Phase-Transformation-Driven Orientation Selection and Anisotropic Properties in Gallium Microfibers.

Ga-based liquid-metal (Ga-LM) microfibers are promising one-dimensional phase-change materials for variable-stiffness and electrically tunable devices. However, their solid-state properties remain difficult to control because of the polymorphism of Ga and the highly anisotropic bonding in the ambient-pressure stable α-Ga phase. Here, we investigate crystallographic orientation selection in Ga microfibers under different triggered phase-transformation pathways and clarify its influence on electrical and mechanical properties. During the triggered liquid-solid transition, the axial orientation of the resulting α-Ga single-crystal fibers is governed by the orientation of the α-Ga seed crystal and the local interfacial contact conditions. In contrast, after the triggered β-Ga→α-Ga solid-solid transition, no obvious inheritance from the initial α-Ga axial orientation is observed; instead, the final α-Ga fibers preferentially adopt an axial orientation close to [0 1 0]. This preferential orientation is attributed to a low-mismatch, low-strain transformation pathway associated with the β-Ga→α-Ga transition. The resulting α-Ga fibers exhibit pronounced electrical and mechanical anisotropy, especially between the [0 1 0] direction and the [1 0 0]/[0 0 1] directions. This work establishes a link among triggered transformation pathways, seed/interface-controlled orientation selection, and anisotropic properties in Ga microfibers, providing a strategy for tailoring liquid-metal fibers for programmable electronic and mechanically adaptive devices.