![]() Thin-film bulk acoustic resonator(FBAR) Reference FBAR can achieve 3X mass sensitivity compared to QCM. Their mass sensitivity is proportional to their resonance frequency. They resonate in the frequency range up to 10 GHz. Thin-film Bulk Acoustic Resonator (FBAR) technology įBAR is special case of QCM with piezoelectric films thicknesses ranging from only several micrometers down to tenth of micrometers using MEMS technology. The operation frequency of the SAW device ranges from the MHz to GHz range, mainly depending on the interdigital transducer’s design and piezoelectric material :į r e s = V R λ -shear modulus of piezoelectric material Surface acoustic wave (SAW) and bulk acoustic wave (BAW) are two most commonly used technologies in sensor applications. Compressional waves (also called P wave) are waves in which the displacement of the particle is along the same direction as the propagation direction of the wave. Shear waves (also called S wave) have particle displacements that are normal to the direction of wave propagation, as for surface water waves. Mechanical waves for sensor applications are of two different types: shear waves and compressional waves. If the wave propagates on the surface of the substrate, it is known as a surface wave and if wave propagating through the substrate is called a bulk wave. Piezoelectric acoustic wave devices are described by the mode of wave propagation through or on a piezoelectric substrate. Conventional piezoelectric materials includes quartz, LiNbO3, AlN and LiTaO3.Īcoustic Wave Propagation Modes Piezoelectric materials provide the transduction between electrical and mechanical response conversion of electrical signal into mechanical acoustic waves and vice versa. Acoustic waves sensors use piezoelectric materials to generate and detectĪcoustic waves. Changes in velocity/amplitude can be monitored by measuring the natural frequency or phase characteristics of the sensor, which can then be correlated to the corresponding physical or chemical quantity being measured. Changes to the characteristics of the propagation path affect the velocity and/or amplitude of the wave. An acoustic wave is excited and propagates through or on the surface of the material. Their detection mechanism is based on acoustic wave propagation. They have many applications for pressure, chemical concentration, temperature or mass sensors. Piezoelectric Acoustic Wave technologies have been used for over 60 years. 3.2.2 Thin-film Bulk Acoustic Resonator (FBAR) technology.3.2.1 Quartz Crystal Microbalance (QCM) technology.
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