Recent Progress in Materials Issues for Piezoelectric MEMS

Abstract

Piezoelectric materials play a crucial role in a large number of devices and applications modern society would not like to miss. Mobile phones and ultrasonic imaging are just the most prominent ones. Since two decades, miniaturization of mechanical devices in silicon technology is a major research direction in engineering known under name of MEMS, which stands for micro-electro-mechanical systems. Piezoelectricity fits very well into this concept and was expected right from the beginning to play its role in MEMS. The breakthrough was made with RF filters in mobile phones working on the principle of standing thickness waves in AlN films. What counts here is acoustic quality and stability. The force champion among piezoelectric thin film materials, Pb(Zr,Ti)O 3 gave more problems in processing, and requires more patience to meet requirements and needs for a mass applications. It seems, however, that the breakthrough is imminent. This article attempts to give an overview of the field, highlighting recent achievements, introduce operation principles, and describe some applications.

Piezoelectric MEMS for energy harvesting

“…76 The piezoelectric coeffi cient of both KNN and PZT fi lms showed almost the same value of e 31,f = −10 C/m 2 . 77 The relative dielectric constants of the KNN and PZT fi lms were 744 and 872, respectively. Measurements were performed at the resonance frequency of each cantilever (KNN: 1.0 kHz, PZT: 0.89 kHz; acceleration 10 m/s 2 ).…”

Ultrasound assisted particle and cell manipulation on-chip

“…However, both of these are relatively expensive materials so they point towards the possibility to use a separate sterile microfluidic component, such as a capillary, to reduce the cost of disposal and replacement for each biological sample [30]. It is also possible to integrate piezoelectric materials in thick [53] or thin film [54,55] form, or indeed bonded bulk material [56], with other components. Requiring an additional level of fabrication sophistication, typically including photolithography [57], this approach may be very useful when the number of devices is high and may be a key issue in differentiating acoustic manipulation from optical manipulation [58], where integration is still much harder.…”

Electrohydrodynamic jet printing of PZT thick film micro-scale structures

“…Micro-electromechanical systems (MEMS) containing active piezoelectric components are of great importance in the fields of sensors, actuators and transducers [1][2][3]. The most commonly used piezoelectric material is lead zirconate titanate (PZT) because of its high piezoelectric constant, relative permittivity and electromechanical coupling coefficient [4].…”