on the TiO2 surface aids for increased gas adsorption due to the presence of additional surface-active sites. The results conclude that among different TiO2 precursor materials used for the GO/TiO2 composite preparation, the composite prepared with AHFT has the highest vapor sensing ability. The sensitivity of the composite functionalized QCM resonator for the EtOH vapor ranged from 20,000 ppm to 12 ppm. In this sensor, the GO amount in the range between 30% and 50% gives the highest sensor sensitivity for all the gases and vapors examined. It was found that a single sensor for different gases can be prepared using the same materials in the composite but with different mass ratios.

Intelligent Mobile Electronic Nose System Comprising a Hybrid Polymer-Functionalized Quartz Crystal Microbalance Sensor Array.

We devised a low-cost mobile electronic nose (e-nose) system using a quartz crystal microbalance (QCM) sensor array functionalized with various polymer-based thin active films (i.e., polyacrylonitrile, poly(vinylidene fluoride), poly(vinyl pyrrolidone), and poly(vinyl acetate)). It works based on the gravimetric detection principle, where the additional mass of the adsorbed molecules on the polymer surface can induce QCM resonance frequency shifts. To collect and process the obtained sensing data sets, a multichannel data acquisition (DAQ) circuitry was developed and calibrated using a function generator resulting in a device frequency resolution of 0.5 Hz. Four prepared QCM sensors demonstrated various sensitivity levels with high reproducibility and consistency under exposure to seven different volatile organic compounds (VOCs). Moreover, two types of machine learning algorithms (i.e., linear discriminant analysis and support vector machine models) were employed to differentiate and classify those tested analytes, in which classification accuracies of up to 98 and 99% could be obtained, respectively. This high-performance e-nose system is expected to be used as a versatile sensing platform for performing reliable qualitative and quantitative analyses in complex gaseous mixtures containing numerous VOCs for early disease diagnosis and environmental quality monitoring.

Comparison of the absolute mass sensitivity of ring electrode QCM and standard QCM using electrodeposition

In this work, we experimentally measured the absolute mass sensitivity of quartz crystal microbalance (QCM) resonators with one ring electrode on the sensing side and compared it to standard QCM resonators with disc electrodes on both sides using electrodeposition. This method allows to compare the absolute mass sensitivity of a ring electrode QCM and standard QCM resonators. The results showed that the average absolute mass sensitivity of a QCM resonator with a ring electrode on one side and a disc electrode on the other side is larger than the one of standard resonators with disc electrodes on both sides. If the ring electrode is facing the electrolyte, the absolute mass sensitivity is 10.28% higher, and for the disc electrode side it is still 5.33% higher. This shows that the ring electrode geometry improves the absolute mass sensitivity in comparison to a standard electrode structure, and therefore reveals a path to improve QCM detection sensitivity in electrochemical research.

Measurement of the mass sensitivity of QCM with ring electrodes using electrodeposition

A practical method for calculating the mass sensitivity of quartz crystal microbalance (QCM) resonators with ring-shaped Au electrodes on one side based on electrodeposition is presented in this communication. While for standard QCMs, an average mass sensitivity can be calculated despite its approximately Gaussian distribution, the mass sensitivity of QCMs with an asymmetrical electrode structure is difficult to calculate. However, non-standard electrode geometries might be beneficial for sensor applications especially in the area of electrochemistry. By measuring the resonance frequency change of a quartz crystal during deposition and applying Faraday’s law, we determined the mass sensitivity of QCM resonators with a ring electrode. We also studied the influence of the gold electrode thicknesses on the mass sensitivity of the ring-shaped and disc shaped electrodes. The experimental results showed that the mass sensitivity of the ring-shaped electrodes was 5%∼20% higher than those of the disc shaped electrodes. This method is practical and convenient for determining the mass sensitivity of the QCM with ring electrode, and it can be extended to measure QCMs with symmetrical and asymmetrical electrode structures. Such resonators with modified electrode structures may be of interest for studying electrochemical processes where a higher mass sensitivity is desirable.

Fabrication of LB thin film of pillar[5]arene-2-amino-3-hydroxypyridine for the sensing of vapors

This paper reported that a novel pillar[5]arene derivative (P5-AP) concluding ten 2-Amino-3-hydroxypyridine fragments was structured for preparing a macrocycle with an appropriate cavity for sensing harmful organic vapors. Thin films of P5-AP were fabricated using a modified Langmuir–Blodgett (LB) method and the formation of these thin films was verified by Quartz Crystal Microbalance (QCM) and UV–vis absorption spectrum. The interaction or response of P5-AP film coated onto suitable substrates to six different organic vapors (aromatic and chlorinated aliphatic hydrocarbons) was investigated via QCM and Surface Plasmon Resonance (SPR) methods. The overall results showed that gas sensor components comprising of P5-AP LB films have potentials for rapid and sensitive detection harmful organic vapors.

Multichannel QCM-Based System for Continuous Monitoring of Bacterial Biofilm Growth

Quartz crystal microbalance (QCM) sensors are becoming a good alternative to analytical methods for the measurement of bacterial growth in liquid media culture. For this purpose, two essential resonance parameters allow the monitoring of biofilm formation: the series resonance frequency shift and the change of the resistance at this frequency. Nevertheless, several problems arise in determining these parameters, as their relative variation is very small. This means that an accurate procedure must be implemented for the measurement of the QCM resonance parameters, including the automatic calibration of the frequency response effects of the measurement circuits and the automatic compensation of the static electrical capacitance of the QCM. In this article, a novel multichannel system for on-line monitoring of biofilm formation based on QCM sensors is proposed. QCM resonance parameters are determined from the electrical impedance analysis by means of an auto-balanced impedance bridge. This configuration has allowed the implementation of an affordable multichannel measurement instrument. Obtained results, based on binary mixtures of water–glycerol measurements and real microorganism experiments, are in good agreement with the theoretical behavior. These results show the great potential of this instrument to be used for monitoring microbial growth and biofilm formation.

Mass measurement of graphene using quartz crystal microbalances

Current wafer-scale fabrication methods for graphene-based electronics and sensors involve the transfer of single-layer graphene by a support polymer. This often leaves some polymer residue on the graphene, which can strongly impact its electronic, thermal, and mechanical resonance properties. To assess the cleanliness of graphene fabrication methods, it is thus of considerable interest to quantify the amount of contamination on top of the graphene. Here, we present a methodology for the direct measurement of the mass of the graphene sheet using quartz crystal microbalances (QCMs). By monitoring the QCM resonance frequency during removal of graphene in an oxygen plasma, the total mass of the graphene and contamination is determined with sub-graphene-monolayer accuracy. Since the etch-rate of the contamination is higher than that of graphene, quantitative measurements of the mass of contaminants below, on top, and between graphene layers are obtained. We find that polymer-based dry transfer methods can increase the mass of a graphene sheet by a factor of 10. The presented mass measurement method is conceptually straightforward to interpret and can be used for standardized testing of graphene transfer procedures in order to improve the quality of graphene devices in future applications.

Improvement QCM Quality By Polystyrene Coating and Bovine Serum Albumin as Immobilization Agent

Polystyrene (PS) thin film with various concentration of mass (1%, 3%, and 5%) has been deposited onto Quartz Crystal Microbalance (QCM) surface by a spin coating method. The purpose of this research is the improvement of Bovine Serum Albumin (BSA) immobilization into the QCM surface. The QCM resonance frequency has been investigated by means of Impedance Analyzer. The film thickness was calculated by the Sauerbrey equation. The surface roughness of the PS layer was observed by noncontact Topography Measuring System (TMS-1200). Calculation result using a Sauerbrey equation shows the thickness of the PS layer increases with the increasing PS concentration. The QCM/PS with 1% and 5% concentration of mass has rougher morphology and more frequency shifts caused by BSA injection compared to 3% concentration of PS.

QCM-Micropillar-Based Coupled Resonators in the Detection of Gas Mass Flow Rates

We report the discovery of a micropillar-based quartz crystal microbalance (QCM) coupled resonator sensor (CRS) in detecting flow rates of gases with different densities. The fabricated QCM CRS was housed in a stainless steel chamber and the resonance frequency changes associated with gas flow at small values of mass flow rates inside the chamber were measured. Argon and helium were used as the test gases. The results obtained revealed an extraordinary sensitivity to mass flow rate changes under room temperature and flow rates as low as 20 sccm. Moreover, the QCM-CRS system was able to differentiate the densities of the two gases. Identical experiments conducted using a bare QCM showed that the mass flow rates had negligible effects on the QCM resonance frequency response. Thus, it is evident that a coupled resonance phenomenon plays a significant role in enabling the QCM to be sensitive to small mass changes caused by differences in flow rates. We propose that the QCM-CRS system can be used as a new class of mass flow sensing element, especially for flow measurement in vacuum processing systems.

Effect of Properties of Phosphate Buffer Saline Solutions on Vibrational Characteristics of a Quartz Crystal Microbalance Resonator

Effect of Properties of Phosphate Buffer Saline Solutions on Vibrational Characteristics of a Quartz Crystal Microbalance Resonator

Hybrid temperature effect on a quartz crystal microbalance resonator in aqueous solutions**Project supported by the National Natural Science Foundation of China (Grant No. 61672094).

The quartz crystal microbalance (QCM) is an important tool that can sense nanogram changes in mass. The hybrid temperature effect on a QCM resonator in aqueous solutions leads to unconvincing detection results. Control of the temperature effect is one of the keys when using the QCM for high precision measurements. Based on the Sauerbrey’s and Kanazawa’s theories, we proposed a method for enhancing the accuracy of the QCM measurement, which takes into account not only the thermal variations of viscosity and density but also the thermal behavior of the QCM resonator. We presented an improved Sauerbrey equation that can be used to effectively compensate the drift of the QCM resonator. These results will play a significant role when applying the QCM at the room temperature.

Development of a Flow Injection Based High Frequency Dual Channel Quartz Crystal Microbalance.

When the quartz crystal microbalance (QCM) is used in liquid for adsorption or desorption monitoring based bio- or chemical sensing applications, the frequency shift is not only determined by the surface mass change, but also by the change of liquid characteristics, such as density and viscosity, which are greatly affected by the liquid environmental temperature. A monolithic dual-channel QCM is designed and fabricated by arranging two QCM resonators on one single chip for cancelling the fluctuation induced by environmental factors. In actual applications, one QCM works as a specific sensor by modifying with functional membranes and the other acts as a reference, only measuring the liquid property. The dual-channel QCM is designed with an inverted-mesa structure, aiming to realize a high frequency miniaturized chip and suppress the frequency interference between the neighbored QCM resonators. The key problem of dual-channel QCMs is the interference between two channels, which is influenced by the distance of adjacent resonators. The diameter of the reference electrode has been designed into several values in order to find the optimal parameter. Experimental results demonstrated that the two QCMs could vibrate individually and the output frequency stability and drift can be greatly improved with the aid of the reference QCM.

SENSITIVITY OF TIACALIXARENE FILMS TOWARDS SET OF THE ALIPHATIC ALCOHOLS

The manuscript presented is dedicated to the investigation of adsorption features of tiacalixarene films modified by lower and upper microcyclic rims as well as bridged sulfur atoms towards aliphatic alcohols. They were used as sensitive coating for gas sensors based on quartz crystal microbalance (QCM).Experiments were carried out with 8-channel chemosensory system of “Electronic Nose” (EN) type that had been developed and created in our Institute. Sensitive layers on the sensory elements (QCM resonators) have been deposited by means of dropping technique (small amount of an appropriable calixarene dissolved in chloroform was dropped on the sensor surface) with the following drying in the inert (argon vapor) media until total evaporation of solvent. Kinetics of sensor responses on high concentration level (close to saturated vapor pressure) as well as on consequent injection of analytes in the concentration range 10 – 1600 ppm have been obtained. It was shown that tiacalixarene films with phosphorus containing functional groups possessed the best sensitivity amid all matter under study. Concentration dependencies of the sensors array with calixarene films mentioned above represented good linearity towards set of aliphatic alcohols (from methanol to pentanol) in the overall concentration range under study. Detection limits reached values as lower as 10 ppm for “heavy” alcohols and 20-30 ppm for “light” one. It turned out the response magnitude on linear “heavy” alcohols (butanol, pentanol) was higher than on their isomers.