Hybrid‐type stretchable interconnects with double‐layered liquid metal‐on‐polyimide serpentine structure

We demonstrate a new double‐layer structure for stretchable interconnects, where the top surface of a serpentine polyimide support is coated with a thin eutectic gallium–indium liquid metal layer. Because the liquid metal layer is constantly fixed on the solid serpentine body in this liquid‐on‐solid structure, the overall stretching is accomplished by widening the solid frame itself, with little variation in the total length and cross‐sectional area of the current path. Therefore, we can achieve both invariant resistance and infinite fatigue life by combining the stretchable configuration of the underlying body with the freely deformable nature of the top liquid conductor. Further, we fabricated various types of double‐layer interconnects as narrow as 10 μm using the roll‐painting and lift‐off patterning technique based on conventional photolithography and quantitatively validated their beneficial properties. The new interconnecting structure is expected to be widely used in applications requiring high‐performance and high‐density stretchable circuits owing to its superior reliability and capability to be monolithically integrated with thin‐film devices.