In this work, we have developed a family of planar micro-thermoelectric generators (μTEGs), integrating a novel 2.5D thermopile topology periodically folded and distributed onto a multi-membrane, capable of converting heat directly into useful electrical energy. This novel kind of thermopile presents a high integration density, and uses thermocouples based on metallic thermoelectric materials (Chromel and Constantan) that are electrically associated either in series or in parallel. All these characteristics allows to reduce drastically the internal electrical resistance compared to our former family of μTEGs (by a factor of 1/1000, down to a hundred Ohms). A 3D thermal modelling in COMSOL Multiphysics® was used to design the optimal dimensions of the modules so they would deliver the maximum output power. The fabrication of these devices is made by CMOS-compatible processes. The harvesting of one Watt of heat leads to thermo-generated electrical powers of a few hundred microwatts.