Self-healing Interconnects with Nearly Plastic Stretching of Repairs

Abstract

Flexible electronic systems such as roll-up displays and wearable devices promise exciting possibilities that could change the way humans interact with the environment. However, they suffer from poor reliability of interconnects and devices. Interconnects on flex are prone to open-circuit failures due to mechanical stress, electrostatic discharge, and environmental degradation. Passive approaches such as the use of stretchable conductors and novel geometries improve their response to mechanical stress but cannot salvage the interconnect if a fault were to occur. Active approaches using self-healing techniques can repair a fault and have been demonstrated with use of methods that use relatively rare materials, change conventional interconnect-fabrication processes, address only faults due to mechanical stress, or do not permit stretching. In this work we discuss a self-healing technique that overcomes these limitations and demonstrate heals having metallic conductivity and nearly plastic stretchability. This is achieved by dispersion of conductive particles in an insulating fluid encapsulated over the interconnect. Healing is automatically triggered by the electric field appearing in the open gap of a failed interconnect, irrespective of the cause of failure. The field polarizes the conductive particles, causing them aggregate and chain up to bridge the gap and repair the fault. Using dispersions of copper microspheres in silicone oil, we show self-healing interconnects with the stretchable heal having conductivity of about 5 × 10 5 S/m and allowing strains from 12 to 60. Previously, stretchable interconnects used materials other than copper. Here we effectively show self-healing, stretchable copper. This work promises high-speed, self-healing, and stretchable interconnects on flex, thereby improving system reliability.