Direct Visualization of Cross-Sectional Strain Distribution in Flexible Devices

For flexible devices that inevitably undergo repetitive deformations, it is important to evaluate and control the mechanical strain imposed on the flexible systems for enhancing the reliability. In this paper, a novel experimental method to directly visualize cross-sectional strain distribution in the thin flexible devices is proposed. Digital image correlation (DIC) is effectively adapted by using microscopic images of the cross section for accurate analysis of the microscale deformations. To conduct the DIC strain analysis, speckle patterning is accomplished by using microparticles from diamond-abrasive suspensions with optimized fabrication conditions. First, the cross-sectional micro-DIC analysis is performed successfully for 100 μm-thick substrates. Full-field strain quantification and easy inspection of a neutral plane are demonstrated and compared with results of finite element analysis simulation. Using the presented method, generation of multiple neutral planes is clearly visualized for a trilaye...