In-plane and out-of-plane structural response of spiral interconnects for highly stretchable electronics

Stretchable electronics are commonly used as a diverse class of interconnected architectures, which accommodate large strain during stretching. A systematic understanding of the underlying mechanism of these interconnects, i.e., stress/strain states is essential to optimize the spiral designs. Here, we demonstrate the in-depth structural response of the spiral-island system when subjected to in-plane and out-of-plane stretchings. We use numerical modeling to simulate the stresses and strains along the arm of the spiral when stretched at a prescribed displacement of 1000 μm. We show the strain contours for spirals connected in-series. Our results show that the additional spirals connected in-series share the prescribed displacement equally and thus lower the von Mises stresses and principal strains. We also compare the stress generated in arms for single spiral and triangular configurations, especially when we stretch out these configurations in-plane and out-of-plane. The evolved stress depends on the angular position of spirals for triangular configuration. For the out-of-plane case, we stretch the spirals vertically and diagonally outward, i.e., along the z direction and x-z directions, respectively. Our results show that spirals experience higher stress during stretching along the x-z direction. However, for the out-of-plane z direction stretching, the spiral's end, which is connected to the island, experiences higher stress as compared to that of x-z direction case. We use 3D printing to additively manufacture the replica for single spiral and triangular configuration and perform the tensile out-of-plane stretching. Our experimental results for elongations corroborate with numerical calculations.