Advanced liquid metal interfaces: engineering embodied cognition in closed-loop human-machine ecosystems

The persistent discord between rigid electronics and dynamic biological systems necessitates paradigm-shifting materials to realize seamless human-machine symbiosis. As inherently adaptive mediators, gallium-based liquid metals (Ga-LMs) have evolved beyond traditional flexible circuitry to pioneer disruptive closed-loop interfaces in neuroprosthetics, responsive robotics, and embodied artificial intelligence. Dynamic interfacial engineering provides a foundational strategy for orchestrating Ga-LMs' solid-liquid duality through field-guided topological adaptation, reversible morphological reconfiguration, and stimuli-responsive self-organization. In this review, we present the hierarchical design of Ga-LMs-enabled cybernetic systems from molecular-scale mediation to functional macroscopic assemblies. We provide a mechanistic perspective on how the electronic compliance, energy transduction efficiency, and adaptive response fidelity of these interfaces can be regulated via interfacial dynamics. Meanwhile, by emphasizing significant capabilities of Ga-LMs in smart healthcare, soft robotics, and intelligent assistive devices, this review identifies persistent challenges in long-term operational stability, biosafety protocols, and heterogeneous system interoperability as pivotal frontiers requiring concerted research efforts. Finally, we examine how such approaches advance closed-loop electronics through self-passivating architectures and bioresorbable designs, while highlighting critical challenges in chronic biocompatibility and cross-system interoperability. We call for intensified focus on interfacial decoding strategies to fully unlock liquid metals' potential as human-machine interfaces for cognitive-physical harmonization in closed-loop human-machine ecosystems.