Liquid Metal Spreading on Metallic Surfaces Suppressed by Carbon Nanotubes

Abstract

Gallium-based liquid metal alloys, particularly eutectic gallium-indium (eGaIn), are widely utilized and have become key materials in producing soft, stretchable devices due to their high conductivity and fluidity at room temperature. However, the extensive application of eGaIn is hindered by its selective wettability, adhesion to specific surfaces, and wetting-induced spreading, which can lead to device failures. Gallium oxide, often a component in eGaIn, tends to adhere to various surfaces, causing embrittlement or dissolution of solid/metallic contacting parts. Therefore, understanding and controlling these interactions is crucial for practical applications. In this study, we present a straightforward method to suppress the spreading of eGaIn using carbon nanotubes (CNTs). We demonstrate that dispersing functionalized CNTs homogeneously in eGaIn suppresses its spreading on metallic surfaces. Additionally, the agglomeration of CNT bundles within the eGaIn influences the surface tension of the composite. A higher concentration of CNTs in the resulting CNT/eGaIn liquid-state composite inhibits spreading for up to 30 days. Employing the CNT/eGaIn interconnect as a proof of concept, we observed that this interconnect exhibits mechanical longevity and electrical stability, demonstrating the long-term stability of the device. Furthermore, this work elucidates the general mechanism in the reaction-diffusion-spreading process for gallium-based liquid metal alloys and metal (eGaIn-Pt) systems. In this system, CNTs act as an inhibitor, restricting gallium diffusion and spreading. This study proposes an alternative method for controlling the wetting and spreading of eGaIn using CNTs on metallic surfaces