Using Thermal Spray and Laser Micromachining to Fabricate Sensors

The use of thermal spray to fabricate sensors directly onto engineering components is an emerging technology. The capabilities for sensor fabrication are considerably enhanced with the use of laser micromachining, in which feature sizes as small as 15-20 μm can be achieved. Such feature sizes are required for a variety of sensors, including strain and heat flux sensors, thermopiles and microheaters. Ultrafast lasers—lasers with pulse durations ≲1 ps—are particularly well suited for the multimaterial/multilayer processing required to fabricate sensors from materials deposited using thermal spray. In this work, the key issues associated with laser micromachining of thermal spray coatings for sensor applications are presented. Both resistive strain gages and microheaters are discussed in detail as representative sensor designs that require the fine feature and linewidth capability that laser micromachining provides, including details of their fabrication and practical design restrictions. This article summarizes with recommendations for future work.