It is well known that Strain gauges are commonly used for Non-destructive Testing (NDT) and Structural Health Monitoring (SHM) in various fields such as automotive, aerospace, robot and electronic industries. To monitor the structural health exactly, the strain gauge must be transformed conformally on the 3D surface of the structure. However, the conventional 2 dimensional strain gauges cannot be conformally transformed to free-form 3 dimensional surfaces.
In this work, we have fabricated a strain gauge directly on curved surfaces using 3D printing technique. We have formulated shear-thinning conductive inks to prevent inks from flowing down during the printing process. After that, we uniformly printed the inks along curved surfaces of the structure by controlling the distance between a dispensing nozzle and curved surfaces, printing speed and applied pressure. The printed pattern was locally sintered by using 808 nm diode laser in order to prevent damages of the base structure during sintering process. To investigate the feasibility of the strain gauge as a sensor to measure deformation of a structure, we evaluated changes in resistance of the strain gauge depending on the strain applied to the structure.