  Flexible electronic systems such as roll up displays, wearable devices etc.
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 using methods that
either use relatively rare materials, change conventional interconnect
fabrication processes, only address 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 using a 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 copper-silicone oil dispersions, we
show self healing interconnects with the stretchable heal having conductivity
of about $5 \times 10^{5}$ Sm 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.
