Abstract
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.
Highlights
Sensors have become indispensable in chemical and biological analytics
The oldest and still most commonly used acoustic sensor devices are quartz crystal microbalances (QCMs), known as quartz microbalances (QMBs), which belong to bulk acoustic wave (BAW)
Since acoustic sensor devices are operated at high frequencies ranging from MHz to GHz, multiplexing techniques are recommended to avoid interference and crosstalk resulting from this closeness as they would affect the signal responses [75,76]
Summary
Sensors have become indispensable in chemical and biological analytics. If samples contain more than one analyte of interest, sensor arrays are advantageous because they enable the detection of more than one analyte in a single measurement run, if analyte-specific coatings are available. If only selective coatings are at hand, sensor arrays are even a must for the reliable detection of a single analyte. Acoustic sensors and biosensors offer label-free, fast, sensitive, and low-cost detection of analytes in both gaseous and liquid samples. Chemical sensor arrays with selective coatings for the characterization of complex gaseous mixtures are called “electronic noses” (e-noses), while their counterparts for liquid samples are known as “electronic tongues” (e-tongues) [14,15]. A variety of coating materials for acoustic chemical sensor arrays has been developed, with polymer-based coatings representing the largest group. Biosensors represent the combination of a transducer with an analyte-specific biorecognition element They can be used as single components for specific detection of the corresponding analytes. Coatings for acoustic biosensor arrays have been predominated by antibodies as specific capture molecules for the corresponding analytes. Applications of multi-sensor and virtual sensor arrays for multi-analyte detection are summarized, with the main focus on research work of the past decade
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