Three-dimensional patterned distribution of thermal conductivity in the volume for effective thermal concentration

For thermal devices and electronic systems, heat flow manipulation is critical to meet various needs. In this article, based on transformation thermodynamics, three-dimensional (3D) structures in the volume for patterned thermal conductivity were designed and fabricated. The 3D structures in the volume acting as heat flow routes can be achieved as pre-designed, providing a promising method to manipulate heat flow applied to the localized thermal concentration, thermal cloaking, etc. Simulation and experiments show that, by the 3D structures for thermal concentration, the heat flow could be concentrated to the pre-designed region, 7.0 K higher compared to the isotropic sample without any internal structures, and with a temperature gradient of over 1.3 K mm-1 to the surroundings (the heat source is 361 K), indicating an effective heat concentration. It also reveals that the heat flow could be accurately manipulated by carefully designing the geometric and material parameters of the internal structures, providing an alternative method to construct a 3D matrix for heat flow manipulation in the volume.