Quartz Crystal Microbalance Array Research Articles

Towards an E-nose: Metal-organic frameworks based quartz crystal microbalance array for fruit ripeness indexing

Ethylene is a hormone for fruit ripening control, and for the purpose of maintaining plant quality, ethylene monitoring is crucial. Due to the simple structure and limited functionality, the technical realization of ethylene detection by an artificial sensor remains a challenge. In this paper, we present a metal-organic frameworks (MOFs) array based electronic nose (e-nose) for rapid and accurate determination of ethylene. Six zirconium-based MOFs with systematically modified pore sizes and π-π binding sites have been prepared and fabricated into a sensor array using quartz crystal microbalance (QCM) technology. By virtue of the synergistic features of six MOF sensors, selectivity detection of ethylene has been achieved. The detection limit reaches to 0.27 ± 0.02 ppm, and high selectivity and stability (98.29 % ± 0.88 %) could also be confirmed. By submitting data to machine learning algorithm, an e-nose system could be established for discriminating ethylene from mixtures with a qualitative accuracy of 90.30 % and quantitative accuracy of 98.89 %. Practical evaluation suggests that the e-nose could index the fruit quality based on the accurate detection of ethylene released during fruit ripeness. This work demonstrates the promising potential of fabricating MOFs based e-nose systems for practical monitoring applications by selectively detecting challengeable target molecules.

Strong Interface Interaction of ZnO Nanosheets and MnSx Nanoparticles Triggered by Light over Wide Ranges of Wavelength to Enhance Their Removal of VOCs

The characteristics of the surface and interface of nanocomposites are important for exerting multi-functional properties and widening interdisciplinary applications. These properties are mainly depending on the electronic structures of materials. Some key factors, such as the surface, interface, grain boundaries, and defects take vital roles in the contribution of desired properties. Due to the excellent sensitivity of the QCM (quartz crystal microbalance) device, the surface and interface features of the nanocomposite were studied with the aid of the gas-response of the sensors (Sensor’s Gas-Sensitivity) in this work. To make full use of the visible light and part of NIR, a ZnO/MnSx nanocomposite was constructed using hydrothermal synthesis for narrowing the bandgap width of wide bandgap materials. The results indicated that the absorbance of the resulting nanocomposite was extended to part of the NIR range due to the introduction of impurity level or defect level, although ZnO and MnS belonged to wide bandgap semiconductor materials. To explore the physical mechanism of light activities, the photoconductive responses to weak visible light (650 nm, etc.) and NIR (near-infrared) (808 nm, 980 nm, and 1064 nm, etc.) were studied based on interdigital electrodes of Au on flexible PET (polyethylene terephthalate) film substrate with the casting method. The results showed that the on/off ratio of ZnO/MnSx nanocomposite to weak visible light and part of NIR light were changed by about one to five orders of magnitude, with changes varying with the amount of MnSx nanoparticle loading due to defect-assisted photoconductive behavior. It illustrated that the ZnO/MnSx nanocomposite easily produced photo-induced free charges, effectively avoiding the recombination of electrons/holes because of the formation of strong built-in electrical fields. To examine the surface and interface properties of nanocomposites, chemical prototype sensor arrays were constructed based on ZnO, ZnO/MnSx nanocomposite, and QCM arrays. The adsorption response behaviors of the sensor arrays to some typical volatile compounds were examined under a similar micro-environment. The results exhibited that in comparison to ZnO nanosheets, the ZnO nanosheets/MnSx nanocomposite increased adsorption properties to some typical organic volatile compounds significantly. It would have good potential applications in photo-catalysts, self-cleaning films, multi-functional coatings, and organic pollutants treatment (VOCs) of environmental fields for sustainable development. It provided some reference value to explore the physical mechanism of materials physics and photophysics for photo-active functional nanocomposites.

Identification of sweetpotato black spot disease caused by Ceratocystis fimbriata by quartz crystal microbalance array

Sweetpotato black spot disease caused by Ceratocystis fimbriata is a major sweetpotato disease that not only affects yield and storage but also damages human or animal health. Herein, a four-element quartz crystal microbalance (QCM) gas sensor array based on molecularly imprinted polymers (MIPs) and zeolitic imidazolate frameworks (ZIFs) materials were reported to differentiate healthy sweetpotatoes and sick sweetpotatoes. Several volatile organic compounds, namely citronellol, heptanal, benzaldehyde, and 2-pentylfuran, were selected for detection based on the results of gas chromatography-mass spectrometry (GC-MS). The MIPs and ZIFs were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption, and the results show that materials were successfully obtained. The four sensors based on the as-prepared materials exhibited excellent sensitivity and selectivity toward target gases. Finally, the sensor array was applied to identify sick sweetpotatoes. Frequency shift was selected as the eigenvalue and quadratic support vector machine (QSVM) and weighted k-nearest neighbor (WKNN) models were employed for discrimination. QSVM and WKNN exhibited 100% accuracy in classification, proving that the sensor array can be used for the identification of Ceratocystis-fimbriata-infested sweetpotatoes. This study may contribute to the development of gas sensor arrays for use in agri-food quality control and protection.

Odorant binding proteins from Hermetia illucens: potential sensing elements for detecting volatile aldehydes involved in early stages of organic decomposition

Organic decomposition processes, involving the breakdown of complex molecules such as carbohydrates, proteins and fats, release small chemicals known as volatile organic compounds (VOCs), smelly even at very low concentrations, but not all readily detectable by vertebrates. Many of these compounds are instead detected by insects, mostly by saprophytic species, for which long-range orientation towards organic decomposition matter is crucial. In the present work the detection of aldehydes, as an important measure of lipid oxidation, has been possible exploiting the molecular machinery underlying odour recognition in Hermetia illucens (Diptera: Stratiomyidae). This voracious scavenger insect is of interest due to its outstanding capacity in bioconversion of organic waste, colonizing very diverse environments due to the ability of sensing a wide range of chemical compounds that influence the choice of substrates for ovideposition. A variety of soluble odorant binding proteins (OBPs) that may function as carriers of hydrophobic molecules from the air-water interface in the antenna of the insect to the receptors were identified, characterised and expressed. An OBP-based nanobiosensor prototype was realized using selected OBPs as sensing layers for the development of an array of quartz crystal microbalances (QCMs) for vapour phase detection of selected compounds at room temperature. QCMs coated with four recombinant H. illucens OBPs (HillOBPs) were exposed to a wide range of VOCs indicative of organic decomposition, showing a high sensitivity for the detection of three chemical compounds belonging to the class of aldehydes and one short-chain fatty acid. The possibility of using biomolecules capable of binding small ligands as reversible gas sensors has been confirmed, greatly expanding the state-of the-art in gas sensing technology.

Acoustic Array Biochip Combined with Allele-Specific PCR for Multiple Cancer Mutation Analysis in Tissue and Liquid Biopsy.

Regular screening of point mutations is of importance to cancer management and treatment selection. Although techniques like next-generation sequencing and digital polymerase chain reaction (PCR) are available, these are lacking in speed, simplicity, and cost-effectiveness. The development of alternative methods that can detect the extremely low concentrations of the target mutation in a fast and cost-effective way presents an analytical and technological challenge. Here, an approach is presented where for the first time an allele-specific PCR (AS-PCR) is combined with a newly developed high fundamental frequency quartz crystal microbalance array as biosensor for the amplification and detection, respectively, of cancer point mutations. Increased sensitivity, compared to fluorescence detection of the AS-PCR amplicons, is achieved through energy dissipation measurement of acoustically "lossy" liposomes binding to surface-anchored dsDNA targets. The method, applied to the screening of BRAF V600E and KRAS G12D mutations in spiked-in samples, was shown to be able to detect 1 mutant copy of genomic DNA in an excess of 104 wild-type molecules, that is, with a mutant allele frequency (MAF) of 0.01%. Moreover, validation of tissue and plasma samples obtained from melanoma, colorectal, and lung cancer patients showed excellent agreement with Sanger sequencing and ddPCR; remarkably, the efficiency of this AS-PCR/acoustic methodology to detect mutations in real samples was demonstrated to be below 1% MAF. The combined high sensitivity and technology-readiness level of the methodology, together with the ability for multiple sample analysis (24 array biochip), cost-effectiveness, and compatibility with routine workflow, make this approach a promising tool for implementation in clinical oncology labs for tissue and liquid biopsy.

Identification of Sweetpotato Black Spot Disease Caused by Ceratocystis Fimbriata by Quartz Crystal Microbalance Array

Identification of Sweetpotato Black Spot Disease Caused by Ceratocystis Fimbriata by Quartz Crystal Microbalance Array

Identification of Sweetpotato Black Spot Disease Caused by Ceratocystis Fimbriata by Quartz Crystal Microbalance Array

Identification of Sweetpotato Black Spot Disease Caused by Ceratocystis Fimbriata by Quartz Crystal Microbalance Array

A Fast Method for Monitoring the Shifts in Resonance Frequency and Dissipation of the QCM Sensors of a Monolithic Array in Biosensing Applications

Improvement of data acquisition rate remains as an important challenge in applications with Quartz Crystal Microbalance (QCM) technology where high throughput is required. To address this challenge, we developed a fast method capable of measuring the response of a large number of sensors and/or overtones, with a high time resolution. Our method, which can be implemented in a low-cost readout electronic circuit, is based on the estimation of $\Delta {f}_{r}$ (frequency shift) and $\Delta {D}$ (dissipation shift) from measurements of the sensor response obtained at a single driving frequency. By replacing slow fitting procedures with a direct calculation, the time resolution is only limited by the physical characteristics of the sensor (resonance frequency and quality factor), but not by the method itself. Capabilities of the method are demonstrated by monitoring multiple overtones with a single 5 MHz sensor and a Monolithic QCM array comprising 24 50MHz-sensors. Accuracy of the method is validated and compared with the state-of-the-art, as well as with a reference method based on impedance analysis.

A High Frequency Dual Inverted Mesa QCM Sensor Array with Concentric Electrodes

Quartz Crystal Microbalance (QCM) is a candidate technology for high sensitivity application. This mass sensor's property depends on the piezoelectric property of the AT-cut quartz crystal. QCM has been widely employed for gas detection due to its comparative advantages including high mass sensitivity, potential for array configuration, low cost, ease of fabrication as well as wide range of available sensitive material compatibility. However, its application has been limited due to two main disadvantages of the non-uniform mass sensitivity across the electrodes and lower frequency of operation. In this work, in order to overcome these disadvantages, a novel concentric electrode structure combined with the dual inverted mesa structure has been proposed and implemented. It is demonstrated that the developed and optimized concentric electrode has provided a uniform displacement across the QCM's sensing electrode. In addition, the dual inverted mesa design has been implemented in the QCM array in which a high fundamental resonant frequency of 33 MHz has been achieved without interference between the adjacent channels in the sensor array. The interference between the adjacent high frequency QCM channels has been eliminated and therefore, each QCM can function as an individual gas sensor when coated with the designed sensing layers. For 33 MHz, the interference has been eliminated at the optimal center to center between electrode distance (c2c). In the case of 10 MHz array, c2c value of 6 mm is achieved which is lower than the value of c2c achieved on a traditionally un-etched QCM array which was found equal to 6.5 mm. Therefore, the proposed QCM array design is shown to reduce the overall size while enhancing the device sensitivity, uniformity and performance.

OSTEMER polymer as a rapid packaging of electronics and microfluidic system on PCB

A new heterogeneous integration method is presented that allows the integration of a microfluidic platform and a multi-channel quartz crystal microbalance array on a printed circuit board (PCB) using a dry adhesive bonding method. In this work, the microfluidic platform is a replica molded using a UV-curable OSTEMER 322 Crystal Clear polymer. The OSTEMER acts both as a final package for the cartridge and as a functional material for hosting molded microfluidic channels, the input reservoirs and the waste reservoir. The method is demonstrated by the integration of an array of 24 of a 150 MHz high fundamental frequency quartz crystal microbalance (HFF-QCM) to the OSTEMER microfluidic packaging. The resulting bond interface is shown to be completely homogeneous and void free, and the package is tested to a differential pressure of up to 4 bars. The leak test of the cartridge is performed by pressurizing a microfluidic channel with an aqueous solution using an external peristaltic pump for more than 4 h. The cartridge performance is evaluated by the electrical characterization. Q-factor values of 9507 and of 650 are achieved in air and DI water, respectively. Results show that this simple integration method of the HFF-QCM is a promising way to integrate microfluidics into the more complex heterogeneous system.

Organic/inorganic nanocomposites of ZnO/CuO/chitosan with improved properties

To extend the visible light response of ZnO, ZnO/CuO heterostructured nanocomposite was synthesized by a hydrothermal approach. At the same time, chitosan (Ch) is considered as a very promising natural polymer. It holds not only abundant resource and low cost, but also has excellent adsorption properties to a broad range of organic pollutants and some heavy metal ions. To improve the adsorption properties of ZnO/CuO nanocomposite, ZnO/CuO/chitosan organic-inorganic composites were prepared with precipitation method. The as-prepared nanocomposites were characterized by TEM (Transmission electron microscopy), SAED pattern (Selected Area Electron Diffraction), SEM (scanning electron microscopy), UV–Vis (Ultraviolet–visible spectroscopy), PL (Photoluminescence), XRD (X-ray diffraction), TGA (Thermo Gravimetric Analyzer), Fourier transform infrared spectroscopy spectra (FTIR) et al. To examine the surface and interface properties of nanocomposites, chemical prototype sensor arrays were constructed based on ZnO, ZnO/CuO, ZnO/Cu2O, ZnO/CuO/chitosan, ZnO/Cu2O/chitosan nanocomposites and QCM (quartz crystal microbalance) arrays devices. The adsorption response behaviors of the sensor arrays to some typical volatile compounds were examined under similar conditions. The results indicated that with comparison to ZnO nanostructure, the ZnO/CuO nanocomposite exhibited enhanced adsorption properties to some typical volatile compounds greatly, and the adsorption properties of ZnO/CuO/chitosan are much better than that of ZnO/CuO nanocomposite. The adsorption of ZnO/CuO system is super to that of ZnO/Cu2O. Therefore, ZnO/CuO/chitosan nanocomposite not only showed broadening visible light response, but also possessed of excellent adsorption properties, and has good potential applications in photocatalysts, chemical sensors, biosensors, self-cleaning coating fields et al.

Multichannel quartz crystal microbalance array: Fabrication, evaluation, application in biomarker detection

A multichannel quartz crystal microbalance array (MQCM) with three pairs of gold electrodes was fabricated for detection of two biomarkers: acetone and nitric oxide (NO). The gold electrodes were deposited symmetrically on an AT-cut 10 MHz circular quartz plate using photolithography, sputtering, and lift-off technologies. The effect of gold layer thickness on MQCM performance was investigated and the optimized thickness was 101 nm. The simulation values of the electric parameters C0, Cq, Lq, and Rq in the Butterworth–Van Dike equivalent circuit for the MQCM device were 97 pF, 1.3 pF, 1.05 mH, and 9.8 Ω, respectively. Simulation values were in the theoretical range, which indicated that the fabricated MQCM device had good resonance performance. Two types of nanocomposites, titanium dioxide–multiwalled carbon nanotubes and cobalt (II)phthalocyanine–silica, were synthesized as sensing materials. The sensing mechanism is based on coordination adsorption of target molecules onto the sensing material, resulting in a resonant frequency shift of modified QCM sensor. A linear range from 4.33 to 129.75 ppmv for acetone was obtained and one from 5.75 to 103.45 ppbv for NO.

TECHNOLOGY OF CHEMICAL RECOGNITION WITH THE SENSOR ARRAYS: FUNDAMENTAL PROBLEMS AND TECHNICAL IMPLEMENTATION

In this work fundamental problems and technical implementations of sensor arrays for chemical images recognition are studied. In our opinion the main fundamental problem at the moment is the absence of an adequate physical-chemical model of interaction of the analyte molecule with sensitive layer which does not allow to predict, at least preliminary, reaction of sensor to a contact with complex mixture of different molecules in different concentrations. Another fundamental problem limiting applicability of the electronic nose devices is lack of reproducibility of responses of the same sensors array to the same analyte. Three types of multisensor systems developed at ISP NASU are considered, namely the quartz crystal microbalance array, conductive polymers and the sensors based on optical principle. The results obtained during the operation of the three systems are shown, taking into account some of the mentioned fundamental and empirical regularities in the multisensor arrays.

Miniature quartz crystal-resonator-based thermogravimetric detector.

In this work, a new design for a microheater combined with a quartz crystal microbalance (QCM) array for thermogravimetric analysis is presented. Each QCM consists of two electrodes to excite thickness-shear-mode vibrations and one microheater to increase the temperature on the crystal backside. In addition, all the electrode pads are patterned on the crystal backside, making the design of the QCM compact and user-friendly. Finally, the proposed QCM array was employed to separate ethanol from methanol. This was successfully achieved via thermal desorption spectra calculated by differentiating the frequency changes.

Sensor Arrays Based on Polycyclic Aromatic Hydrocarbons: Chemiresistors versus Quartz-Crystal Microbalance

Arrays of broadly cross-reactive sensors are key elements of smart, self-training sensing systems. Chemically sensitive resistors and quartz-crystal microbalance (QCM) sensors are attractive for sensing applications that involve detection and classification of volatile organic compounds (VOCs) in the gas phase. Polycyclic aromatic hydrocarbon (PAH) derivatives as sensing materials can provide good sensitivity and robust selectivity towards different polar and nonpolar VOCs, while being quite tolerant to large humidity variations. Here, we present a comparative study of chemiresistor and QCM arrays based on a set of custom-designed PAH derivatives having either purely nonpolar coronas or alternating nonpolar and strongly polar side chain termination. The arrays were exposed to various concentrations of representative polar and nonpolar VOCs under extremely varying humidity conditions (5-80% RH). The sensor arrays' classification ability of VOC polarity, chemical class and compound separation was explained in terms of the sensing characteristics of the constituent sensors and their interaction with the VOCs. The results presented here contribute to the development of novel versatile and cost-effective real-world VOC sensing platforms.

Analysis of a monolithic, two-dimensional array of quartz crystal microbalances loaded by mass layers with nonuniform thickness

We study free thickness-shear vibrations of a monolithic, two-dimensional, and periodic array of quartz crystal microbalances loaded by mass layers with gradually varying thickness. A theoretical analysis is performed using Mindlin's two-dimensional plate equation. It is shown that the problem is mathematically governed by Mathieu's equation with a spatially varying coefficient. A periodic solution for resonant frequencies and modes is obtained and used to examine the effects of the mass layers. Results show that the vibration may be trapped or untrapped under the mass layers. The trapped modes decay differently in the two in-plane directions of the plate. The mode shapes and the decay rate of the trapped modes are sensitive to the mass layer thickness.

Array of MIP-Based Sensor for Fruit Maturity Assessment

Traditionally, fruits are harvested through conventional methods which are based on smell, texture and harvesting time. This analytical technique has many disadvantages in terms of objectivity and subjectivity. By determining various fruits volatile released during pre-matured until matured period, one can actually selectively establish the exact time of a fruit to ripe. The aromatic volatile compounds emitted by Harumanis mango were analyzed using GCMS and found that terpenes hydrocarbon e.g. limonene, α-pinene, β-pinene, α-terpinene, γ-terpinene and 3-carene are the major volatiles that released by the ripe mango. In this work, MIP (Molecularly Imprint Polymer) based sensor array were fabricated and tuned to mango aroma volatiles. HyperChem software simulation is used to obtain key information such as the Binding Energy (ΔE) between the template and the functional monomer that lead to the stable MIP. Designing the MIP using HyperChem is an advantage into saving time and cost compare to trial and error experimental methods. Array of different MIPs template e.g. limonene, α-pinene and β-pinene were synthesis and coated onto the surface of QCMs (Quartz Crystal Microbalance) followed by polymerization and removal of templates molecules that will leave the cavity of selective templates. These QCM arrays are able to distinguish between different terpenes gases released by maturity and ripeness mango due to its selectivity and sensitivity properties of sensor response. The findings of this study is a great breakthrough for the agricultural sector as volatile sensing of chemical markers could determine the optimal harvest time of the local fruits and ensuring the quality and standards.

Differential solute gas response in ionic-liquid-based QCM arrays: elucidating design factors responsible for discriminative explosive gas sensing.

An eight-sensor array coupling a chemoselective room-temperature ionic liquid (RTIL) with quartz crystal microbalance (QCM) transduction is presented in this work in order to demonstrate the power of this approach in differentiating closely related analytes in sensory devices. The underlying mechanism behind the specific sensory response was explored by (i) studying mass loading and viscoelasticity effects of the sensing layers, predominantly through variation in damping impedance, the combination of which determines the sensitivity; (ii) creation of a solvation model based on Abraham's solvation descriptors which reveals the fact that polarizability and lipophilicity are the main factors influencing the dissolution of gas analytes into the RTILs; and (iii) determination of enthalpy and entropy values for the studied interactions and comparison via a simulation model, which is also effective for pattern discrimination, in order to establish a foundation for the analytical scientist as well as inspiration for synthetic pathways and innovative research into next-generation sensory approaches. The reported sensors displayed an excellent sensitivity with detection limit of <0.2%, fast response and recovery, and a workable temperature range of 27-55 °C and even higher. Linear discriminant analysis (LDA) showed a discrimination accuracy of 86-92% for nitromethane and 1-ethyl-2-nitrobenzene, 71% for different mixtures of nitromethane, and 100% for these analytes when thermodynamic parameters were used as input data. We envisage applications to detecting other nitroaromatics and security-related gas targets, and high-temperature or real-time situations where manual access is restricted, opening up new horizons in chemical sensing.

A Monolithic QCM Array Designed for Mounting on a Flow Cell

A monolithic quartz crystal microbalance (QCM) array fabricated with the excitation electrodes located on the airside and the gold conductive layer on the sensing side was evaluated as a biosensor array in a simple flow cell. The electrode configuration of the new QCM is suitable for sensor applications in flow-cell systems compared with standard QCM because the mounting of the QCM on the flow cell and the electric interconnection between the excitation electrode and oscillation circuit does not require considerable skill and effort. Frequency response to the adsorption of human IgG to anti-human IgG antibody at the concentrations of 0.1-100 g/ml was successfully measured, and the results showed that this new sensor can be an alternative to the standard QCM. In addition, the affinity difference between the reference QCM coated with bovine serum albumin for reducing nonspecific binding and the antibody-immobilized QCM to anti-human IgG antibody was simultaneously measured by using the monolithic QCM array within the flow cell. The monolithic QCM array designed for mounting on a flow cell will be expected to use for studying a surface science in a microchannel.

Real-time measurement of photocatalytic reactions using a monolithic QCM array

This paper reports a real-time measurement of photocatalytic reactions by using a miniaturized quartz-crystal microbalance (QCM) array. The QCM was miniaturized and integrated on the same quartz plate using microfabrication techniques. Two QCMs were located close to each other, with one of the QCMs used as a reference sensor for the accurate and independent determination of mass change effects and environmental change effects. The QCM output was compensated for frequency shifts induced by ultra violet (UV) irradiation by subtracting the frequency shift of the reference sensor. The minimum detectable frequency shift under the irradiation was within 1 Hz. The measured photodecomposition speed of methylene blue dye on a TiO2-coated QCM agreed well with that evaluated by the standard optical testing method under dry condition. The developed method enabled us to measure the photodecomposition of a surfactant on a TiO2-coated QCM with sub-nanogram mass resolution in real time.