A high-frequency, high-stiffness piezoelectric actuator for microhydraulic applications

A piezoelectric actuator capable of high-frequency, high-stiffness actuation in microhydraulic systems was fabricated and experimentally characterized to frequencies in excess of 100 kHz. This high-frequency, high-stiffness actuation is enabled through integration of bulk piezoelectric cylinders (1 mm×1 mm) beneath a silicon micromachined tethered piston structure using a thin-film AuSn eutectic alloy as the piezoelectric-to-silicon bond layer. The actuator structure, with dimensions 10 mm×10 mm×2 mm, is comprised of a bonded stack of micromachined silicon, silicon-on-insulator (SOI), and borosilicate glass layers. Devices were successfully fabricated and tested that incorporate polycrystalline PZT-5H and single-crystal PZN-PT piezoelectric material arranged in different configurations. The microfabrication, device assembly, experimental testing procedures, and actuator performance are discussed in this paper. Issues such as piezoelectric material preparation, requisite dimensional tolerancing, micromachining of the silicon tethered structures, and integration of different arrangements of piezoelectric elements within the actuator structure are detailed