Patterning of thin film strain gauges on 3D-surfaces

Metal thin film strain gauges applied directly on the surface of components offer good long term stability even in harsh environments and at elevated temperatures. They consist of vacuum deposited isolation and sensing films. A direct-write laser patterning process based on picosecond laser pulses has been developed to overcome the restriction to 2D-surfaces caused by photolithographic patterning. We present results of tensile test of strain sensors patterned in v-notches milled in aluminum samples. The thermal coefficient of resistance (TCR) and the gauge factor are not affected by Laser patterning of conductor widths of 13 μm and larger. Therefore, the developed process is suitable to pattern miniaturized thin film strain gauges on D-surfaces.
Due to the exploration of 3D-surfaces, the prerequisite for new sensing methods has been created to develop new applications which require the patterning of sensors on curved surfaces, such as bearings and shafts. The direct-write pproach enables cost reductions for patterning of individualized products, such as medical implants.