Wireless gas sensing based on a passive piezoelectric resonant sensor array through near-field induction

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We developed a wireless and passive piezoelectric resonant sensor for contimuous volatile organic compound detection. An equivalent circuit is proposed to model the sensing system, and Lamb wave resonators are adopted to demonstrate the wireless interrogation achieved by near-field inductive coupling. The wireless sensing system is employed to monitor the ethanol vapor concentration, and the sensitivity of the wireless sensor barely degrades compared to that of the wired one. Further, we simultaneously and wirelessly tracked several resonance frequencies of a monolithic sensor array, which demonstrates its potential for high-throughput and real-time point-of-care test. Published by AIP Publishing.

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... Les ondes de Lamb agissent sur toute l'épaisseur d'un matériau selon deux modes, le mode symétrique et le mode antisymétrique (Figure I.9). Les épaisseurs mises en jeu sont de l'ordre de grandeur des longueurs d'ondes voire plus petites [61,65]. Les ondes de Lamb sont notamment utilisées pour le contrôle non destructif par ultrasons [66]. ...
... Les ondes de Lamb sont notamment utilisées pour le contrôle non destructif par ultrasons [66]. Ce type d'onde se retrouve dans les MEMS de type FBAR (Film Bulk Acoustic wave Resonator) et est exploité dans des capteurs de gaz [67], d'humidité [65] et de particules [68,69] [72,75] ou électromagnétiques [72,76]. La récupération du signal de vibration peut être faite par voie piézorésistive [70,7274], piézoélectrique [68,72,77], capacitive [72,75] ou encore optique [71,72,76,78]. ...
Les particules fines ont un impact réel sur la qualité de vie et la santé de millions de personnes dans les grandes zones urbaines, notamment en Asie. Pour les détecter et quantifier leur concentration, les capteurs de particules optiques sont les plus couramment étudiés, mais restent relativement chers et volumineux. Les transducteurs MEMS micropoutres sont largement utilisés pour des applications gravimétriques, pour la détection de particules ou de gaz, ce qui requiert des sensibilités massiques (Sm) élevées et des limites de détection (LOD) basses. Pour cela les micropoutres les plus adaptées sont celles ayant des fréquences de résonance (f0) et facteurs de qualité (Q) élevés, avec de faibles bruits de mesure et des masses faibles. Les micropoutres silicium sont couramment utilisées en tant que capteurs gravimétriques et sont de sérieux candidats pour répondre aux caractéristiques souhaitées. Cependant, la sérigraphie a le potentiel pour une fabrication moins chère, plus rapide et aussi à grande échelle. Pour ces micropoutres, l'actionnement et la lecture de f0 sont possibles par effet piézoélectrique. Bien qu'il existe des solutions inorganiques prometteuses sans plomb, les céramiques de titano-zirconate de plomb (PZT) possèdent encore les meilleures propriétés parmi les matériaux piézoélectriques. Des micropoutres fabriquées en technologie hybride couches épaisses sérigraphiées, à actionnement et lecture piézoélectriques intégrés, libérées à l'aide d'une couche sacrificielle polyester et avec co-cuisson de toutes les couches pour leurs libérations sont présentées ici. Différentes géométries ont été testées de 1 mm à 2 mm de large et de 1 mm à 8 mm de long, pour une épaisseur d'environ 100 μm. Une masse volumique ρ PZT = 7200 kg/m³ a été obtenue (≈ 93%ρ PZT massif). Enfin, avec une micropoutre 1×2×0,1 mm³, une sensibilité Sm ≈ 85 Hz/μm et une LOD de 70 ng ont été trouvées, permettant des applications en détection de particules.
... On the contrary, wireless communication using Bluetooth or LCbased sensors provides more freedom to move users' feet. Thus, wearable sensors based on wireless communication technologies have gained more attention in medical and biomedical applications as well as smart assistive robotics [38][39][40][41][42][43][44][45] . Wireless sensors can be categorized as active and passive devices based on the power supply methods. ...
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A pressure monitoring structure is a very useful element for a wearable device for health monitoring and sports biomechanics. While pressure sensors have been studied extensively, battery-free functions working in wireless detection have not been studied much. Here, we report a 3D-structured origami-based architecture sensor for wireless pressure monitoring. We developed an architectured platform for wireless pressure sensing through inductor-capacitor (LC) sensors and a monopole antenna. A personalized smart insole with Miura-ori origami designs has been 3D printed together with conductive 3D printed sensors seamlessly. Wireless monitoring of resonant frequency and intensity changes of LC sensors have been demonstrated to monitor foot pressure for different postures. The sensitivity of the wireless pressure sensor is tunable from 15.7 to 2.1 MHz/kPa in the pressure ranges from 0 to 9 kPa and from 10 to 40 kPa, respectively. The proposed wireless pressure-sensing platform can be utilized for various applications such as orthotics, prosthetics, and sports gear.
... Taking the advantage of small size, long lifetime and no physical connection, the passive wireless sensor is essential to many industrial and medical applications [1] including intraocular eye pressure testing [2] in medical sensing, tire pressure monitoring [3] in automotive applications and pressure sensing at high temperature [4]. Recently, inductor-capacitor (LC) passive wireless sensors [5] have been proposed for pressure [6], strain [7], temperature [8], humidity [9], biochemical [10], gas [11] and so on. Typically, the capacitor changes in response to the parameter of interest, resulting in a shift in resonant frequency. ...
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A noteworthy challenge in actual wireless sensors is the intrinsic sensing resolution and the sensitivity associated with the response to external perturbation to be measured. To address the issue, we report the realization of enhanced sensitivity in a passive wireless sensing system, consisting of three coupled passive resonators. The input wave is exploited as an effective gain in our open system, thus the ideal parity-time (PT) symmetry can be established, rather than balancing real gain and loss. Then the third-order exceptional points are obtained in ternary PT symmetric systems. With the extrinsic perturbation imposed on any one of resonators, we demonstrate analytically and experimentally that the resonance response of the system follows the cube-root dependence on perturbation. Making use of the effective gain, our results pave a new way, to the best of our knowledge, to realize the ultra-sensitivity of a passive wireless sensing system.
... Thin film Lamb wave transducers take the advantages of compact size, good CMOS compatibility and erosion resistance [11], [12], [13], [14]. The lowest order anti-symmetry or flexural mode (A 0 ) in aluminum nitride (AlN) thin film Lamb wave transducers has been demonstrated the potentials for physical, chemical and biological detection [15], [16], [17]. A 0 mode is able to present a small attenuation in sensing once phase velocity C p of the flexural wave is lower than the sound phase velocity C L in liquid mediums [18], [19]. ...
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A two-port local resonating (TPLR) method for thin film Lamb wave sensor is proposed. Based on properties of multi-modes analyzed by numerical simulation and experimental measurement, the TPLR method is able to generate the second-order flexural mode A02 (A0i, i = 2). Density and sound velocity of liquid solutions can be decoupled based on the first-order flexural mode A01 (A0i, i = 1) and the A02 mode, and solutions with the same density such as CH3CH2OH and CH3OH can be successfully distinguished on a single Lamb wave device. When the phase velocity of A02 mode is close to the sound velocity of liquid, compared with the traditional delay-line configuration, smaller period of interdigital transducers (IDTs) and device miniaturization by the TPLR method can be realized. Generation of new modes with the TPLR method demonstrates an alternative for multi-parameters sensing of Lamb wave sensors.
... Microwave gas sensors are emerging as cheap and label-free techniques, and the lack of selectivity can be overcome by combining with highly selective materials [16][17][18][19][20]. Among different types of gas sensors, MEMS piezoelectric gas sensors, such as surface acoustic wave (SAW) resonators [21], Lamb wave resonators (LWR) [22] and film bulk acoustic resonators (FBAR) [23][24][25] have triggered a lot research interest due to their low power consumption, micrometer-scaled sizes, and relatively high sensitivities. Compared with quartz crystal microbalance (QCM), however, they suffer from relatively low Q values, which may result in poor limit of detection (LOD), large phase noise, and instability when integrating with oscillating circuits. ...
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This paper demonstrates a novel micro-size (120 µm × 200 µm) piezoelectric gas sensor based on a piezotransduced single-crystal silicon bulk acoustic resonator (PSBAR). The PSBARs operate at 102 MHz and possess high Q values (about 2000), ensuring the stability of the measurement. A corresponding gas sensor array is fabricated by integrating three different self-assembled monolayers (SAMs) modified PSBARs. The limit of detection (LOD) for ethanol vapor is demonstrated to be as low as 25 ppm with a sensitivity of about 1.5 Hz/ppm. Two sets of identification code bars based on the sensitivities and the adsorption energy constants are utilized to successfully discriminate isopropanol (IPA), ethanol, hexane and heptane vapors at low and high gas partial pressures, respectively. The proposed sensor array shows the potential to form a portable electronic nose system for volatile organic compound (VOC) differentiation.
In this article, we report a vector-network-analyzer-free and real-time LC wireless capacitance readout system based on perturbed nonlinear parity-time (PT) symmetry. The system is composed of two inductively coupled reader-sensor parallel RLC resonators with gain and loss, respectively. By searching for the real mode that requires the minimum saturation gain, the steady-state frequency evolution as a function of the sensor capacitance perturbation is analytically deduced. The proposed system can work in different modes by setting different perturbation points. In particular, at the exceptional point of PT symmetry, the system exhibits high sensitivity. Experimental demonstrations revealed the viability of the proposed readout mechanism by measuring the steady-state frequency of the reader resonator in response to the change of trimmer capacitor on the sensor side. Our findings could impact many emerging applications such as implantable medical device for health monitoring, parameter detection in harsh environment, sealed food packages, etc.
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With the development of the Internet of Things, the requirement of a wide range of human-centered services may now make use of as many computing resources for media technologies and holographic images. The IoT system can monitor the status of equipment in real-time with a robust infrared image recognition algorithm. However, few researchers discuss data mining on images with valuable information. In this study, we present a generic approach that is based on the mining decision tree and holographic image improvement data analysis. We employed advanced data mining techniques to achieve image stability and use light to form a three-dimensional image with real space. The suggested model improves digital image signal transmission and noise through the grey neural network technique and, furthermore, utilization decision tree induction to create attributes-to-target label relations from image pixels. The experimental results show that the suggested approach may be highly efficient and effective for interactive image systems and image mining. Our approach may also be widely utilized and includes extremely efficient convergence systems for essential framework elements.
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Deployment of 5G network infrastructure is a timely opportunity for millimeter-sized battery-free sensors. However, millimeter-wave (mmW) devices often suffer from high conversion loss and path loss that are heavily limiting their communication/detection distance, especially for the case of harmonic transponders based on Schottky diodes. A deep and comprehensive parametric understanding of the second-harmonic generation mechanism of Schottky diodes in the mmW 5G bands can help us to identify suitable diodes or guide diode fabrication to reduce transponder conversion loss. This work reveals that both diode nonlinear junction resistance and capacitance contribute to the second-harmonic generation across the mid-band (sub-7 GHz) and high-band (mmW) 5G frequency bands. However, the nonlinear junction capacitance dominates the second-harmonic generation in the mmW bands. Without Joule heating during the conversion process, the capacitive nonlinearity is more efficient than the resistive nonlinearity, which means that a Schottky diode with a lower junction capacitance will efficiently reduce its associated conversion loss. The VDI GaAs zero bias diode with a low zero bias nonlinear junction capacitance (19.19 fF) shows superior conversion loss performance, which indicates that it can be employed to enhance the detection distance of battery-free harmonic transponders in the mmW 5G bands.
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In this work, it is reported for the first time the use of a network of periodic optical resonant nanopillars for sensing vapors of volatile organic components. In particular, this work evaluates the presence of methanol, ethanol, isopropanol, acetic acid, propionic acid, and toluene vapors at different working distances between the transducer and the surface of the sample in the liquid state, obtaining the sensing curve response of each one of them. In addition, it studies the thin film of liquid condensed onto the nanopillar surface, estimating their corresponding thickness value by means of numerical photonic simulations and their correlation with the corresponding vapor pressure of different specimens.
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Over the last two decades, piezoelectric resonant sensors based on micro-electromechanical systems (MEMS) technologies have been extensively studied as such sensors offer several unique benefits, such as small form factor, high sensitivity, low noise performance and fabrication compatibility with mainstream integrated circuit technologies. One key challenge for piezoelectric MEMS resonant sensors is enhancing their quality factors (Qs) to improve the resolution of these resonant sensors. Apart from sensing applications, large values of Qs are also demanded when using piezoelectric MEMS resonators to build high-frequency oscillators and radio frequency (RF) filters due to the fact that high-Q MEMS resonators favor lowering close-to-carrier phase noise in oscillators and sharpening roll-off characteristics in RF filters. Pursuant to boosting Q, it is essential to elucidate the dominant dissipation mechanisms that set the Q of the resonator. Based upon these insights on dissipation, Q-enhancement strategies can then be designed to target and suppress the identified dominant losses. This paper provides a comprehensive review of the substantial progress that has been made during the last two decades for dissipation analysis methods and Q-enhancement strategies of piezoelectric MEMS laterally vibrating resonators.
For point-of-care applications, integrating sensors into a microfluidic chip is a nontrivial task, since conventional detection modules are bulky and microfluidic chips are small in size, and their fabrication processes are not compatible. In this work, a solid-state microfluidic chip with on-chip acoustic sensors using standard thin-film technologies is introduced. The integrated chip is essentially a stack of thin films on silicon substrate, featuring compact size, electrical input (fluid control) and electrical output (sensor read-out). These features all contribute to portability. In addition, by virtue of processing discrete micro-droplets, the chip provides a solution to the performance degradation bottleneck of acoustic sensors in liquid-phase sensing. Label-free immunoassays in serum are carried out and the viability of the chip is further demonstrated by result comparison with commercial ELISA in prostate-specific antigen sensing experiments. The solid-state chip is believed to fit specific applications in personalized diagnostics and other relevant clinical settings where instrument portability matters.
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In this paper, we have modeled and analyzed affinities and kinetics of volatile organic compounds (VOCs) adsorption (and desorption) on various surface chemical groups using multiple self-assembled monolayers (SAMs) functionalized film bulk acoustic resonator (FBAR) array. The high-frequency and micro-scale resonator provides improved sensitivity in the detections of VOCs at trace levels. With the study of affinities and kinetics, three concentration-independent intrinsic parameters (monolayer adsorption capacity, adsorption energy constant and desorption rate) of gas-surface interactions are obtained to contribute to a multi-parameter fingerprint library of VOC analytes. Effects of functional group's properties on gas-surface interactions are also discussed. The proposed sensor array with concentration-independent fingerprint library shows potential as a portable electronic nose (e-nose) system for VOCs discrimination and gas-sensitive materials selections.
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This paper reports on the implementation of an ultraminiature 140 MHz narrowband filter based on aluminum nitride Lamb wave resonators. Monolithically integrated with a pair of on-chip capacitors and cascaded with a pair of inductors, the filter is well matched to 50 ohm, showing a remarkably high performance. A low pass-band insertion loss of 2.78 dB and steep filter skirts are achieved. The form factor of the monolithic microelectromechanical systems filter is more than ten times smaller than its surface acoustic wave counterpart in the intermediate frequency band and it involves much simpler matching circuits.
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Continuous monitoring of internal physiological parameters is essential for critical care patients, but currently can only be practically achieved via tethered solutions. Here we report a wireless, real-time pressure monitoring system with passive, flexible, millimetre-scale sensors, scaled down to unprecedented dimensions of 1 × 1 × 0.1 cubic millimeters. This level of dimensional scaling is enabled by novel sensor design and detection schemes, which overcome the operating frequency limits of traditional strategies and exhibit insensitivity to lossy tissue environments. We demonstrate the use of this system to capture human pulse waveforms wirelessly in real time as well as to monitor in vivo intracranial pressure continuously in proof-of-concept mice studies using sensors down to 2.5 × 2.5 × 0.1 cubic millimeters. We further introduce printable wireless sensor arrays and show their use in real-time spatial pressure mapping. Looking forward, this technology has broader applications in continuous wireless monitoring of multiple physiological parameters for biomedical research and patient care.
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Topical Review This work makes an overview of the progress made during the last decade with regard to a novel class of piezoelectric microwave devices employing acoustic Lamb waves in micromachined thin film membranes. This class of devices is referred to as either thin film Lamb wave resonators or piezoelectric contour-mode resonators both employing thin film aluminum nitride membranes. These devices are of interest for applications in both frequency control and sensing. High quality factor Lamb wave resonators exhibiting low noise, low loss and thermally stable performance are demonstrated and their application in high resolution gravimetric and pressure sensors further discussed. A specific emphasis is put on the ability of these devices to operate in contact with liquids. Future research directions are further outlined.
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Lamb-wave devices are characterized by high sensitivity to surface perturbations due to acoustic energy confinement in a thin piezoelectric membrane. In this paper, a Lamb-wave delay line device based on a single crystalline GaN membrane is presented. The observed operating frequency of 178.82 MHz was found to be in excellent agreement with numerical analysis predictions. The device as a chemical sensor was evaluated during the application of various concentrations of glycerol on the device surface; its ability to operate as a biosensor was also assessed during the detection of the specific binding of a protein (IgG) to the device surface.
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In this letter, temperature compensation for aluminum nitride AlN Lamb wave resonators operating at high temperature is presented. By adding a compensating layer of silicon dioxide SiO2 , the turnover temperature can be designed for high temperature operation by varying the normalized AlN film thickness hAlN and the normalized SiO2 film thickness hSiO2. With different designs of hAlN and hSiO2, the Lamb wave resonators were well temperature-compensated at 214 ° C, 430 ° C, and 542 ° C, respectively. The experimental results demonstrate that the thermally compensated AlN Lamb wave resonators are promising for frequency control and sensing applications at high temperature.
We report wireless actuation of a Lamb wave micromechanical resonator from a distance of over 1 m with an efficiency of over 15%. Wireless actuation of conventional micromechanical resonators can have broad impact in a number of applications from wireless communication and implantable biomedical devices to distributed sensor networks.
Herein, we report the fabrication of a highly stretchable, transparent gas sensor based on silver nanowire-graphene hybrid nanostructures. Due to its superb mechanical and optical characteristics, the fabricated sensor demonstrates outstanding and stable performances even under extreme mechanical deformation (stable until 20% of strain). The integration of a Bluetooth system or an inductive antenna enables the wireless operation of the sensor. In addition, the mechanical robustness of the materials allows the device to be transferred onto various nonplanar substrates, including a watch, a bicycle light, and the leaves of live plants, thereby achieving next-generation sensing electronics for the 'Internet of Things' area.
These last 10 years, smaller, less expensive, and higher performance sensors are required for gas sensing applications. To date no true detection principle has been recognized as the best candidate for such application. Microsytems or Micro/Nano ElectroMechanical Systems (M/NEMS) used as gravimetric detectors are among the probable candidates. The technology can indeed be manufactured en masse and can provide multi-gas analysing platform. In this paper, we present a comprehensive overview of micro/nano sensors based on the gravimetric effect to detect an absorbed gas on top of their surfaces. The paper provides a comparison between different electromechanical devices (Bulk Acoustic Wave, Surface Acoustic Wave, Capacitive Micro-machined Ultrasonic Transducer, Micro/Nano cantilevers) with an introduction to gas adsorption mechanisms, material selection, detection principles and design guidance useful to researchers or engineers.
In this paper, we present a micromachined film bulk acoustic resonator (FBAR) to detect protein-ligand interactions in real-time. The surface of the FBAR device has a thin layer of gold deposited on it to immobilize thiol-modified biotin. The resonant frequency of the biotin modified FBAR was measured to decrease by 170 ppm when exposed to streptavidin solution with a concentration of 5×10−7 M, corresponding to an added mass of 120 pg on the FBAR surface due to the biotin-streptavidin interaction. Consequently, the biotin modified FBAR can be used to observe in real time the biotin-streptavidin interaction without the use of labeling or molecular tags. The FBAR can be used in a variety of protein-ligand systems, and be designed for testing in array formats to give high throughput screening for drug discovery.
This paper reports simple yet precise equations for automated wireless measurement of the resonance frequency, Q -factor, and coupling coefficient of inductively coupled passive resonant LC circuits. This allows remote sensing of all physical and chemical quantities that can be measured with capacitance transducers. Formerly reported front-end circuit concepts for wireless sensor readout, i.e., phase dip measurement and the dip meter, are subsequently discussed. It is shown that, due to fundamental system limitations, the formerly reported circuit concepts are not applicable if the distance between the sensor and the readout electronic circuit becomes too small, resulting in large coupling coefficients. Therefore, we present an improved concept for an analog front-end circuit of the readout system that overcomes these limitations and hence allows wireless sensor readout under a wider range of operating distances.
We present real-time detection of airborne Vaccinia viruses using quartz crystal microbalance (QCM) in an integrated manner. Vaccinia viruses were aerosolized and neutralized using an electrospray aerosol generator, transported into the QCM chamber, and captured by a QCM crystal. The capture of the viruses on the QCM crystal resulted in frequency shifts proportional to the number of viruses. The capture rate varied linearly with the concentration of initial virus suspensions (8.5×10<sup>8</sup>–8.5×10<sup>10</sup> particles / ml ) at flow rates of 2.0 and 1.1 l / min . This work demonstrates the general potential of mass sensitive detection of nanoscale biological entities in air.
An AlN/3C-SiC composite layer enables the third-order quasi-symmetric (QS(3)) Lamb wave mode with a high quality factor (Q) characteristic and an ultra-high phase velocity up to 32395 ms(-1). A Lamb wave resonator utilizing the QS(3) mode exhibits a low motional impedance of 91 Ω and a high Q of 5510 at a series resonance frequency (f(s)) of 2.92 GHz, resulting in the highest f(s)·Q product of 1.61 × 10(13) Hz among the suspended piezoelectric thin film resonators reported to date.
An AlN thin film electro-acoustic resonator has been fabricated employing a reactive sputtering process for the deposition of an AlN thin film with inclined c-axis for excitation of the shear mode for operation in liquid media. The main objective is to investigate the efficiency of the micro-fluidic channel system integrated in the silicon wafer underneath the AlN resonator. A comparative study between the shear mode thin film bulk acoustic resonator (FBAR) and a quartz crystal microbalance (QCM) using a competitive antibody–antigen association process for detection of drug molecules is presented.
Piezoelectric microelectromechanical systems (MEMS) resonant sensors, known for their excellent mass resolution, have been studied for many applications, including DNA hybridization, protein-ligand interactions, and immunosensor development. They have also been explored for detecting antigens, organic gas, toxic ions, and explosives. Most piezoelectric MEMS resonant sensors are acoustic sensors (with specific coating layers) that enable selective and label-free detection of biological events in real time. These label-free technologies have recently garnered significant attention for their sensitive and quantitative multi-parameter analysis of biological systems. Since piezoelectric MEMS resonant sensors do more than transform analyte mass or thickness into an electrical signal (e.g., frequency and impedance), special attention must be paid to their potential beyond microweighing, such as measuring elastic and viscous properties, and several types of sensors currently under development operate at different resonant modes (i.e., thickness extensional mode, thickness shear mode, lateral extensional mode, flexural mode, etc.). In this review, we provide an overview of recent developments in micromachined resonant sensors and activities relating to biochemical interfaces for acoustic sensors.
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