Imbibition-Induced Autonomous Wetting of Liquid Metal

Gallium-based liquid metal alloys (GaLMs) are in liquid phase at room temperature and have the attractive properties, including high electrical/thermal conductivity, low toxicity, and high deformability, making them ideal for use in stretchable and deformable electronic pathways. Controlling the interfacial characteristics of GaLMs with underlying substrates is essential for depositing, printing, and patterning GaLMs. However, the high surface tension of GaLMs makes it difficult to create thin films with uniform height. We present an effective method for producing flat thin films and patterns of GaLMs, by introducing microstructured metallic features on which GaLMs rapidly and spontaneously spread in the absence of a native oxide. The enhanced wetting characteristics of GaLMs on the microstructured metallic surface are induced by imbibition, which enables large-area uniform coating and patterning of the liquid metal. The GaLM-coated polymer substrates prepared by the method maintain electrical connectivity even in a stretched state and after repetitive stretching cycles. The imbibition-induced wetting principle of the liquid metal provides several advantages: 1) coating and patterning GaLMs occurs spontaneously without external force, 2) the thermodynamically-favorable wetting of GaLMs forms stable metallic thin film, and 3) the thickness of the GaLM thin film can be well-controlled by varying heights of the metal-coated microstructures. This approach also reduces the amount of GaLM required for thin film formation, making it a cost-effective and efficient method for electronic applications.