From Patterning Precision to Biological Performance: Oxide Layer Kinetics in Gallium-Based Liquid Metals.

Abstract

Gallium-based liquid metals (GaLMs) have emerged as transformative materials for biomedical devices, flexible electronics, and soft robotics, owing to their room-temperature fluidity, high electrical conductivity, and favorable biocompatibility. However, achieving high-resolution patterning and predictable biological performance remains challenging due to the dynamic native Ga₂O₃ oxide layer, whose formation, rupture, passivation, and reformation govern interfacial wetting, charge transfer, and bio-interfacial interactions. This review critically examines how oxide layer kinetics provide a unifying framework linking patterning strategies to biological outcomes. We systematically evaluate four classes of patterning techniques, namely physical template, additive manufacturing, laser patterning, and selective wetting, based on their distinct oxide manipulation mechanisms, i.e., harnessed, transiently disrupted, permanently ablated, or locally eliminated. The resulting microstructural features, including oxide integrity, surface topography, and interface chemistry, dictate long‑term electrical stability, corrosion resistance, and tissue response. A three‑layer analytical framework is introduced to connect oxide properties to interfacial events and ultimately to biological outcomes. Evidence strength is graded to distinguish well‑established mechanisms from knowledge gaps, notably the lack of chronic in vivo data beyond six months and the unmonitored contact resistance drift under cyclic physiological loading. Finally, we identify future directions centered on oxide‑guided adaptive functionalities. This review provides a mechanistic foundation for rational design of GaLM‑based bioelectronics and highlights critical pathways toward clinical translation. STATEMENT OF SIGNIFICANCE: • Establishes oxide layer kinetics (Ga₂O₃ formation and dissolution) as the unifying mechanism governing interfacial energy and patterning fidelity in gallium-based liquid metals. • Unifies state-of-the-art patterning strategies including injection, template printing, photolithography, direct writing, 3D printing, laser patterning, and selective wetting under a framework of interface engineering. • Demonstrates functional integration of patterned GaLMs into soft electrodes, electronic skins, implantable bioelectronics, and soft robotics with exceptional mechanical compliance and biocompatibility. • Outlines critical challenges such as contact resistance drift and proposes future directions including in situ oxide passivation, biodegradable composites, and stimuli-responsive architectures for clinical translation.