Temperature-responsive thermal composites enabled by liquid-metal impregnation of fatty-acid–cellulose nanofiber phase-change frameworks

Flexible thermal-management materials must simultaneously deliver high latent heat, high thermal conductivity, and mechanical compliance—a combination that conventional solid-state phase change material (PCM) composites cannot satisfy, because crystalline fatty acids become rigid and leakage-prone upon solidification. Herein, we report a temperature-responsive flexible composite assembled entirely from intrinsically deformable constituents: a lauric-acid (LA) phase-change framework reinforced by cellulose nanofibers (CNF) and a gallium-based liquid metal (LM) impregnated into the porous framework. The LA-CNF framework, prepared by a physicochemical ball-milling route, provides latent heat while its interconnected fibrillar network suppresses external leakage of the impregnated LM. The LM contributes additional latent heat, a high through-plane thermal conductivity, and—critically—liquid-state fluidity above the LA melting point that renders the composite conformally flexible at its operating temperature. The interconnected fibrillar network further confines both the molten fatty acid and the mobile liquid metal, mitigating PCM/LM leakage while preserving deformability. By engineering the composite, a conditional (temperature-gated) flexibility is realized: the material is form-stable and handleable below the transition, yet becomes compliant and self-conforming above it.