Design of thermal diodes using asymmetric thermal deformation of a Kirigami structure

Driving heat flow in one direction and blocking in the other direction can provide a potential advantage in thermal engineering – e.g., thermal management and energy harvesting. Pushing the idea toward a passive operation of the thermal diode can save more thermal energy, yet extremely challenging. In this work, we design a Kirigami structure that can function as a thermal diode providing a symmetry-breaking of heat flux activated by an asymmetric thermal deformation. Large thermal deformation of the metamaterial by an asymmetric arrangement of bilayer-hinges in a symmetric Kirigami geometry is the fundamental principle for the design of thermal diodes. Analytical modeling of thermomechanical deformation, thermal resistance, and thermal rectification together with finite element simulations can help select two base materials and geometric modifications, finally generating a phase-map for the design of thermal diodes with the Kirigami structure. The asymmetric heat flow powered by a large directional thermal deformation can maximize a thermal rectification ratio, which is the essential requirement for the design of thermal diodes. The designed thermal diodes with the Kirigami structure produce a record-high thermal rectification ratio of ~240, implying that we open a new avenue of mechanical metamaterials in thermal engineering. The developed innovation can potentially be applied for the next generation thermal devices such as heat engines, refrigeration, thermal regulations of buildings, and thermal logic devices.