Article

Miniaturized polymer coated film bulk acoustic wave resonator sensor array for quantitative gas chromatographic analysis

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Abstract

This paper reports a novel miniaturized detector for gas chromatography based on film bulk acoustic resonator (FBAR) sensor array. Polymer coated FBAR demonstrated detection limit of parts per million (ppm) concentrations for several volatile organic vapors. Orthogonal selectivity between n-pentane and acetone is achieved by integrating different polymer coated FBARs as sensor array. A prototype of chromatographic instrument using FBAR sensor array as detector was demonstrated by facile hyphenation of the device with commercial separation column. Such GC system is used to quantitative identification of dual gas mixture by employing principal component analysis (PCA). This MEMS chemical sensor technology offers high sensing performance, miniaturized size, and low power consumption, which are critical for development of portable gas chromatography.

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... Coating the detector with nanomaterials (metal organic frameworks (MOFs)) significantly enhanced the detector response (20 times). Later, we showed that different polymer-coated FBAR sensor arrays could provide quantitative detection and identify overlapping dual mixtures through the PCA method in GC [37]. ...
... SEM image of a film bulk acoustic resonator (left) and structure schematic (right)[36,37]. Reproduced with permission from Ref.[36], Copyright 2018, Elsevier; Reproduced with permission from Ref.[37], Copyright 2016, American Chemical Society. ...
... SEM image of a film bulk acoustic resonator (left) and structure schematic (right)[36,37]. Reproduced with permission from Ref.[36], Copyright 2018, Elsevier; Reproduced with permission from Ref.[37], Copyright 2016, American Chemical Society. ...
Article
Micro gas chromatography (μGC) has been continuously gaining attention since the last century owing to multiple favorable characteristics, such as its small size, low power consumption and minimal production and maintenance costs. μGC has the potential to provide practical solutions to emerging analytical challenges in security, health, and environment. In this review, we summarize recent advances in micro detectors for μGC, including the study of the miniaturization of conventional detectors and the development of novel detectors for μGC chromatography.
... Hu et al. [184] developed polymer-coated FBAR sensor array for gas chromatographic analysis of different organic vapors. They integrated FBAR sensor array with a commercial gas separating column outlet and from other side connected to network analyzer equipped with a computer for data processing. ...
... Table 5. Comparison of different GC-sensor systems with developed FBAR sensor in terms of limit of detection, dynamic range, linearity, application field and data process method, adapted with permission from [184]. Guo et al. [190] presented a theoretical approach to study VOC sensor based on polymeric layer coated diaphragm integrated with FBAR. ...
Article
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Acoustic devices have found wide applications in chemical and biosensing fields owing to their high sensitivity, ruggedness, miniaturized design and integration ability with on-field electronic systems. One of the potential advantages of using these devices are their label-free detection mechanism since mass is the fundamental property of any target analyte which is monitored by these devices. Herein, we provide a concise overview of high frequency acoustic transducers such as quartz crystal microbalance (QCM), surface acoustic wave (SAW) and film bulk acoustic resonators (FBARs) to compare their working principles, resonance frequencies, selection of piezoelectric materials for their fabrication, temperature-frequency dependency and operation in the liquid phase. The selected sensor applications of these high frequency acoustic transducers are discussed primarily focusing on the two main sensing domains, i.e., biosensing for working in liquids and gas/vapor phase sensing. Furthermore, the sensor performance of high frequency acoustic transducers in selected cases is compared with well-established analytical tools such as liquid chromatography mass spectrometry (LC-MS), gas chromatographic (GC) analysis and enzyme-linked immunosorbent assay (ELISA) methods. Finally, a general comparison of these acoustic devices is conducted to discuss their strengths, limitations, and commercial adaptability thus, to select the most suitable transducer for a particular chemical/biochemical sensing domain.
... The objective of adding specific coating materials is to functionalize the resonator for it to capture specific volatile organic compounds (VOCs), enabling the development of a new M/NEMS biosensors generation for the biomedical domain due to their increased effective interaction surface. Some strategies arrange several individual nanoelectromechanical sensors in an array configuration [10], while others consider larger surface resonating structures such as cantilevers [11,12], film bulk acoustic wave resonators (FBARs) [13], capacitive micromachined ultrasonic transducers (CMUTs) [14] and membrane resonators [15]. Increasing the sensing element surface improves the sensor-target interaction, and it also eases the functionalization process that requires the deposition of polymer coatings or other materials that must adhere on top of a micromachined surface. ...
... Increasing the sensing element surface improves the sensor-target interaction, and it also eases the functionalization process that requires the deposition of polymer coatings or other materials that must adhere on top of a micromachined surface. Such a deposition is performed through a variety of methods, such as airbrushing [12,16], ink jetting [17] or spin coating [13]. The accommodation of a functionalization phase into commercial technology is not a straightforward technique and, in fact, very few works combining a CMOS-MEMS resonator with a functionalization polymer are available [18]. ...
Article
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Based on experimental data, this paper thoroughly investigates the impact of a gas fluid flow on the behavior of a MEMS resonator specifically oriented to gas sensing. It is demonstrated that the gas stream action itself modifies the device resonance frequency in a way that depends on the resonator clamp shape with a corresponding non-negligible impact on the gravimetric sensor resolution. Results indicate that such an effect must be accounted when designing MEMS resonators with potential applications in the detection of volatile organic compounds (VOCs). In addition, the impact of thermal perturbations was also investigated. Two types of four-anchored CMOS-MEMS plate resonators were designed and fabricated: one with straight anchors, while the other was sustained through folded flexure clamps. The mechanical structures were monolithically integrated together with an embedded readout amplifier to operate as a self-sustained fully integrated oscillator on a commercial CMOS technology, featuring low-cost batch production and easy integration. The folded flexure anchor resonator provided a flow impact reduction of 5× compared to the straight anchor resonator, while the temperature sensitivity was enhanced to −115 ppm/°C, an outstanding result compared to the −2403 ppm/°C measured for the straight anchored structure.
... FBAR arrays have also been used as electronic noses to achieve discrimination of VOCs. [22][23][24] A single FBAR can also function as a virtual sensor array with temperature modulation to detect and discriminate VOCs. 25 The surfaces of FBARs are typically functionalized with polymers, 18 supramolecular monolayers, 25 or self-assembled monolayers 23,24 to realize selectivity and improved adsorption. Surface functionalization of the sensors plays a key role in recognition, sensitivity, selectivity, stability, and reversibility. ...
... FBAR arrays have also been used as electronic noses to achieve discrimination of VOCs. [22][23][24] A single FBAR can also function as a virtual sensor array with temperature modulation to detect and discriminate VOCs. 25 The surfaces of FBARs are typically functionalized with polymers, 18 supramolecular monolayers, 25 or self-assembled monolayers 23,24 to realize selectivity and improved adsorption. Surface functionalization of the sensors plays a key role in recognition, sensitivity, selectivity, stability, and reversibility. ...
Article
Full-text available
Film bulk acoustic wave resonators have demonstrated great potential in the detection of volatile organic compounds owing to their high sensitivity, miniature size, low power consumption, capacity for integration, and other beneficial characteristics. However, it is necessary to functionalize the surfaces of these resonators to enhance the adsorption and discrimination of volatile organic compounds. Here, we report a convenient and reliable method for functionalizing the surfaces of film bulk acoustic wave resonators with hydrophobins via self-assembly to enable highly sensitive and polarity sensitive detection of volatile organic compounds. Experiments conducted using various concentrations of five volatile organic compounds possessing different polarities demonstrated that the hydrophobin coating enhanced the responsivity of the proposed sensor. The obtained results were in good agreement with the Brunauer–Emmett–Teller model of multilayer physisorption, which suggests that the hydrophobin coating enhanced the sensitivity by improving the monolayer adsorption capacity. Our work demonstrates that the combination of multifunctional biosurfactants and microelectromechanical devices can permit high-performance gas sensing.
... Correspondingly, gaseous samples have consisted of indoor, outdoor, or artificial air, breath, and headspace of liquid or solid samples, such as wastewater, food, and plants [25,[37][38][39][40][41][42][43][44]. Further applications include the use as detector for gas chromatography (GC) instead of mass spectrometry (MS) [45,46] and the use as sensor node in sensor networks [47]. In contrast to that, the use of acoustic sensor arrays as e-tongues or biosensor arrays for liquid samples has been much less common. ...
... An FBAR array with two polymer coatings was successfully applied for quantitative detection of three alkanes and one ketone after GC. Furthermore, binary mixtures of one of the alkanes and the ketone (i.e., pentane and acetone), which could not be separated by the GC column, could be differentiated by the array [46]. ...
Article
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Bulk acoustic wave (BAW) and surface acoustic wave (SAW) sensor devices have successfully been used in a wide variety of gas sensing, liquid sensing, and biosensing applications. Devices include BAW sensors using thickness shear modes and SAW sensors using Rayleigh waves or horizontally polarized shear waves (HPSWs). Analyte specificity and selectivity of the sensors are determined by the sensor coatings. If a group of analytes is to be detected or if only selective coatings (i.e., coatings responding to more than one analyte) are available, the use of multi-sensor arrays is advantageous, as the evaluation of the resulting signal patterns allows qualitative and quantitative characterization of the sample. Virtual sensor arrays utilize only one sensor but combine it with enhanced signal evaluation methods or preceding sample separation, which results in similar results as obtained with multi-sensor arrays. Both array types have shown to be promising with regard to system integration and low costs. This review discusses principles and design considerations for acoustic multi-sensor and virtual sensor arrays and outlines the use of these arrays in multi-analyte detection applications, focusing mainly on developments of the past decade.
... Over the past few years there has been a growing demand for high-throughput separations in numerous fields (e.g., environmental, food, clinical or biological analysis), where either the time response delivery must be reduced, or the productivity enhanced (or in the ideal case both), considering the large number of analyzed samples and diversity of compounds. In order to achieve these goals robust analytical techniques such as liquid chromatography and gas chromatography has been utilized [1][2][3][4] . Although gas chromatography (GC) is in some cases faster, and provides higher separation efficiency, having better properties for combination with a wide range of sensitive and selective detectors, it also has some limitations such the requirement that the molecules to be analyzed must be thermally stable and sufficiently volatile. ...
... Polymer-based gas sensors have attracted considerable attention as a result of their many advantages over commercially available metal oxide gas sensors, such as room temperature operation, numerous types of polymers available for sensing materials, and their low manufacturing cost [1][2][3][4][5][6][7]. Despite these advantages, they are not widely applied, because of the serious drawback that most polymers are not conductive. ...
Article
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A cellulose nanocrystal (CNC)-reinforced polymethylmethacrylate (PMMA) fiber was obtained via electrospinning, and then attached between the two tines of a quartz tuning fork (QTF). The change in the resonance frequency of the CNC/PMMA composite fiber-coated QTF (CP-QTF) was measured upon being exposed to various concentrations of ethanol vapor. The frequency decreased as the ethanol vapor concentration increased, because the modulus of the composite fiber decreased due to the adsorption of the ethanol vapor. The composite fiber obtained at a high relative humidity (RH; 60% RH, CP60 fiber) produced a highly porous structure as a result of the moisture adsorption-induced phase separation of PMMA. The porosity of the CP60 fiber was higher than that of a CNC/PMMA composite fiber obtained at 30% RH (CP30 fiber) or that of a plain PMMA fiber obtained at 60% RH (P60 fiber), because hygroscopic CNCs promote moisture adsorption. The CP60 fiber-coated QTF (CP60-QTF) exhibited a greater frequency change and faster response time than P60-QTF and CP30-QTF upon exposure to ethanol vapor at the same concentration. The enhanced performance of CP60-QTF was attributed to its higher surface area and larger fiber modulus.
... According to the Sauerbrey equation, a FBAR sensor, resonating at the gigahertz range, offers higher sensitivity than QCM, which has the resonating frequency at several megahertz [29][30][31][32][33]. We are quite interested in applying FBAR gas sensors as GC detectors and have firstly reported the facile hyphenation of the FBARs with GC [34,35]. In this study, we aimed to develop a microfluidic FBAR (mFBAR) gas sensor for in-line detection in GC. ...
Article
Full-text available
A microfluidic film bulk acoustic wave resonator gas sensor (mFBAR) adapted specifically as an in-line detector in gas chromatography was described. This miniaturized vapor sensor was a non-destructive detector with very low dead volume (0.02 μL). It was prepared by enclosing the resonator in a microfluidic channel on a chip with dimensions of only 15 mm × 15 mm × 1 mm. The device with polymer coating showed satisfactory performance in the detection of organophosphorus compound, demonstrating a very low detection limit (a dozen parts per billion) with relatively short response time (about fifteen seconds) toward the simulant of chemical warfare agent, dimethyl methylphosphonate. The in-line detection of the mFBAR sensor with FID was constructed and employed to directly measure the concentration profile on the solid surface by the mFBAR with the controlled concentration profile in the mobile phase at the same time. The difference of peak-maximum position between mobile phase and solid phase could be a convenient indicator to measure mass transfer rate. With the response of the mFBAR and FID obtained in one injection, an injection mass-independent parameter can be calculated and used to identify the analyte of interest.
... Jizhou Hu et al developed a prototype chromatographic system by simple hyphenation of miniaturized sensitive gravimetric gas sensors with a commercial separation column. A 1.21-GHz FBAR (film bulk acoustic resonator) was successfully fabricated through a standard MEMS fabrication process and served as a novel detector for gas chromatography [17]. ...
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Traditional algorithms cannot readily address the fact that artificial olfaction in a dynamic ambient environment requires continuous selection and execution of the optimal algorithm to detect different gases. This paper presents a deep learning WCCNN-BiLSTM-many-to-many GRU (wavelet coefficient convolutional neural network–bidirectional long short-term memory–many-to-many-gated recurrent unit) model for qualitative and quantitative artificial olfaction of gas based on the automatic extraction of time-frequency domain dynamic features and time domain steady-state features. The model consists of two submodels. One submodel recognizes a gas by the WCCNN-BiLSTM model, and the experiments based on actual data from our fabricated artificial olfactory system demonstrate that the gas recognition accuracy is nearly 100%. The other submodel quantifies the gas by the many-to-many GRU model with less labeled data; this submodel is comparable to conventional algorithms such as DT (decision tree), SVMs (support vector machines), KNN (k-nearest neighbor), RF (random forest), AdaBoost, GBDT (gradient-boosting decision tree), bagging, and ET (extra tree) according to PCA (principal component analysis) dimensionality reduction. The experimental results of 10-fold cross-validations show that the proposed many-to-many GRU outperforms the aforementioned conventional algorithms with remarkable metrics and can maintain higher concentration estimation accuracy for different unknown gases with less labeled data.
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Gravimetric resonators based on Micro/Nanoelectromechanical System (M/NEMS) are potential candidates in developing smaller, less expensive, and higher performance gas sensors. Metal organic frameworks (MOFs), with high surface areas, recently come into focus as advanced nano-porous sensitive materials in micro gravimetric gas sensors. The surface of MOFs on those sensors is critical in offering water stability and varying absorption behaviors. However, the influences of surface on sensing performance are less explored and the strategy to tune surface properties of MOFs mounted on gravimetric resonators is still rare. In this paper, a straightforward strategy to engineer surface properties of MOFs, specifically Cu3(benzenetricarboxylate)2 (known as HKUST-1), is reported and the surface hydrophilicity/hydrophobicity of HKUST-1 is tuned by chemical vapor deposition combined with monolayer self-assembly. It is found out that the hybrid inorganic and organic surface engineering strategy not only preserves the absorption capacity of inner MOFs but also significantly enhances sensor stability toward water.
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Thesis
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