Surface structural coloration and chromatic regulation of liquid metals by thermal oxidation processing

Dynamic color regulation is one of the most striking optical phenomena in nature. Many organisms regulate their surface micro-nano structures to control the interference and scattering of light, thereby exhibiting colorful physical appearances. Liquid metals (LMs) possess both metallic and fluid characteristics, demonstrating vast potential for various applications. However, the single silver-white appearance limits the application of LMs in optics. Herein, we propose a concept for achieving color display through the structural regulation of oxide layer on LMs surfaces. The LMs were placed in a thermally activated state, then oxide layers on their surfaces were mechanically stripped off to expose metal atoms. In the air, the surface atoms of LMs are oxidized, reconstructed and undergo phase transformation under thermal drive to form a shell with optical interference effects, resulting the color gradually changing from silvery white to deep gold. This strategy quickly endows LMs with uniform, stable and non-fading color, while maintaining their inherent electrical conductivity and fluidity. Particularly, this technology innovatively regulates the color of LMs by atomic oxidation and structural adjustment. This finding reveals the dependency between the oxide layer control and optical properties of LMs, laying the foundation for their application in flexible displays, bionic camouflage, information encryption, and multimodal human-machine interfaces. Thermally induced restructuring of the native oxide on gallium-based liquid metals yields stable, pigment-free structural colors. Controlled oxidation produces gallium oxide layer with distinct optical constants, enabling irreversible gold coloration and revealing a tunable pathway for functional, color-encoded liquid metal systems.