A Cr-N thin film displacement sensor for precision positioning of a micro-stage

A Cr-N thin-film displacement sensor with a millimeter-scale measurement range is proposed for nanometric positioning of a developed micro-stage. The sensor was designed in a compact size of 14 mm (L) × 1 mm (W) × 0.1 mm (T). A leaf spring made of zirconium oxide, which was employed as the support and guideway of the moving plate in the micro-stage, was employed as the substrate of the sensor. The Cr-N thin film was sputtered directly on one side of the leaf spring to form a Wheatstone bridge circuit with four active strain gauges. Based on the finite element method (FEM), it was verified that both tensile and compressive strains could be generated on the same side of the leaf spring. In order to arrange the strain gauges at the appropriate strain areas of the leaf spring, the relationship between the geometric parameters and the strain distribution of the leaf spring was also investigated by FEM. Experimental results have indicated that the developed sensor had a good linearity and a high sensitivity, which would be applicable for detection of the nanometric displacement of the micro-stage.