Design, Modeling and Validation of a Flexible Strain Sensor Based on Moire Patterns and Image Processing

This paper reports a new flexible strain sensor using the moire pattern as the transducing signal, which can be used to map the strain/stress on a planar surface or a curved surface. Different from our previously reported flexible strain sensor based on the nanopore thin film, which uses the reflected optical signal as the transducing signal. This type of strain sensor has the following unique features: one grating (G1) is fabricated on a flexible substrate, the other grating (G2), which has a slightly different pitch, is simply stored in a computer. Images of G1 under different strains/stresses are taken using a smartphone camera. Then moire patterns are formed by superimposing the images of the two gratings (G1 and G2) in a computer. Finally, the strain/stress is determined by feature extraction of the moire patterns using image processing.