Beyond Planar Graphene: Roughness‐Conforming Microlaminates Enable Superior Heat Removal

ABSTRACT The escalating cooling demands of high‐heat‐flux electronic systems require materials that deliver efficient heat spreading, phase‐change enhancement, and scalable manufacturability—capabilities rarely found simultaneously on a single platform. Here, we introduce a microlaminate strategy that translates graphene's intrinsically two‐dimensional phonon transport into three‐dimensional heat removal from localized hot spots, without relying on volumetric composites or geometry‐dominated architectures. As a representative implementation, we demonstrate graphene‐based microlaminates integrated with laser‐microstructured copper, where the metal serves as a technologically relevant model substrate rather than a fundamental constraint. The interface‐engineered microlaminates preserve graphene's ultrahigh in‐plane thermal conductance, while enabling efficient coupling to macroscopic heat‐rejection pathways. Experiments and supporting analyses reveal exceptional performance across multiple thermal‐management regimes: (a) ∼20% reduction in hotspot temperature under single‐phase liquid cooling at heat fluxes approaching ∼150 W cm −2 , (b) ∼15% enhancement in heat‐transfer coefficient during dropwise condensation, and (c) record in‐plane effective thermal conductivity of ∼1.5 × 10 4 W m −1 K −1 in vapor‐chamber heat spreaders – among the highest reported for thermal‐management devices to date. While copper is employed here as a model system, the microlaminate framework is material‐agnostic and readily extendable to other thermally conductive substrates, establishing a general pathway for integrating planar nanomaterials into three‐dimensional thermal platforms.