Transforming heat transfer with thermal metamaterials and devices

The demand for sophisticated tools and approaches in heat management and control has triggered the fast development of fields that include conductive thermal metamaterials, nanophononics, and far-field and near-field radiative thermal management. In this Review, we offer a unified perspective on the control of heat transfer, summarizing complementary paradigms towards the manipulation of physical parameters and the realization of unprecedented phenomena in heat transfer using artificial structures. The Review is divided into three parts that focus on the three main categories of heat flow control. Thermal conduction and radiation, at both the macroscale and microscale, are emphasized in the first and second parts. The third part discusses efforts to actively introduce heat sources or tune the material parameters with multiphysical effects in conduction, radiation and convection. We conclude by analysing the challenges in this research area and surveying new possible directions, in particular topological thermal effects, heat waves and quantum thermal effects. Artificial structures with novel thermal properties are promising for heat-transfer applications. This Review provides an overview of thermal metamaterials and devices, discussing the working principles underlying the manipulation of thermal conduction and radiation at different length scales.