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In this paper, a set of flexible aeroMEMS sensor arrays for flow measurements in boundary layers is presented. The
sensor principle of these anemometers is based on convective heat transfer from a hot-film into the fluid. All sensors
consist of a nickel sensing element and copper tracks. The functional layers are attached either on a ready-made
polyimide foil or on a spin-on polyimide layer. These variants are necessary to meet the varying requirements of
measurements in different environments. Spin-on technology enables the use of very thin PI layers, being ideal for
measurements in transient flows. It is a unique characteristic of the presented arrays that their total thickness can be
scaled from 5 to 52 μm. This is essential, because the maximum sensor thickness has to be adapted to the various
thicknesses of the boundary layers in different flow experiments. With these sensors we meet the special requirements of
a wide range of fluid mechanics. For less critical flow conditions with much thicker boundary layers, thicker sensors
might be sufficient and cheaper, so that ready-made foils are perfect for these applications. Since the presented sensors
are flexible, they can be attached on curved aerodynamic structures without any geometric mismatches. The entire
development, starting from theoretical investigations is described. Further, the micro-fabrication is explained, including
all typical processes e.g. photolithography, sputtering and wet-etching. The wet-etching of the sensing element is
described precisely, because the resulting final dimensions are critical for the functional characteristics.
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