AF: Thick-Film Piezoelectrics for MEMs: Optimisation & Applications

This proposal follows on from a recent ROPA investigation into the combination of thick-film piezoelectrics (PZT) and silicon micromachining for MEMS applications. The ROPA investigation successfully optimised the combined processing techniques and MEMS devices have been fabricated using this approach. This proposal addresses the main disadvantage of thick-film PZT layers, namely the relatively poor minimum feature size possible with thick-film printing techniques. Reducing the feature size will enable smaller MEMS devices to be fabricated incorporating thick-film printed piezoelectrics. This will reduce the unit cost of such devices and enable the thick-film printed PZT material to be used in a much wider range of applications. In addition, the proposed research aims to improve the mechanical and piezoelectric properties of the printed PZT layer by investigating isostatic pressing. Hot and cold isostatic pressing, whereby the PZT layer is compressed from all sides at both elevated and room temperatures, will be evaluated. Isostatic pressing will result in a densified film with improved mechanical properties and coupling to the substrate. The denser material will also be able to be poled at higher field strengths thereby increasing the piezoelectric activity of the material. To demonstrate the benefits of these developments, an accelerometer will be fabricated similar to the device developed during the ROPA investigation. The two devices will then be compared directly. In addition, an active microvalve for microfluidic applications will also be designed and fabricated. This will be integrated on a microfluidic circuit board providing an essential component within this complete integrated microfluidic system. It is intended to obtain industrial interest in the research during the duration of the project and it is likely this will influence the design of the demonstrator.