Mechanical reliability of self-similar serpentine interconnect for fracture-free stretchable electronic devices

Abstract

Currently, silicon (Si)-based island–interconnect structures are emerging in next-generation stretchable electronic devices such as flexible medical implants, soft robotics, and wearables. Various geometrical designs are being used as interconnects for promising stretchable electronic systems. Among them, self-similar serpentine interconnects (SS-interconnects) are widely used due to their high areal efficiency and stretchability. However, to date, pertinent devices choose random parameters of SS-interconnects since the detailed design guidelines are still elusive. Additionally, no study has revealed how the lateral size or width affects the stretchability during in-plane and out-of-plane stretching. Here, we show how the mechanics could help get the optimized Si-based SS-interconnect without losing its areal efficiency. Our numerical and experimental results show that thin interconnects attain 70%–80% higher stretchability than thicker counterparts. The numerical and experimental results match well. Numerical results indicate the areas prone to break earlier, followed by experimental validation. We devise how induced stress could predict the fracture conditions for any given size and shape of an interconnect. Our results demonstrate that the larger width plays a crucial role in out-of-plane stretching or rotation, i.e., the stress values are 60% higher for the larger width of SS-interconnect during rotation (up to 90°). Our calculations reveal the fracture-free zone for SS-interconnects, showing the figure-of-merit. We demonstrate the detailed guidelines that could help choose the right parameters for fracture-free SS-interconnects for required stretchability, devising the next-generation stretchable and wearable electronic devices.