Recent Progress in Polymeric Flexible Surface Acoustic Wave Devices: Materials, Processing, and Applications

Recently, there has been a remarkable increase in interest in piezoelectric thin films, particularly zinc oxide (ZnO) and aluminum nitride (AlN), deposited on flexible polymeric substrates. This is due to the rapid expansion of fields such as robotics, wearable devices, and the Internet of Things (IoT). These thin-film layered structures have a wide range of applications, such as energy harvesting, sensing and biosensing, microfluidic sorting, pumping and mixing, and telecommunications. One of the most promising platforms is piezoelectric acoustic-based thin-film devices on inexpensive, recyclable, or disposable polymeric substrates. Their reliability, reproducibility, conformability, small size, and wireless control capabilities make them a leading candidate for the development of new wireless, fully automated, and digitized microsystems for IoT and wearable devices. This review examines recent advancements in the engineering of ZnO and AlN thin films on polymeric, flexible, and conformable surface acoustic wave (SAW) devices. Topics covered include the materials used, piezoelectric film deposition, device fabrication, and the latest applications of this technology as sensors and actuators.