Thermal metamaterials for radiative plus conductive heat flow control

In this Letter, we show that the heat transferred from a thermal composite hot body emitter may be selectively directed in the far field toward a cold body receiver of choice through the enhanced design of both the anisotropic thermal conductivity of the emitter body and its surface emissivity. Specifically, focused radiosity of a representative cylindrical emitter in a preferential direction is attained by optimizing the layout of high and low thermally conductive materials within the solid in combination with an angularly varying emissivity surface profile. The relationship between the multi-body view factor scene and the thermal metamaterial design is clarified by way of numerical experiments. Subsequent gradient-based co-optimization of the thermal composite confirms the working principles of the device and reveals non-intuitive material and surface coating layouts that further enhance the directional radiative intensity of the emitter. The principles are extendable to the engineering of arbitrarily s...