Dear Colleagues,

Acoustic wave devices have been used in materials characterization and in chemical and biological sensing for quite some time. The earliest device utilized was the thickness shear mode (TSM) device, commonly known as the quartz crystal microbalance (QCM), which was first used in the 1950s, with many commercial instruments available today from various vendors for operation in gas, liquid and high pressure environments, and with features such as dissipation monitoring integrated. Starting in the 1970s, Rayleigh wave surface acoustic wave (SAW) devices have been demonstrated in gas phase chemical sensing. Shear horizontal wave propagation in suitable cuts of piezoelectric materials has since allowed for liquid phase operation and construction of label-free biosensors using SAW devices. Additionally, there is considerable literature on the use of the QCM as a biosensor. At higher frequencies of operation, SAW devices are much more sensitive as biosensors, while the electronics to realize small, point-of-care systems is slightly more complex. With the integration of an antenna, SAW devices are capable of wireless and remotely powered operation as sensors for physical, chemical, and biological applications. Other types of acoustic waves generated in piezoelectric materials such as acoustic plate mode (APM) and flexural plate mode (FPM) have also been tried as chemical and biological sensors in the literature to a lesser extent. Recently, SAW devices have been realized on piezoelectric films deposited on flexible substrates such as Kapton and polyethylene naphthalate (PEN), with applications to physical, chemical, and biological sensors, especially in IoT applications. Many advances in sensing materials and schemes have been described recently, such as the use of nanomaterials to increase sensitivity and decrease limits of detection to the pg/ml levels often required in biosensing applications. Integration with other sensing modalities such as optical and electrochemical has also been described to obtain more reliable determinations.  Rayleigh surface acoustic waves have been described in the removal of nonspecifically bound proteins, in mixing, and in lysing of cells, all in the interest of obtaining better outcomes from sensor systems constructed from acoustic wave devices. Portable electronics have been configured to achieve small footprints. Finally, theoretical understanding of these devices has progressed via modeling, including finite elements. All of these types of advances in the use of acoustic wave devices in biological sensing are welcome as contributions to this Special Issue of Sensors and are invited from researchers around the world.

Prof. Dr. Venkat R. Bhethanabotla
Guest Editor

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• acoustic wave
• quartz crystal microbalance
• surface acoustic waves
• biosensor
• immunosensor
• point-of-care sensor
• flexible substrate
• biomarker quantification
• nonspecific binding removal
• mixing biosensor system
• biosensor theory