Numerical and experimental analysis of the effect of metal tie layers on improving electrical properties of gold coated poly (dimethylsiloxane) flexible multi-layered films during folding

To improve folding electrical properties of flexible electronics, this study presents a new adhesive stress analysis of depositing an adhesion layer between the conductive film electrode and the flexible substrate during folding test by a folding test platform. The folding test platform controls folding curvature of the flexible conductive substrates, folding times, and velocities in this study. Moreover, the electrical properties of flexible conductive substrates are measured during folding testing by the folding test platform. Eventually, this study successfully analyzes residual strain, adhesive stress, and electrical properties of flexible gold coated on polydimethylsiloxane substrates with chromium, nickel, and titanium adhesion layers up to 0.5/cm folding curvature during folding testing. The chromium adhesion layer had the best performance based on the largest adhesive stress, only 3.74 Ω resistance increase and 4.53 Ω maximum resistance up to 0.5/cm folding curvature during folding test by a folding test platform. The experimental result with chromium adhesion layer is consistent with adhesive stress analysis and provides a better adhesive strength between gold and polydimethylsiloxane than nickel and titanium materials for folding test. Therefore, adhesive stress analysis is adapted to evaluate the foldable electronics performance for improving folding characteristics easier.