Wiring up Liquid Metal: Stable and Robust Electrical Contacts Enabled by Printable Graphene Inks

Gallium-based liquid metal alloys (GaLMAs) are a unique class of advanced materials with the potential to offer unprecedented opportunities in stretchable and reconfigurable electronics. Despite their promise, the development of liquid metal electronics must overcome several challenges for widespread application. In particular, stable electrical contacts have been identified as a critical challenge for the integration of GaLMAs in electronic circuits and systems. Since gallium alloys rapidly with most metals, GaLMAs lead to unstable or mechanically sensitive interfaces when combined with metal electrodes or interconnects, thereby preventing the reliable integration of eutectic gallium-indium (eGaIn) functionality with conventional electronics. Here, printed graphene is demonstrated as a reliable and high-performance interfacial layer to enable electrical connections to eGaIn. A thin film (≈100 nm) of graphene printed between conventional silver leads and eGaIn acts as a physical barrier, effectively passivating the surface against alloying while retaining the ability to conduct current across the interface. Moreover, graphene interfacial contacts offer excellent durability, with thermal stability to 300 °C, robust tolerance to mechanical bending, and chemical inertness. By leveraging this unique strategy to stabilize liquid metal contacts, a reconfigurable liquid metal electrical switch is fabricated with significantly improved longevity.