Ultrafast Laser Patterning of Thin Films on 3-D Shaped Surfaces for Strain Sensor Applications

A femtosecond laser patterning process of thin film sensors on component surfaces is reported. This method is particularly useful for patterning of strain sensors which are sputter deposited directly on curved surfaces. The ablation behavior of NiCr film irradiated by femtosecond laser pulses at non-normal angles of incidence is modeled and experimentally verified with linear and circular beam polarization for incidence angles up to 80. It is shown that the ablation threshold behavior can be described when including polarization and angle dependent Fresnel reflection into the laser ablation model. The laser process is finally demonstrated by patterning NiCr thin film sensors on a non-planar surface of a mechanical component for a machine tool.