Surface acoustic wave (SAW) devices

CO2 and SO2 Interactions with Methylated Poly(ethylenimine)-Functionalized Capacitive Micromachined Ultrasonic Transducers (CMUTs): Gas Sensing and Degradation Mechanism

“…Resonant gravimetric detection − is more amenable toward miniaturization and integration into the equipment by using little power while still maintaining the required sensitivity and selectivity . Some gravimetric detection methods have proven to be useful in many applications with numerous methods developed including quartz crystal microbalances (QCM), film bulk acoustic resonators (FBARs), surface acoustic wave (SAW) sensors, − micro- and nanocantilevers, − and capacitive micromachined ultrasonic transducers (CMUTs). ,− QCM is a low-cost, real-time measurement technique with the limit of quantification (LOQ)the lowest concentration of the analyte in a sample that can be quantifiedranging from 0.001 to 0.5 Hz/ppm with signal-to-noise (SNR) ranging from 1 to 300. Unlike QCMs, FBARs use shear wave excitation on bulk machined freestanding resonance structures, such as microbridges, microplates, and microcantilevers with thin piezoelectric films.…”

Lithium Niobate MEMS Antisymmetric Lamb Wave Resonators with Support Structures

“…Currently, predominant commercial solutions include surface acoustic wave (SAW) resonators and thin-film bulk acoustic wave resonators (FBARs), which are known for their high performance and cost-effectiveness [1,2]. However, conventional SAW devices, fabricated using bulk lithium niobate (LiNbO 3 ) or lithium tantalate (LiTaO 3 ), encounter challenges in achieving ultra-high frequencies because of limitations on electrode width and the relatively low phase velocity (v) of acoustic modes propagating through the piezoelectric substrates [3,4]. While the resonance frequency (f s ) of FBARs is primarily determined by their thickness, allowing for an increase in f s by merely reducing the thickness of the electrode and piezoelectric layer, this reduction in thickness inevitably leads to compromised deposition quality and increased ohmic loss [5,6].…”

Methylated Poly(ethylene)imine Modified Capacitive Micromachined Ultrasonic Transducer for Measurements of CO2 and SO2 in Their Mixtures

“…Some of these have already been used for different applications and have the potential for integration into mobile applications. Some examples of such sensors based on resonant gravimetry include film bulk acoustic resonators (FBARs) [12,13,14], quartz crystal microbalance (QCM) [15,16,17,18], surface acoustic wave (SAW) sensors [19,20,21,22], micro and nanocantilevers [23,24,25,26,27] and Capacitive Micromachined Ultrasound Transducers (CMUTs) [28,29,30,31,32,33]. CMUTs can be fabricated in different sizes and shapes with optimized features fulfilling needed mass sensitivity of the resonator, the limit of detection and signal to noise ratio (SNR).…”