  This paper introduces a thermal energy harvester turning thermal gradients
into electricity by coupling a bimetallic strip to an electret-based converter:
the bimetallic strip behaves as a thermal-to-mechanical power converter turning
thermal gradients into mechanical oscillations that are finally converted into
electricity with the electret. Output powers of 5.4uW were reached on a hot
source at 70{\deg}C, and, contrary to the previous proofs of concept, the new
devices presented in this paper do not require forced convection to work,
making them compatible with standard conditions of thermal energy harvesting
and environments such as hot pipes, pumps and more generally industrial
equipment. Finally, ten energy harvesters have been parallelized and combined
to a self-starting power management circuit made of a flyback converter to
supply a battery-free Wireless Temperature Sensor Node, sending information
every 100 seconds after its startup state.
