Micro sensor systems for aeronautical application in harsh environment

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Mankind's increasing desire for mobility has led to growing air traffic which is associated with increasing burdens on the population and the environment. Technical solutions are sought to considerably reduce noise and pollutant emissions. A high-lift system can reduce flow-induced noise, since it provides sufficient lift for a safe flight even at lower speeds, thereby reducing noise near airports. Actively controlled high lift systems require local sensing of flow and pressure as feedback. Miniaturized sensors with smallest space requirements can be integrated evenly distributed in airfoils and provide local information on the fluid pressure and wall shear stress. However, the harsh conditions during high-lift experiments in a water tunnel as well as in future aircraft operation require a special protection. For wall shear stress measurements, a fully flexible, 7 μm thin hot-film sensor based on polyimide foil substrate is adapted for the application in water. For pressure measurements, a surface passive sensor concept leading to a flip-chip mountable piezoresistive sensor with a flat and waterproof surface is developed. This completely new design is realized using innovative manufacturing processes such as femtosecond laser ablation of glass. Both types of sensors are combined to form an integrated sensor system including amplification electronics to be used in water. It enables the measurement of pressure and wall shear stress at nearly the same location. Furthermore, a flexible, foil-like sensor system for combined pressure and wall shear stress measurements is manufactured and investigated.