Highly Reliable Liquid Metal–Solid Metal Contacts with a Corrugated Single‐Walled Carbon Nanotube Diffusion Barrier for Stretchable Electronics

Liquid metals (LMs) are a special case of metals that exist in a liquid at room temperature, making them one of the most attractive conductive materials in stretchable electronics. In many cases, however, the LM attacks other metals in contact with the LM through penetration, embrittlement, and alloying. To address these critical issues, there have been efforts to introduce robust barriers, which can preserve the underlying metals without degradation. For example, graphene is employed as a flexible barrier owing to its chemical inertness and impermeability. Nevertheless, this material is difficult to utilize in stretchable electronics because its defects result in inevitable fracture, even at a low strain (< 6%). In addition, it is a challenge to pattern the graphene layer on the point‐of‐interest area in a facile manner. Herein, it is shown that the insertion of single‐walled carbon nanotubes (SWCNTs) at the liquid metal–solid metal interface provides a proper barrier for LM under large deformation conditions. A tangled 1D structure of the SWCNTs formed from a solution process greatly suppresses the crack generation/propagation and maintains conductivity even under large strains, which facilitates the use of SWCNTs as stretchable barriers with long‐term reliability through the introduction of a corrugated structure. A corrugated single‐walled carbon nanotube (SWCNT)/silver nanoparticle (AgNP) bilayer is introduced as a stretchable and impermeable diffusion barrier to prevent eutectic gallium–indium (EGaIn) penetration at liquid metal‐solid metal contacts. The SWCNTs effectively prevent EGaIn from migrating from the contact and extend the lifetime of the AgNP film. The corrugated structure of the film allows the utilization of the liquid metal for stretchable electronics with long‐term reliability.