Surface acoustic wave (SAW) devices are used in many distinct application areas, which include electronics, microelectromechanical (MEMS) sensors or even microfluidic lab-on-a-chip (LoC) devices. The electrode geometry usually exhibits a narrow frequency band response – this can be directly utilized in radio frequency filters or oscillators. As the wavespeed of the acoustic wave propagating on the surface of a material is extremely sensitive to changes in material properties, such as temperature, pressure or mass loading due to foreign substances, SAW sensors can be designed for these modalities. Deformation and elongation of a cantilever structure changes propagation delay between a set of transducers – thus an accelerometer is realizable. Surface waves can be coupled into fluid-filled microchannels generating forces; a promising application for lab-on-a-chip devices.

In the previous two blog posts the physical basis of piezoelectricity and the main groups of materials were presented, focusing on the selection of a material for a specific purpose. In this blog post we discuss in what configuration piezoelectric materials can be used and illustrate some example device structures.

In the previous blog post a grouping of piezoelectric materials was given into three categories: crystalline structures, engineered perovskite-like ceramics, and polymers. In this blog post a comparison of these groups is provided to aid the reader choosing a suitable material for a specific application.

In this first blog post of the piezoelectrics series, a brief overview is provided on the fundamentals of the phenomenon. Piezoelectric materials allow conversion of energy from the mechanical domain to the electrical domain and vice versa. They can be used to create various sensors or actuators: applied periodic electrical signal can result in the generation of ultrasonic waves for imaging purposes; stresses, such as observed for a cantilever suspending a mass in an accelerometer can be translated to electrical signals.

Traditional high data rate communication realized by electric components – such as A/D converters, encoders, modulators, amplifiers, processors and similar integrated circuits – faces a challenge as further increase of frequency would result in cooling problems due to the generated amount of thermal energy in the form of Joule heating. An alternative approach is light-based information transfer in guided structures, such as optical fibers. However, optical fibers occupy relatively large spaces due to the limited minimum size of bends allowed by the small refractive index difference between the wave guiding core and the outer cladding.