Validation of a phase-mass characterization concept and interface for acoustic biosensors

Design, Optimization and Performance Assessment of Single Port Film Bulk Acoustic Resonator through Finite Element Simulation

In this paper, the study is supported by design, FEA simulation, and practical RF measurements on fabricated single-port-cavity-based acoustic resonator for gas sensing applications. In the FEA simulation, frequency domain analysis was performed to enhance the performance of the acoustic resonator. The structural and surface morphologies of the deposited ZnO as a piezoelectric layer have been studied using XRD and AFM. The XRD pattern of deposited bulk ZnO film indicates the perfect single crystalline nature of the film with dominant phase (002) at 2θ = 34.58°. The AFM micrograph indicates that deposited piezoelectric film has a very smooth surface and small grain size. In the fabrication process, use of bulk micro machined oxide (SiO2) for the production of a thin membrane as a support layer is adopted. A vector network analyzer (Model MS2028C, Anritsu) was used to measure the radio frequency response of the resonators from 1 GHz to 2.5 GHz. As a result, we have successfully fabricated an acoustic resonator operating at 1.84 GHz with a quality factor Q of 214 and an effective electromechanical coupling coefficient of 10.57%.

Recent Advances in Quartz Crystal Microbalance Biosensors Based on the Molecular Imprinting Technique for Disease-Related Biomarkers

The molecular imprinting technique is a quickly developing field of interest regarding the synthesis of artificial recognition elements that enable the specific determination of target molecule/analyte from a matrix. Recently, these smart materials can be successfully applied to biomolecule detection in biomimetic biosensors. These biosensors contain a biorecognition element (a bioreceptor) and a transducer, like their biosensor analogs. Here, the basic difference is that molecular imprinting-based biosensors use a synthetic recognition element. Molecular imprinting polymers used as the artificial recognition elements in biosensor platforms are complementary in shape, size, specific binding sites, and functionality to their template analytes. Recent progress in biomolecular recognition has supplied extra diagnostic and treatment methods for various diseases. Cost-effective, more robust, and high-throughput assays are needed for monitoring biomarkers in clinical settings. Quartz crystal microbalance (QCM) biosensors are promising tools for the real-time and quick detection of biomolecules in the past two decades A quick, simple-to-use, and cheap biomarkers detection technology based on biosensors has been developed. This critical review presents current applications in molecular imprinting-based quartz crystal microbalance biosensors for the quantification of biomarkers for disease monitoring and diagnostic results.

Biomarkers and Detection Platforms for Human Health and Performance Monitoring: A Review

Human health and performance monitoring (HHPM) is imperative to provide information necessary for protecting, sustaining, evaluating, and improving personnel in various occupational sectors, such as industry, academy, sports, recreation, and military. While various commercially wearable sensors are on the market with their capability of "quantitative assessments" on human health, physical, and psychological states, their sensing is mostly based on physical traits, and thus lacks precision in HHPM. Minimally or noninvasive biomarkers detectable from the human body, such as body fluid (e.g., sweat, tear, urine, and interstitial fluid), exhaled breath, and skin surface, can provide abundant additional information to the HHPM. Detecting these biomarkers with novel or existing sensor technologies is emerging as critical human monitoring research. This review provides a broad perspective on the state of the art biosensor technologies for HHPM, including the list of biomarkers and their physiochemical/physical characteristics, fundamental sensing principles, and high-performance sensing transducers. Further, this paper expands to the additional scope on the key technical challenges in applying the current HHPM system to the real field.

Sensing of Airborne Infochemicals for Green Pest Management: What Is the Challenge?

One of the biggest global challenges for our societies is to provide natural resources to the rapidly expanding population while maintaining sustainable and ecologically friendly products. The increasing public concern about toxic insecticides has resulted in the rapid development of alternative techniques based on natural infochemicals (ICs). ICs (e.g., pheromones, allelochemicals, volatile organic compounds) are secondary metabolites produced by plants and animals and used as information vectors governing their interactions. Such chemical language is the primary focus of chemical ecology, where behavior-modifying chemicals are used as tools for green pest management. The success of ecological programs highly depends on several factors, including the amount of ICs that enclose the crop, the range of their diffusion, and the uniformity of their application, which makes precise detection and quantification of ICs essential for efficient and profitable pest control. However, the sensing of such molecules remains challenging, and the number of devices able to detect ICs in air is so far limited. In this review, we will present the advances in sensing of ICs including biochemical sensors mimicking the olfactory system, chemical sensors, and sensor arrays (e-noses). We will also present several mathematical models used in integrated pest management to describe how ICs diffuse in the ambient air and how the structure of the odor plume affects the pest dynamics.

Lateral field excited quartz crystal microbalances for biosensing applications

The most common bulk acoustic wave device used in biosensing applications is the quartz crystal microbalance (QCM), in which a resonant pure shear acoustic wave is excited via electrodes on both major faces of a thin AT-cut quartz plate. For biosensing, the QCM is used to detect the capture of a target by a target-capture film. The sensitivity of the QCM is typically based solely on the detection of mechanical property changes, as electrical property change detection is limited by the electrode on its sensing surface. A modification of the QCM called the lateral field excited (LFE) QCM (LFE-QCM) has been developed with a bare sensing surface as both electrodes are now on a single face of the quartz plate. Compared to the QCM, the LFE-QCM exhibits significantly higher sensitivity to both electrical and mechanical property changes. This paper presents theoretical and experimental aspects of LFE-QCMs. In particular, the presence and strength of the usual and newfound LFE-QCM modes depend on the electrical properties of the film and/or sensing environment. This work also presents examples of experimental setups for measuring the response of an LFE-QCM, followed by results of LFE-QCMs used to detect liquid electrical and mechanical properties, chemical targets, and biological targets. Finally, details are given about the attachment of various target-capture films to the LFE-QCM surface to capture biomarkers associated with diseases such as cancer.

Gas sensors based on mass-sensitive transducers part 1: transducers and receptors-basic understanding

The scientific interest in gas sensors is continuously increasing because of their environmental, medical, industrial, and domestic applications. This has resulted in an increasing number of investigations being reported in the literature and communicated at conferences. The present review, organized in two parts, addresses the peculiarities of gas sensors based on mass-sensitive transducers, starting with their structure and functionality and progressing to implementation and specific use. In this first part of the review, we discuss the constructional peculiarities and operation regions and the physical and chemical processes governing the reception and transduction functions and the way in which they influence the sensor sensing parameters/features. Scientific outcomes and trends in research into gas sensors based on mass sensitive transducers are also considered.

Quartz Crystal Microbalance Electronic Interfacing Systems: A Review

Quartz Crystal Microbalance (QCM) sensors are actively being implemented in various fields due to their compatibility with different operating conditions in gaseous/liquid mediums for a wide range of measurements. This trend has been matched by the parallel advancement in tailored electronic interfacing systems for QCM sensors. That is, selecting the appropriate electronic circuit is vital for accurate sensor measurements. Many techniques were developed over time to cover the expanding measurement requirements (e.g., accommodating highly-damping environments). This paper presents a comprehensive review of the various existing QCM electronic interfacing systems. Namely, impedance-based analysis, oscillators (conventional and lock-in based techniques), exponential decay methods and the emerging phase-mass based characterization. The aforementioned methods are discussed in detail and qualitatively compared in terms of their performance for various applications. In addition, some theoretical improvements and recommendations are introduced for adequate systems implementation. Finally, specific design considerations of high-temperature microbalance systems (e.g., GaPO₄ crystals (GCM) and Langasite crystals (LCM)) are introduced, while assessing their overall system performance, stability and quality compared to conventional low-temperature applications.

High-frequency phase shift measurement greatly enhances the sensitivity of QCM immunosensors

In spite of being widely used for in liquid biosensing applications, sensitivity improvement of conventional (5-20MHz) quartz crystal microbalance (QCM) sensors remains an unsolved challenging task. With the help of a new electronic characterization approach based on phase change measurements at a constant fixed frequency, a highly sensitive and versatile high fundamental frequency (HFF) QCM immunosensor has successfully been developed and tested for its use in pesticide (carbaryl and thiabendazole) analysis. The analytical performance of several immunosensors was compared in competitive immunoassays taking carbaryl insecticide as the model analyte. The highest sensitivity was exhibited by the 100MHz HFF-QCM carbaryl immunosensor. When results were compared with those reported for 9MHz QCM, analytical parameters clearly showed an improvement of one order of magnitude for sensitivity (estimated as the I50 value) and two orders of magnitude for the limit of detection (LOD): 30μgl(-1) vs 0.66μgL(-1)I50 value and 11μgL(-1) vs 0.14μgL(-1) LOD, for 9 and 100MHz, respectively. For the fungicide thiabendazole, I50 value was roughly the same as that previously reported for SPR under the same biochemical conditions, whereas LOD improved by a factor of 2. The analytical performance achieved by high frequency QCM immunosensors surpassed those of conventional QCM and SPR, closely approaching the most sensitive ELISAs. The developed 100MHz QCM immunosensor strongly improves sensitivity in biosensing, and therefore can be considered as a very promising new analytical tool for in liquid applications where highly sensitive detection is required.

Love wave immunosensor for the detection of carbaryl pesticide

A Love Wave (LW) immunosensor was developed for the detection of carbaryl pesticide. The experimental setup consisted on: a compact electronic characterization circuit based on phase and amplitude detection at constant frequency; an automated flow injection system; a thermal control unit; a custom-made flow-through cell; and Quartz/SiO₂ LW sensors with a 40 μm wavelength and 120 MHz center frequency. The carbaryl detection was based on a competitive immunoassay format using LIB-CNH45 monoclonal antibody (MAb). Bovine Serum Albumin-CNH (BSA-CNH) carbaryl hapten-conjugate was covalently immobilized, via mercaptohexadecanoic acid self-assembled monolayer (SAM), onto the gold sensing area of the LW sensors. This immobilization allowed the reusability of the sensor for at least 70 assays without significant signal losses. The LW immunosensor showed a limit of detection (LOD) of 0.09 μg/L, a sensitivity of 0.31 μg/L and a linear working range of 0.14–1.63 μg/L. In comparison to other carbaryl immunosensors, the LW immunosensor achieved a high sensitivity and a low LOD. These features turn the LW immunosensor into a promising tool for applications that demand a high resolution, such as for the detection of pesticides in drinking water at European regulatory levels.

A multi-parameter decoupling method with a Lamb wave sensor for improving the selectivity of label-free liquid detection

In this paper, a liquid multi-parameter decoupling method with only one Lamb wave sensor is presented. In a Lamb wave sensor, antisymmetric modes (A(01) mode for low frequency, A(03) mode for high frequency) and symmetric modes (S(0) mode) are used to detect multiple parameters of a liquid, such as its density, sound velocity, and viscosity. We found they can play very different roles in the detections. For example, the A(01) mode is very sensitive to the liquid's density but the A(03) mode is sensitive to the sound velocity. Here, the A(0) mode is used to identify the density of the detected liquid and with this density value we obtained the viscosity by the amplitude shifts of the S(0) mode. This could be a way to distinguish an unknown liquid with high sensitivity or to solve the problem of selectivity of label-free detection on biosensors.

Quartz crystal microbalance based on passive frequency to voltage converter

In dynamics of evaporation or drying of microdrops from a solid surface, a faster and precise quartz crystal microbalance (QCM) is needed. The fast QCM based on frequency to voltage converter is an attractive and powerful tool in the investigation of the dynamic regime of evaporation to translate the frequency shift in terms of a continuous voltage change. The frequency shift monitoring in fast QCM applications is a real challenge for electronic processing interface. Originally developed as a frequency shift processing interface, this novel passive frequency to voltage converter can produce faster, stable, and accurate results in regard to the QCM sensor behavior. In this article, the concept and circuit of passive frequency to voltage converter will be explained followed by static and dynamic characterization. Experimental results of microdrops evaporation will be given.