Abstract: A micromechanical pressure relief valve arrangement comprises a stack of wafers. An active pressure relief valve is realized within the stack of wafers. A passive pressure relief valve is also realized within the stack of wafers, arranged in parallel to the active pressure relief valve. A check valve, also realized within the stack of wafers, is arranged in series with both the active pressure relief valve and the passive pressure relief valve.

Abstract: A filter comprises a stack of wafers (28). Each of the wafers has a through hole (6). Edges (7) of the holes together define an internal tube. An interface (32) between adjacent wafers defines filter channels. The filter channels comprises first coarse filter channels (20), second coarse filter channels (22) and fine filter channels (26). The first coarse filter channels are open towards an outer rim (5), extend in a direction from the outer rim and are closed towards the internal tube. The second coarse filter channels are arranged in an opposite manner. The fine filter channels connect the first and second coarse filter channels. The first and second coarse filter channels extend radially (R) and the fine filter channels extend tangentially (T). The first and second coarse filter channels are defined by recesses in a surface of a first wafer and the fine filter channels are defined by recesses, each one encircling the hole, in a surface of a second wafer.