Enhanced Thermal Invisibility Effect in an Isotropic Thermal Cloak with Bulk Materials

A thermal cloak is well known for hiding objects from thermal signature. A bilayer thermal cloak made from inner insulation layer and outer isotropic homogeneous layer could realize such thermal protection. However, its thermal protection performance can be suppressed for low-thermal-conductivity surrounding media. We propose a tri-layer thermal cloak model by adding a transition layer between the insulation layer and the outer layer. Numerical simulations and theoretical analysis show that, under the same geometry size and surrounding thermal conductivity, the performance of the thermal cloak can be significantly enhanced by introducing a transition layer with higher thermal conductivity and an outer-layer with lower thermal conductivity. The tri-layer cloak proposed provides a design guidance to realize better thermal protection using isotropic bulk materials.