  Recently, heat manipulation has gained the attention of scientific community
due to its several applications. In this letter, based on transformation
thermodynamic (TT) methodology, a novel material, which is called thermal-null
medium (TNM), is proposed that enables us to design various thermal
functionalities such as thermal bending devices, arbitrary shape heat
concentrators and omnidirectional thermal cloaks. In contrary to the
conventional TT-based conductivities, which are inhomogeneous and anisotropic,
TNMs are homogeneous and easy to realize. In addition, the attained TNMs are
independent of the device shape. That is if the geometry of the desired device
is changed, there is no need to recalculate the necessitating conductivities.
This feature of TNM will make it suitable for scenarios where
re-configurability is of utmost importance. Several numerical simulations are
carried out to demonstrate the TNM capability and its applications in
directional bending devices, heat concentrators and thermal cloaks. The
proposed TNM could open a new avenue for potential applications in solar
thermal panels and thermal-electric devices.
