Table 1.
An overview of high frequency acoustic devices for chemical/biochemical sensor applications. The acoustic wave type, operating frequency, sensitivity, nature of piezoelectric materials, dielectric constants, acoustic wave velocity, temperature coefficient of frequency, working medium, availability, manufacturing costs, commercial success and general comments are described briefly.
| Quartz Crystal Microbalance (QCM) | Surface Acoustic Wave (SAW) | Film Bulk Acoustic Resonator (FBAR) | |
|---|---|---|---|
| Acoustic Wave Type | Bulk | Surface | Bulk |
| Operating Frequency | 5–200 MHz | 100–1500 MHz | 1.0–4.5 GHz |
| Sensitivity | Low | Intermediate | High |
| Common Piezoelectric Materials | Quartz | Quartz, LiNbO3, LiTaO3 | AlN, ZnO |
| Dielectric Constant | Quartz = 3.8 | LiNbO3 = 29 LiTaO3 = 43 |
AlN = 8.5 ZnO = 8.8 |
| Acoustic Wave Velocity (m/s) | Quartz = 3158 | LiNbO3 = 3488–3992 LiTaO3 = 3230–3394 |
AlN = 5600 ZnO = 2558 |
| Temperature Coefficient of Frequency (TCF) (ppm/°C) | Quartz ≅ 0 | LiNbO3 = 75–94 LiTaO3 = 35–64 |
AlN = 25 ZnO = 40 |
| Working Medium | Liquids and Gases | Gases | Liquids and Gases |
| Availability | Common and Easily Available | Common and Easily Available | Not Easily available |
| Manufacturing Costs | Low | Moderate | High |
| Commercial Adaptability | Medium | High | - |
| General Comments | Most common and widely used acoustic transducer for sensor applications. QCMs have low fabrication costs. But has comparatively low sensitivity due to low resonance frequency. | Well known and widely used for gas phase sensor applications and found a number of commercial applications. However, not commonly used for liquid phase sensing. | Highly sensitive acoustic transducer for gaseous and liquid phase sensing. Not commonly available as advance fabrication techniques are need for their manufacturing thus, has high costs. |