Augmentation of Liquid Metal Particle Mechanics via Non-Native Oxide Nanoshells

Abstract

Room-temperature liquid metal particles based on gallium have become significantly important for developing next-generation soft electronics. Eutectic gallium-indium (EGaIn) alloys can be fabricated into core-shell particles discretely encapsulated by a passivating oxide. Application of mechanical stimuli results in rupturing the molten core through the oxide shell, merging EGaIn particles to form conductive pathways. Generally, the mechanical properties of EGaIn are largely defined by the native oxide which imparts viscoelastic properties to the fluid. In this work, the practical implications of EGaIn deformation and fracture behavior with the native oxide and a non-native inorganic silica shell are demonstrated. To augment the mechanical properties of EGaIn, silica nanoshells are introduced as a chemically inert coating to enable brittle fracture of particles. In situ single-particle nanoindentation characterization reveals the environmental and geometrical considerations for particle deformation and fracture. Silica-coated EGaIn particles reach stiffness values at least an order of magnitude higher than that of native EGaIn particles. The thickness of the silica shell can be tailored to further modify the mechanical behavior of EGaIn, enabling potential pressure-sensitive conductivity. These results provide additional pathways to understand the design and implementation of functionalized EGaIn particles for future applications in mechanoresponsive electronics, plasmonics, and therapeutics.