Hierarchical nanostructures are crucial to mitigate ultrasmall thermal point loads.

Here we show that hierarchical structures based on one-dimensional filaments such as carbon nanotubes lead to superior thermal management networks, capable of effectively mitigating high-density ultrasmall nanoscale heat sources through volumetric heat sinks at micrometer and larger scales. The figure of merit of heat transfer is quantified through the effective thermal conductance as well as the steady-state temperature distribution in the network. In addition to providing an overall increased thermal conductance, we find that hierarchical structures drastically change the temperature distribution in the immediate vicinity of a heat source, significantly lowering the temperature at shorter distances. Our work brings about a synergistic viewpoint that combines advances in materials synthesis and insight gained from hierarchical biological structures, utilized to create novel functional materials with exceptional thermal properties.