Arbitrarily polygonal transient thermal cloaks with natural bulk materials in bilayer configurations

Transient thermal cloak has been attracting considerable attention due to the excellent performance in terms of heat-front maintenance and stable heat protection. However, their inhomogeneous and extreme parameters usually require challenging realization with metamaterials, thus leading to time-consuming and complicated fabrication even after some simplifications. In this paper, we propose a novel method to design an arbitrarily N-sided polygonal transient thermal cloak with nonsingular and homogenous material parameters. We further demonstrate that such cloak can be realized with only four kinds of natural bulk materials in bilayer configuration throughout. The multilayered materials can be easily arranged in a planarly stratified configuration due to all the flat boundaries, which makes the proposed cloaks much easier in fabrication and application. Simulation results validate the proposed scheme applicable to both steady-state and time-dependent cases with excellent performance. Based on the fact that an arbitrary shape can be approached by a polygon, our work actually opens up an avenue to arbitrarily shaped transient thermal cloaks made with natural bulk materials in bilayer configurations.