#1.4 Objectives of this work
The state of the art presented above enables to show the
#Requirements for wall-mounted wall shear stress sensors
Therefore, considering the current state of the art in WSS sensors and SiC MEMS devices, an ideal technological process must meet at least the following three constraints to realize a thermal wall shear stress sensor.
Electrical insulation of the active elements. Because a thermal anemometer is electrically heated, the sensing material should be made with a completely electrically insulated pattern. In a calorimetric design, this applies to the surrounding measurement resistors too.
Free-standing structures. In a similar manner to the current insulation, the heating and sensing elements should also be thermally insulated from the substrate. Because end-conduction effects are unavoidable and can only be minimized by reducing the thermal conductivity of the material itself, the contact area with the substrate should be as small as possible.
Flexibility in design. In order to make the process iterable toward more complex architectures, the active elements should be easy to place in the design. Particularly, to make a calorimeter, three wires should be placed in close proximity.