  We report on an optimized micro-machined thermal flow-rate sensor as part of
an autonomous multi-parameter sensing device for water network monitoring. The
sensor has been optimized under the following constraints: low power
consumption and high sensitivity, while employing a large thermal conductivity
substrate, namely silicon. The resulting device consists of a platinum
resistive heater deposited on a thin silicon pillar ~ 100 $\mu$m high and 5
$\mu$m wide in the middle of a nearly 100 $\mu$m wide cavity. Operated under
the anemometric scheme, the reported sensor shows a larger sensitivity in the
velocity range up to 1 m/s compared to different sensors based on similar high
conductivity substrates such as bulk silicon or silicon membrane with a power
consumption of 44 mW. Obtained performances are assessed with both CFD
simulation and experimental characterization.
