This paper deals with the design of a compact, generic membrane structure suitable for vibration energy harvesting (VEH). A hybrid fluid diaphragm architecture is proposed. It allows the resonant frequency to match the classical low frequencies ambient excitations to be harvested. A semi analytical model has been developed and validated so the proposed structure can be easily tuned for a given application. The next step will consist in designing a piezoelectric structure which will be integrated to the HFD.