The objective of the project was to develop and manufacture µSJA based on silicon technologies. To reach the required output velocities of the µSJA, the chamber and the exit channel or nozzle were optimised using different analytic and numeric methods. Based on the results of the optimisation, a design was investigated and transferred to silicon based structures. The production of the µSJA was performed in the clean rooms of the ZfM and realized on wafer-level. The two different parts of the µSJA, the cavity and the diaphragm were micro-machined and wafer bonded in order to form the actuator. The diaphragm-wafer’s backside was wet etched in order to produce a membrane in two different thicknesses, 40 µm and 70 µm. The cavity-wafer in contrast, was prepared by a sequential etching process with the same etchant. In the first step the orifice was preliminary etched with a depth of 400 µm. The second step equated the continuing etching of the orifice and the production of the cavity geometry. The achievements of these two processes were 3D nozzle structures of the orifice in a required aspect ratio and a very small cavity, resulting in a higher pressure gradient which leads to a much higher jet velocity compared to a dry anisotropic etched orifice combined with a huge cavity. This created the main advantage compared to known layouts.

Then, the two parts were bonded to form a small cavity with an orifice on the one side and a diaphragm on the opposite side. Finally, the piezo disc was mounted on the back side of the diaphragm into the wet etched cavity. To integrate the electro mechanical transducer, in this case the PZT element, into the system, reactive bonding technologies for the use of PZT silicon bonding were investigated. Thus, the strength of the low temperature bond of the ceramics, concerning low inducted mechanical stress, can be optimised.