Printed Miniature Loudspeaker
It has six corners and is about the size of a 1-cent piece: In an additive manufacturing process, miniature loudspeakers can be produced efficiently and cost-effectively as part of piezoelectric microelectromechanical systems.
Piezoelectric microelectromechanical systems, so-called piezo-MEMS, are true technical all-rounders because the ultra-thin piezoelectric layers fulfill actuator or sensor functions: Either they expand when an electric field is applied or they convert mechanical motion into electrical voltage. Accordingly, they are in demand in communications or medical technology, for example, as sensors or actuators in pumps, valves or loudspeakers – in each case in miniature format. The thin films are usually made of lead zirconate titanate (PZT), currently the most powerful and functional piezoelectric ceramic. Preferably, piezoelectric layers with a thickness of a few μm are used, which can be structured very precisely by etching or direct printing.
Laser-assisted printing processes
Until now, conventional vacuum and mask-based manufacturing methods have been used to produce piezo-MEMS, but these methods are very time-consuming and cost-intensive, especially for the manufacture of small batches. As part of the Generator project, Fraunhofer ILT, together with other partners, developed a process combination of digital inkjet printing and laser crystallization as a favorable alternative.
A multilayer actuator with a total layer thickness of 2 to 3 µm was built out of several 20 to 30 nm thin PZT layers. Thanks to this design, the actuator is said to offer better performance and higher reproduction quality than conventional actuators.